JP4015680B2 - Optical element module - Google Patents

Description

  The present invention relates to an optical element module used for optical fiber communication. In particular, the present invention relates to an optical element module that is resistant to environmental temperature fluctuations.

  In order to couple optical elements such as optical waveguides and optical fibers, an optical element module that installs optical elements inside the housing and connects the optical fibers introduced from the outside of the housing to the optical elements inside the housing is adopted. Has been. The structure of a conventional optical element module is shown in FIG. 1 (see, for example, Patent Document 1 and Patent Document 2).

  In FIG. 1, 50 is an optical element module, 51 is a housing, 52 is an optical waveguide protective plate covering the optical waveguide, 53a and 53b are optical fiber holding parts, 54 is an optical fiber core wire, 55 is a bare optical fiber, and 56 is A tape optical fiber, 57 is a bare optical fiber, and 58 and 59 are adhesive fixing portions.

  The types of optical fibers described in this application are shown in FIGS. In FIG. 2, 30a is an optical fiber core part, 30b is an optical fiber cladding part, 31 is a primary coating, and 32 is a secondary coating. An optical fiber that has been subjected to secondary coating is referred to as an optical fiber core wire, an optical fiber that has been primary coated is referred to as a primary coated optical fiber, and an optical fiber that has not been subjected to primary coating is referred to as a bare optical fiber. Usually, the outer diameters of the optical fiber core wire, the primary coated optical fiber, and the bare optical fiber are 900 μm, 250 μm, and 125 μm, respectively. In FIG. 3, 30a is an optical fiber core part, 30b is an optical fiber cladding part, 31 is a primary coating, and 33 is a secondary coating for forming a tape fiber. In a tape optical fiber, an optical fiber up to secondary coating is called a tape optical fiber, an optical fiber coated with primary coating is called a primary coated optical fiber, and an optical fiber not coated with primary coating is called a bare optical fiber.

  The optical element module 50 shown in FIG. 1 has one light input and four light outputs, and branches input light from one optical fiber into four by an optical waveguide in which a four-branch optical circuit is formed. The branched light is optically output to four optical fibers. An optical fiber is connected to the input / output end face of the optical waveguide, and the optical waveguide or the like is installed in the housing. An optical fiber core 54 for light input is guided from the outside into the housing 51, and the primary coating and the secondary coating are removed to form a bare optical fiber 55. The bare optical fiber 55 is accommodated in an optical fiber holding portion 53a having a V-groove or the like, and is fixed to the optical waveguide in a state where the input portion of the optical waveguide (not shown) is aligned with the optical axis. The tape optical fiber 56 for optical output is guided into the housing 51 from the outside, and the primary coating and the secondary coating are removed to form a bare optical fiber 57. The bare optical fiber 57 is accommodated in an optical fiber holding portion 53b having a V-groove or the like, and is fixed to the optical waveguide in a state where the input portion of the optical waveguide (not shown) and the optical axis are aligned.

  A stable connection between the bare optical fibers 55 and 57 and the optical waveguide is maintained by fixing the optical waveguide protection plate 52 to the upper surface of the optical waveguide and increasing the contact area with the optical fiber holding portions 53a and 53b. . The optical waveguide is fixed to the bottom of the casing 51 with an adhesive. The optical fiber core 54 for optical input is fixed by the casing 51 and the adhesive fixing portion 58, and the tape optical fiber 56 for optical output is also fixed by the casing 51 and the adhesive fixing portion 59. The

  With the construction of an optical access line network that conforms to the recent PON (Passive Optical Network) topology, there is a need to install an optical element module with a built-in optical waveguide in an outdoor facility, and the optical element module has a structure suitable for outdoor use. It became necessary to do. In particular, in order to accommodate an optical fiber in a narrow outdoor facility, it is necessary to use a primary coated optical fiber as an optical fiber for light input and light output.

  In a conventional optical element module, it has been found that when an optical fiber for light input and light output is simply a primary coated optical fiber, stable characteristics cannot be obtained in an environment where temperature changes are severe. A temperature cycle test was conducted when the optical fiber for inputting light in the conventional optical element module was a primary coated optical fiber. The test results are shown in FIG. In FIG. 4, the horizontal axis represents the test time, and the vertical axis of the upper graph in FIG. 4 represents the increased optical loss of the optical element module at this time. As a result of performing a temperature cycle test from −40 ° C. to + 75 ° C. with 8 hours as one cycle, it was found that the optical loss of the optical element module fluctuates greatly when the environmental temperature of the optical element module changes.

  As a cause of the large fluctuation of the optical loss as shown in FIG. 4, when the environmental temperature changes, especially when the environmental temperature becomes low, the primary coated optical fiber and the housing of the optical element module contract. Stretching stress is generated between two points: an optical fiber holding part that bonds and fixes the primary coated optical fiber for light input and an adhesive fixing part that is fixed to the housing with an adhesive. It has been clarified that microbending occurs in the primary coated optical fiber, leading to an increase in optical loss.

  Even if the optical fiber core in FIG. 2 (c) is used as an optical fiber for light input and light output, a deviation occurs between the primary coating and the secondary coating fixed with an adhesive. Therefore, even if the environmental temperature is lowered, the light loss does not increase. The same applies to the tape optical fiber of FIG. Even if the outer side of the secondary coating of the tape optical fiber is fixed with an adhesive, a deviation occurs between the primary coating and the secondary coating, and the stress on the primary coating is reduced, so the environmental temperature becomes low. However, there is no increase in optical loss.

JP-A-7-13039

JP-A-5-66318

  In order to solve such a problem, the present invention provides a fluctuation of optical loss with respect to a wide range of temperature fluctuations even when the primary coated optical fiber is used as an optical fiber for light input or light output. An object of the present invention is to provide an optical element module with a small amount.

In order to achieve the above-described object, the present invention provides a casing, an optical element fixed to the bottom surface inside the casing, and the outside and the inside of the casing, and is fixed to one end of the casing. And a primary coated optical fiber that is inserted through the pipe and connected to the optical element, and is movably held within the pipe with a diameter smaller than the diameter of the pipe, and connected to the optical element. An optical element module comprising: a tape optical fiber having a primary coating layer and a secondary coating layer, and a secondary coating layer as an outermost layer fixed to the other end of the casing.

  According to the first invention of the present application, an optical element module having temperature stability against environmental temperature fluctuations can be provided by loose contact between the primary coated optical fiber and the pipe.

In the present invention, the pipe is fixed to one end of the housing via a first rubber boot,
An optical element module is also included in which the tape optical fiber is bonded and fixed to the other end of the housing via a second rubber boot.

The invention of the present application includes an optical element module characterized in that the internal gap of the optical element module is filled with a gel material.

According to the present invention, the proof stress against mechanical stress such as vibration and impact applied to the optical element module is improved.

  As described above, according to the present invention, even when a primary coated optical fiber is used for light input or light output of an optical element module, it is possible to prevent microbending of the optical fiber due to fluctuations in environmental temperature. Thus, an optical element module having temperature stability can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments.
(Embodiment 1)
Examples of embodiments of the present invention are shown in FIG. 5, FIG. 6, FIG. 7, and FIG. 5 is a plan sectional view of the optical element module, FIG. 6 is a sectional view taken along line AA ′ in FIG. 5, FIG. 7 is a sectional view taken along line CC ′ in FIG. 5, and FIG. It is sectional drawing in the -D 'line. 5 is a cross-sectional view taken along line BB ′ in FIG. 5, 6, 7, and 8, 1 is an optical element module, 5 is an optical waveguide protection plate, 7 is an optical waveguide chip as an optical element, 21 is a primary coated optical fiber, 22 is a tape optical fiber, 23a and 23b are rubber boots, 24 are pipes, 25a and 25b are optical fiber holding portions, 26 is an internal space of the optical element module, 27 is a lower housing, 28 is an upper housing, and 29 is a primary coated optical fiber.

  The optical waveguide chip 7 is formed with a 1 × 4 optical splitter circuit that divides the light input into four on the waveguide chip substrate. An optical waveguide protection plate 5 covering the upper surface of the optical waveguide chip is bonded and fixed to the optical waveguide chip 7 to protect the optical waveguide, and at the same time, the optical waveguide protection plate 5 and the optical waveguide chip 7 are integrated into an input / output end face (see FIG. (Not shown). Optical fiber holders 25a and 25b that respectively hold the primary coated optical fiber 21 for light input and the tape optical fiber 22 are abutted and fixed to the input / output end faces. The lower casing 27 is formed by fitting an upper casing 28 having a U-shaped cross section with each other to form a casing of the optical element module.

  An optical fiber for optical input is a single core, and a primary coated optical fiber having an outer diameter of 0.25 mm is used assuming use in an outdoor facility. By using the primary coated optical fiber, the fusion splicing with the primary coated optical fiber wired in the outdoor facility becomes easy. One end of the primary coated optical fiber 21 is held by the optical fiber holding unit 25a in a bare optical fiber state where the primary coating has been removed. The holding method is, for example, pressing and fixing to the V-groove. The end surface of the optical fiber holding portion 25a that is abutted against the optical waveguide chip 7 is an inclined surface that is inclined by a predetermined angle with respect to the optical axis of the optical fiber, and the inclined end surface of the optical waveguide chip 7 that is set to the same angle is mutually connected. It is connected. The other end of the primary coated optical fiber 21 is inserted through the inside of a pipe 24 that conducts between the outside and the inside of the housing, and is led to the outside.

  The pipe 24 is designed so that the optical axis of the optical waveguide chip 7 is aligned with the optical axis of the optical waveguide chip 7 from the primary coated optical fiber 21 with the primary coated optical fiber 21 inserted through the pipe 24. The rubber boot 23a is fixed to the end of the housing 28. The pipe 24 is preferably made of a material that is elastic and does not deform with respect to temperature changes, such as a nylon tube. The inner diameter of the pipe 24 is made larger than the outer diameter of the primary coated optical fiber 21. For example, a pipe having an inner diameter of 1 mm and a round cross section is preferable with respect to the outer diameter of the primary coated optical fiber of 250 μm. The length of the pipe 24 is set to be longer than the length of the through hole of the rubber boot 23a in consideration of bending of the primary coated optical fiber inserted through the pipe 24 due to handling or the like. For example, it is preferable that the rubber boot 23a protrudes about 1 mm inside the optical element module and protrudes about 5 mm outside the optical element module.

  The optical fiber for optical output is a four-core tape optical fiber. One end of the tape optical fiber 22 is held by the optical fiber holding portion 25b in the state of a bare optical fiber from which the primary coating has been removed. As a holding method, for example, the four V-grooves corresponding to the optical fiber interval of the four-core tape optical fiber are pressed and bonded and fixed. The end surface of the optical fiber holding portion 25b that is abutted against the optical waveguide chip is an inclined surface that is inclined by a predetermined angle with respect to the optical axis of the optical fiber, and is connected to the inclined end surface of the optical waveguide chip 7 that is set to the same angle. Has been. The other end of the tape optical fiber 22 is guided through the through hole of the rubber boot 23b. Further, the tape jacket of the tape optical fiber is removed to make the primary coated optical fiber, which can be fusion-bonded with another primary coated optical fiber in the outdoor equipment. The rubber boot 23b and the tape optical fiber 22 are fixed with an adhesive so that the tape optical fiber 22 does not move relative to the rubber boot 23b.

  When a primary coated optical fiber is used as an optical fiber for light input or light output, a loose structure is formed by using a pipe without bonding between the primary coated optical fiber and the rubber boot. By adopting such a loose structure, the primary coated optical fiber can move freely in the pipe. Therefore, even if the environmental temperature fluctuates and the primary coating of the primary coated optical fiber and the housing contract and expand, light No stress is applied to the fiber cladding / core. As a result, microbending associated with fluctuations in environmental temperature does not occur, and optical loss does not increase.

  If a tape optical fiber is used, the stress accompanying the fluctuation of the environmental temperature is absorbed at the boundary between the primary coating and the secondary coating. Therefore, even if the tape optical fiber 22 is bonded and fixed to the rubber boot 23b, Does not increase optical loss.

  Next, a method for manufacturing the optical element module of the present embodiment will be described. The optical waveguide chip is formed by depositing a lower cladding layer and a core layer on a Si substrate or a quartz substrate by a flame deposition method using a known method for producing a silica-based glass waveguide, and using a waveguide mask. A core pattern of an optical branch circuit is formed on the lower clad by lithography and reactive ion etching, and an upper clad layer is further deposited by a flame deposition method, followed by a core portion filling step.

  In order to connect an optical fiber to the input / output end of the optical waveguide chip, an optical waveguide protection plate is attached to the optical waveguide chip. For this purpose, an adhesive is applied to the upper surface of the upper clad layer of the optical waveguide chip, the adhesive is cured while pressing the optical waveguide protection plate, and the optical waveguide chip and the optical waveguide protection plate are fixed. In this case, an optical waveguide protection plate may be attached to each of the optical waveguide chips, but a plurality of optical waveguide chips that are exposed at the input / output end surfaces but connected to the side surfaces are cut out from the wafer and collectively Then, the optical waveguide protection plate is attached, the input / output end faces are polished, and then the optical waveguide chip and the optical waveguide protection plate are separated together to obtain an optical waveguide chip with the optical waveguide protection plate. It is efficient because the optical waveguide protection plate can be attached and polished in a lump.

  An optical fiber for optical input and an optical fiber for optical output are connected to the obtained optical waveguide chip with an optical waveguide protective plate. Also, an optical fiber array substrate on which optical fibers are arranged so as to correspond to a plurality of optical waveguide chips is prepared, and this is collectively connected and fixed to an optical waveguide chip to which an optical waveguide protection plate is attached and connected. If each optical waveguide chip is separated, the connection of the optical fibers to a plurality of optical waveguide chips can be processed in a lump, which is more efficient.

  Next, the primary coated optical fiber for light input connected to the optical waveguide chip is inserted into a pipe fixed to the rubber boot. Also, the optical fiber for optical output connected to the optical waveguide chip is inserted into the through hole of the rubber boot and bonded and fixed to the rubber boot in advance.

  Finally, the two rubber boots are fixed to the inner sides of both ends of the U-shaped lower casing with an adhesive, and the internal gap of the optical element module is filled with a gel material. After that, an adhesive is applied to the adhesive surface of the U-shaped upper casing, and the adhesive is placed on the U-shaped lower casing.

  A temperature cycle test was performed on the optical element module thus obtained. The test results are shown in FIG. In FIG. 9, the horizontal axis represents the test time, and the vertical axis of the upper graph in FIG. 9 represents the increased optical loss of the optical element module at this time. As a result of performing a temperature cycle from −40 ° C. to + 75 ° C. with 8 hours as one cycle, even if the environmental temperature of the optical element module changes, the optical loss varies greatly as in the conventional optical element module. That was gone.

  This is because the primary coated optical fiber for optical input and the pipe through which the primary coated optical fiber is inserted even if the environmental temperature becomes low and the housing of the primary coated optical fiber or the optical element module contracts. This is because the structure has a loose structure, so that no stretching stress is generated on the optical fiber, and as a result, no increase in optical loss occurs.

  In this embodiment, a primary coated optical fiber is used as an optical fiber for light input. However, when a primary coated optical fiber is used as an optical fiber for light output, the primary coated optical fiber is provided on a rubber boot. It is desirable to let it pass through a pipe. Moreover, although the optical waveguide chip is taken as an example of the optical element installed inside the housing, the same effect can be obtained with an optical semiconductor light emitting element or a light receiving element.

(Embodiment 2)
Examples of embodiments of the present invention are shown in FIG. 10, FIG. 11, FIG. 12, and FIG. 10 is a plan sectional view of the optical element module, FIG. 11 is a sectional view taken along line AA ′ in FIG. 10, FIG. 12 is a sectional view taken along line CC ′ in FIG. 10, and FIG. It is sectional drawing in the -D 'line. FIG. 10 is a cross-sectional view taken along line BB ′ in FIG. 10, 11, 12, and 13, 1 is an optical element module, 5 is an optical waveguide protection plate, 7 is an optical waveguide chip as an optical element, 21 is a primary coated optical fiber, 22 is a tape optical fiber, 23a and 23b are rubber boots, 24 is a pipe, 25a and 25b are optical fiber holding portions, 27 is a lower housing, 28 is an upper housing, and 29 is a primary coated optical fiber.

  The difference from the first embodiment is that the optical waveguide chip has two optical inputs and eight optical outputs. The two optical inputs are used for the purpose of, for example, a redundant configuration in which one is used for current and the other for backup, or one is used for signals and the other is used for testing at different wavelengths.

  In this embodiment, two primary coated optical fibers are used for light input. As in the first embodiment, the two primary-coated optical fibers are inserted through the pipe 24 provided in the rubber boot. The inner diameter of the pipe 24 is made larger than the outer diameter of the primary coated optical fiber 21. For example, with respect to the outer diameter of the primary coated optical fiber of 250 μm, a pipe having a short diameter of 0.5 mm, a long diameter of 1 mm and an elliptical cross section is preferable. The length of the pipe 24 is set to be longer than the length of the through hole of the rubber boot 23a in consideration of bending of the primary coated optical fiber inserted through the pipe 24 due to handling or the like. For example, it is preferable that the rubber boot 23a protrudes about 1 mm inside the optical element module and protrudes about 5 mm outside the optical element module.

  Also, for light output, two four-core tape optical fibers are used to obtain eight light outputs. That is, at one end, four optical fiber ribbons are stacked in two stages, and at the connection side with the optical waveguide chip, the two optical fiber ribbons are alternately assembled in a primary coating state, and are arranged in a row in the V groove. An arrayed conversion optical fiber is used. In the array conversion optical fiber, the array pitch of the optical fibers at the connection portion with the optical waveguide chip is narrowed to 125 μm corresponding to the outer diameter of the bare optical fiber. Therefore, the waveguide interval of the corresponding optical waveguide is also reduced, so that the optical waveguide chip can be reduced in size, and consequently the optical element module can be reduced in size. Instead of the array conversion optical fiber, the secondary coating of the 8-fiber optical tape fiber can be removed to form a primary coating optical fiber, which can be connected to the optical waveguide chip.

  A temperature cycle test was performed on the optical element module thus obtained. The test results are the same as in FIG. As a result of performing a temperature cycle from −40 ° C. to + 75 ° C. with 8 hours as one cycle, even if the environmental temperature of the optical element module fluctuates, the optical loss greatly fluctuates as in the conventional optical element module. That was gone.

  In this embodiment, a primary coated optical fiber is used as an optical fiber for light input. However, when a primary coated optical fiber is used as an optical fiber for light output, the primary coated optical fiber is provided in a rubber boot. It is good also as letting it pass through a pipe. Moreover, although the optical waveguide chip is taken as an example of the optical element installed inside the housing, the same effect can be obtained with an optical semiconductor light emitting element or a light receiving element.

(Embodiment 3)
In this embodiment, the gel-like material is filled into the internal space of the optical element module described in the first or second embodiment. For example, in FIGS. 10 and 11, the gel material 41 is filled in the internal space of the optical element module 1. By filling the gel material, the resistance to mechanical stress such as vibration and impact applied to the optical element module is improved.

  On the other hand, the gap between the primary coated optical fiber 21 and the pipe 24 is not normally leaked due to the surface tension of the gel material, but the ambient temperature fluctuates, and the expansion and contraction of the housing and the gel When the expansion and contraction of the materials do not match, for example, when the expansion of the gel-like material is larger than the expansion of the casing, or when the contraction of the gel-like material is smaller than the contraction of the casing, the gel-like material of the casing Leakage occurs between the primary coated optical fiber 21 and the pipe 24.

  Therefore, the difference between the volume of the gel-like material and the volume of the internal gap of the optical element module that occur with the fluctuation of the environmental temperature is set to be smaller than the volume between the pipe 24 and the primary coated optical fiber 21. It is preferable to do. With such a setting, even if the volume of the gel-like material expands or contracts as the environmental temperature fluctuates, the gel-like material advances in the space between the pipe 24 and the primary coated optical fiber 21. The gel-like material will not leak even if the ambient temperature fluctuates simply by retreating or retreating.

  The inner space of the optical element module described in Embodiment 1 may be filled with a gel material. Also in this case, the difference between the volume of the gel-like material and the volume of the internal air gap of the optical element module generated with the fluctuation of the environmental temperature is made smaller than the volume between the pipe and the primary coated optical fiber. It is preferable to set.

  The optical element module according to the present invention can be used for optical fiber communication.

It is sectional drawing explaining the structure of the conventional optical element module. It is a figure explaining the kind of optical fiber demonstrated by this application. It is a figure explaining the kind of optical fiber demonstrated by this application. It is a temperature cycle test result when the optical fiber for light input is made into the primary coating in the conventional optical element module. It is sectional drawing of the optical element module which is the embodiment of this invention. It is sectional drawing of the optical element module which is the embodiment of this invention. It is sectional drawing of the optical element module which is the embodiment of this invention. It is sectional drawing of the optical element module which is the embodiment of this invention. It is a temperature cycle test result of the optical element module which is the embodiment of the present invention. It is sectional drawing of the optical element module which is the other embodiment of this invention. It is sectional drawing of the optical element module which is the other embodiment of this invention. It is sectional drawing of the optical element module which is the other embodiment of this invention. It is sectional drawing of the optical element module which is the other embodiment of this invention.

Explanation of symbols

1: Optical element module 5: Optical waveguide protective plate 7: Optical waveguide chip 21: Primary coated optical fiber 22: Tape optical fiber 23a: Rubber boot 23b: Rubber boot 24: Pipe 25a: Optical fiber holding portion 25b: Optical fiber holding portion 26 : Internal gap 27 of optical element module: Lower housing 28: Upper housing 29: Primary coated optical fiber 30a: Optical fiber core 30b: Optical fiber cladding 31: Primary coating 32: Secondary coating 33: Secondary coating 41 for forming a tape fiber: Gel-like material 50: Optical element module 51: Housing 52: Optical waveguide protection plates 53a, 53b covering the optical waveguide: Optical fiber holder 54: Optical fiber core wire 55: Bare Optical fiber 56: Tape optical fiber 57: Bare optical fiber 58, 59: Adhesive fixing part

Claims (3)

A housing,
An optical element fixed to the bottom surface inside the housing;
A pipe that is electrically connected to the outside and the inside of the housing and fixed to one end of the housing;
A primary coated optical fiber inserted through the pipe and connected to the optical element and held movably within the pipe with a diameter smaller than the diameter of the pipe;
A tape optical fiber connected to the optical element, having a primary coating layer and a secondary coating layer, wherein the outermost secondary coating layer is fixed to the other end of the housing;
An optical element module comprising: The pipe is fixed to one end of the housing via a first rubber boot;
The optical element module according to claim 1, wherein the tape optical fiber is bonded and fixed to the other end of the housing via a second rubber boot.   The optical element module according to claim 1, wherein a gel material is filled in an internal space of the optical element module.

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