JP2019020489A - Filling resin, connection structure, and waveguide groove filling structure - Google Patents

Abstract

To provide a filling resin, a connection structure, and a waveguide groove filling structure that enable little absorption of light and suppression of temperature elevation and deterioration, thereby suppressing an increase in transmission loss even in high-power light transmission.SOLUTION: As a filling resin for a connection (junction) part between a waveguide 501 and optical fibers 505, and waveguide grooves, a fluorosilicone which is obtained by substituting hydrogen in a silicone basically comprising a siloxane bond with fluorine or a resin (fluorine gel) which has a perfluoropolyether in a main chain of a silicone is used.SELECTED DRAWING: Figure 5

Description

  The present invention belongs to the field of optical communications, and particularly relates to a resin for filling high-power of 100 mW or more into a fiber and a waveguide, a waveguide between fibers, and a waveguide groove.

  In the field of optical communications, a connector is used to connect fibers, an adhesive is used to connect a fiber and a waveguide, and waveguides are connected, and a wave plate or athermal resin is formed in a groove dug in the waveguide. In the case of filling, the resin is filled.

  However, when the input power becomes a high power of 100 mW to several W, the temperature rises due to the absorption of the adhesive and the resin, deterioration is observed, and loss is increased.

  For example, when fibers are connected with an MT (Mechanical Transferable) connector, the matching gel is filled, but there is a drawback that the resin burns when a power of several W is applied.

  In order to connect the waveguide and the fiber, the fiber block to which the fiber is fixed and the waveguide are connected, and an epoxy or acrylic adhesive is used between them. However, when a high power of several W is applied, the adhesive burns and there is a problem that the loss becomes very large.

  If a wave plate is still inserted into the groove dug in the waveguide, or the athermal AWG's athermal groove is filled with resin and light of several watts is input, the refractive index changes due to absorption of the resin, and the AWG There was a problem that the characteristics of the deteriorated.

  The wavelength dependence of the loss of the conventional acrylic adhesive is shown in FIG. There is an increase in loss due to large absorption at 1200 nm and 1400 nm, and the loss is 1.5 dB / cm in the 1.55 μm band C band (1535 nm to 1565 nm). The band where the highest power of EDFA can be obtained is the C band, and several watts of light can be put into this band, but if several watts of light is put, the acrylic adhesive will burn and the worst fiber will be the fiber fuse. Wake up.

  The conventional athermal AWG uses the fact that the polarities of the temperature coefficient dn / dT of the refractive index of the resin and the temperature coefficient dn / dT of the refractive index of the glass are reversed, so that the temperature dependence of the wavelength is offset. Is filled with resin. An example is shown in Patent Document 1.

  The resin is filled with a silicone resin having a large dn / dT. The spectrum of the loss of dimethyl silicone filling the athermal groove is shown in FIG. The loss in the C band is 1.8 dB / cm. When transmitting light of 10 mW or less, this level of loss is not a problem, but when transmitting high power of 100 mW or more, temperature compensation works well due to the temperature rise of the resin part even with this level of loss. If the high power is further applied, the adhesive and resin deteriorate.

  Thus, in the communication wavelength band, it has been desired to develop a resin with a small loss for filling between the fiber and the waveguide.

  The loss of resin in the communication wavelength band is disclosed in detail in Non-Patent Document 1.

  Among them, fluorinated polyimide, deuterated silicone, and UV acrylate are listed as materials having little loss at 1550 nm. At 1.55 μm of fluorinated polyimide, 0.4 dB / cm, deuterated silicone is 0.42 dB / cm, and UV acrylate is 0.24 dB / cm. However, these materials have many problems when used to connect fibers and waveguides. That is, polyimide needs to be imidized by heating at about 300 ° C., and the fiber and the waveguide are deteriorated by heating. Silicon deuteration is very costly and deuterated silicone is not commercially available.

  We simulated the temperature when the optical input power was changed by digging grooves in the waveguide and filled with resin with various losses. The result is shown in FIG. The groove width was 37 μm, the waveguide core width was 13 μm, and the core thickness was 6 μm. For example, in the case of a silicone gel of 1.8 dB / cm, when 1 W is input, the temperature reaches 80 ° C. and temperature independence cannot be achieved. When 2 W is input, the temperature becomes 140 ° C. and the resin deteriorates. In order to prevent deterioration of the resin, it is necessary to set the temperature to 50 ° C. or less with 1 W input.

  Therefore, the absorption coefficient of the resin to be filled may be 0.7 dB / cm or less.

Japanese Patent No. 343697

Maruno “Formation of polymer optical waveguide and its device characteristics” Optics 31 (2) (2002) 81 (11) -87 (17)

  The conventional filling resin between waveguides or between fibers has a problem of reducing light absorption, suppressing temperature rise and deterioration, and suppressing increase in transmission loss even in transmission of high power light.

  The present invention has been made in view of the above problems, and aims to reduce light absorption, suppress temperature rise and deterioration, and suppress increase in transmission loss even in transmission of high-power light.

  The present invention is that the resin does not deteriorate even when high power is applied in the communication wavelength band, so that the necessary absorption coefficient of the resin is clarified and a resin that satisfies the requirement is discovered. By replacing the resin with a smaller loss than conventional epoxy adhesives, acrylic adhesives, and silicone resins, absorption of light is reduced, temperature rise and deterioration are suppressed, and loss increases even at high power input. Absent.

  In order to suppress the temperature rise, a resin with a low loss in the communication wavelength band may be filled. There are few reports measuring the loss of the communication wavelength band of resin, and there are only a few reports as materials for polymer waveguides for optical communications. Therefore, the transmission spectra of about 100 kinds of materials were measured, and a material with less loss at 1535 nm to 1565 nm was searched.

  The absorption spectrum of a material in which hydrogen was fluorinated or deuterated was measured. FIG. 4 shows the result. Since deuterated silicone absorbs CD at around 1500 nm, the loss is larger than before deuteration. Fluorosilicone in which hydrogen of silicone based on a siloxane bond is replaced with F reduces absorption at 1200 nm, 1400 nm, and 1535 nm as described above by replacing C—H with C—F. It achieves absorption of 7 dB / cm and has high power resistance that is the subject of the present invention.

  Further fluorination, perfluoropolyether in the main chain of silicone, the so-called “fluorine gel” written by the following formula has almost no absorption of 1200 nm, 1400 nm, 1535 nm, which is CH absorption, In the wavelength band from 1535 nm to 1565 nm, a surprisingly low loss of 0.1 dB / cm was shown.

  The loss of these materials is summarized in Table 1. Of these, the loss of 0.7 dB / cm or less was found to be only fluorine gel and fluorosilicone containing both silicon and fluorine in addition to oxygen, carbon and hydrogen.

  Resin containing fluorine includes fluororubber and Teflon, but the loss is not reduced only by containing fluorine. There are various types of resins containing silicon, typically silicone, but the loss is not reduced simply by containing silicon. When both silicone and fluorine were contained and the amount thereof was 1 mol% or more, a reduction in loss was observed.

  The temperature rise was estimated when the groove was filled with a resin (commonly called fluorine gel) containing perfluoropolyether in the main chain of silicone. From FIG. 3 showing the result of the simulation, even if a high power of 2 W is input, the temperature is suppressed to 130 ° C. → 28 ° C. by replacing the silicone with fluorine gel. It can be seen that even if high power is input, there is no increase in loss and no deterioration.

  In order to achieve the above object, the present invention is characterized by having the following configuration.

One aspect of the filling resin of the present invention is a filling resin between opposing waveguides that transmits high power light of 100 mW or more in a communication wavelength band of 1100 to 1600 nm.
The loss is 0.7 dB / cm or less in a communication wavelength band of 1100 to 1600 nm.

  The filling resin contains 1 mol% or more of silicon and fluorine in addition to oxygen, carbon, and hydrogen.

  The filling resin is characterized in that the main chain includes a portion of perfluoropolyether and the structure is represented by the following chemical formula.

The opposing waveguides are
Optical fiber and optical fiber,
It is a waveguide formed on a substrate and cut by a groove, or an optical fiber and a waveguide formed on the substrate.

The connection structure is a connection mechanism between opposing waveguides that allows high power light of 100 mW or more in a communication wavelength band of 1100 to 1600 nm to pass therethrough.
In the communication wavelength band of 1100 to 1600 nm, the waveguides are fixed facing each other in a state where a resin having a loss of 0.7 dB / cm or less is filled between the facing waveguides.

In the connection structure, the opposing waveguide is a waveguide formed on an optical fiber and a substrate,
The connection structure is a fiber block in which the optical fiber is fixed and bonded to the substrate by an adhesive, and the adhesive is prevented from flowing into a region filled with the resin between the opposing waveguides. A fiber block having a groove to be
The opposing waveguides are an optical fiber and an optical fiber,
The connection structure is a connector for fixing the optical fiber to face each other.

In the connection structure, the opposing waveguide is a waveguide formed on a substrate,
The connection structure is a groove formed on the substrate so as to cut the waveguide, and is a groove filled with the resin.

  A film of MgF, CaF, or LiF is provided on an end face of the opposing waveguide under the following conditions.

n ₀ is the refractive index of the waveguide core, n ₁ is the refractive index of MgF, CaF, or LiF, and n ₂ is the refractive index of the resin between the waveguides and between the fibers.

  According to the present invention, in place of conventional siloxane cross-linked silicone, acrylic adhesive, and epoxy adhesive, H of silicone is fluorinated, or the main chain of silicone that has been further fluorinated is perfluoroether. In the wavelength region of 1100 nm to 1600 nm, the loss is low (0.7 dB / cm to 0.1 dB / cm), and the temperature of the athermal AWG resin rises when high power light of 100 mW or more is input. There is an effect to suppress.

It is a figure which shows the wavelength dependence of the loss of the conventional acrylic adhesive. It is a figure which shows the spectrum of the loss of dimethyl silicone. It is a figure which shows temperature (simulation) at the time of filling resin in a waveguide groove | channel and inputting high power light. It is a figure which shows the wavelength dependence of the loss of deuterated silicone, fluorinated silicone, and a fluorine gel. (A) It is a top view which shows the waveguide groove filling structure of Example 1 of this invention. (B) It is a three-dimensional view which shows the waveguide groove filling structure of Example 1 of this invention. It is a figure which shows MT connector of Example 2 of this invention. (A) It is a top view which shows the waveguide groove | channel filled with resin. (B) It is a three-dimensional view which shows the waveguide groove | channel filled with resin. It is a figure which shows the athermal AWG provided with the Mach-Zehnder interferometer (MZI) provided with the groove | channel filled with resin. It is a figure which shows the temperature independent arrayed-waveguide diffraction grating of Example 4 of this invention.

  Hereinafter, embodiments of the filling resin, the optical wavelength multiplexing / demultiplexing circuit, the temperature-independent arrayed waveguide diffraction grating, the connection structure, and the waveguide groove filling structure of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the description of the embodiments described below, and it is obvious to those skilled in the art that various changes in form and details can be made without departing from the spirit of the invention disclosed in this specification and the like. . Further, the configurations according to the different embodiments can be implemented in combination as appropriate. Note that in the structures of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals, and repetitive description thereof is omitted.

[Example 1]
In this embodiment, when fluorine gel is used for connecting a waveguide and a fiber, an example in which a grooved fiber block is used, a fluorine gel is used for the core portion, and an acrylic adhesive is used for the bonding portion is shown.

  The structure of the first embodiment for connecting the fiber and the waveguide is shown in FIG. FIG. 5A is a top view showing a waveguide groove filling structure. FIG. 5B is a three-dimensional view showing a waveguide groove filling structure. This structure is provided in the waveguide 501, the waveguide core 502 provided in the waveguide 501, the fiber block 503 for fixing the fiber, the acrylic adhesive 504, the fiber 505 passing through the fiber block 503, and the fiber block 503. And an adhesive inflow preventing groove 506 and a resin 507 (commonly called fluorine gel) containing perfluoropolyether in the main chain of silicone. The waveguide 501 and the fiber block 503 are joined to the acrylic adhesive 504 and the silicone main chain via a resin 507 containing perfluoropolyether.

  Normally, the entire surface of the fiber 505 and the waveguide 501 are bonded with an acrylic adhesive, but there is a drawback that if high-power light of 1 W or more is applied, the fiber 505 and the waveguide 501 burn. Therefore, a resin (fluorine gel) containing perfluoropolyether in the silicone main chain is filled between the fiber and the waveguide. Fluorine gel cannot be used as an adhesive because of insufficient adhesive strength. Therefore, an adhesive inflow prevention groove 506 was provided in the fiber block 503, and an acrylic adhesive 504 as an adhesive was filled on both sides, and a fluorine gel 507 was filled in the center. By doing so, the resin 507 can be connected without deterioration even when high-power light of 1 W or more is input at 1535 nm. Even when light of 1100 nm to 1600 nm was applied, the temperature rise was small, the resin 507 did not deteriorate, and the loss did not increase.

[Example 2]
An example in which a resin fluorine gel having perfluoropolyether in the main chain is used for the adhesion portion of the MT connector and the fluorine gel is filled is shown.

  When connecting multi-core fibers, the MT connector shown in FIG. 6 is used. As shown in FIG. 6, the MT connector has a structure in which a multi-core optical fiber is fixed to a ferrule 604 integrally formed of resin and aligned with two guide pins 603. The ferrule 604 has a performance that can be used to connect a single mode optical fiber. Further, the MT connector includes a boot 602, a ribbon fiber 605, and a clip 606. In the case of multiple cores, it is difficult to make physical contact between the fiber cores. Therefore, it is necessary to apply a matching gel 601 mainly made of silicone between the fibers on the end surfaces. However, this matching gel has a drawback that it burns when a high power of 1 W or more is applied. So I applied fluorine gel instead of the matching gel. By replacing the silicone matching gel with a fluorine gel, no increase in loss was observed even when a high power of 1 W or more was applied.

[Example 3]
A case where a waveguide groove is filled with fluorine gel and a case where a resin having a main chain of perfluoropolyether (fluorine gel) is filled into A-AWG (arrayed waveguide diffraction grating) are shown.

  The waveguide groove is dug so as to cut the waveguide as shown in FIG. The waveguide includes a groove 701 filled with resin, a waveguide 702 having a groove 701 on the surface, a waveguide core 703 passing through the waveguide, and a filled resin 704. Conventionally, this groove has been filled with dimethyl silicone resin. However, as described above, dimethyl silicone has a loss of 1.8 dB / cm, and when several hundred mW is added, the temperature rises and the athermal condition cannot be satisfied. For this reason, it replaced with the fluorine gel.

  A thermal groove of an athermal AWG (Patent Document 3: Japanese Patent Application Laid-Open No. 2010-44349) equipped with the MZ interferometer shown in FIG. 8 in the preceding stage was filled with a resin having a perfluoroether called a fluorine gel as a main chain. The athermal AWG includes a first slab waveguide 801, an arrayed waveguide 802, a second slab waveguide 803, a second input / output waveguide 804, a divided triangular groove (resin insertion) 805, and a first input / output waveguide. 806, a temperature-dependent phase difference generation coupler 807, a first arm waveguide 808, a second arm waveguide 809, a directional coupler 810, a temperature compensation material filling groove 811, and a temperature compensation material filling groove 812. The divided triangular groove (resin insertion) 805, the temperature compensation material filling groove 811 and the temperature compensation material filling groove 812 correspond to the athermal groove.

  For comparison, a sample filled with ordinary dimethyl silicone was also prepared. The input power was set to 1 mW and 200 mW, and the temperature dependence of the transmission spectrum and the transmission wavelength was measured. As a result, the conventional silicone-filled silicone does not have a flat top when the high power of 200 mW is applied, and the temperature dependence of the wavelength is about 300 pm shorter than the temperature dependence at the time of 1 mW input. For this reason, even if it is going to eliminate temperature dependence, a wavelength will change a lot with input power.

  On the other hand, in the case of filling the fluorine gel, the shape of the spectrum did not collapse even when a high power of 200 mW was input, and the temperature dependence of the wavelength hardly changed.

  Similarly, when a fluorosilicone in which H of normal dimethylsilicone is replaced with F is filled, substantially the same effect is observed.

  By filling the conventional silicone main chain part with perfluoropolyether in this way, even when high-power light is input, the temperature rise of the athermal AWG can be suppressed, and the transmission spectrum There is an effect that the shape and the temperature dependence of the transmission wavelength are not changed. Not only the structural formula shown above, but also the one obtained by replacing H of silicone crosslinked with siloxane with fluorine was effective.

  Although the structural formula cannot be strictly described, the above effect was observed for the resin having a Si content and a F content of 1 mol% or more in addition to oxygen, carbon, and hydrogen.

[Example 4]
The fluorine gel and fluorosilicone filled in Example 1 have a refractive index of 1.31 to 1.33, which is lower than the refractive index of glass of 14.5. For this reason, there exists a fault that the loss by refractive index mismatch arises in the wall surface part of a groove. In order to solve this drawback, it is effective to form an AR coat on the wall surface.

The reflectivity at the material interface of refractive indices n ₁ and n ₂ is given by:

  For example, there is 0.33% reflection between fluorine gel and quartz glass. Since about 5 to 10 grooves are usually provided, a reflection loss of 0.33 × 2 × (5 to 10) = 3 to 6% occurs. In order to suppress this, it is effective to apply an AR coat to the groove wall surface of the temperature-independent arrayed waveguide grating.

Fluorine gel and fluorosilicone have a refractive index n _{2 of} 1.3 to 1.33, and the material in the case where AR is provided between glass materials having a refractive index n ₀ of 1.46 is a refractive that satisfies the following formula It is necessary to select a material with a rate n ₁ ,

A material having a refractive index of 1.38 to 1.39, that is, CaF, MgF, or LiF is suitable.

These materials

What is necessary is just to form by the film thickness d of the conditions of these. In the case of 1.55 μm, CaF, MgF, or LiF may be formed to about 280 nm.

  Usually, the AR coating is formed perpendicular to the reflecting surface, but when it is attached to the groove wall surface, a sputtering method is effective. As shown in FIG. 9, AR coating was applied to the entire wall surface by sputtering using a sputtering target 906 and plasma 907. The temperature-independent arrayed waveguide diffraction grating includes a Si substrate 901, a waveguide clad (quartz glass) 902, an AR coating film 903, a fluorine gel or fluorosilicone 904, and a waveguide core 905.

  By attaching AR to the wall surface, the loss could be reduced by 0.3 dB.

  In this embodiment, the AR coat is formed on the wall surface of the waveguide groove, but the AR coat may be formed on the end face of the fiber or the waveguide.

501 Waveguide 502 Waveguide core 503 Fiber block for fixing fiber 504 Acrylic adhesive 505 Fiber 506 Adhesive inflow preventing groove 507 Resin 601 containing gel containing perfluoropolyether in main chain of silicone 602 Boot 603 Guide bottle 604 Ferrule 605 Ribbon fiber 606 Clip 701 Fill groove 702 Waveguide 703 Waveguide core 704 Filled resin 801 First slab waveguide 802 Array waveguide 803 Second slab waveguide 804 Second input / output waveguide 805 Divided triangular groove (resin insertion)
806 First input / output waveguide 807 Temperature-dependent phase difference generation coupler 808 First arm waveguide 809 Second arm waveguide 810 Directional couplers 811 and 812 Temperature compensation material filling groove 901 Si substrate 902 Waveguide cladding (Quartz glass)
903 AR coating film 904 Fluorine gel or fluorosilicone 905 Waveguide core 906 Sputter target 907 Plasma

Claims (8)

In a filling resin for opposing waveguides that transmits high power light of 100 mW or more in a communication wavelength band of 1100 to 1600 nm,
A filled resin characterized by having a loss of 0.7 dB / cm or less in a communication wavelength band of 1100 to 1600 nm.   2. The filled resin according to claim 1, comprising 1 mol% or more of silicon and fluorine in addition to oxygen, carbon, and hydrogen. The filled resin according to claim 1 or 2, wherein the main chain includes a perfluoropolyether moiety, and the structure is represented by the following chemical formula.

The opposing waveguides are
Optical fiber and optical fiber,
4. The waveguide according to claim 1, wherein the waveguide is a waveguide formed on a substrate and cut by a groove, or a waveguide formed on an optical fiber and the substrate. 5. Filling resin as described. In a connection mechanism between opposing waveguides that allow high power light of 100 mW or more in a communication wavelength band of 1100 to 1600 nm to pass through,
A connection structure, wherein a waveguide is opposed and fixed in a state where a resin having a loss of 0.7 dB / cm or less in a communication wavelength band of 1100 to 1600 nm is filled between the opposed waveguides. The opposing waveguide is a waveguide formed on an optical fiber and a substrate,
The connection structure is a fiber block in which the optical fiber is fixed and bonded to the substrate by an adhesive, and the adhesive is prevented from flowing into a region filled with the resin between the opposing waveguides. A fiber block having a groove to be
The opposing waveguides are an optical fiber and an optical fiber,
The connection structure according to claim 5, wherein the connection structure is a connector that fixes the optical fiber to face each other. The opposing waveguide is a waveguide formed on a substrate,
The connection structure according to claim 5, wherein the connection structure is a groove formed on the substrate so as to cut a waveguide, and is a groove filled with the resin. The connection structure according to any one of claims 5 to 7, wherein a film of MgF, CaF, or LiF is provided on an end face of the opposing waveguide under the following conditions.

n ₀ is the refractive index of the waveguide core, n ₁ is the refractive index of MgF, CaF, or LiF, and n ₂ is the refractive index of the resin between the waveguides and between the fibers.

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