JPH11271563A - Optical fiber array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber array which is free of breaking of an optical fiber and has small degradation in the polarized light crosstalk of an optical waveguide. SOLUTION: After two end 10a and 10b of an optical fiber are out along V-shaped grooves 30a and 30b of a substrate 16, the polarization maintaining plane of the optical fiber 10 is matched with the direction of the polarization plane of light propagated in the optical waveguide 22. Then the surface of a lid base board 16B is coated with thermosetting resin and put over a base board 16A, and the gap between the V-shaped grooves 30a and 30b and optical fiber 10 is filled with resin, which is heated at 60 deg.C to adhere and fix the optical fiber with the resin layer; and the free end surface 16a of the optical fiber in the end surface of the array 16 is polished and fixing the array 16 to the optical fiber 10 is thus completed. The resin layer has one or more cavity parts whose diameters is in a range of 10 to 500 μm in total.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber array for connecting an optical waveguide chip and an optical fiber.

[0002]

2. Description of the Related Art An optical fiber array is generally used to connect an optical waveguide chip and an optical fiber.
This optical waveguide chip includes a GaAs-based or InP-based semiconductor waveguide chip, an oxide film formed on Si, a dielectric (glass) waveguide chip using a glass substrate, LiNb.
There are many types, such as a ferroelectric crystal waveguide chip made of O ₃ or LiTaO ₃ crystal. Applications include, for example, sensors and measurement related to optical fiber gyros, optical fiber communication related to high-speed modulators, optical information processing related to A / D converters, and light source / optical conversion related to laser diode arrays. A wide variety of applications are being considered.

[0003] In the case of manufacturing an optical fiber gyro as described above, two ends of an optical fiber derived from a fiber coil formed by winding a long optical fiber around a cylindrical object and a phase modulator are incorporated. A polarization-maintaining optical fiber array is used to connect the optical waveguide chip with the polarization plane held in a fixed direction.

The polarization-maintaining optical fiber array includes, for example, two substrates, one of which has a groove formed therein, and an optical fiber embedded in the groove to hold the polarization plane in a predetermined direction. After that, the two substrates are overlapped, and the gap between the groove and the optical fiber is filled with a room-temperature-curable resin such as epoxy or a thermosetting resin, or an ultraviolet-curable resin such as an acrylic resin and cured. It is formed by forming a resin layer and fixing the optical fiber to the groove of the array.

[0005]

In such a conventional optical fiber array, a cavity may be formed in the resin layer due to a variation in the filling amount of the resin or a variation in the degree of progress of the curing in each part of the resin layer. . With such a cavity, stress due to bending or twisting when handling the optical fiber is likely to occur, which may break the optical fiber.

The present invention has been made in view of such a problem, and does not cause disconnection of an optical fiber.
It is another object of the present invention to provide an optical fiber array in which polarization crosstalk of an optical waveguide is less deteriorated.

[0007]

An optical fiber array according to the present invention is an optical fiber array for connecting an optical waveguide chip and an optical fiber, wherein two optical fibers for sandwiching and disposing the optical fiber are provided. A groove for holding and fixing the optical fiber is formed in at least one of the two substrates, and the optical fiber is fixed to the groove by a resin layer; Has one or more cavities having a total diameter in a range of 10 μm to 500 μm.

[0008] This makes it possible to obtain an optical fiber array in which the optical fiber is not broken and the polarization crosstalk of the optical waveguide is less deteriorated. here,
If the sum of the diameters of the cavities is less than 10 μm, the deterioration of the polarization crosstalk of the optical waveguide is greatly increased due to the residual stress of the resin layer. Increase. It is more preferable that the sum of the diameters of the hollow portions is in the range of 100 μm to 450 μm. Therefore, the optical fiber array according to the present invention is a polarization-maintaining optical fiber array for connecting the optical waveguide chip and the optical fiber while maintaining the polarization plane in a fixed direction. It is more preferable that at least one of the above is formed with a groove for holding and fixing the polarization plane of the optical fiber in a certain direction.

In the optical fiber array according to the present invention, the groove is formed to have a V-shaped predetermined length, and a counterbore extending wider than the groove is formed to extend in the groove. Is fixed to the groove by a resin layer. Here, the counterbore portion refers to an escape groove for allowing the fiber coating portion to escape.

By fixing the fiber core, the polarization plane of the fiber can be fixed.

Still further, in the optical fiber array according to the present invention, the optical fiber is any one of an elliptical core fiber, a panda fiber, an elliptical jacket fiber, and a rod band fiber.

Thus, the effects of the present invention can be suitably exhibited.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical fiber array according to the present invention is applied to, for example, a polarization-maintaining optical fiber array for connecting an optical waveguide chip and an optical fiber while maintaining the polarization plane in a fixed direction. The embodiment will be described below with reference to FIGS.

The optical fiber array according to the present embodiment
As shown in FIG. 1, a first optical fiber 10, 12 and an optical waveguide chip 14 are fixed so as to regulate the joining direction.
And a second array 16, 18. The optical waveguide chip 14 is formed by forming an optical waveguide (for example, a Y-shaped optical waveguide) 22 having a predetermined shape on, for example, a LiNbO ₃ substrate 20, and a phase modulator 24 is provided on the optical waveguide 22.
And a polarizer 26 are provided.

As shown in FIG. 2, the two ends of the optical fiber 10 (for example, the start end 10a and the end 10b connected to the fiber coil of the optical fiber gyro) are connected to the optical waveguide chip 14 in the joining direction. First array 16 to regulate
And the optical fiber 12 as shown in FIG.
At one end (eg, an optical fiber 1 connected to a light source).
The second end 12a) is fixed to a second array 18 that regulates the bonding direction with the optical waveguide chip 14, and the optical fibers 1 are passed through the first and second arrays 16 and 18.
The ends 10a, 10b and 12a of the optical waveguide chips 14 and 10 are optically coupled to the optical waveguide chip 14.

More specifically, as shown in FIG. 2, the first array 16 has two V-shaped grooves 30a and 30b extending on one principal surface toward one end surface and another V-shaped groove on the other end surface. A substrate 16A in which a wide counterbore portion (escape groove for bonding) 32 extending continuously is formed, and each groove 30 of the substrate 16A is formed.
a, 30b, and 32B for closing the cover. The interval between the two V-shaped grooves 30a and 30b is the same as the interval that matches the optical axis of the two branch paths in the optical waveguide 22 shown in FIG.

When assembling the first array 16, first, as shown in FIG. 2, the two ends 1 of the optical fiber 10 are inserted into the V-shaped grooves 30a and 30b of the substrate 16A.
After crawling 0a and 10b, the polarization preserving surface of the optical fiber 10 is adjusted to the direction of the polarization plane of the light propagating through the optical waveguide 22. After that, the lid substrate 16B is covered from above, and the epoxy resin is filled in the gap between the V-shaped grooves 30a and 30b and the optical fiber 10, and the epoxy resin is heated at a temperature of 60 ° C. to bond and fix the two. Of the optical fiber 10 in the end face of the array 16
By polishing the free end surface 16a of the first array 16, the operation of fixing the first array 16 to the optical fiber 10 is completed.

The second array 18, as shown in FIG.
A substrate 18A in which one V-shaped groove 34 extending toward one end surface of one main surface and a wide counterbore portion (escape groove for bonding) 36 extending toward the other end surface are continuously formed.
And a lid substrate 18B for closing each groove 34, 36 of the substrate 18A.

When assembling the second array 18, first, one end 12a of the optical fiber 12 is laid in the V-shaped groove 34 of the substrate 18A, and then the polarization of the optical fiber 12 is adjusted. The wave preserving surface is aligned with the direction of the plane of polarization of light propagating through the optical waveguide 22. Then, from above, the lid substrate 1
8B, the free end face 18a of the optical fiber 12 is polished in the end face of the second array 18, and the fixing operation of the second array 18 to the optical fiber 12 is completed.

When the optical fibers 10 and 12 are fixed to the first and second arrays 16 and 18 using a resin,
Epoxy resin (made by Cemedine Co., Ltd. EP
001), the resin is discharged at a discharge speed of 0.0016 g / sec or less as the discharge speed of the dispenser so that a cavity portion under the following predetermined conditions is formed in the solidified resin layer. , 12 are adjusted in the plane of polarization, fixed in arrays 16 and 18, and left at room temperature for 1 hour.
The resin was heated and cured at a temperature of ° C.

The above-mentioned cavities under predetermined conditions are one or more cavities having a total diameter in the range of 10 μm to 500 μm, and the effects of these cavities were found by the following experiments.

That is, by changing the discharge speed of the dispenser when the optical fiber is fixed to the array using a resin or the standing time at room temperature, an array in which cavities of various sizes are formed in the solidified resin layer is formed. Produced. As for arrays, ten pieces were prepared for each of the resin layers having the same cavity. By observing the countersunk portion of the prepared array with a transmission microscope, the circle equivalent diameter of each cavity (portion) was measured, and the sum of the diameters of the cavity portions was obtained.

With respect to the optical fibers bonded to the array by the resin layers having the hollow portions of various sizes, the disconnection rate and the polarization crosstalk of the optical fibers were determined. FIG. 4 shows the results. Here, disconnection rate (unit%)
The arrays 16 and 18 were alternately charged every 60 minutes into a thermal shock tester at temperatures of -40 ° C and 80 ° C, and after repeating this cycle 100 times, the same number of samples were disconnected due to thermal stress of the resin. This is the ratio of the condition to the total number of samples. In FIG. 4, when the disconnection rate is 0%, the cycle is set to 130.
No disconnection occurred even when repeated 0 times. The polarization crosstalk (unit: dB) is obtained by measuring the polarization (Px) in the horizontal direction and the polarization (Py) in the vertical direction with respect to the optical axis by the same method as the optical axis adjustment described later. 10 × log (Py / P
x).

As shown in FIG. 4, the disconnection rate is 0% when the total diameter of the cavity is up to 450 μm, and when it exceeds 500 μm, the disconnection occurs and the disconnection rate sharply increases thereafter. When the total diameter was 1000 μm, the disconnection rate reached 40%. On the other hand, the polarization crosstalk is about 2 if the sum of the diameters of the cavities is 100 μm or more.
Although about 5 dB is secured, the sum of the diameters of the hollow portions is 10
When it is smaller than 0 μm, it deteriorates rapidly,
When the sum of the diameters of the cavities became smaller than about 10 μm, the polarization crosstalk including those without the cavities deteriorated to 15 dB. Therefore, in consideration of the balance between the disconnection rate and the polarization crosstalk, the sum of the diameters of the cavity portions is set to fall within the range of 10 μm to 500 μm.
Under the conditions described above, the first and second optical fibers 10 and 12 are connected.
Are fixed to the arrays 16 and 18 using a resin.

On the other hand, the optical waveguide chip 14 is manufactured as follows. First, for example, an optical waveguide 22 having a predetermined shape is formed on one main surface (functional surface) of, for example, a _3- inch wafer (for example, a LiNbO ₃ substrate) by, for example, vacuum evaporation or the like, and at the same time, a polarizer 26 and a phase modulator are formed on the optical waveguide 22. A plurality of optical IC patterns are formed on one wafer by forming the container 24 (not shown). Next, several optical ICs
After the optical IC pattern is cut out from the wafer into a set by using a dicing apparatus having a diamond cutter, for example, the end face of each set, in particular, the first and second arrays 16 and 18 are joined. The surface is polished. Thereafter, each of the optical IC patterns is cut from each group by using the same dicing device to separate the optical IC patterns into a large number of optical waveguide chips.
4 is obtained (see FIG. 1).

Then, the first and second arrays 16 and 18 to which the optical fibers 10 and 12 are already fixed are bonded to one optical waveguide chip 14, respectively. Of the two end surfaces of the optical waveguide chip 14, the second array 18 is provided on the end surface near the polarizer 26, and the first array 18 is provided on the end surface near the phase modulator 24.
Arrays 16 are joined together with their optical axes aligned.

At the time of joining the arrays 16 and 18, the optical axes are adjusted so that the light output becomes the strongest, and the bonding is performed with an adhesive.

More specifically, first, a second array 18 is bonded to one end face of the optical waveguide chip 14 with, for example, an adhesive. At this time, a light source is provided on the open end side of the optical fiber 12, while a photodetector is arranged on the other end surface side of the optical waveguide 22 (not shown), and the output is made through two branch paths of the optical waveguide 22. While the light from the light source to be measured is measured by the photodetector, the polarization maintaining surface of the optical fiber 12 is
In FIG. 1, the optical axis is adjusted in three directions orthogonal to XYZ in FIG. When the optical axis adjustment is completed, the second array 18 and the optical waveguide chip 1
4 are joined by an adhesive.

The second array 18 and the optical waveguide chip 1
When the bonding with the optical waveguide chip 14 is completed,
The first array 16 is adhered to the other end surface of the first member by, for example, an adhesive. At this time, while measuring the light from the light source propagated through the optical waveguide 22 with a photodetector (not shown), the polarization preserving surface of the optical fiber 10 coincides with the polarization direction of the optical waveguide 22. In FIG. 1, the optical axis adjustment is performed in the three orthogonal XYZ directions and the rotation direction of the two cores (starting end 10a and end 10b) of the optical fiber 10. When the optical axis adjustment is completed, the first array 16 and the optical waveguide chip 1
4 are joined by an adhesive. Thus, the optical fiber arrays 16 and 18 according to the present embodiment, and the optical waveguide chip 14 and the optical fibers 10 and 12 joined by the optical fiber arrays 16 and 18 are completed.

[0030]

As described above, the optical fiber array according to the present invention is an optical fiber array for connecting an optical waveguide chip and an optical fiber, the optical fiber array for holding the optical fiber therebetween. A plurality of substrates, at least one of the two substrates is formed with a groove for holding and fixing the optical fiber, the optical fiber is fixed to the groove by a resin layer, The resin layer has one or more cavities having a total diameter in the range of 10 μm to 500 μm.

Therefore, it is possible to obtain an optical fiber array in which the optical fiber is not broken and the polarization crosstalk of the optical waveguide is hardly deteriorated.

[Brief description of the drawings]

FIG. 1 is a perspective view of an optical fiber and an optical waveguide chip connected by an optical fiber array according to the present embodiment.

FIG. 2 is an exploded perspective view showing a state in which an optical fiber whose end is branched is fixed to an optical fiber array.

FIG. 3 is an exploded perspective view showing a state in which an optical fiber having one end is fixed to an optical fiber array.

FIG. 4 is a diagram showing the relationship between the sum of the diameters of the hollow portions of the resin layer of the optical fiber array and the disconnection rate and polarization crosstalk of the optical fiber.

[Explanation of symbols]

10, 12 optical fiber 14 optical waveguide chip 16, 18 array 20 LiNbO ₃ substrate 22 optical waveguide 24 phase modulator 26 polarizer 30a, 30b, 34
... V-shaped grooves 32, 36 ... counterbore

Claims (4)

[Claims] 1. An optical fiber array for connecting an optical waveguide chip and an optical fiber, wherein the optical fiber array has two substrates for holding the optical fiber therebetween. A groove for holding and fixing the optical fiber is formed in at least one of the substrates, and the optical fiber is fixed to the groove by a resin layer. The resin layer has a total diameter. An optical fiber array having one or more cavities in a range of 10 μm to 500 μm. 2. The optical fiber array according to claim 1, wherein said optical fiber array is a polarization-maintaining optical fiber array for connecting an optical waveguide chip and an optical fiber while maintaining a polarization plane in a fixed direction. An optical fiber array, characterized in that at least one of the two substrates is provided with a groove for holding and fixing the polarization plane of the optical fiber in a fixed direction. 3. The optical fiber array according to claim 1, wherein the groove is formed to have a V-shaped predetermined length, and extends into the groove to be wider than the groove. The optical fiber array is characterized in that the optical fiber is fixed to the groove by a resin layer. 4. An optical fiber array according to claim 3, wherein said optical fiber is one of an elliptical core fiber, a panda fiber, an elliptical jacket fiber, and a rod band fiber. array.