CN104181640A - Optical switching module based on liquid crystal variable-focus lens - Google Patents

Abstract

The invention discloses an optical exchange device based on a liquid crystal zoom lens, which comprises an input fiber collimator, a liquid crystal zoom cylindrical mirror, a first lens and an output fiber collimator; On the axis, the liquid crystal zoom cylindrical mirror is set off-axis on the front focal plane of the first lens; the output fiber collimator is set off-axis on the exit light path side of the first lens; the light output by the input fiber collimator is used as the liquid crystal zoom The incident light of the cylindrical mirror, the outgoing light of the liquid crystal zoom cylindrical mirror as the incident light of the first lens, the distance between the outgoing light of the first lens and the optical axis By adjusting the magnitude of the electric field applied to the liquid crystal zoom cylindrical mirror, the angle between the outgoing light of the liquid crystal zoom cylindrical mirror and the optical axis of the first lens is changed Thus, the distance between the outgoing light of the first lens and the optical axis is changed; the present invention generates a plurality of selectable output ports for input optical signals through a liquid crystal zoom lens and an appropriate optical system design to realize the optical switch function.

Description

A light exchange module based on liquid crystal zoom lens

technical field

The invention belongs to the technical field of optical communication, and more specifically relates to an optical switch and a wavelength selection switch based on a liquid crystal zoom lens.

Background technique

With the growth of people's demand for communication bandwidth and the increasing complexity of communication services, telecom operators put forward higher requirements for the flexibility of optical communication network configuration, based on wavelength division multiplexing technology and reconfigurable optical add-drop multiplexing technology The intelligent optical network has developed rapidly. Optical switches and wavelength selective switches are important devices and modules in optical communication systems, and are increasingly used in intelligent optical networks. Compared with electrical switches, optical switches and wavelength selective switches do not undergo "optical-electrical-optical" conversion, which can improve the reliability and flexibility of the network, and are necessary devices to realize all-optical networks.

An optical switch is an optical device with one or more input/output ports. It can realize line switching of optical signals between input/output ports. Optical switches can realize optical cross-connection and line self-healing in optical networks. Protection and other functions. The wavelength selective switch is also an optical device with one or more input/output ports, which can realize wavelength granular line switching between the input/output ports, and the wavelength selective switch can be used to form a flexible reconfigurable optical splitter. Insertion and multiplexing nodes are crucial to improving the performance of intelligent optical networks. The difference between an optical switch and a wavelength selective switch is that the exchange of optical signals by the former is wavelength-independent, and all optical wavelengths of an input port can only be exchanged to the same output port at the same time; the exchange of optical signals by the latter is wavelength-dependent Yes, different optical wavelengths of an input port can be switched to different output ports respectively.

Common technical solutions for optical switches include mechanical optical switches, thermo-optical switches, magneto-optical switches, electro-optic switches, MEMS (micro-electromechanical system) optical switches, waveguide optical switches, etc. Common technical solutions for wavelength selective switches include MEMS, LCOS (liquid crystal on silicon), liquid crystal, etc. Among them, there is an existing wavelength selective switch based on liquid crystal technology, which cooperates with a birefringent wedge prism through a liquid crystal unit, controls the polarization direction of the beam through the liquid crystal unit, and allows the beam to pass through the birefringent wedge prism with o light or e light to generate Different deflection angles, and through a certain optical system design, the selection and exchange of the beam output port is realized. The feature of this solution is that the optical signal passes through a liquid crystal unit + birefringent wedge prism combination structure, and only two possible output ports can be selected. In order to select multiple possible output ports (such as 8), it is necessary to combine 3 such The combined structure is connected in series, so the port scalability of the device is poor, and it is difficult to realize a wavelength selective switch with a large number of ports.

The liquid crystal material has a characteristic of electrically controlled birefringence, and the refractive index of the liquid crystal material can be changed by applying an electric field. Based on this, a zoom lens can be made, that is, the lens can be adjusted by applying an electric field.

Contents of the invention

Aiming at the defects of the prior art, the object of the present invention is to provide an optical switching device and an optical switching method based on a liquid crystal zoom lens.

The optical exchange device based on the liquid crystal zoom lens provided by the present invention comprises an input fiber collimator, a liquid crystal zoom cylindrical mirror, a first lens and an output fiber collimator; the input fiber collimator is arranged on the first lens On the optical axis, the liquid crystal zoom cylindrical mirror is arranged off-axis on the front focal plane of the first lens; the output fiber collimator is arranged off-axis on the exit light path side of the first lens; the input The light output by the fiber collimator is used as the incident light of the liquid crystal zoom cylinder lens, and the exit light of the liquid crystal zoom cylinder lens is taken as the incident light of the first lens, and the distance between the exit light of the first lens and the optical axis is distance changing the angle between the outgoing light of the liquid crystal zoom cylindrical mirror and the optical axis of the first lens by adjusting the magnitude of the electric field applied to the liquid crystal zoom cylindrical mirror Thereby changing the distance between the outgoing light of the first lens and the optical axis; wherein, _f1 is the focal length of the first lens, f is the focal length of the liquid crystal zoom cylinder, and d is the liquid crystal zoom cylinder and the first lens The distance between the optical axes.

Wherein, the included angle between the outgoing light of the liquid crystal zoom cylindrical lens and the optical axis of the first lens

Wherein, the optical switching device further includes a plurality of output fiber collimator arrays respectively arranged on the outgoing light paths of the first lens.

Wherein, the light exchange device also includes a grating and a second lens; the second lens is arranged between the input fiber collimator and the liquid crystal zoom cylinder lens, and the optical axis of the second lens is the same as that of the first lens The optical axes coincide; the grating is arranged on the front focal plane of the second lens; the light output by the input fiber collimator passes through the grating and then dispersed into m channels of light with different wavelengths, the wavelengths of which are λ ₁ , λ ₂ ... …λ _m , and then become m paths of horizontal light after passing through the lens; each path of horizontal light is deflected by a certain angle after passing through the liquid crystal zoom cylindrical lens and is incident on the first lens, and m paths of light are output by the first lens; The magnitude of the electric field on the liquid crystal zoom cylindrical mirror changes the refractive index of the liquid crystal zoom cylindrical mirror, so that the outgoing light of the required wavelength is output through the output fiber collimator, realizing the function of a wavelength selective switch.

The present invention also provides an optical exchange device based on a liquid crystal zoom lens, comprising an input fiber collimator, a liquid crystal zoom lens, a grating, a second lens, an output fiber collimator array, and a plane reflector; the input fiber The collimator is arranged on the optical axis of the second lens, the grating is arranged on the front focal plane of the second lens, the liquid crystal zoom cylindrical lens is arranged on the rear focal plane of the second lens, and the plane reflector is arranged on the liquid crystal zoom The plane side of the cylindrical mirror; the output fiber collimator array and the input fiber collimator are arranged on the same horizontal plane; the light output by the input fiber collimator passes through the grating and is dispersed into m channels of light with different wavelengths, and the wavelengths are respectively It is λ ₁ , λ ₂ ... λ _m , and then becomes m paths of horizontal light after passing through the lens; each path of horizontal light is incident on the convex side of the liquid crystal zoom cylindrical mirror and then reflected by the plane mirror, and then passes through the liquid crystal zoom cylindrical mirror It will be deflected at a certain angle and incident on the second lens, and the m-path light will be output by the second lens; by adjusting the magnitude of the electric field applied to the liquid crystal zoom cylinder lens, the refractive index of the liquid crystal zoom cylinder lens will be changed, so that the required The outgoing light of the wavelength is output through the output fiber collimator, realizing the function of the wavelength selective switch.

The present invention also provides an optical exchange device based on a liquid crystal zoom lens, comprising an input fiber collimator, a liquid crystal zoom lens, a grating, a second lens and an output fiber collimator array; in the liquid crystal zoom lens A reflective film is coated on the plane of the second lens; the input fiber collimator is arranged on the optical axis of the second lens, the grating is arranged on the front focal plane of the second lens, and the liquid crystal zoom cylinder lens is arranged on the second lens On the rear focal plane, the output fiber collimator array and the input fiber collimator are arranged on the same horizontal plane; the light output by the input fiber collimator passes through the grating and then is dispersed into m channels of light with different wavelengths, the wavelengths of which are λ _1. λ ₂ ... λ _m , and then become m paths of horizontal light after passing through the lens; after each path of horizontal light is incident on the convex side of the liquid crystal zoom cylindrical mirror, since the plane of the liquid crystal zoom cylindrical mirror is coated with a reflective film, it will The light path is reflected, and then deflected at a certain angle after passing through the liquid crystal zoom cylinder lens and incident on the second lens, and the m-path light is output by the second lens; by adjusting the magnitude of the electric field applied to the liquid crystal zoom cylinder lens, the The refractive index of the liquid crystal zoom cylindrical lens makes the output light of the required wavelength output through the output fiber collimator, realizing the function of the wavelength selective switch.

The invention proposes an optical switching module structure based on a liquid crystal zoom lens, through which a liquid crystal zoom lens and an appropriate optical system design generate multiple selectable output ports for input optical signals to realize the optical switch function. The variable-focus liquid crystal lens is made into an array structure, and different wavelengths in the input wavelength division multiplexing optical signal are spread on different units of the array through a grating dispersion, and the output port of each wavelength can be independently controlled, thereby realizing Wavelength selective switch function.

The invention proposes an optical exchange module based on a liquid crystal zoom lens, including an input fiber collimator, a liquid crystal zoom cylinder, a lens and an output fiber collimator, and the liquid crystal zoom cylinder is placed off-axis on the front focal plane of the lens superior. The light from the input fiber collimator first passes through the liquid crystal zoom cylinder lens, and the refraction index of the liquid crystal zoom cylinder lens can be adjusted through the transmission voltage, thereby controlling the deflection angle of the beam. After the light passes through the lens, it becomes a horizontal light output. Whether the light beam enters the output fiber collimator can be controlled by the voltage, and the function of the optical switch is realized.

Description of drawings

Figure 1 is a schematic diagram of the electro-optic effect of liquid crystals.

FIG. 2 is a schematic diagram of a liquid crystal zoom lens.

Fig. 3 is a top view of an optical switching module based on a liquid crystal zoom lens.

Fig. 4 is a top view of a multi-channel optical switch based on a liquid crystal zoom lens.

Fig. 5 is a top view of a transmissive structure of a wavelength selective switch based on a liquid crystal zoom lens.

Fig. 6 is a side view of a transmissive structure of a wavelength selective switch based on a liquid crystal zoom lens.

Fig. 7 is a top view of a reflective structure of a wavelength selective switch based on a liquid crystal zoom lens.

Fig. 8 is a side view of a reflective structure of a wavelength selective switch based on a liquid crystal zoom lens.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The invention proposes an optical switching module structure based on a liquid crystal zoom lens, through which a liquid crystal zoom lens and an appropriate optical system design generate multiple selectable output ports for input optical signals to realize the optical switch function. The variable-focus liquid crystal lens is made into an array structure, and different wavelengths in the input wavelength division multiplexing optical signal are spread on different units of the array through a grating dispersion, and the output port of each wavelength can be independently controlled, thereby realizing Wavelength selective switch function.

The invention proposes an optical exchange module based on a liquid crystal zoom lens, including an input fiber collimator, a liquid crystal zoom cylinder, a lens and an output fiber collimator, and the liquid crystal zoom cylinder is placed off-axis on the front focal plane of the lens superior. The light from the input fiber collimator first passes through the liquid crystal zoom cylinder lens, and the refraction index of the liquid crystal zoom cylinder lens can be adjusted through the transmission voltage, thereby controlling the deflection angle of the beam. After the light passes through the lens, it becomes a horizontal light output. Whether the light beam enters the output fiber collimator can be controlled by the voltage, and the function of the optical switch is realized.

A wavelength selective switch based on a liquid crystal zoom lens proposed by the present invention adds a coaxial grating and another lens on the basis of the optical switch, the grating is placed on the front focal plane of the lens, and the output fiber is collimated The device is changed to a collimator array. The light from the input fiber collimator is dispersed into light of different wavelengths after passing through the grating, and becomes multi-channel horizontal light through the lens. After passing through the liquid crystal zoom cylinder lens, it deflects at a certain angle and hits the second lens, and finally outputs it. Adjusting the refraction index of the liquid crystal zoom cylinder lens through the voltage can make the desired wavelength enter any output fiber collimator, so as to realize the function of the wavelength selective switch.

The main idea of the present invention is to use the liquid crystal material to make the lens. Due to the electro-optical characteristics of the liquid crystal material, its refractive index can be adjusted by the applied voltage, so that the focal length of the lens can be adjusted, and then realize the functions of optical switch and wavelength selective switch.

Now in conjunction with accompanying drawing, the present invention will be further described:

As shown in Figure 1, in a nematic liquid crystal, driven by an external electric field, the director of the liquid crystal molecules forms an angle θ with the electric field, and birefringence occurs at this time. When the normal of the extraordinary light e light wave is in the same direction as the electric field, its refractive index _n2 can be expressed by the following formula: Among them, n _o is the refractive index of ordinary light o light, n _e is the refractive index of e light when the director of liquid crystal molecules is perpendicular to the direction of the electric field, and the angle θ depends on the magnitude of the applied electric field, so the refraction of the liquid crystal material can be adjusted by the electric field Rate.

As shown in Figure 2, based on the electro-optic effect of liquid crystal materials, liquid crystal materials are used to make plano-convex lenses. The refractive index of this lens can be adjusted by applying an electric field, thereby changing the focal length f of the lens, and the focal length is continuously adjustable.

Referring to accompanying drawing 3, in the specific embodiment of this light exchange module based on liquid crystal zoom lens, comprise input fiber optic collimator 111, liquid crystal zoom cylinder mirror 112, first lens 113 and output fiber optic collimator 114, liquid crystal zoom column The surface mirror 112 is placed off-axis on the front focal plane of the first lens 113 . The light from the input fiber collimator 111 first passes through the liquid crystal zoom lens 112, and the refractive index of the liquid crystal zoom lens 112 can be adjusted by applying a voltage, thereby controlling the deflection angle of the beam. After the light passes through the first lens 113, it becomes a horizontal light output. Whether the light beam enters the output fiber collimator 114 can be controlled by the applied voltage, realizing the function of an optical switch.

The liquid crystal material has a characteristic of electrically controlled birefringence, and the refractive index of the liquid crystal material can be changed by applying an electric field. Based on this, a zoom lens can be made, that is, the lens can be adjusted by applying an electric field. Therefore, in the embodiment of the present invention, the focal length f of the liquid crystal zoom cylinder lens 112 can be controlled by an applied electric field; with reference to Fig. 1, the azimuth angle θ of the liquid crystal director is changed by an applied electric field, according to formula (1), the The refractive index changes, thus changing the focal length.

The off-axis distance of the liquid crystal zoom cylindrical mirror 112 is d, and its focal length is controlled by voltage to be f, then the beam deflection angle is: The exit height of the light beam after passing through the first lens 113 is: Where f ₁ is the focal length of the first lens 113 .

It can be seen from the above formula that the output position of the output beam can be controlled by changing the focal length f of the liquid crystal zoom cylindrical lens 112 through voltage, thereby controlling whether the beam enters the output fiber collimator 114, thus realizing the function of an optical switch. Since the focal length f of the liquid crystal zoom cylindrical lens 112 is continuously adjustable, the output position r is also continuously variable, and the present invention has the advantage of being continuously adjustable.

As shown in Figure 4, the output fiber collimator 114 in the optical switch structure in Figure 3 is changed to a fiber collimator array 117, and by adjusting the focal length f of the liquid crystal zoom cylindrical mirror 112, the light beam can enter the fiber collimator array 117 In any collimator, the function of multi-channel optical switch is realized.

Referring to accompanying drawings 5 and 6, in the specific embodiment of the transmissive structure of the wavelength selective switch based on the liquid crystal zoom lens, a coaxial grating 115 and another lens 116 are added on the basis of the multi-channel optical switch, and the grating 115 is placed on the front focal plane of this lens 116. The light from the input fiber collimator 111 passes through the grating 115 and is dispersed into multiple paths of light with different wavelengths, the wavelengths are λ ₁ , λ ₂ , λ ₃ etc., and passes through the second lens 116 to become multiple paths of horizontal light. After passing through the liquid crystal zoom cylinder lens 112, it deflects at a certain angle and hits the first lens 113, and finally outputs it. Adjusting the refractive index of the liquid crystal zoom lens 112 through voltage can make the desired wavelength enter any output fiber collimator, thereby realizing the function of a wavelength selective switch.

Same as the optical switch, the output height of the light beam after passing through the first lens 113 is: By changing the focal length f of the liquid crystal zoom cylindrical lens 112 with a voltage, the output position d of the output beam of any wavelength can be controlled, thereby controlling the beam of any wavelength to enter any output fiber collimator of the output fiber collimator array 117 .

Fig. 7 and Fig. 8 are the reflective structure based on the wavelength selective switch of liquid crystal zoom lens, different from the transmissive structure is that a reflection mirror 118 is added behind the liquid crystal zoom cylindrical mirror 112 or a reflection mirror 118 is added at the back of the liquid crystal zoom cylindrical mirror 112 A reflective film is coated on the plane, and the grating 115 and the liquid crystal zoom cylindrical mirror 112 are respectively located on the front and rear focal planes of the lens 116 . The light from the input fiber collimator 111 passes through the grating 115 and is dispersed into multiple paths of light with different wavelengths, the wavelengths of which are λ ₁ , λ ₂ , λ ₃ , λ ₄ etc., and passes through the lens 116 to become multiple paths of horizontal light. It will be reflected after passing through the liquid crystal zoom cylindrical mirror 112, and then deflected at a certain angle after passing through the liquid crystal zoom cylindrical mirror 112 to be incident on the second lens 116 and finally output. Adjusting the refractive index of the liquid crystal zoom lens 112 through voltage can make the desired wavelength enter any output fiber collimator, thereby realizing the function of a wavelength selective switch.

Compared with the transmissive structure, the reflective structure can fold the optical path and reduce the size of the device.

On the basis of the above theoretical knowledge, the light exchange module and the wavelength selective switch structure based on the liquid crystal zoom lens proposed by the present invention use liquid crystal materials to make lenses, and utilize the electro-optical characteristics of liquid crystal materials to realize liquid crystal zoom lenses. Functions of optical switches and wavelength selective switches.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (6)

1. A light exchange device based on a liquid crystal zoom lens, characterized in that it comprises an input fiber collimator (111), a liquid crystal zoom lens (112), a first lens (113) and an output fiber collimator (114 ); The input fiber collimator (111) is arranged on the optical axis of the first lens (113), and the liquid crystal zoom cylindrical lens (112) is arranged off-axis at the front focus of the first lens (113). On the surface; the output fiber collimator (114) is arranged off-axis on the exit light path side of the first lens (113); The light output by the input fiber collimator (111) is used as the incident light of the liquid crystal zoom lens (112), and the outgoing light of the liquid crystal zoom lens (112) is used as the incident light of the first lens (113), The distance between the outgoing light of the first lens (113) and the optical axis Changing the angle between the outgoing light of the liquid crystal zoom cylindrical lens (112) and the optical axis of the first lens (113) by adjusting the magnitude of the electric field applied to the liquid crystal zoom cylindrical lens (112) Thereby changing the distance between the outgoing light of the first lens (113) and the optical axis; Wherein, f is the focal length of the _first lens (113), f is the focal length of the liquid crystal zoom cylinder (112), and d is the distance between the optical axis of the liquid crystal zoom cylinder (112) and the first lens (113) distance. 2. The optical switching device according to claim 1, characterized in that, the included angle between the outgoing light of the liquid crystal zoom cylindrical lens (112) and the optical axis of the first lens (113) 3. The optical switching device according to claim 1, characterized in that, the optical switching device also includes a plurality of output fiber collimator arrays (117) that are respectively arranged on the outgoing light path of the first lens (113) ). 4. The optical switching device according to claim 3, characterized in that, the optical switching device further comprises a grating (115) and a second lens (116); The second lens (116) is arranged between the input fiber collimator (111) and the liquid crystal zoom cylinder lens (112), and the optical axis of the second lens (116) is connected to that of the first lens (113). Optical axis coincidence; The grating (115) is arranged on the front focal plane of the second lens (116); The light output by the input fiber collimator (111) passes through the grating (115) and then is dispersed into m paths of light with different wavelengths, the wavelengths of which are λ ₁ , λ ₂ ... λ _m , and then passes through the lens (116) to become m paths Horizontal light; every road of horizontal light deflects a certain angle after passing through the liquid crystal zoom cylinder lens (112) and is incident on the first lens (113), and the m road light is output by the first lens (113); The magnitude of the electric field on the liquid crystal zoom cylindrical mirror (112) changes the refractive index of the liquid crystal zoom cylindrical mirror (112), so that the outgoing light of the required wavelength is output through the output fiber collimator, realizing the function of a wavelength selective switch. 5. A light exchange device based on a liquid crystal zoom lens, characterized in that it comprises an input fiber collimator (111), a liquid crystal zoom lens (112), a grating (115), a second lens (116), an output optical fiber collimator array (117) and plane mirror (118); The input fiber collimator (111) is arranged on the optical axis of the second lens (116), the grating (115) is arranged on the front focal plane of the second lens (116), and the liquid crystal zoom cylinder lens (112 ) is arranged on the rear focal plane of the second lens (116), and the plane reflector (118) is arranged on the plane side of the liquid crystal zoom cylinder lens (112); the output fiber collimator array (117) is collimated with the input fiber Straightener (111) is arranged on the same horizontal plane; The light output by the input fiber collimator (111) passes through the grating (115) and then is dispersed into m paths of light with different wavelengths, the wavelengths of which are λ ₁ , λ ₂ ... λ _m , and then passes through the lens (116) to become m paths Horizontal light: each road horizontal light is incident on the convex side of the liquid crystal zoom cylinder (112) and then reflected by the plane reflector (118), and then deflected by a certain angle after passing through the liquid crystal zoom cylinder (112) and incident on the first On the two lenses (116), m road light is output by the second lens (116); by adjusting the size of the electric field applied to the liquid crystal zoom cylinder (112), the refractive index of the liquid crystal zoom cylinder (112) is changed, The outgoing light of the required wavelength is output through the output fiber collimator, realizing the function of the wavelength selective switch. 6. A light exchange device based on a liquid crystal zoom lens, characterized in that it comprises an input fiber collimator (111), a liquid crystal zoom lens (112), a grating (115), a second lens (116) and an output optical fiber A collimator array (117); a reflective film is coated on the plane of the liquid crystal zoom cylindrical mirror (112); The input fiber collimator (111) is arranged on the optical axis of the second lens (116), the grating (115) is arranged on the front focal plane of the second lens (116), and the liquid crystal zoom cylinder lens (112 ) is arranged on the rear focal plane of the second lens (116), and the output fiber collimator array (117) is arranged on the same horizontal plane as the input fiber collimator (111); The light output by the input fiber collimator (111) passes through the grating (115) and then is dispersed into m paths of light with different wavelengths, the wavelengths of which are λ ₁ , λ ₂ ... λ _m , and then passes through the lens (116) to become m paths Horizontal light: After each road of horizontal light is incident on the convex side of the liquid crystal zoom cylinder (112), since the plane of the liquid crystal zoom cylinder (112) is coated with a reflective film, the light path will be reflected, and then pass through the liquid crystal zoom cylinder After the mirror (112), it will be deflected at a certain angle and incident on the second lens (116), and the m path light will be output by the second lens (116); The size changes the refractive index of the liquid crystal zoom cylindrical mirror (112), so that the outgoing light of the required wavelength is output through the output fiber collimator, realizing the function of a wavelength selective switch.