JPH07281049A - Manufacture of fiber accumulated optical part - Google Patents

Abstract

PURPOSE:To facilitate fiber groove work of a holding board, simplify fixing work without increasing the fiber installing number so much to the holding board, and improve mass-productivity. CONSTITUTION:A large number of straight line-shaped fiber grooves 12 continuing over the full length are formed in parallel at the same pitch on a holding board 10. Beam size magnifying fibers 14 are respectively arranged in the respective fiber grooves 12, and a fiber array 15 is formed. A device inserting groove 16 which extends in the inclination (alpha) direction to the fiber arranging direction and crosses the fiber array 15 in a beam size magnifying position, is formed on the holding board 10, and a light device 18 is installed in the device inserting groove 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical component in which a parallel plate type optical device is inserted into a fiber array for integration. More specifically, the beam size expanding fibers are arranged in a large number of linear fiber grooves formed over almost the entire length on the holding substrate, and the device insertion groove extending in the direction of the inclination angle α with respect to the fiber arrangement direction is held by the holding groove. The present invention relates to a method of manufacturing a fiber integrated optical component which is formed on a substrate and has an optical device mounted thereon. This technology uses optical isolators, optical switches, optical filters,
It can be applied to a thin type optical device such as an optical attenuator that transmits light.

[0002]

2. Description of the Related Art Recently, a fiber integrated optical isolator has been developed in which a parallel plate optical isolator chip is inserted and integrated in a fiber array in which a large number of optical fibers are arranged. In this type of optical isolator, a TEC (Thermally-diffused Expanded Correlation) is used as an optical fiber.
e) Use a beam-size expanding fiber called a fiber. This fiber is a fiber in which the core diameter is enlarged by locally heating an ordinary single-mode fiber. By using this fiber, the diffraction loss of the spatial propagation of the signal light is reduced, and there is no lens. In addition, the distance that the signal light can propagate in space is made longer so that an optical isolator chip can be inserted.

The original fiber integrated optical isolator was
The structure was such that the optical device was mounted perpendicular to the fiber arrangement direction. Specifically, a large number of linear fiber grooves (V grooves) are formed in parallel on a silicon substrate by etching, and the beam size expanding fibers are fixed to the respective fiber grooves. Then, a device insertion groove is formed in the silicon substrate so as to cross the fiber perpendicularly to the fiber arrangement direction and at the beam size expansion position, and the optical isolator chip is mounted in the device insertion groove. There is. The optical isolator having this structure does not require a lens and can be assembled without performing complicated optical adjustment. Therefore, the optical isolator is excellent in mass productivity and has a simple structure.

However, in the above fiber integrated optical isolator, since the optical isolator chip is mounted perpendicular to the fiber array, the amount of reflected return light that the incident light reflects at the end face of the optical isolator chip and returns to the signal transmitting side. Is large, which may adversely affect the transmitting side device. Therefore, a structure has been proposed in which an optical isolator chip is mounted at a slight angle to the fiber arrangement direction to suppress reflected return light. In this structure, the optical axes of the incident light and the outgoing light in the optical isolator chip are deviated due to the refraction because the optical isolator chip is arranged obliquely with respect to the fiber arrangement direction. for that reason,
The optical axis shift amount (incident light −
The amount of shift of emitted light is estimated, the fiber groove on the incident side and the fiber groove on the output side are shifted by the shift amount, and are separately formed on the silicon substrate to dispose the optical fiber.

[0005]

However, a work for forming a large number of fiber grooves with high precision by separately shifting the optical isolator chip on both sides (incident side and exit side) by the optical axis shift amount in the fiber arrangement direction. Is difficult to carry out by machining suitable for mass production. Also, if one optical fiber is to be arranged continuously over the entrance-side fiber groove and the exit-side fiber groove, it will have to be forcibly bent at the mounting part of the optical isolator chip, and the optical fiber will be damaged. Or a positional shift occurs, which causes characteristic deterioration. Therefore, the attachment of each optical fiber to the substrate must be performed separately with the tips of the incident side and the emitting side aligned,
Since the number of attachments is doubled, the work becomes complicated, and as a result, mass productivity decreases.

An object of the present invention is to easily fabricate a fiber groove in a holding substrate, to increase the number of fibers to be mounted on the holding substrate, and to fix the fiber easily. An object of the present invention is to provide a method for manufacturing an optical component. Another object of the present invention is to provide a method for manufacturing a fiber integrated optical component that can reduce reflected return light and reduce coupling loss.

[0007]

The present invention is a method of manufacturing a fiber integrated optical component in which a parallel plate type optical device is inserted and integrated in a fiber array in which a large number of beam size expanding fibers are arranged. . In order to achieve the above-mentioned object, in the present invention, a large number of linear fiber grooves that are continuous over substantially the entire length of the holding substrate are formed in parallel and at the same pitch, and a beam size expanding fiber is provided in each of the fiber grooves. The fiber array is arranged. Here, in order that the optical axis shift amount (incident light-emission light shift amount) in the optical device matches an integer multiple of the fiber array pitch, the inclination angle α of the normal line of the optical device incident surface with respect to the incident light, the optical device Set the refractive index and thickness of. And
A device insertion groove extending in a direction of an inclination angle α with respect to the fiber array direction and traversing the fiber array at a beam size expansion position is formed in the holding substrate, and the optical device is mounted in the device insertion groove. Usually, the optical axis shift amount in an optical device is set to about 1 or 2 times the fiber arrangement pitch.

The optical device may be a combination of an optical device body and a transparent compensating plate, and the transparent compensating plate may adjust the optical axis shift amount. Here, as the transparent compensating plate, one having a large refractive index and being transparent at a used wavelength is used. This transparent compensating plate is useful especially when it is desired to reduce the total thickness of the optical device and when the tilt angle cannot be increased. The optical device is a thin element that transmits light, and is, for example, an optical isolator, an optical switch, an optical filter, an optical attenuator, or the like.

[0009]

The light incident on the optical device from a certain incident side fiber is shifted in the optical axis at the emitting side because the optical device is obliquely mounted and is stored in the same fiber groove as the incident side fiber. It cannot be coupled to the output fiber. However, in the present invention, the inclination angle α of the normal line of the optical device incident surface to the incident light and the refractive index of the optical device are adjusted so that the optical axis shift amount in the obliquely mounted optical device matches an integer multiple of the fiber array pitch. Also, since the thickness is set, the light incident on the optical device from a certain incident side fiber is emitted with a shift amount of the optical axis, and is coupled to the emission side fiber existing at that position. That is, the light entering the optical device from a certain fiber on the incident side is not on the fiber on the emitting side housed in the same fiber groove as the fiber on the incident side, but on the emitting side of the fiber groove which is deviated by about 1 pitch or 2 pitches from the fiber Will be coupled to the fiber. Since the optical device has a parallel plate shape, the optical axis shift amount between the incident light and the outgoing light is constant, and the optical fibers are coupled to the corresponding outgoing fibers by shifting the same pitch with respect to each incoming fiber. Most of the side fiber array and most of the exit side fiber array are coupled. Fibers that do not have such a coupling relationship are
Normally, the number of optical circuits is 1 or 2 on the incident side and the number of optical fibers on the outgoing side. However, the required number of optical circuits can be secured by arranging a large number of fibers in consideration of the number in advance.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a process explanatory drawing showing an embodiment of a method for manufacturing a fiber integrated optical component according to the present invention. As shown in FIG. 1A, on a holding substrate 10 made of silicon, glass, or the like, a large number of linear fiber grooves 12 having a V-shaped cross section are formed in parallel and at the same pitch over substantially the entire length. For example, in the case of a 16-core fiber array, about 17 to 18 fiber grooves are formed (in FIG. 1, only 6 fiber grooves are drawn to simplify the drawing). When such a holding substrate is made of silicon, for example, a fiber groove is formed by selectively etching the surface of the silicon wafer by a photolithography method, and then the silicon wafer is cut and separated into a predetermined size. Can be obtained at. In the case of a holding substrate made of glass (for example, low expansion crystallized glass), the fiber groove can be easily and efficiently formed by high-precision machining. Beam size expanding fiber 14 in each fiber groove 12
Are placed and bonded using an ultraviolet curable adhesive or the like.
The beam size expanding fiber 14 used here is a fiber in which the diameter of the core part is expanded by locally heating the fiber as described above, and the expanded core part (beam size expanding part 13). The respective fibers 14 are arranged so that is positioned substantially at the center of the holding substrate 10.

Thus, as shown in FIG. 1B, a large number of beam size expanding fibers 14 are provided on the holding substrate 10.
Are regularly arrayed at a constant pitch and the fiber array 15
Becomes Although not shown, a fiber pressing plate may be bonded above the holding substrate 10 on which the fiber array 15 is formed, or a reinforcing plate may be bonded below, if necessary. For example, quartz or glass is used as the fiber pressing plate and the reinforcing plate.

Next, as shown in FIG. 1C, the device inserting groove 1 is formed in the holding substrate 10 by using a micro-lapping apparatus.
6 is formed. For this groove processing, a diamond blade is used, and it is formed so as to extend from above the fiber pressing plate in the direction of the inclination angle α with respect to the fiber arrangement direction and to traverse the fiber array 15 at the beam size expansion position. In this way, while holding down the fiber with the fiber holding plate,
The cutting conditions of the blade are adjusted so that the tip of the cut portion of the beam size expanding fiber does not swing or turn over, and the cutting surface of the beam size expanding fiber 14 is made to be substantially mirror surface. A parallel plate type optical device 18 is inserted into the device insertion groove 16 and fixed with an ultraviolet curable adhesive or the like. The optical device 16 is, for example, a polarization separation element in the case of an optical isolator.
A Faraday rotator (for example, a bismuth-substituted iron garnet single crystal film) and a half-wave plate serving as a polarization compensating plate are laminated and integrated between a plurality of rutile plates.

FIG. 2 shows a plan view of the fiber integrated optical component thus obtained. Here, the optical device 1
The optical axis shift amount at 8 is set so as to match one pitch of the fiber array. For example, the incident light from the incident side fiber 14a-1 at the right end with respect to the incident direction of light has its optical axis shifted to the left by one pitch of the fiber array due to refraction when passing through the optical device 18, and thus the right end. To the second exit side fiber 15b-2. The same applies to the following, and the incident light from the second entrance-side fiber 14a-5 from the left end is coupled to the left-end exit-side fiber 14b-6. In this way, the entrance-side fiber array 15a is coupled to the exit-side fiber array 15b while being displaced by one pitch.
Since the incident side fiber 14a-6 at the left end and the output side fiber 14b-1 at the right end are not used, the number of the fiber grooves 12 (the number of fibers) should be one more than the actually required number.

In order to shift the optical axis by exactly one pitch of the fiber array so as to couple it to the output side fiber array, the formation pitch of the fiber groove and the optical axis shift amount in the optical device should match. Good. Once the arrangement pitch of the fiber grooves is determined, the tilt angle of the normal line of the optical device incident surface to the incident light, the refractive index of the optical device, and the thickness are adjusted so as to match the pitch. As shown in FIG. 3, the inclination angle of the normal to the incident surface of the optical device with respect to the incident light is α, and the optical device 1
8, the refractive index of n is 8, the thickness is d, the refractive index of the core portion of the beam size expanding fiber 14 is n _f , and the ultraviolet curable adhesive 20
Let n _b (where n _b = n _f ), the optical axis shift amount S in the optical device 18 is S = d {sin (α−K) / cos K} where K = sin ^{− 1} (n _f / n × sin α). Therefore, in a range where the optical axis shift amount S matches one pitch of the fiber array and the reflected return light can be reduced,
Moreover, each parameter is determined within a range that does not impair the characteristics of the optical device.

Next, a specific design example of this structure will be described. Sixteen fiber grooves are formed on a holding substrate at a pitch of 125 μm, and fibers are arranged in the groove to form a 16-core fiber array. A polarization-independent optical isolator element with a total thickness of 2.3 mm (two birefringent plates, one half-wave plate,
In the case of one Faraday rotator), the optical axis shift amount S generated when the tilt angle α = 5 ° was 70 μm. Therefore, the fiber array has a width of 2.3 mm and an inclination angle α = 9.
A device insertion groove is formed at an angle of °, and an optical isolator element is installed in it. The optical axis shift amount generated at this time is 125
μm, which matches the fiber arrangement pitch described above, and the coupling loss between the incident side fiber and the emitting side fiber is sufficiently small.

FIG. 4 is an enlarged view of a main part showing another example of the present invention, which is an example in which a transparent compensating plate is also used. When the optical device body is very thin, it may be difficult to match the optical axis shift amount with the array pitch by selecting the parameters of the optical device body only as described above. If the thickness of the optical device is forcibly increased to match, the diffraction loss between the fibers becomes large. In such a case, the optical device 22 may be a combination of the optical device body 24 and the transparent compensating plate 26. Here, the transparent compensation plate 26 is
A material that has a larger refractive index than the optical device body 24 and is transparent at the wavelength used is used. With this configuration, it is possible to reduce the total thickness of the optical device 22 as compared with the case where only the optical device body 24 is used. As described above, the transparent compensating plate is used for the purpose of increasing the shift amount of the optical axis and is effective when the total thickness of the optical device is limited. The combination method may be provided in the front stage of the optical device body as shown in FIG. 4, may be provided in the rear stage, or may be sandwiched in the optical device body. Examples of the material of the transparent compensating plate include various optical glasses (particularly heavy flint glasses such as SF-58 and 59 having a relatively large refractive index) and garnet crystals (eg gadolinium gallium) as optically isotropic materials.・ Garnet, yttrium, iron, garnet, etc.) can be used, and as optically anisotropic materials, TiO ₂ , T
eO ₂ , LiNbO ₃ or the like can be used.

The present invention is not limited to such a configuration. The optical axis shift amount in the optical device may be an integer multiple of the fiber array pitch. In practice, it is preferable that the fiber array pitch is the same as that of each of the above-mentioned embodiments, or about twice the fiber array pitch. This is because when the optical axis shift amount is large, the optical path length of the optical device becomes long, the loss due to scattering or the like increases, and the number of unused fibers increases. It goes without saying that the optical device to be inserted between them is arbitrary as long as it is a transmissive type and thin, and may be an optical filter element, an optical switch element, an optical attenuating element, etc. other than the optical isolator element.

[0018]

According to the present invention, since the optical axis shift amount in the optical device matches the integer multiple of the fiber array pitch in advance, the light axis of the light entering the optical device from the incident side fiber shifts. Since the exit side fiber which is displaced by an integer pitch exists at that position and is coupled to it, the fiber integrated optical component with low coupling loss can be finally manufactured.
Further, in the present invention, although the optical device is arranged obliquely with respect to the fiber array, a large number of linear fiber grooves continuous over substantially the entire length of the holding substrate are arranged in parallel and at the same pitch. Since it is sufficient to form the groove, it is possible to adopt inexpensive and mass-productive machining for forming the groove. Further, in the present invention, since it is sufficient to dispose a continuous fiber from the incident side to the output side in a continuous linear fiber groove, as compared with the conventional method of separately fixing the input side fiber and the output side fiber, The fiber arrangement and fixing work are halved, improving productivity.

[Brief description of drawings]

FIG. 1 is a process explanatory view showing an embodiment of a method of the present invention.

FIG. 2 is a schematic plan view of a fiber integrated optical component obtained as a result.

FIG. 3 is an enlarged view of a main part of the fiber integrated optical component.

FIG. 4 is an enlarged view of a main part of another example of the fiber integrated optical component manufactured by the present invention.

[Explanation of symbols]

 10 Holding Substrate 12 Fiber Groove 14 Beam Size Enlarging Fiber 15 Fiber Array 16 Device Insertion Groove 18 Optical Device

Claims (2)

[Claims] 1. A method of manufacturing a fiber integrated optical component in which a parallel plate type optical device is inserted and integrated in a fiber array in which a large number of beam size expanding fibers are arranged, and a substantially total length of the optical fiber is formed on a holding substrate. A large number of continuous linear fiber grooves are formed in parallel at the same pitch, and the fibers are fixed in the respective fiber grooves to form a fiber array. The optical axis shift in the optical device is an integer of the fiber array pitch. The inclination angle α of the normal to the incident surface of the optical device with respect to the incident light, the refractive index and the thickness of the optical device are set so that they coincide with each other, and the fiber array extends in the direction of the inclination angle α with respect to the fiber arrangement direction and Is formed in the holding substrate, and the optical device is mounted in the device insertion groove. Method for producing a fiber integrated optical components. 2. The manufacturing method according to claim 1, wherein the optical device comprises a combination of an optical device body and a transparent compensating plate, and the optical axis shift amount in the fiber array direction is adjusted by the refractive index and the thickness of the transparent compensating plate. Method.