CN103185970B

CN103185970B - The optical routing method and apparatus of translation polarised light, control optical signal, selection wavelength

Info

Publication number: CN103185970B
Application number: CN201110449977.8A
Authority: CN
Inventors: 林先锋
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-12-29
Filing date: 2011-12-29
Publication date: 2016-05-25
Anticipated expiration: 2031-12-29
Also published as: CN103185970A; CN105892083A; CN105892083B

Abstract

A method for translation polarised light, described method comprises: switch the polarization state of polarised light, the variation that the variation by described polarised light in polarization state is converted on locus obtains the first translation rear polarizer light; Described the first translation rear polarizer light is reflected simultaneously by the polarization state 90-degree rotation of polarised light; The variation that variation by rotation rear polarizer light in polarization state is converted on propagation path obtains the second translation rear polarizer light. Also disclose a kind of device of translation polarised light herein, controlled the method and apparatus of optical signal, and selected the optical routing method and apparatus of wavelength. After the application embodiment of the present invention, can improve the optical signal quality of route, reduce the volume of route device simultaneously.

Description

Optical routing method and device for translating polarized light, controlling optical signal and selecting wavelength

Technical Field

The present invention relates to the field of optical communication technologies, and in particular, to an optical routing method and apparatus for translating polarized light, controlling optical signals, and selecting wavelengths.

Background

Fiber optic communication networks are the mainstay of modern information society, carrying almost all modern data communications, including telephony, television, the internet, mobile communications, and the like. The existing optical fiber communication system is mainly based on a light Wavelength Division Multiplexing (WDM) technology, and different wavelength signals are multiplexed into the same optical fiber for transmission, so that the capacity of the optical fiber communication system is greatly increased. However, due to the lack of intelligent optical fiber devices, the optical wavelength routing of the conventional WDM system is fixed, the optical wavelength routing must be determined when the network design is performed, and the construction and maintenance of the network must be manually performed. Meanwhile, because the requirement of network bandwidth is difficult to predict and plan in advance, when the network is upgraded or new data services are provided, the network design and adjustment construction are often required to be carried out again. These disadvantages result in high construction and operation maintenance costs of the conventional WDM system, which hinders the further development of the WDM optical network.

The advent of reconfigurable optical add-drop multiplexers (ROADMs) changed this aspect. The WDM network node constructed by ROADM can switch the routing direction of the optical signal with different wavelengths according to the remote control signal, namely, dynamically configure the upper and lower service wavelengths and manage the power of each service wavelength, thereby avoiding the re-design and adjustment construction of the optical network when the network is upgraded or new data service is provided. Meanwhile, because ROADM is compatible with all service wavelengths, different working wavelengths can be selected without limitation, thereby greatly improving the flexibility of the network. Therefore, the application of ROADM makes WDM optical network evolve into new generation optical network with high intelligence, which not only can greatly reduce the operation and maintenance cost of network, but also can rapidly provide various new data services, and has become the development direction of WDM optical network.

A conventional 1 x 2ROADM core architecture is shown in fig. 1 and consists of an input wavelength division Demultiplexer (DEMUX)101, a 1 x 2 optical switch array 102, two output Variable Optical Attenuator (VOA) arrays 103 and 105, and two output wavelength division Multiplexers (MUXs) 104 and 106. The input and output port media of a ROADM are both optical fibers where the WDM wavelengths transmitted and their spacing are fixed, as shown by the spectrum at the input in fig. 1. Each bar in the spectrum represents a wavelength signal, its width represents its channel bandwidth, and its height represents its power level. The input signal shown in fig. 1 includes m wavelength signals λ 1 to λ m, whose powers are different from each other. When the optical signals enter the DEMUX module 101 of the ROADM through the input port, the optical signals are separated according to the wavelength and are respectively output by the output ports λ 1 to λ m of the DEMUX module 101, and each wavelength corresponds to one output port. These optical signals then enter an optical switch array 102 consisting of m 1 x 2 optical switches, each optical switch in the array corresponding to one wavelength, having an input connected to an output port of the corresponding wavelength on the DEMUX, and having two output ports corresponding to input ports of the corresponding wavelength on the MUX104 and MUX106, respectively. Therefore, by remotely controlling the switching state of each optical switch in the optical switch array 102, the routing direction of each wavelength can be selected, so that the input wavelength signals are divided into two groups and respectively go to the two MUXs of the ROADM. The two sets of wavelength signals leave the optical switch array and go to the corresponding MUX front VOA arrays 103 and 105, respectively. Both arrays consist of m VOAs, one wavelength for each VOA, and the power of the optical signal passing through them is adjusted according to a remote control signal. The last two groups of wavelength signals reach corresponding input ports of the MUX104 and the MUX106, and are respectively combined to output port 1 and output port 2 for output. As shown in fig. 1, a ROADM distributes m input wavelength signals of different powers to two output ports in a selected combination, and by adjusting the output power of each wavelength, a flat output spectrum is achieved (i.e., uniform power at each wavelength). Of course, any output spectrum can be obtained by adjusting the output power of each wavelength according to the requirements of practical application.

The structure of the multiple output ports 1 × NROADM is similar to 1 × 2ROADM except that the optical switch array is composed of 1 × N optical switches, and the number of VOA arrays MUX is N. The specific working principle is the same as that of the node 1 x 2, and the description is omitted here. It can be easily deduced that the structure of N × 1 (i.e., N inputs, 1 output) ROADM is the same as 1 × NROADM, except that the DEMUX and MUX function is reversed.

Because the existing ROADM system is composed of discrete devices with single function, the existing ROADM system not only has a large number, but also has complicated connection among the devices, so that the system is huge in volume. The devices forming the system are all independently packaged optical fiber devices, optical signals in the optical fiber devices are converted through optical fibers, internal media and the optical fibers, and each conversion brings about the degradation of the quality of the optical signals and the loss of optical power, so that the performance of the whole system is greatly limited.

Disclosure of Invention

The embodiment of the invention provides a method for translating polarized light, which can improve the quality of a routed optical signal and reduce the volume of a routing device.

The embodiment of the invention also provides a device for translating the polarized light, which can improve the quality of the optical signal of the route and reduce the volume of the route device.

The embodiment of the invention also provides a method for controlling the optical signal, which can improve the quality of the optical signal of the route and reduce the volume of the routing device.

The embodiment of the invention also provides a device for controlling the optical signal, which can improve the quality of the optical signal of the route and reduce the volume of the routing device.

The embodiment of the invention also provides an optical routing method for selecting the wavelength, which can improve the quality of the optical signal of the route and reduce the volume of a routing device.

The embodiment of the invention also provides an optical routing device for selecting the wavelength, which can improve the quality of the optical signal of the route and reduce the volume of the routing device.

The technical scheme of the embodiment of the invention is as follows:

a method of translating polarized light, the method comprising:

switching the polarization state of the polarized light, and converting the change of the polarized light in the polarization state into the change of the polarized light in the spatial position to obtain first polarized light after translation;

reflecting the first translated polarized light while rotating the polarization state of the polarized light by 90 degrees;

and converting the change of the polarized light after rotation on the polarization state into the change on the propagation path to obtain second polarized light after translation.

The switching the polarization state of the polarized light includes: the polarization state of the polarized light is switched by changing the driving voltage.

An apparatus for translating polarized light, the apparatus comprising at least one polarization modulator, at least one beam translation plate, an optical rotation plate, and a mirror;

the polarization modulator is used for switching the polarization state of the polarized light and outputting the polarized light input by the light beam translation sheet;

the light beam translation sheet is used for converting the change of the polarized light input by the polarization modulator on the polarization state into the change on the space position to obtain the translated polarized light, and converting the change of the polarized light input by the optical rotation sheet on the polarization state into the change on the space position to be input into the polarization modulator;

the optical rotation sheet is used for rotating the polarization state of the polarized light after translation by 90 degrees;

a mirror for reflecting the polarized light.

The polarization modulator switches the polarization state of polarized light by changing the driving voltage.

A method of controlling an optical signal, the method comprising:

completely separating an extraordinary light component and an ordinary light component in incident light to obtain separated polarized light;

switching the polarization state of the separated polarized light, and converting the change of the polarized light in the polarization state into the change of the polarized light in a spatial position to obtain first polarized light after translation;

converting the change of the polarized light after rotation on the polarization state into the change on the transmission path to obtain second polarized light after translation;

and synthesizing the second polarized light after the translation and emitting the light.

The completely separating the extraordinary and ordinary light components in the incident light includes:

dividing incident light into an extraordinary light component and an ordinary light component;

rotating the extraordinary and ordinary components to the same polarization direction;

and rotating the same polarization state of the polarized light by 45 degrees to obtain the polarized light corresponding to the extraordinary light component of the incident light and the polarized light corresponding to the ordinary light component of the incident light, wherein the polarization states of the corresponding polarized light are the same.

the extraordinary light component and the ordinary light component are respectively rotated by 90 degrees;

separating the rotated extraordinary light component and the ordinary light component;

A device for controlling optical signals comprises an input-output array, a splitting-combining module, at least one polarization modulator, at least one beam translation plate, an optical rotator and a reflector;

an input-output array for receiving incident light and outputting emergent light;

the splitting and combining module is used for completely separating the extraordinary light component and the ordinary light component in the incident light to obtain separated polarized light and synthesize the polarized light returned by the polarization modulator;

the polarization modulator is used for switching the polarization state of the separated polarized light to obtain switched polarized light;

the light beam translation sheet is used for converting the change of the switched polarized light in the polarization state into the change of the switched polarized light in the space position to obtain the translated polarized light;

the optical rotator is used for rotating the polarization state of the polarized light after translation;

a mirror for reflecting the polarized light.

The divide-shut module includes: a uniaxial crystal, at most two reversible optical rotation plates and an irreversible optical rotation plate;

the uniaxial crystal is used for dividing incident light into an extraordinary light component and an ordinary light component and synthesizing two beams of polarized light with mutually vertical polarization states;

the reversible optical rotation sheet is used for rotating the extraordinary ray component and the ordinary ray component to the same polarization direction, and respectively rotating the two beams of rotated polarized light to obtain two beams of polarized light with mutually vertical polarization state directions;

the irreversible polaroid is used for rotating the polarization state of the polarized light with the same polarization state by 45 degrees to obtain two beams of polarized light with the same polarization state, and rotating the polarization state of the two beams of polarized light after translation by 45 degrees.

The divide-shut module includes: a first uniaxial crystal, a first reversible optical rotation sheet, a second uniaxial crystal, at most two optical rotation sheets and an irreversible optical rotation sheet;

the first uniaxial crystal is used for dividing incident light into an extraordinary ray component and an ordinary ray component and synthesizing two beams of polarized light with mutually vertical polarization states;

the first reversible polarimeter is used for respectively rotating the extraordinary ray component and the ordinary ray component by 90 degrees and respectively rotating the polarization states of the two beams of polarized light with polarization state directions perpendicular to each other by 90 degrees;

the second uniaxial crystal is used for separating the rotated extraordinary light component and the ordinary light component and increasing the distance between two beams of polarized light with mutually vertical polarization states; the optical axis of the second uniaxial crystal is opposite to the direction of the first uniaxial crystal;

The input-output array includes:

the optical fiber array is used for receiving external incident light and outputting internal emergent light;

and the micro lens array is used for collimating external incident light and converging internal emergent light.

The optical rotator is an optical rotation sheet or a polarization modulator, and the polarization modulator rotates the polarization state of the polarized light after translation through driving voltage so as to adjust the power of emergent light.

An optical routing method for selecting wavelengths, the method comprising:

completely separating an extraordinary light component and an ordinary light component in incident light to obtain polarized light with consistent polarization state;

separating the polarized light with consistent polarization state according to different wavelengths;

respectively switching the polarization state of the polarized light, and converting the change of the polarized light in the polarization state into the change of the polarized light in the spatial position to obtain first polarized light after translation;

and respectively synthesizing the second polarized light after the translation with the selected wavelength for different exit ports, and obtaining the exit light with the selected wavelength at the exit ports.

The separating the polarized light with consistent polarization state according to different wavelengths comprises:

collimating the polarized light with the consistent polarization state;

separating the collimated polarized light according to different wavelengths;

and refracting the separated polarized light into a group of parallel polarized light, and then converging the polarized light on the same plane.

An optical routing device for selecting wavelengths, the device comprising: the system comprises an input/output array, a splitting and combining module, a dispersion module, at least one polarization modulator, at least one light beam translation sheet, an optical rotation module and a reflector;

the input/output array is used for receiving incident light with different wavelengths and outputting emergent light with selected wavelength;

the splitting and combining module is used for completely separating the extraordinary light component and the ordinary light component in the incident light to obtain polarized light with consistent polarization state and synthesize the polarized light returned by the dispersion module;

the dispersion module is used for separating the polarized light with the consistent polarization state according to different wavelengths and combining the selected polarized light with different wavelengths;

a polarization modulator for switching a polarization state of the separated polarized light;

the light beam translation sheet is used for converting the change of the polarized light on the polarization state into the change on the space position to obtain the polarized light with different wavelengths after translation, and inputting the polarized light with different selected wavelengths into the polarization modulator;

the optical rotation module is used for rotating the polarization state of the polarized light with different wavelengths after translation;

a reflector for reflecting polarized light of different wavelengths;

the end face of the input and output array is positioned in the outer focal plane of the dispersion module, and the reflecting mirror is superposed with the outer focal plane of the dispersion module.

The dispersion module includes:

the first lens is used for collimating the incident polarized light with the consistent polarization state and converging the emergent polarized light with different selected wavelengths to an outer focal plane of the first lens;

the diffraction grating is used for separating the collimated polarized light according to different wavelengths and combining the polarized light with different selected wavelengths;

the second lens is used for refracting the separated polarized light with different wavelengths into a group of parallel polarized light and converging the polarized light on a focal plane outside the second lens; collimating the polarized light reflected from the focal plane outside the second lens, and refracting the collimated polarized light to the focal direction inside the second lens;

the focal length of the first lens is equal to that of the second lens, the inner focal points of the first lens and the second lens coincide, and the center of the diffraction grating is located at the inner focal points of the first lens and the second lens.

The dispersion module includes:

the third lens is used for collimating the polarized light with the consistent polarization state, refracting the separated polarized light output by the reflection type diffraction grating into a group of parallel polarized light, and simultaneously respectively converging the parallel polarized light to a focal plane on the left side of the third lens; the polarized light reflected from the focal plane on the left side of the third lens is collimated, the collimated polarized light is refracted towards the focal direction on the right side of the third lens, and emergent polarized light which is combined by the reflection type diffraction grating and comprises the selected different wavelengths is converged to the focal plane on the left side of the third lens;

a reflection type diffraction grating for separating the collimated polarized light according to different wavelengths and combining the polarized light of different selected wavelengths;

the center of the reflection type diffraction grating is located at the right focal point of the third lens.

The dispersion module includes:

the reflecting spherical mirror is used for collimating the polarized light with the consistent polarization state, refracting the separated polarized light output by the reflection type diffraction grating into a group of parallel polarized light, and simultaneously respectively converging the parallel polarized light to a focal plane of the reflecting spherical mirror; collimating the polarized light reflected from the focal plane of the reflective spherical mirror, refracting the collimated polarized light to the focal direction of the reflective spherical mirror, and converging the emergent polarized light which is combined by the reflection type diffraction grating and comprises the selected different wavelengths to the focal plane of the reflective spherical mirror;

the center of the reflection type diffraction grating is located at the focal point of the reflective spherical mirror.

The polarization modulator is a first polarization modulator array, and the optical rotation module is a second polarization modulator array;

the first polarization modulation array independently modulates the polarization state of the polarized light of each wavelength; the light-passing surface of the light beam translation plate covers all pixels of the first polarization modulation array;

the second polarization modulation array independently modulates the polarization state of the polarized light with each wavelength; the reflective surface of the mirror covers all pixels of the second polarization modulation array.

As can be seen from the above technical solutions, in the embodiment of the present invention, a device for obtaining a control optical signal is added to a device for translating polarized light; a dispersion module is further added in the device for controlling the optical signal to obtain an optical routing device for selecting the wavelength. Due to the adoption of the technical scheme, the optical structure is simplified, the miniaturization of the device is realized, the quality of the routed optical signal can be improved, and the size of the routing device is reduced.

Drawings

Fig. 1 is a schematic diagram of a core architecture of a conventional 1 x 2ROADM in the prior art;

FIG. 2 is a schematic flow chart of a method for translating polarized light;

FIG. 3 is a schematic diagram of an apparatus for translating polarized light;

FIG. 4A is a cross-sectional view of the liquid crystal switching cell 310 and the operation of applying a voltage V0;

FIG. 4B is a cross-sectional view of the liquid crystal switching cell 310 and the operation of applying the voltage V1;

FIG. 5A is a schematic diagram illustrating the operation of the switching unit 310 applying the voltage V0;

FIG. 5B is a schematic diagram illustrating the operation of the switching unit 310 applying the voltage V1;

FIG. 6A is a schematic diagram of 4 alternative output coordinates working in FIG. 1;

FIG. 6B is a schematic diagram of 4 alternative output coordinate operations 2;

FIG. 6C is a schematic diagram of 4 alternative output coordinate operations 3;

FIG. 6D is a schematic diagram 4 of 4 alternative output coordinate operations;

FIG. 7 is a flowchart illustrating a method of controlling an optical signal;

FIG. 8 is a schematic diagram of an apparatus for controlling optical signals;

fig. 9A is a schematic diagram of forward beam splitting of the splitting and combining module 900;

fig. 9B is a schematic diagram of a reverse light combination of the combining and combining module 900;

fig. 9C is a schematic diagram of the combining and combining module 900 not normally combining light in the reverse direction;

fig. 9D is a schematic operation diagram 4 of the clutch module 900;

FIG. 10 is a schematic diagram of an apparatus for controlling optical signals capable of adjusting output optical power;

FIG. 11 is a flowchart illustrating a method for selecting a wavelength for optical routing;

FIG. 12A is a schematic diagram of a wavelength selective optical routing device;

fig. 12B is a schematic structural diagram of an optical routing device with 1 × 2 wavelength selection;

FIG. 13A is a schematic diagram of a lateral structure of an array of tunable switching modules;

FIG. 13B is a schematic diagram of a vertical structure of an array of adjustable switching modules;

FIG. 14 is a schematic diagram of a wavelength selective optical routing device;

fig. 15 is a schematic view of a wavelength selective optical routing device.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.

In the embodiment of the invention, an input/output array and a splitting and combining module are added on the basis of a device for translating polarized light to obtain a device for controlling optical signals; on the basis of the device for controlling the optical signal, a dispersion module is added to obtain an optical routing device for selecting the wavelength.

The device for translating the polarized light not only can realize the precise switching of the polarized light, but also can flexibly adjust the switching amount of the polarized light through the optical thicknesses of the polarization modulator and the light beam translation plate. The device for controlling the optical signal adopts a unique polarization splitting/combining design, all the abnormal lights corresponding to the input light and the output light are completely separated from all the abnormal lights after being translated by the splitting and combining module, and therefore the polarization state consistency of all the lights can be realized only by one group of wave plates. The ordinary rays or the extraordinary rays of different ports do not need to be completely separated, and the light spots can be overlapped with each other when leaving the polarization splitting crystal without influencing the extinction ratio of the polarized light. By adopting the technical scheme, the polarization optical structure is greatly simplified, and the input and output ports of the polarization optical structure can be formed by a single optical fiber array with very small intervals, so that the miniaturization of the device for controlling the optical signals is realized. The device for controlling the optical signal not only has simple structure and easy assembly, but also has few components and small volume. Meanwhile, because the micro optical fiber array is used as an input port and an output port, the volume of the micro optical fiber array is hardly increased along with the increase of the number of the ports, and therefore extremely high stability and reliability are realized.

The optical routing device for selecting the wavelength is a classic 4F system and is characterized in that the mapping of the space distance on the front focal plane and the rear focal plane is 1: 1. This feature, in combination with the small-space fiber array port used by the apparatus for controlling optical signals of the present invention, can greatly reduce the optical thickness of the device for translating polarized light, thereby improving the performance of the optical system and reducing the package size of the system. Another feature in 4F systems is that the light corresponding to all ports passes through the common focus of the two lenses, i.e. the position of the diffraction grating of the dispersive element. Therefore, the size of the diffraction grating only needs to be larger than the size of a single light spot, and the system requirement is met, so that the requirement of the system on the area of the diffraction grating is greatly reduced. Meanwhile, the light spot transformed by the main lens is larger than that of the independent collimator, and the area of the light spot shining on the diffraction grating is correspondingly larger, so that the diffraction resolution of the whole optical system is higher.

The technical scheme of the invention is explained in detail in the following with the accompanying drawings.

Referring to fig. 2, a schematic flow chart of a method for translating polarized light specifically includes the following steps:

step 201, the polarization state of the polarized light is switched, and the change of the polarized light in the polarization state is converted into the change of the polarized light in the spatial position to obtain the first polarized light after the translation.

The polarization state of the polarized light is switched without changing the propagation path of the polarized light. When the polarization state of the polarized light changes, the change of the polarization state of the polarized light is converted into the change of the polarization state on the space position, and the polarized light after the first translation is obtained. Wherein the polarized light can be switched by changing the driving voltage.

Step 202, reflecting the first translated polarized light and rotating the polarization state of the polarized light by 90 degrees.

And reflecting the polarized light after the first translation, and rotating the polarization state of the polarized light by 90 degrees at the same time.

Step 203, converting the change of the polarization state of the rotated polarized light into a change of the polarization state of the rotated polarized light on the propagation path to obtain second translated polarized light.

The polarization state of the polarized light before step 202 changes by 90 degrees from the polarization state of the polarized light after step 202, and this change in polarization state is converted into a change in the propagation path of the polarized light before step 202 and after step 202, thereby obtaining a second translated polarized light.

Referring to fig. 3, a schematic structural diagram of an apparatus for translating polarized light is shown, specifically:

the means for translating polarized light, i.e., the switching module 300, is composed of a plurality of switching units 310 and a reflecting unit 320. Wherein each switching unit 310 is composed of a polarization modulator 311 and a beam-shifting plate 312. The polarization modulator 311 functions to switch the polarization state of incident light, but it does not change the propagation path of the incident light. The translation of the incident light by the switching unit 310 is performed by the beam translation sheet 312 therein. The beam shifting plate 312 is a parallel plate made of uniaxial birefringent crystal, and its characteristic is that the polarization state of the incident light determines whether it shifts when it exits. The reflection unit 320 is composed of an optical rotation plate 321 and a reflection mirror 322, and functions to reflect the incident polarized light along the original path and rotate the polarization state by 90 degrees. The optical rotation plate 321 is a 45-degree faraday rotation plate, and the polarization state of the reflected light is rotated by 45 degrees and then reflected, and then the polarization state of the reflected light is rotated by 45 degrees. The optical rotation plate 321 is a quarter-wave plate made of birefringent crystal, and after the polarized light is reflected by the mirror, the polarization state is rotated by 90 degrees.

The polarization modulator 311 can modulate the polarization state of incident polarized light according to an external driving signal, and technologies that can achieve this function include liquid crystal technology, electro-optic technology, and magneto-optic technology. The beam translation plate 312 is a parallel plate made of uniaxial birefringent crystal, and can convert the change of the polarization state of the polarized light into a change of the spatial position, that is, can make the polarized light translate when the polarization state changes. Materials from which the beam-translating plate can be made include, but are not limited to, yttrium vanadate (YVO4) crystals, lithium niobate crystals, and calcite crystals.

Polarized light enters the switching module 300 along the positive direction of the Z axis, and exits along the negative direction of the Z axis after being subjected to translation switching by each switching unit 310 and reflection by the reflection unit 320, and the Y-axis coordinate of the exiting light is different from that of the incident light, i.e., a translation is generated relative to the incident light. If the number of switching units 310 is N, the Y-axis coordinate of the outgoing light has 2^NAnd (4) selecting. These Y-axis coordinates are determined by the amount of translation of each beam translation plate 312, and selection of which Y-axis coordinate is output is achieved by controlling the state of each polarization modulator 311.

The following explains a specific working principle of the switching module based on the liquid crystal technology by taking the switching module as an example. Fig. 4A is a cross-sectional view of a liquid crystal switching unit 310 and a schematic diagram of the liquid crystal switching unit, wherein a polarization modulator 311 is a liquid crystal cell and mainly comprises two glass substrates 401, a liquid crystal layer 402, and two transparent electrodes 403 plated on the glass substrates. The liquid crystal layer 402 is sandwiched between two transparent electrodes 403, and an external driving voltage may be applied to the liquid crystal layer 402 through the transparent electrodes 403.

Liquid crystal is a condensed substance, the structure and characteristics of which are between those of solid crystal and isotropic liquid, and is ordered fluid. The chemical structure of liquid crystals is asymmetric, and therefore the dielectric and optical properties are also asymmetric, having the same birefringence as crystals. Assuming that the thickness of the liquid crystal layer 402 is d, the optical axis is in the X-Y plane and at 45 degrees to the Y axis, and the difference between the refractive indices of the ordinary ray (O ray) and the extraordinary ray (E ray) is Δ n, the phase retardation of the incident light is

＝Δnd

When equal to the incident wavelength λ or an integral multiple thereof, the liquid crystal layer 402 corresponds to a full waveplate of the incident light, and the polarization state of the incident light is not changed after passing through it. When the polarization is equal to λ/2 or an odd multiple thereof, the liquid crystal layer 402 corresponds to a half-wave plate of the incident light, and can rotate the polarization of the incident light with the polarization state perpendicular or parallel to the Y-Z plane by 90 degrees.

When an electric field is applied to the liquid crystal layer 402, the alignment direction of its molecules changes, and the birefringence, i.e., the refractive index difference Δ n, changes accordingly, resulting in an Electrically Controlled Birefringence (ECB) effect. Therefore, by utilizing the electric control birefringence effect of the liquid crystal, the phase delay of the liquid crystal box to incident polarized light can be changed by changing the driving voltage of the liquid crystal box, so that the modulation of the polarization state of the light is realized.

Assuming λ and λ/2, the corresponding driving voltages are V0 and V1, respectively, and the polarization state modulation by the polarization modulator 311 is shown in FIG. 4A and FIG. 4B, respectively. In FIG. 4A, incident light having a polarization state perpendicular to the Y-Z plane (indicated by the dots on the light) remains unchanged after passing through the polarization modulator 311 driven at a voltage V0. In FIG. 4B, however, the incident light of the same polarization state, after passing through the polarization modulator 311 with a driving voltage of V1, becomes parallel to the Y-Z plane (indicated by the small horizontal line on the light), i.e., is rotated 90 degrees with respect to the incident polarization state.

In addition to the ECB mode, the liquid crystal can also implement the above-mentioned polarization state modulation function in other various operation modes, including Twisted Nematic (TN) and Super Twisted Nematic (STN) modes. The detailed operation principle of the liquid crystal is not included in the present invention, and will not be described herein.

The beam translation plate 412 of fig. 4 is illustrated as a crystal of yttrium vanadate having a thickness T and a crystal optical axis 404 in the Y-Z plane and at an angle a to the crystal surface. When the driving voltage of the polarization modulator 311 is V0, the polarization state of the incident light passing through the polarization modulator 311 is not changed, and therefore the polarization state is still perpendicular to the Y-Z plane where the optical axis 404 is located when the incident light enters the beam-shifting plate 312, as shown in fig. 4A. In this case, the incident light is refracted in the beam translation plate 312 according to the refraction rule of the ordinary light, so that no shift occurs in the Y-axis direction, and the outgoing light and the incident light are on the same straight line, and the Y-axis coordinate is not changed.

When the driving voltage of the polarization modulator 311 is V1, the polarization state of the incident light is rotated by 90 degrees after passing through the polarization modulator 311, and becomes linearly polarized light parallel to the Y-Z plane, as shown in fig. 4B. In this case, the polarization state of the incident light is parallel to the main cross section of the beam translation plate 312 (i.e., the plane where the optical axis 404 is located), and thus the light is refracted in the beam translation plate 312 according to the refraction rule of the extraordinary rays, and the deviation occurs in the Y-axis direction, and the deviation direction is consistent with the direction of the optical axis 404, i.e., the positive direction of the Y-axis. The final emergent light and the incident light are not on the same straight line, but on two parallel straight lines with the distance d.

That is, the beam translation plate translates the incident light by a distance d along the Y-axis in the Y-Z plane, and if the Y-axis coordinate of the incident light is 0, the Y-axis coordinate of the outgoing light is + d. The translation distance d of the light beam translation sheet is determined by the thickness T and the optical axis direction a of the crystal, and the required translation distance d can be obtained by selecting the proper crystal thickness T and the proper optical axis direction a according to the characteristics of the crystal.

The detailed operation of the switching module will be described below by taking the switching module (as shown in fig. 5) including one of the switching units 310 as an example.

Referring to fig. 5A, a polarized light beam with a polarization state perpendicular to the Y-Z plane and a Y-axis coordinate of 0 is incident on the switching unit 310 along the positive direction of the Z-axis. When the driving voltage is V0, the polarization state is not changed after passing through the switching unit 310, and the Y-axis coordinate is not changed, and the driving voltage continues to enter the reflection unit 320 in the positive Z-axis direction. The optical rotation plate 321 in the reflection unit 320 is a quarter-wave plate of incident light, the optical axis of which is in the X-Y plane (perpendicular to the Y-Z plane) and makes an angle of 45 degrees with the Y axis. The polarized light passes through the optical rotation sheet 321, is reflected by the mirror 322, changes the propagation direction to the negative Z-axis direction, and then passes through the optical rotation sheet 321 again along the original path. The effect of the polarized light passing through the quarter-wave plate twice is equivalent to that passing through the half-wave plate once, and the optical axis of the wave plate forms an angle of 45 degrees with the polarization state thereof, so that the polarization state is rotated by 90 degrees after the polarized light is reflected by the reflection unit 320, and becomes parallel to the Y-Z plane, and the propagation direction becomes the negative direction of the Z axis.

When the polarized light continues to enter the switching unit 310 again in the negative Z-axis direction, the beam shifting plate 312 enters first, and the polarization state of the polarized light becomes parallel to the Y-Z plane (i.e., the main section of the beam shifting plate 112), so that the polarized light is refracted in the beam shifting plate 312 according to the refraction rule of the extraordinary rays and is shifted in the Y-axis direction. Meanwhile, the incident direction is the Z-axis negative direction, so the offset direction is the Y-axis negative direction. If the translation distance of the beam translation plate 312 is d, the Y-axis coordinate of the emergent polarized light is-d. The polarized light finally passes through the polarization modulator 311 again, and since the driving voltage is V0, the polarization state of the polarized light is not changed, and the polarization state of the finally emergent light is parallel to the Y-Z plane.

Fig. 5B shows the operation principle of the switching module when the driving voltage of the polarization modulator 311 is V1. The same incident light is translated by a distance d after passing through the switching unit 310, and the Y-axis coordinate emitted from the beam translation piece 312 is + d. At the same time, its polarization state is rotated by 90 degrees to become parallel to the Y-Z plane. The polarized light exits from the switching unit 310 and continues to enter the reflection unit 320 along the positive Z-axis direction, the propagation direction changes to the negative Z-axis direction after being reflected by the reflection unit 320, and the polarization state is rotated by 90 degrees again to be perpendicular to the Y-Z plane. Therefore, when the polarized light enters the beam translation plate 312 again along the negative direction of the Z axis, the polarized light will be refracted according to the refraction rule of the ordinary light, no shift occurs in the Y axis direction, and the Y axis coordinate of the emergent light is still + d. Finally, the polarized light passes through the polarization modulator 311 again, and the polarization state of the polarized light is rotated by 90 degrees for the third time due to the driving voltage of V1, and the polarization state of the final emergent light is parallel to the Y-Z plane.

In summary, the switching module including one switching unit can select two output coordinates + d and-d (assuming that the coordinate of the input light is 0), and the output coordinates can be selected by controlling the driving voltage, i.e. the modulation state, of the polarization modulator in the switching unit. The drive voltage corresponding to coordinate-d is V0, i.e., a modulation state that does not rotate the polarization state, in which case the translation of the polarized light occurs as it propagates in the negative Z-direction, so the direction of translation is the negative Y-direction and the output coordinate is-d, as shown in fig. 5A. And the driving voltage corresponding to the coordinate + d is V1, i.e. the modulation state that rotates the polarization state by 90 degrees, in this case the polarization light is translated when it propagates in the positive Z-axis direction, so the direction of translation is the positive Y-axis direction and the output coordinate is + d, as shown in fig. 5B.

In more cases, the switching module comprises a plurality of switching units as shown in fig. 3. For any one switching unit in a switching module (hereinafter referred to as a multi-unit switching module) comprising a plurality of switching units, it is easy to say that the number of 90-degree rotations of the polarization state (including 90-degree rotations of the reflective unit) experienced by the polarized light during the process from leaving the switching unit in the positive direction of the Z-axis to returning the switching unit in the negative direction of the Z-axis is necessarily odd. That is, the polarized light must have a polarization state 90 degrees to exit when it returns to the switching unit. Therefore, the polarized light must be translated once and only once while passing through the beam translation plate of each switching unit twice. If the translation occurs as it propagates in the positive Z-axis direction, then the direction of the translation is the positive Y-axis direction. If the translation occurs as it propagates in the negative Z-axis direction, then the direction of the translation is the negative Y-axis direction. By controlling the modulation state of the polarization modulator of the switching unit, it is possible to select whether the polarized light is translated when propagating in the positive direction of the Z axis or the polarized light is translated when propagating in the negative direction of the Z axis, that is, the direction of translation of the polarized light can be selected.

Therefore, it can be concluded that each switching unit in the multi-unit switching module translates the incident light, and the translation amount of the final emergent light is the sum of the translation amounts of all the switching units. Each switching unit is independent to the translation of the polarized light, so that the position of the switching unit in the switching module, namely the sequence does not influence the translation amount of the final emergent light. Because each switching unit has positive and negative translation directions, if the number of the switching units contained in the switching module is N and the translation amounts are different, the Y-axis coordinate of emergent light has at most 2^NSeed selectionAnd (6) selecting. The Y-axis coordinate of the outgoing light can be selected by controlling the driving voltage of each switching unit, i.e., the translation direction of each switching unit.

According to the conclusion, the switching module with any number of output ports and output coordinates can be designed. The following description will be made in detail by taking an example of a switching module in which 4 output coordinates can be selected and the input and output coordinates are arranged at an equal interval d.

First, at least two switching units are required to satisfy the 4 selectable output coordinates. In order to obtain an equidistant arrangement of input and output coordinates, the result of arbitrary addition and subtraction combinations of the translation distances of the two switching means must be an integer multiple of d. The switching module obtained according to these requirements is shown in fig. 6A, 6B, 6C, and 6D, and two switching units 610 and 620, and a reflection unit 320 are sequentially arranged along the positive direction of the Z-axis. The translation distances of the beam translation pieces 612 and 622 of the two switching units are respectively designed to be 1.5d and 0.5d, so as to achieve the effect of equal-interval output.

The detailed working and control states of the switching module and the corresponding output results are shown in table one, and the specific paths of the light rays in the four states are shown in fig. 6A to 6D. In the case where the Y-axis coordinate of the input light is 0, four output coordinates are-2 d, -d, + d, and +2d, respectively, which are exactly equally spaced on both sides of the input coordinate, and each output coordinate corresponds one-to-one to a combination of four driving voltages of the switching unit.

Watch 1

It should be noted that in the multi-cell switching module, although the driving voltages of the switching cells and the shifting directions (positive or negative) thereof are in one-to-one correspondence, the correspondence relationship is not fixed, and the same driving voltage may correspond to the opposite shifting directions in different switching states. For example, the translation direction corresponding to the driving voltage V1 of the switching unit 620 in the switching state 3 is the Y-axis negative direction rather than the positive direction. This is because the polarization state of the polarized light when it first reaches the switching unit 620 is parallel to the Y-Z plane, not perpendicular to the Y-Z plane. Therefore, the translation direction is determined according to the propagation direction of the polarized light when the polarized light is translated, and the translation direction is positive when the polarized light is propagated along the positive direction of the Z axis, and is negative when the polarized light is propagated along the negative direction. Similarly, if the polarization state of the input light is parallel to the Y-Z plane rather than perpendicular to the Y-Z plane, the translational switching of the input light by the switching module is still effective, and the number and coordinates of the output ports are not changed, but only the combination of the driving voltages corresponding to each output coordinate is different.

Further, the relationship between the translation direction and the propagation direction of the above beam translation plate (i.e., the translation of polarized light occurring when the polarized light propagates in the positive direction of the Z axis is positive, and vice versa is negative) is based on the premise that the beam translation plate is made of yttrium vanadate crystal, that is, uniaxial positive crystal, and the optical axis direction thereof is as shown in fig. 4. If the beam-shifting film is made of a uniaxial negative crystal, or if the optical axis of the crystal is in the opposite direction to that shown in fig. 4 (symmetrical about the Z axis), then the shift of the polarized light as it propagates in the positive direction along the Z axis is negative, and vice versa, positive. The principle related to this is the basic theory of crystal optics and will not be described in detail here.

Next, the operating principle of a switching module, in which 8 output coordinates can be selected and the input and output coordinates are arranged at equal intervals d, is analyzed, and the parameters and the operating state are shown in table two. Because 8 is 2³Therefore, the switching module includes three switching units, and the translation distances of the beam translation pieces are respectively 2.5d, 1.0d and 0.5d (which can be arranged in any order), so as to achieve the effect of equal-interval output.

In the case where the Y-axis coordinate of the input light is 0, 8 output coordinates are-4 d, -3d, -2d, -d, + d, +2d, +3d, and +4d, respectively, and are distributed at exactly equal intervals on both sides of the input coordinate. Each output coordinate corresponds to a combination of the translation directions of the switching unit one by one, and each combination of the translation directions also necessarily corresponds to a combination of the fixed driving voltage, and the corresponding relationship is determined by the polarization state of the incident light and the specific structure of the switching module, which is not described in detail herein.

Watch two

According to the technical scheme, more output coordinates can be determined, namely, more switching modules containing more switching units can be determined. And the output coordinate of each switching module can be adjusted by changing the translation amount of each switching unit so as to meet the requirement of practical application.

The above-discussed means for translating polarized light switches linearly polarized light with a fixed polarization state, whereas the polarization state of light propagating in a conventional optical fiber is random and not fixed. Therefore, the apparatus for controlling an optical signal using an optical fiber as an input/output port must include a switching module in addition to the above apparatus for shifting polarized light. The function of the splitting and combining module is to divide input light with random polarization states into two components with fixed polarization states, so that the device for translating the polarized light can switch the two components, and the two components are recombined and output after the switching is finished.

Referring to fig. 7, a flow chart of a method for controlling an optical signal is shown, which specifically includes the following steps:

and 701, completely separating the extraordinary light component and the ordinary light component in the incident light to obtain the separated polarized light.

Wherein the complete separation of the extraordinary and ordinary light components in the incident light comprises two ways:

the first method is as follows:

The second method comprises the following steps:

Step 702, switching the polarization state of the separated polarized light, and converting the change of the polarization state of the polarized light into the change of the spatial position to obtain the first polarized light after translation.

The polarization state of the polarized light is switched without changing the propagation path of the incident light. When the polarization state of the polarized light changes, the change of the polarization state of the polarized light is converted into the change of the polarization state on the space position, and the polarized light after the first translation is obtained. Wherein the polarized light can be switched by changing the driving voltage.

Step 703, reflecting the first translated polarized light and rotating the polarization state of the polarized light by 90 degrees.

Reflecting the first translated polarized light while rotating the polarization state of the polarized light by 90 degrees.

Step 704, converting the change of the polarization state of the rotated polarized light into a change of the polarization state of the rotated polarized light on a propagation path to obtain second polarized light after translation, synthesizing the second polarized light after translation, and emitting the second polarized light.

The polarization state of the polarized light before the step 703 and the polarization state of the polarized light after the step 703 are changed by 90 degrees, and the change of the polarization state is converted into the change of the polarized light on the propagation path before the step 703 and after the step 703, so that the polarized light after the second translation is obtained, and the polarized light after the second translation is synthesized and emitted.

As shown in fig. 8, a 1 × 2 apparatus for controlling optical signals is taken as an example, and the apparatus for controlling optical signals is analyzed. The apparatus for controlling an optical signal includes: the input/output array 800, the combining and splitting module 900 and the polarized light translation device 300 are sequentially arranged along the positive direction of the Z axis. The input/output array 800 is composed of an optical fiber array 810 and a microlens array 820, which are all arranged closely at a distance d along the Y-axis direction, and the optical fiber ports and the microlenses are in one-to-one correspondence. The middle port of the array is an input port, the Y-axis coordinate of the input port is set to be 0, the two output ports are symmetrically distributed on two sides of the input port, and the corresponding Y-axis coordinates are + d and-d respectively.

Polarized light with random polarization state enters from the input optical fiber, is collimated by the corresponding micro lens, and then enters the combining and combining module 900. The incident polarized light is split into two components with polarization states perpendicular to the Y-Z plane by the polarization splitting and combining module 900 along the Y-axis direction, and then enters the device 300 for translating polarized light. Since the number of output ports is 2, the apparatus 300 for shifting polarized light only includes one switching unit, and the shifting distance is d.

That is, the device 300 for shifting polarized light has two switching states, which respectively shift the input light by the distance d in the positive and negative directions of the Y-axis, and the shifting effect of the two components of the incident polarized light is identical. In the former switching state, two components of the incident polarized light are simultaneously translated by a distance d in the positive direction of the Y axis, and the polarization state is rotated to be parallel to the Y-Z plane, and then returned to the optical splitting and combining module 900 in the negative direction of the Z axis, and the path of the light is shown by the solid line in fig. 8. At this time, since both components of the polarized light are translated by a distance d along the positive direction of the Y axis, the Y axis coordinate of the polarized light merged by the merging and merging module 900 is + d, and the Y axis coordinate exactly corresponds to the output port 1 in the input/output array 800, so that the polarized light is converged into the optical fiber 1 by the micro lens for output. In the latter switching state, the two components of the incident polarized light are simultaneously translated by a distance d along the negative direction of the Y axis, the Y axis coordinate after being combined by the splitting and combining module 900 is-d, and corresponds to the output port 2 in the input/output array 800, so that the incident polarized light is converged into the optical fiber 2 by the micro lens for output, and the specific light path is shown by the dotted line in fig. 8. Thus, by selecting the switching state, i.e. the driving voltage, of the means for translating polarized light, the selection of the optical output port can be achieved.

The structure is adopted to completely separate the non-seeking light component and the seeking light component corresponding to all the ports and then respectively switch the two components. The structure does not require that the ordinary rays or the ordinary rays corresponding to different ports are completely separated, the polarization states of all the rays are consistent by the optical rotator, and the structure is greatly simplified compared with the traditional comb-shaped polarization light splitting/combining structure, namely the structure that one port corresponds to one group of optical rotation sheets. Meanwhile, the structure can use an input/output port array with very small space, thereby greatly reducing the optical thickness and size of the switching module and greatly improving the optical performance of the device for controlling the optical signal.

The clutch module 900 will be described in detail with reference to fig. 9A, 9B, 9C, and 9D.

Fig. 9 is a schematic diagram of the operation of the clutch module 900. The crystal structure comprises uniaxial crystals 901 in the positive direction of the Z axis, and the optical axis direction is shown as 902, taking the uniaxial positive crystal as an example of yttrium vanadate crystal. The uniaxial crystal has a function of dividing input light with random polarization states into two beams of polarized light with mutually perpendicular polarization states, or combining the two beams of polarized light with mutually perpendicular polarization states into one beam of polarized light. The reversible optical rotation plate includes 903 and 904, which are half-wave plates of incident light made of crystal, and functions to rotate the polarization states of two polarized lights perpendicular to each other to the same polarization direction, respectively, and both at 45 degrees to the Y axis, and this rotation is reversible. The irreversible rotation piece 905, which is a crystal of yttrium iron garnet or bismuth-doped thin film, can perform 45 degrees of polarization state of polarized light by means of magneto-optical effect, and the rotation direction is fixed and is independent of the direction of the polarized light propagation, so that the rotation is irreversible.

The forward light splitting process of the splitting and combining module is shown in fig. 9A.

After a beam of polarized light with random polarization states (equivalent to a component perpendicular to a Y-Z plane and two components parallel to the Y-Z plane, which are respectively represented by points and small transverse lines on the light ray) enters the uniaxial crystal 901 along the positive direction of a Z axis, the two components are respectively refracted according to the refraction rules of ordinary light and extraordinary light, the two components are separated along the direction of the Y axis after being emitted, and the separation distance is determined by the thickness of the uniaxial crystal 901 and the direction of the optical axis. The position of the polarized light after passing through each optical element and its polarization state are shown in a series of boxes below the figure, the position is indicated by small circles, the polarization state is indicated by small horizontal lines in the circles, and the observation direction is the positive direction of the Z axis.

It can be seen that the two polarized light components are polarized perpendicular to each other after leaving the uniaxial crystal 901, and then enter the reversible polarizers 903 and 904, respectively, and are rotated by 45 degrees in different directions, respectively. Thus, the polarization states of the two polarized light components become parallel to each other after passing through the reversible rotation plate, and both are at positive 45 degrees to the Y-axis (assuming that the positive direction of the Y-axis is clockwise to positive, and vice versa, negative). Finally, the two polarized light components pass through the irreversible rotator 905, the polarization state is rotated by 45 degrees again, the rotation direction is clockwise, and the polarization state of the final emergent light is perpendicular to the Y-Z plane.

The number of the reversible optical rotation pieces contained in the splitting and combining module is not more than two, and the reversible optical rotation pieces correspond to the extraordinary light component and the extraordinary light component of all the input and output ports in the uniaxial crystal 901 respectively. The two reversible polarimeters rotate the polarization states of the extraordinary and extraordinary components of the input light, which are perpendicular to each other, to be coincident, and simultaneously rotate the extraordinary and extraordinary components, which are returned to be coincident in polarization state, to be perpendicular to each other. Compared with the traditional method that each input/output port respectively uses a pair of reversible optical rotation plates to perform comb-shaped light splitting and combining, the technical scheme has the characteristics that only two fixed reversible optical rotation plates are used, and the number of the reversible optical rotation plates is only equivalent to that of the reversible optical rotation plates required by one port in the traditional comb-shaped light splitting and combining method. More importantly, the technical scheme can realize the minimization of the distance between the input and output ports by only using two reversible optical rotation sheets, thereby realizing the miniaturization of the device for controlling the optical signals.

In summary, the splitting and combining module splits the incident polarized light with random polarization into two components with fixed polarization and both perpendicular to the Y-Z plane, and the distance between the two components can be selected by the uniaxial crystal 901.

The reverse light combining process of the combining and combining module 900 is shown in fig. 9B.

The two polarized light components are reflected by the device 300 for translating polarized light, and then the polarization state is rotated by 90 degrees, becomes parallel to the Y-Z plane, and returns to the irreversible rotator 905 along the negative direction of the Z axis. Because the optical rotation direction is independent of the propagation direction of the polarized light and is a fixed clockwise direction, the polarization states of the two polarized light components are rotated clockwise by 45 degrees to be positive 45 degrees with the Y axis, and are consistent with the polarization states of corresponding positions in the light splitting process. Since the reversible optical rotation plates 903 and 904 and the uniaxial crystal 901 both act on polarized light reversibly, the two polarized light components are recombined into a beam of polarized light in any polarization state according to the original splitting path.

If the polarization states of the two polarized light components returning to the irreversible rotator 905 in the negative direction of the Z-axis are not parallel to the Y-Z plane but perpendicular to the Y-Z plane, they become negative 45 degrees to the Y-axis after being rotated clockwise by 45 degrees by the irreversible rotator 905 and 90 degrees to the polarization state of the corresponding position in the light splitting process, as shown in fig. 9C. In this case, the reversible rotation plates 503 and 504 will rotate the polarization states of the two polarized light components to be perpendicular to the Y-Z plane and parallel to the Y-Z plane, respectively, and to be opposite to the polarization states at the corresponding positions in the splitting process, respectively. That is, the component regularly refracted with the ordinary ray in the polarization splitting/combining crystal 901 during the splitting becomes the refraction with the extraordinary ray, and the component regularly refracted with the extraordinary ray during the splitting becomes the refraction with the ordinary ray. Therefore, the two polarized light components will be further separated from being combined into one polarized light.

Since the refractive indices of the two components of polarized light in the uniaxial crystal 901 are different (i.e., the propagation velocities are different), and the lengths of the propagation paths are different, the phenomenon that the two components are not synchronized at subsequent optical interfaces, i.e., polarization mode dispersion, is caused. In order to remove polarization mode dispersion, a combination of the first uniaxial crystal 906 and the second uniaxial crystal 909, and the first reversible optically-active plate 908 disposed therebetween as shown in fig. 9D may be used in place of the uniaxial crystal 901 in practical applications. The first uniaxial crystal 906 and the second uniaxial crystal 909 are each half the spectral distance of the uniaxial crystal 901, and have optical axes 907 and 910 opposite in direction (symmetrical about the Z axis). The first reversible plate 908 is a half wave plate with an optical axis in the X-Y plane and at 45 degrees to the Y axis.

When the polarized light of the random polarization state is incident on the first uniaxial crystal 906 in the positive direction of the Z axis, the polarized light is divided into two components, wherein the ordinary light component is not translated, and the extraordinary light component is translated in the negative direction of the Y axis, and the translation distance is half of that of the uniaxial crystal 901. Then both components pass through the half wave plate 908 and the polarization state is rotated by 90 degrees, so that the original ordinary component becomes the extraordinary component after entering the second uniaxial crystal 909, and is translated in the positive Y-axis direction by half the distance of the uniaxial crystal 901. While the original extraordinary component becomes the ordinary component, and no shift occurs. The polarization states of the two polarized light components that ultimately emerge, and the separation distance, are exactly the same as when a single uniaxial crystal 901 is used. But since each component experiences one ordinary refraction and one extraordinary refraction and the respective propagation paths are exactly the same length, both components will emerge from the second uniaxial crystal 909 simultaneously, without polarization mode dispersion.

In some applications, it is required that the apparatus for controlling the optical signal not only has the function of selecting the output port, but also can adjust the power of the output light. In this case, this function can be achieved by simply replacing the fixed plate in the means for translating the polarized light with a polarization modulator, as shown in fig. 10 (again using a 1 x 2 optical switch as an example).

The phase retardation generated by the polarization modulator 1011 is determined by the driving voltage V, and when the phase retardation is equal to λ/2 or an integral multiple thereof, the polarized light passes through the polarization modulator 1011 twice, which is equivalent to passing through a full wave plate, and the polarization state thereof will remain unchanged. Therefore, the reflecting unit constituted by the polarization modulator 1011 and the mirror 1022 functions at this time only to reflect the incident light along the original path without changing the polarization state thereof. Both components of the polarized light will return back along the incident path regardless of the switching state of the switching unit 310, as shown by the solid and dashed optical paths in the figure. That is to say, the switching module does not translate the incident light, the Y-axis coordinate of the emergent light is still 0, and the polarization state of the emergent light is the same as that of the incident light and is perpendicular to the Y-Z plane.

From the foregoing analysis of the assembly module 900, it can be seen that if the polarization states of the two polarized light components incident along the negative direction of the Z axis are perpendicular to the Y-Z plane, they are further separated and cannot be combined into a polarized light beam. Therefore, the two polarized light components reflected from the device for shifting the polarized light cannot reach any output port, and the output optical power of all the output ports is zero, as shown in fig. 10. When the phase delay generated by the polarization modulator 1011 is equal to λ/4 or an odd multiple thereof, the polarization modulator 1011 is completely equivalent to the fixed rotation plate 321, and the operation of the optical switch is completely the same as that of fig. 8, and the input light will be output from the output port selected by the switching unit 310.

When the phase delay generated by the polarization modulator 1011 is between the two, each polarized light component is further divided into two sub-components after being reflected, wherein the polarization state of one sub-component is rotated by 90 degrees, and the polarization state of the other sub-component is not changed. The two sub-components whose polarization states are rotated by 90 degrees will propagate in the optical path of fig. 8 and finally be output from the output port selected by the apparatus for controlling optical signals. The two sub-components with unchanged polarization states propagate along the light path in fig. 10 and finally cannot reach any output port, i.e. the energy is lost.

Since the total power of the input light is equal to the sum of the powers of all the subcomponents, and the phase delay generated by the polarization modulator 1011 determines the proportion of the powers of different subcomponents in the total power, the proportion of the output light power in the input light power can be controlled by controlling the driving voltage V, thereby realizing the control of the output light power. In order to distinguish from the aforementioned apparatus 300 for translating polarized light, the module 1000 composed of the polarization modulator 1011 and the reflection mirror 1022 is called a power adjustable switching module, which is called an adjustable switching module for short.

It should be noted that the control of the output optical power is performed by the polarization modulator 1011 independently, which is relatively independent from the device translation function for controlling the optical signal, and the selection of the output port is still determined by the switching state of each switching unit in the device for controlling the optical signal. In addition, the phase delay generated by the polarization modulator 1011 is continuously adjustable from a quarter wavelength to a half wavelength, so that the proportion of the output optical power in the input optical power is also continuously adjustable from zero to 100%.

The structure and operation principle of the optical signal control device with 1 × 4, 1 × 8 and more output ports according to the present invention are the same as those of the optical signal control device with 1 × 2, but the size of the input/output port array and the number of switching units included therein are different, and will not be described herein again.

In addition, it is easy to deduce that all the devices for controlling optical signals provided by the present invention can be configured and used not only as 1 × N (i.e. 1 input port, N output ports), but also as N × 1 (i.e. N input ports, 1 output port), and the selection of input/output ports is performed according to the above method, and is not repeated here.

Referring to fig. 11, the method for selecting a wavelength of an optical route specifically includes the following steps:

step 1101, completely separating the extraordinary component and the ordinary component in the incident light to obtain polarized light with the same polarization state.

the first method is as follows:

The second method comprises the following steps:

Step 1102, separating the polarized light with the consistent polarization state according to different wavelengths.

Collimating the polarized light with the consistent polarization state;

separating the collimated polarized light according to different wavelengths;

and refracting the separated polarized light into a group of parallel incident lights, and then converging the incident lights on the same plane.

Step 1103, respectively switching the polarization states of the polarized light, and converting the change of the polarized light in the polarization state into a change in a spatial position to obtain a first polarized light after translation.

The polarization states of the polarized light are respectively switched, and the propagation path of the incident light is not changed. When the polarization state of the polarized light changes, the change of the polarization state of the polarized light is converted into the change of the polarization state on the space position, and the polarized light after the first translation is obtained. Wherein the polarized light can be switched by changing the driving voltage.

And 1104, reflecting the first translated polarized light and rotating the polarization state of the polarized light by 90 degrees.

Step 1105, the change of the polarization state of the rotated polarized light is converted into a change of the propagation path to obtain a second translated polarized light.

The polarization state of the polarized light before step 1104 is changed by 90 degrees from the polarization state of the polarized light after step 1104, and this change in polarization state is converted into a change in the propagation path of the polarized light before step 1104 and after step 1104, thereby obtaining a second shifted polarized light.

Step 1106, synthesizing the second shifted polarized light with the selected wavelength for different exit ports, respectively, and obtaining the exit light with the selected wavelength at the exit ports.

On the basis of the apparatus for controlling optical signals provided by the present invention, a dispersion module 1200 is added to construct an optical routing apparatus for selecting wavelengths, as shown in fig. 12A. The wavelength-selective optical routing device with 1 × N ports is formed by arranging an input/output array 800, a splitting and combining module 900, a dispersion module 1200 and an adjustable switching module array 12700 along the Z-axis direction.

Wherein the dispersive module 1200 is composed of a first lens 1210, a second lens 1220, and a diffraction grating 1230 arranged along the Z-axis. The optical axes of the first lens 1210 and the second lens 1220 coincide and are both parallel to the Z-axis, with the X-axis coordinate coinciding with the input-output array 800. Meanwhile, the focal lengths of the two lenses are equal and the focal points at the inner sides of the two lenses coincide. The diffraction grating 1230 is placed between the two and is centered at the common focal point of the two lenses, i.e., the distance of the diffraction grating 1230 from the first lens 1210 and the second lens 1220 are both equal to the focal length of the lenses. The input-output array 800 includes 1 input port and N output ports, and its end surface coincides with the outer focal plane of the first lens 1210. The tunable switching module array 12700 is formed by arranging tunable switching modules equal to the number of input wavelengths (assumed to be m) in the X-Z plane along the X-axis direction, the number of output coordinates of each tunable switching module is N, and the interval of the output coordinates is consistent with that of the input/output array 800. The Z-axis coordinates of all the adjustable switching modules are the same, and the mirrors thereof coincide with the outer focal plane of the second lens 1220, thereby constituting a 4F optical system, i.e. an optical system with an optical distance of 4 focal lengths from the object plane (optical port) to the image plane (mirrors), as shown in the figure.

One feature of the 4F system is that the distance between the object plane and the image plane is 1: 1 image, and if the incident light on the object plane is translated by a certain distance, the emergent light on the image plane will also move by the same distance, and vice versa.

The wavelengths of the optical signals transmitted in the wdm system and their intervals are fixed, and the spectrum of the optical signals in a specific wavelength band is shown as the spectrum of the input end in fig. 10A. Where each bar represents a wavelength signal, its width represents its bandwidth, and its height represents its power level. The input signal includes m wavelength signals λ 1 to λ m, whose powers are different from each other. These optical signals enter from the input port 800, and are divided into two polarized light components by the splitting and combining module 900 in the Y-Z plane along the Y-axis direction. Since the viewing plane of fig. 10A is the X-Z plane, the two polarized light components of each wavelength are coincident throughout propagation, represented by a ray, referred to as the beam at that wavelength. The beams of all wavelengths then pass through a first lens 1210, are further collimated and then enter a diffraction grating 1230.

The diffraction grating is an optical element with strong dispersion capability, and can diffract incident light with different wavelengths according to different angles, so that light beams with different wavelengths are separated in space. Since the diffraction surface of the diffraction grating 1230 is an X-Z plane and the diffraction point is located at the focal point of the second lens 1220, the light beams with different wavelengths are diffracted by the diffraction grating 1230 and then refracted by the subsequent second lens 1220 to be parallel to the Z axis although the propagation directions are different. At the same time, the second lens 1220 will focus all the collimated beams onto its focal plane, so that the beams of different wavelengths on its focal plane on the right side are completely separated and aligned along the X-axis direction, one X-axis coordinate for each wavelength, as shown in fig. 12A. The tunable switching module array 12700 is sequentially arranged on the right focal plane of the second lens 1220 according to the X-axis coordinates, and each tunable switching module corresponds to one wavelength (λ 1- λ m), so as to perform independent translational switching and proportional adjustment of output power on the light beam with the wavelength.

The light beams at each wavelength are translated and reflected by the corresponding tunable switching module and returned to the dispersion module 1200 in the negative Z-axis direction. Because the translation is done in the Y-Z plane, none of the X-axis coordinates of the beam change, and the beam still returns along the original path in the X-Z plane. The dispersive splitting process in the X-Z plane is completely reversible for the dispersive module 1200, so that the beams of all wavelengths are recombined into one beam in the X-Z plane. In the Y-Z plane, the two polarized light components of each wavelength are further combined into one beam by the subsequent splitting and combining module 900, and then returned to the input-output array 800. In this case, the light beams of different wavelengths are overlapped in the X-Z plane, but have different Y-axis coordinates in the Y-Z plane. The adjustable switching module array 12700 performs independent translations of the beams at each wavelength in the Y-Z plane, which are 1: 1 mapped to the input-output array 1200 by the 4F system. Thus, the output Y-axis coordinate of the light beam at each wavelength, i.e. its output port, is selected by the corresponding adjustable switching module. Meanwhile, since the 4F system does not change the polarization state of the polarized light, the adjustment of the power ratio of the polarized light component by the adjustable switching module is transmitted to the combining and combining module 900 without being affected, thereby realizing the adjustment function of the output power.

In summary, by controlling the tunable switching module array 12700, the output port of each input wavelength can be selected and its output power can be tuned. As shown in fig. 12A, m input wavelengths with different powers are output to N output ports in different combinations, respectively, and by adjusting the output power of each wavelength, a flat output spectrum (i.e., uniform power of each wavelength) is achieved. Of course, any output spectrum can be obtained by adjusting the output power of each wavelength according to the requirements of practical application.

The following takes a 1 x 2 port wavelength-selective optical routing device as an example, and analyzes a specific optical path in the Y-Z plane. From the above analysis, although the diffraction angle of each operating wavelength in the X-Z plane is different from that of the corresponding tunable switching module, the switching principle in the Y-Z plane is completely the same, and therefore, the optical path analysis is performed below by taking only one λ X of the input wavelengths as an example.

As shown in fig. 12B, an optical signal having a wavelength λ x enters the optical routing device having a selected wavelength, is split into two polarized light components along the Y axis by the splitting module 900, and then enters the first lens 1210 along the positive direction of the Z axis. The first lens 1210 collimates and expands the two polarized light components, so that the beam diameter of the two polarized light components is increased to meet the diffraction resolution requirement of the system. Meanwhile, since the optical axis of the first lens 1210 is parallel to the Z axis, two polarized light components are refracted by the first lens 1210 and then travel toward the focal point thereof. Since the diffraction grating 1230 is at the focal point of the first lens 1210, the incident points of the two polarized light components on the diffraction grating 1230 coincide and diffract in the X-Z plane. In the Y-Z plane, the two polarized light components are diffracted and then incident on the second lens 1220 without changing their propagation directions. Since the focal points of the first lens 1210 and the second lens 1220 coincide, with respect to the second lens 1220, the two polarized light components come from the focal points thereof, the traveling direction becomes the positive Z-axis direction after being refracted by the second lens 1220, and the two polarized light components are exchanged in the Y-axis direction after passing through the intersection at the focal point of the lenses. At the same time, the second lens 1220 converges the two collimated polarized light components onto its focal plane, i.e., the mirror surface of the tunable switching module 1000 corresponding to the wavelength λ x. The two polarized light components are then translated, (power scaled) and reflected by the adjustable switching module 1000 in exactly the same way as in the case of the device for controlling the optical signal, and will not be repeated here. Each polarized light component is translated and reflected, and then enters the dispersion module 1200 along the negative direction of the Z axis, and after the same beam expansion and convergence conversion and the subsequent combination of the splitting and combining optical module 900, returns to the input and output array 800.

Since the focal lengths of the first lens 1210 and the second lens 1220 are the same, the amount of translation of the polarized light component by the adjustable switching module 1000 is 1: 1 mapped to the input-output array 800. However, due to the intersection of the incident path and the reflected path of the polarized light component at the focal points of the two lenses, the translation directions of the front end and the rear end of the 4F system are opposite in sign. That is, if the direction of translation of the polarized light component by the adjustable switching module 1000 is positive in the Y-axis direction, then the direction of translation of the polarized light component back to the input-output array 900 is negative.

From the above optical path analysis, when all the light beams propagate between the first lens 1210 and the second lens 1220, that is, in the process of dispersing, splitting and combining light, the light beams are large-diameter collimated light beams expanded by the long-focus lens, which just meets the requirement of the grating diffraction resolution on the diameter of the incident light beams. Meanwhile, since all light beams pass through the common focus of the first and second lenses 1210 and 1220, i.e., the position of the diffraction grating 1230, all incident light spots on the diffraction grating 1230 are coincident. This feature greatly reduces the system's requirements for the area of the diffraction grating 1230.

In addition, since the optical routing device for selecting a wavelength is based on a device for controlling an optical signal, the optical routing device for selecting a wavelength according to the present invention can operate in a 1 × N or N × 1 mode, as in the device for controlling an optical signal. It is easy to deduce that in the N × 1 operating mode, the optical routing device selecting wavelengths may select different wavelength combinations from each input port, and after adjusting the power of the optical signal of each wavelength, combine the optical signals to the output port for output, and the specific process is not repeated here.

In order to facilitate understanding of the above operation principle of the optical routing apparatus for selecting a wavelength, the tunable switching module array is composed of a plurality of independent tunable switching modules. In practice, however, the array of tunable switching modules is not discrete in structure but is an integrated structure as shown in fig. 13.

First, all the polarization adjusters belonging to the same switching unit in the tunable switching module array are integrated into a large liquid crystal cell, i.e., the polarization adjuster array 1311, as shown in fig. 13A (the observation plane is the X-Y plane). The two glass substrates of the liquid crystal cell 1311 (which are superposed in the X-Y viewing plane) are connected by an annular sealing rubber 1301, forming a cavity 1302 inside the rubber, which is filled with liquid crystal. The transparent electrode (ITO) on the inner side of the glass substrate is etched into a linear pixel array lambda 1-lambda m by a photoetching method, wherein the transparent electrodes between any two adjacent pixels are completely separated. Thus, the liquid crystal cell 1311 has the same structure in the Y-Z plane at each pixel location as the liquid crystal cell shown in fig. 4, and each pixel is an independent lead, whose driving voltage can be independently controlled, as an independent polarization adjuster. Meanwhile, the X-axis coordinates of all pixels in the array correspond to the X-axis coordinates of all operating wavelengths on the back focal plane of the first lens 1220, so that the polarization adjuster array 1311 can independently modulate optical signals of all wavelengths.

An adjustable switching module array 1300 based on a polarization adjuster array 1311 is shown in fig. 13B (the viewing plane is the X-Z plane), and is composed of a plurality of switching units 1310 and a reflecting unit 1320. Each switching unit 1310 is in turn composed of a polarization modulator array 1311 and a beam-shifting plate 1312. The beam-shifting plate 1312 covers all pixels of the polarization modulator array 1311 in the X-Y plane, while its optical axis (in the Y-Z plane) has the same direction and thickness as the corresponding device design for controlling the optical signals. The reflection unit 1320 is composed of a polarization modulator array 1311 and a mirror 1322, and the mirror 1322 covers all pixels on the polarization modulator array 1311 in the X-Y plane. Meanwhile, the pixel arrays of all the switching units 1310 and the reflecting units 1320 constituting the adjustable switching module array 1300 are completely overlapped in the X-Y plane, that is, the optical signal of each wavelength passes through corresponding pixels on all the polarization modulator arrays 1311, so that the switching can be performed completely independently. Thus, the adjustable switching module array 1300 is fully equivalent to the adjustable switching module array 12700 shown in FIG. 12.

In fig. 12, the diffraction grating 1230 is a transmission type grating, that is, a grating in which incident light and diffracted light are respectively located on both sides thereof. In practical applications, a reflective grating, i.e. a grating in which the incident light and the diffracted light are on the same side, may be used instead of a transmissive grating, so as to fold the light path and reduce its size significantly, as shown in fig. 14. After the reflection grating 1400 replaces the transmission grating 1230, the incident light is diffracted towards the same side, i.e. the negative direction of the Z axis, which is equivalent to the whole light path is folded along the Z axis direction with the diffraction point as a symmetric point. The folded optical path second lens 1220 is omitted because it overlaps the first lens 1210, and the role of the first lens 1210 in the folded optical path corresponds to the role of the first two lenses. The adjustable switching module array (for example, the integrated adjustable switching module array 1300) is folded and turned over and moved to the left side of the first lens 1210, facing the positive direction of the Z-axis, and the mirror surface thereof coincides with the left focal plane of the first lens 1210. The input/output array 800 and the combining/combining module 900 are close to the adjustable switching module array 1300, and the Z-axis coordinate is unchanged, i.e. the end surface of the input/output array 800 is still overlapped with the left focal plane of the first lens 1210, and the X-axis coordinate can be adjusted according to the size of the adjustable switching module array 1300 and the diffraction angle of the reflection grating 1400 after the optical path is folded, without affecting the effectiveness of the 4F system. It will be readily appreciated that the folded wavelength selective optical routing device shown in fig. 14, whether in the X-Z plane or the Y-Z plane, is fully equivalent to the wavelength selective optical routing device shown in fig. 12, and the specific process is not repeated. The folded wavelength selectable optical routing device is still a 4F system, and its length in the Z-axis direction is shortened from 4F (four focal lengths of the first lens 1210) to 2F (two focal lengths of the first lens 1210).

Similarly, as shown in FIG. 15, a spherical mirror may be used in place of the first lens 1210 to further fold the optical path of the wavelength selective optical routing device shown in FIG. 14. The optical surface 1501 of the spherical reflector 1500 is a spherical surface, and the surface of the spherical reflector is coated with a high-reflection film, so that the spherical reflector reflects incident light and simultaneously has a function of transforming light beams like a lens. The spherical radius of the spherical mirror 1500 is twice the focal length F of the first lens 1210, and the equivalent focal length is half the spherical radius, i.e. equal to the focal length F of the first lens 1210. And its focal point is located to the left of the sphere, at a distance F from the sphere vertex, so its focal plane coincides with the focal plane of the original first lens 1210.

After replacing the first lens 1210 in fig. 14 with the spherical mirror 1500, the optical path of the wavelength-selective optical routing device shown in fig. 14 is folded again in the Z-axis direction with the position of the first lens 1210 as a symmetry point. After the folding, the reflective grating 1400 is also moved to the left focal plane of the spherical mirror 1500, and the optical surface is turned to face the positive direction of the Z axis. The Z-axis coordinates of the adjustable switching module array 1300, the input/output array 800 and the splitting and combining module 1300 are not changed, so the optical routing apparatus for selecting optical wavelengths after being folded again is still a 4F system, and the length of the optical routing apparatus in the Z-axis direction is shortened to F again, as shown in fig. 15. Similarly, the optical path in the X-Z plane or the Y-Z plane of the optical routing device for selecting optical wavelength shown in fig. 15 is completely equivalent to the optical path of the optical routing device for selecting optical wavelength shown in fig. 12, and the detailed process is not repeated.

It should be noted that the positions and relative relationships of the adjustable switching module array 1300, the input/output array 800 (and the corresponding splitting and combining module 900) and the reflective grating 1400 are not fixed, and may be adjusted according to the diffraction angle of the reflective grating 1400 and the size of each module. While the optical path of the optical routing means selecting the wavelengths of light remains identical to the original optical path as long as their Z-axis coordinates are kept unchanged, i.e. the validity of the 4F system is maintained.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method of translating polarized light, the method comprising:

switching the polarization state of the polarized light by using a first polarization modulator, and converting the change of the polarized light in the polarization state into the change of the polarized light in a spatial position by using a first light beam translation sheet to obtain first translated polarized light;

after the polarization state of the polarized light after the first translation is switched by the second polarization modulator, the polarized light sequentially enters the second light beam translation sheet and the optical rotation sheet, is reflected by the reflector and enters the optical rotation sheet again so as to rotate the polarization state of the polarized light by 90 degrees;

the second light beam translation plate is used for converting the change of the polarization state of the rotated polarized light into the change of the polarization state of the polarized light on a transmission path to obtain second translated polarized light, then the second polarization modulator is used for switching the polarization state of the second translated polarized light, the second polarized light enters the first light beam translation plate, and then the first polarization modulator is used for switching the polarization state of the polarized light again.

2. The method of translating polarized light according to claim 1, wherein switching the polarization state of polarized light comprises: the polarization state of the polarized light is switched by changing the driving voltage.

3. A device for translating polarized light is characterized by comprising a first polarization modulator, a second polarization modulator, a first light beam translation sheet, a second light beam translation sheet, an optical rotation sheet and a reflecting mirror; wherein,

and the second polarization modulator is used for switching the polarization state of the polarized light after the second translation, and then the polarized light enters the first light beam translation plate, and then the first polarization modulator is used for switching the polarization state of the polarized light again.

4. The apparatus for translating polarized light according to claim 3, wherein the first and second polarization modulators switch the polarization state of the polarized light by changing a driving voltage.