JPH0894869A - Optical waveguide module - Google Patents

Abstract

PURPOSE: To provide an optical waveguide module capable of easily producing with the efficient reduction of the leakage quantity of speaking between the waveguides. CONSTITUTION: This optical waveguide module is provided with a planer optical waveguide 200 made by forming a core part waveguiding light and a clad part formed around the core part on a substrate 210, optical fibers 110, 120 aligned with the planer waveguide 200, fixed and joined and a light absorbing film 230, which is formed around the clad part of the planer waveguide 200 on the upper part of the substrate 210, consists essentially of a resin material >=-1% to <=8% in the difference of specific refraction factor to the refraction factor of the clad part and in which a light absorbing body is added, and radiant light beam from the core part is introduced to the light absorbing film 230 and absorbed by the light absorbing body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide module used for constructing an optical communication system.

[0002]

2. Description of the Related Art With the progress of optical communication technology, high reliability is required for optical waveguide circuits such as optical branching devices and optical multiplexers used in the construction of optical communication systems. When mounting the optical waveguide circuit, it is general to form an optical waveguide module configured by connecting an optical fiber for optical input / output to a two-dimensional optical waveguide. A conventional typical configuration example of such an optical waveguide module is disclosed in “Japanese Patent Laid-Open No. 5-27”
139 ".

Further, in the recent construction of optical communication systems, miniaturization of optical components is required, and various measures have been taken to improve the degree of integration of optical waveguide circuits. One of the directions of such ingenuity is to reduce crosstalk between optical waveguides. Crosstalk between optical waveguides occurs because the spacing between optical waveguides inevitably becomes narrower as the density of optical waveguide circuits becomes higher.It is a problem when multiple optical waveguides that should operate independently are close to each other. Becomes To prevent such crosstalk,
A glass waveguide as disclosed in Japanese Patent Laid-Open No. 5-215926 has been proposed. FIG. 7 is a configuration diagram of this glass waveguide.

As shown in FIG. 7, this glass waveguide is
(A) Substrate 11, (b) Porous glass layer 12 that is a light scatterer formed on the surface strip of substrate 11, and (c) First clad layer formed on the surface of porous glass layer 12. Thirteen
And (d) the core 15 formed on a part of the surface region of the first cladding layer 13, and (e) on the surface region of the surface of the first cladding layer 13 other than the core formation region and on the surface of the core 15. The formed 2nd clad layer 16 is provided. Then, by optically blocking between the first cladding layer 13 and the substrate 11 with the porous glass layer 12 which is a light scatterer, a part of the propagating light in the first cladding layer 13 leaks to the substrate 11. The amount of leaked light and the substrate 11 to the first cladding layer 1
The amount of stray light entering the 3 side is reduced.

[0005]

As described above, in the conventional optical waveguide module provided with a countermeasure against crosstalk, it is necessary to interpose a non-transparent porous glass layer which is a light scatterer between the cladding layer and the substrate. There is. For this purpose, after forming the porous glass on the substrate, the porous glass layer must not be made transparent in the step of forming the clad layer or core layer. There is a problem that the range and the material selection of the porous glass layer, the core, and the clad layer are limited, and the actual manufacturing is difficult.

Further, since the porous glass layer interposed between the substrate and the clad layer is a light scatterer and not a light absorber, the position of the leaked light from the clad layer is scattered to the clad layer as a result. There is a problem that some of the light from the substrate side enters the cladding layer and becomes stray light.

The present invention has been made in view of the above, and an object thereof is to provide an optical waveguide module which can efficiently reduce the amount of crosstalk between optical waveguide circuits and can be easily manufactured.

[0008]

The optical waveguide module of the present invention comprises: (a) a planar optical waveguide in which a core for guiding light and a clad formed around the core are formed on a substrate. And (b) a material having a relative refractive index difference of -1% or more and 8% or less with respect to the refractive index of the clad, which is formed on the upper part of the substrate so as to surround the clad of the planar waveguide, as a main material And a light absorption film to which a light absorber is added.

The main material of the light absorption film may be a resin material.

Carbon black can be preferably used as the light absorber.

Further, the relative refractive index difference of the refractive index of the main material of the light absorbing film with respect to the refractive index of the clad portion may be 0% or more and 2% or less.

[0012]

In the optical waveguide module of the present invention, signal light is input to the planar waveguide via the optical fiber. The signal light input to the planar waveguide travels in the core portion of the planar waveguide.
A part of the light traveling in the core portion is scattered by the interaction with the substance forming the core portion and is emitted toward the cladding layer. The emitted light reaches the interface between the cladding layer and the light absorption film, either directly or after being reflected by the substrate. The refractive index of the light absorption film is −
Since it has a relative refractive index of 1% or more and 8% or less, the light reaching the light absorption film from the cladding layer side is efficiently input to the light absorption film. When the relative refractive index difference between the clad layer and the light absorbing film is smaller than -1%, the amount of light having an incident angle with a total reflection angle larger than that of the incident light to the light absorbing film is larger than that, and the relative refractive index difference is larger than 8%. Therefore, the amount of reflected light when entering the light absorption film increases, and the input efficiency to the light absorption film decreases. Substantially all of the light that has entered the light absorption film is absorbed by the light absorber in the light absorption film. Further, substantially all of the light input to the light absorption film from the outside of the optical waveguide module is also absorbed by the light absorber in the light absorption film.

The material of the light absorbing film is silicone resin,
Organic materials such as epoxy resin are more desirable than other materials (for example, low melting point glass). When the absorption film does not adhere the waveguide to the module, reflection occurs at the interface and the crosstalk reduction effect disappears. Therefore, a resin that has good adhesion to the waveguide, is easy to mix with the light absorber, and is easy to handle is excellent.

That is, almost all of the light that has once entered the light absorption film is absorbed by the light absorber in the light absorption film and does not return to the cladding layer again. Therefore, light is guided for each individual optical waveguide while efficiently suppressing leakage light or stray light from the optical waveguide of a certain path to transfer to the optical waveguide of another path.

Further, since carbon black has little wavelength dependency with respect to light absorption, the use of carbon black as the light absorber reduces the crosstalk amount in a wide wavelength range. Further, carbon black can be easily mixed with a resin, and a high quality light absorbing film can be easily manufactured.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical waveguide module of the present invention will be described below with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is an external view of an optical waveguide module according to an embodiment of the present invention. In addition, the device of the present embodiment is 2
An optical waveguide module having a functional configuration of × 2 branch and 4 circuits.

As shown in FIG. 1, this device has (a) 8
Optical fiber array 110 in which two optical fibers are arranged
And (b) each planar optical waveguide 200 constituting a 2 × 2 branch 4 circuit optically connected to one end face of each optical fiber of the optical fiber array 110, and (c) on the planar optical waveguide 200. 2 made of a silicone resin (refractive index = 1.50, relative refractive index difference with respect to clad = 2.7%) added with 2% by weight of carbon black
30 and (d) an optical fiber array 120 in which a plurality of optical fibers having one end face optically connected to the other end face of the planar optical waveguide 200 are arranged. Then, in the actual use of this device, an optical fiber group 310 is connected to the other end face of each optical fiber of the optical fiber array 110 for inputting and outputting light, and each optical fiber of the optical fiber array 120 is connected. An optical fiber group 320 is connected to the other end surface.

Here, the planar optical waveguide 200 comprises a silicon substrate 210 and an optical circuit section 220 formed on the silicon substrate 210.

FIG. 2 is an external view of the end faces of the planar optical waveguide 200 and the light absorption film 230. FIG. 2A is an external view of the end face 220 ₁ side and shows eight light input (or output) ports P _{1 to} P corresponding to the core portions separated from each other.
There are _eight . Further, FIG. 2B is an external view of the end face 220 ₂ side, and there are eight light output (or input) ports P ₁ ′ to P ₈ ′ corresponding to the core portions separated from each other.

FIG. 3 is a block diagram of the apparatus of this embodiment, focusing on the optical connection. As shown in FIG. 3, the optical circuit unit 2
Reference numeral 20 denotes a core portion 221 (C _1-
C ₈ ) and the clad part 222 surrounding the core part 221
And Each core C _i corresponds to the port P _i on the end face 220 ₁ side and corresponds to the port P _i ′ on the end face 220 ₂ side. Then, the core part C _i (i = 1, 3, 5, 7)
And an optical waveguide composed of a clad part around the core part C _{i and} an optical waveguide composed of a clad part around the core part C _{i + 1} and the core part C _{i + 1} are 2 × 2. Branch circuit 1
Become a circuit. Further, the fiber array 110, a lid for fixing the substrate 111 which has eight V-grooves are formed, the optical fiber 112 ₁ to 112 ₈ of 8 disposed in the V-groove, the optical fiber 112 ₁ to 112 ₈ And a material 113. Then, the optical fiber 112i is optically connected to the port P _i . Further, the fiber array 120, a lid for fixing the substrate 121 which has eight V-grooves are formed, the eight disposed V-groove and optical fiber 122 ₁ to 122 _8, the optical fiber 122 ₁ to 122 ₈ And a material 123. Then, the optical fiber 122i is optically connected to the port P _i ′.

FIG. 4 is an explanatory diagram of the behavior of the emitted light. When the signal light propagates through the core portion Ci, radiated light is generated by the interaction between the signal light and the substance of the core portion Ci. Most of the generated radiant light crosses the clad part 222 and the clad part 2
22 or the interface between the substrate 210 or the clad portion 222
And reaches the boundary surface between the light absorption film 230 and the light absorption film 230. Most of the light reaching the boundary surface with the substrate 210, and most of the light reflected at the boundary surface with the substrate 210, travels inside the optical circuit unit 220 and forms a boundary between the clad part 222 and the light absorption film 230. Reach the surface.

A part of the light reaching the boundary surface between the clad portion 222 and the light absorption film 230 is incident on the light absorption film. Figure 5
Is a graph showing a change in reflectance of incident light due to a relative refractive index difference of the light absorption film with respect to the clad portion, and an incident angle θ = 8.
The case of 5 °, 80 °, 75 ° and 70 ° is illustrated.
The larger the incident angle, the steeper the change in the reflectance of the incident light due to the relative refractive index difference of the light absorption film with respect to the cladding portion, and the smaller the incident angle, the more gradual the change. This graph was created by calculating the Fresnel reflection formula. From FIG. 5, assuming that the reflectance <20% is surely guaranteed for the light having the incident angle θ <80 °, the relative refractive index difference is −1% to
It can be seen that the range should be set to 8%. When the relative refractive index difference is set in this range, most incident light is input to the light absorption film if the incident angle distribution of the emitted light is substantially uniform. Further, if the reflectance <20% is surely guaranteed for the light of the incident angle θ <85 °, the relative refractive index difference may be set in the range of 0% to 2%. When the relative refractive index difference is set in this range, As a result, more light can be guaranteed to be input to the light absorption film.

The light input to the light absorbing film 230 is absorbed by the light absorber. FIG. 6 is a graph showing changes in light transmittance depending on changes in the carbon black content of the silicone resin. In addition, in FIG. 6, the thickness of the silicone resin film is 10 μm.
m, and the light is vertically incident. Therefore, almost all of the light input to the light absorption film 230 is absorbed by the light absorber and does not enter the cladding portion 222 again. As a result, the amount of crosstalk between the optical branch circuits is reduced.

Table 1 shows the measurement results of the crosstalk characteristics (optical isolation rate) in the device of this embodiment. This measurement is
The output intensity of each port when light with an intensity of −4.5 dBm and a wavelength of 13.1 μm was incident on one port was measured. The numerical values in Table 1 indicate the ratio of the intensity of output light from each port to the intensity of input light (= optical isolation rate, unit: dB). As can be seen from the observation results shown in Table 1, the optical isolation ratio between the optical branch circuits in the device of this example was 60 dB or more.

[0026]

[Table 1]

In order to confirm the effectiveness of the application of the present invention to the device of this embodiment, a device (comparative example 1) in which the light absorption film 230 is removed from the optical waveguide module of this embodiment and the light absorption film has light absorption. An apparatus (Comparative Example 2) in which no body was added was prototyped, and the same measurements as those in Table 1 were performed.

Table 2 shows the measurement results of the device of Comparative Example 1. As can be seen from the observation results shown in Table 2, the optical isolation ratio between the optical branch circuits in the device of Comparative Example 1 is 25 to
It was 45 dB or more.

[0029]

[Table 2]

Table 3 shows the measurement results of the device of Comparative Example 2. As can be seen from the observation results shown in Table 3, the optical isolation ratio between the optical branch circuits in the device of Comparative Example 2 is 35 to 35.
It was 50 dB or more.

[0031]

[Table 3]

From the above measurement results, it is confirmed that the isolation ratio between the optical branch circuits in the device of this embodiment is dramatically improved as compared with the comparative example.

The present invention is not limited to the above embodiment, but can be modified. For example, although carbon black is used as the light absorber in the above embodiments, various metal particles may be used depending on the wavelength of the signal light used. However, metal particles are easily oxidized, so care must be taken when handling. Further, although the optical waveguide module of the embodiment is a 2 × 2 branch 4 circuit, the number of circuits may be other than 4, and the present invention can be applied to any optical circuit as long as it independently functions. It is possible.

[0034]

As described in detail above, according to the optical waveguide module of the present invention, a light absorber is added to the upper portion of the planar optical waveguide formed on the substrate, and the cladding of the planar optical waveguide is added. The relative refractive index difference to the refractive index of the part is -1
Since a light absorbing film made of a resin material having a refractive index of not less than 8% and not more than 8% is formed, leakage light or stray light generated due to scattering in the optical waveguide is efficiently input to the light absorbing film and absorbs light. It is absorbed by the light absorber in the film. As a result,
It is possible to efficiently reduce the amount of crosstalk due to the mixing of light into another optical waveguide circuit when the light travels through one optical waveguide circuit of a plurality of planar optical waveguide circuits that guide light independently.

[Brief description of drawings]

FIG. 1 is an external configuration diagram of an embodiment of an optical waveguide module of the present invention.

FIG. 2 is an external view of an end face of an optical circuit unit of an optical waveguide module according to an example.

FIG. 3 is an optical connection configuration diagram of an optical waveguide module of an example.

FIG. 4 is an explanatory diagram of behavior of emitted light in the optical waveguide module according to the embodiment.

FIG. 5 is a graph showing a change in reflectance of incident light due to a relative refractive index difference of a light absorption film with respect to a clad portion.

FIG. 6 is a graph showing changes in light transmittance depending on changes in the content of carbon black in the silicone resin.

FIG. 7 is a configuration diagram of a conventional optical waveguide module.

[Explanation of symbols]

110, 120 ... Fiber array, 111, 121 ... Base material, 112, 122 ... Optical fiber, 113, 123 ... Lid material, 200 ... Planar optical waveguide, 210 ... Substrate, 220 ...
Optical circuit part, 221 ... Core part, 222 ... Clad part, 23
0 ... Light absorbing film.

Claims (4)

[Claims] 1. A planar optical waveguide in which a core portion for guiding light and a clad portion formed around the core portion are formed on a substrate, and the clad portion of the planar waveguide is surrounded by the planar optical waveguide. A light absorption film formed on the substrate, the main material of which is a material having a relative refractive index difference with respect to the refractive index of the cladding portion of -1% or more and 8% or less, to which a light absorber is added; An optical waveguide module characterized by the above. 2. The main material of the light absorbing film is a resin material,
The optical waveguide module according to claim 1, wherein: 3. The optical waveguide module according to claim 1, wherein the light absorber is carbon black. 4. The relative refractive index difference between the refractive index of the main material of the light absorbing film and the refractive index of the cladding portion is 0% or more and 2% or more.
The optical waveguide module according to claim 1, wherein: