JP2007249099A - Method of manufacturing optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a core end of a self-forming optical waveguide having a branch, at a position as designed. <P>SOLUTION: A wavelength selective mirror 30 is erected inside a transparent housing 10, with an optical fiber 20 inserted and filled with photo setting resin liquid 40 (4.A). The photo setting resin liquid 40 is irradiated with a laser beam λ<SB>w</SB>through the optical fiber 20 and hardened self-convergently to form a core 41. The core 41 grows to reach the wavelength selective mirror 30, with a part continued to grow along the reflected light downward as a core 41rf, and with a part along the transmitted light to the right as a core 41th (4.B). Before the core 41th reaching an optical port P3, the laser beam λ<SB>w</SB>is also introduced from the optical port P3 to an optical port P1, making the core start to grow also from the optical port P3, and making it integrated with the core 41th that passed through the wavelength selective mirror 30. Optical loss is found ≤0.3 dB at the junction between the core grown from the optical port P3 and the core 41th passed through the wavelength selective mirror 30. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a branched optical waveguide (optical module) that uses light of a plurality of wavelengths and uses a total of two or more light emitting elements and light receiving elements.

In a local area LAN or the like by optical communication, a demultiplexing / multiplexing device is used to transmit a plurality of signals by wavelength multiplexing using a single optical fiber. For example, for the two communication wavelengths λ ₁ and λ ₂ , transmission from the central device (server) side to each terminal (client) side is performed at wavelength λ ₁ and transmission from each terminal (client) to the central device (server) is performed. Assume that the operation is performed at a wavelength λ ₂ . In this case, in each of the central unit (server) side and the terminal (client), the use of demultiplexing and multiplexing device, one connected by optical fiber, and to separate the communication wavelength lambda ₁ and lambda ₂ It is possible to send and receive. Such a demultiplexing / multiplexing device has three ports: an optical port for connecting an optical fiber, an optical port with a wavelength λ _{1, and} an optical port with a wavelength λ ₂ , a wavelength λ ₁ , a wavelength λ ₂ , Therefore, it is assumed that wavelength selective mirrors (light interference filters) having different reflection / transmittance are used. The wavelength selective mirror (light interference filter) can be composed of a dielectric multilayer film, and the degree of freedom in setting the wavelength transmittance characteristic (wavelength reflectance characteristic) is high. An optical module including an optical fiber, a light emitting element, and a light receiving element using such a wavelength selective mirror (optical interference filter) having different reflection / transmittance at the wavelength λ ₁ and the wavelength λ ₂ is provided. They have proposed as the following patent document 1.

In addition, the present inventors have proposed a number of self-forming optical waveguides and their manufacturing methods suitable for, for example, the production of the optical module, and have filed patent applications as shown in Patent Documents 2 to 4 below.
JP-A-11-326660 JP 2002-365594 A JP 2004-1499579 A JP 2004-151160 A JP-A-8-320422

When the optical module as described above is manufactured, the wavelength-selective mirror (optical interference filter) has a transmittance of, for example, 50% at the curing wavelength λ _w in order to cure the photocurable resin in a self-collecting manner. The core is formed by photocuring each branch in a self-forming manner with a reflectance of 50%. In other words, when forming an optical waveguide connecting three optical ports by one branch point, light of curing wavelength is introduced from one optical port, and the core is grown to the wavelength selective mirror that is the branch point. The core is grown on one branch by the light transmitted from the branch point and the other branch is grown on the other branch by the reflected light, and the remaining two optical ports are grown.

  However, the end point of the core growth by “self-forming” photocuring does not reach the position as designed, and the design and the optical axis may deviate. In this case, for example, if the optical axis is not aligned when the light emitting / receiving element is assembled to the optical port, the coupling loss may become very large. The optical axis alignment takes work time, and depending on the element to be assembled, the optical axis alignment itself is difficult.

  On the other hand, as in Patent Document 5, there is a technique for joining the cores of an optical waveguide by bidirectional irradiation. However, the description in Patent Document 5 does not clearly indicate that the branch can be applied to the waveguide. Further, there is no mention of specific resins or wavelength selective mirrors. Furthermore, there is no description as to how much light loss is caused by the “waste part of the core” as described below.

  An object of the present invention is to form a self-forming optical waveguide core with high accuracy at a formation position of a light emitting / receiving element or the like in a method of manufacturing an optical module by curing a photocurable resin in a self-collecting manner.

  The invention according to claim 1 is a method of manufacturing an optical module having an optical waveguide obtained by self-condensing a photocurable resin and a branch using at least one wavelength-selective mirror. The mirror has a reflectance of 90% or more with respect to at least one communication wavelength and a transmittance of 90% or more with respect to at least one other communication wavelength, and is a photocurable resin for forming an optical waveguide. For the curing wavelength, the transmittance and the reflectance are each 20% or more, and the photocuring is performed from the position where two or more optical ports are to be formed among the three or more optical ports that the optical module should have. A method for producing an optical module, wherein a cured photocured resin that grows in a self-condensing manner is made to be integrated in the vicinity of a wavelength-selective mirror by allowing light of a curing wavelength to enter the photosensitive resin It is. In this specification, the wavelength-selective mirror and the optical interference filter are synonymous, ignoring the optical loss when passing through it, and adding the transmittance and reflectance to any wavelength is 1 (100%).

  The invention according to claim 2 is characterized in that at least one of the optical ports that the optical module should have is realized by bringing the core end of the optical fiber into contact with the photocurable resin. This means that the core end of the optical fiber is brought into contact with the core of the optical fiber when the core is formed, and the core end of the optical fiber is directly connected to the core that is a cured photocurable resin.

  Since the core begins to grow from the optical port introduced with light having a wavelength for curing the photocurable resin liquid, the optical axis of the formed core and the optical axis of the optical port in the optical port introduced with the curing wavelength light are Must match. Therefore, when manufacturing an optical module having a branch and having three or more optical ports, if the curing wavelength light is introduced from a plurality of optical ports, the core starts to grow from a plurality of locations. In the plurality of optical ports into which the curing wavelength light is introduced, the optical axis of the formed core is manufactured as designed, and when the light receiving and emitting elements are assembled, the optical axes always coincide.

  The wavelength selective mirror (optical interference filter) used in the present invention has a reflectance of 90% or more for at least one communication wavelength and a transmittance of 90% or more for at least one other communication wavelength. desirable. More preferably, the reflectivity is 95% or more for at least one communication wavelength, and the transmittance is 95% or more for at least one other communication wavelength, and more preferably, for at least one communication wavelength. The reflectance is 97% or more with respect to the wavelength, and the transmittance is 97% or more with respect to at least one other communication wavelength.

  In addition, the wavelength selective mirror (light interference filter) is essentially not required to have a transmittance of 0% with respect to the curing wavelength of the photocurable resin for forming the core of the optical waveguide. Actually, if the transmittance is less than 20%, the amount of light transmitted through the wavelength selective mirror (optical interference filter) is small, so that the optical waveguide does not grow sufficiently, and the cured core cannot be integrated. The optical axis remains misaligned. Therefore, it is substantially desirable that the transmittance and the reflectance are each 20% or more with respect to the curing wavelength of the photocurable resin for forming the optical waveguide. More desirably, the transmittance and the reflectance are each 30% or more, and further desirably, the transmittance and the reflectance are each 40% or more.

  As the photocurable resin, any material, any polymerization mechanism (curing mechanism), and photopolymerization initiator can be used depending on the selection of the wavelength of the light source and the design of the wavelength selective mirror (light interference filter). Of course, a mixture may be used. Preferably, it is liquid before curing (before photopolymerization). When the core material is formed and then the uncured photocurable resin is removed and then the clad material is filled and cured, the curing mechanism of the clad material is not limited to photocuring. For example, a thermosetting resin may be used.

First, the essence of the present invention will be described with reference to FIGS. FIG. A is a method of inserting one end of two optical fibers OF1 and OF2 into a photocurable resin liquid, and introducing light having a wavelength capable of curing the photocurable resin liquid from the other end, FIG. 3 is a diagram in which cores C1 and C2 are grown by self-condensing the liquid. FIG. In A, the two optical fibers OF1 and OF2 indicate that their optical axes ax1 and ax2 are parallel to the x-axis direction and are shifted by a distance d. Further, it is assumed that a total reflection mirror M ₁ or a semi-transmission semi-reflection mirror M ₂ is arranged in parallel with the plane y = −x between the two optical fibers OF 1 and OF ₂ . By the transflective mirror M ₂ , the traveling direction of the light from the optical fiber OF1 is partially bent from the positive direction of the x axis to the negative direction of the y axis, and the traveling direction of the light of the optical fiber OF2 is the x axis. It is bent from the negative direction partially in the positive direction of the y-axis. These are shown as ax1 and ax2, respectively.

When the total reflection mirror M ₁ is between the two optical fibers OF 1 and OF 2, the curing wavelength light from the optical fiber OF ₁ is not transmitted to the right side through the total reflection mirror M ₁ , and the light from the optical fiber OF 2 is not transmitted. The curing wavelength light is not transmitted to the left side. Then, the core C1 and C2 is formed by each of the curing wavelength light, because it is formed only by the reach of the respective optical, optical axes of the curing wavelength light from the optical fiber OF1 in the lower left area of the total reflection mirror M ₁ is formed along the ax1 (C1rf), it is formed along the optical axis ax2 of the curing wavelength light from the optical fiber OF2 in the upper right area of the total reflection mirror M ₁ (C2rf). That is, total reflection at the lower left area of the mirror M ₁ has no continuity with the core C2 from the optical fiber OF2, remains the optical axis was shifted, core C1 from the optical fiber OF1 in top right area of the total reflection mirror M ₁ And the optical axis remains misaligned (FIG. 1.B). Then, with respect to the formed optical waveguide, for example by using light of a wavelength that is transmitted through the mirror M _1, also the optical fiber OF1 and the optical fiber OF2 as trying to connect through the core C1 and C2, optical loss growing.

Unlike this, when the optical fiber OF1 and OF2 are between the semi-transmissive and semi-reflective mirror M ₂ , the curing wavelength light from the optical fiber OF1 is partially transmitted to the right side (C1th) and cured from the optical fiber OF2. The wavelength light is partially transmitted to the left side (C2th). Thereby, the reach of each light is shown in FIG. C overlaps as C1 and C2th, C2 and C1th, and the curing range widens on the left and right of the transflective mirror M ₂ (partly thick core is formed). That is, the optical waveguide OWG in which the photocurable resin liquid is cured is shown in FIG. As shown in D, a thick portion L ₁ is formed on the left side of the transflective mirror M ₂ and a thick portion L ₂ is formed on the right side, and the left and right cores of the transflective mirror M ₂ have continuity. Thus, the mirror M ₂ by using the total transmission wavelength light, when connecting the optical fiber OF1 and the optical fiber OF2 through the core C1 and C2, the optical loss is reduced. Thus, the four-way core can be highly continuous.

Above are the same when arranging the two optical fibers OF1 and OF2 the left and lower side of the transflective mirror M _2. FIG. As in A, the optical axis ax1 of the optical fiber OF is parallel to the x-axis direction, the curing light is irradiated in the positive direction of the x-axis, and the optical axis ax2 of the optical fiber OF2 is parallel to the y-axis direction. Then, it is assumed that the curing light is irradiated in the positive direction of the y-axis. Light from the optical fiber OF1 by transflective mirror M ₂ is partially bent in the negative direction of the y-axis, light from the optical fiber OF2 is bent portion in the negative direction of the x-axis. Also in this figure, the optical axis ax1 of the optical fiber OF and the optical axis ax2 of the optical fiber OF2 are shifted by a distance d.

As the cured cores C1 and C2 grow in this way, the respective curing ranges are shown in FIG. B overlaps like C1 and C2rf, C2 and C1rf, and the curing range is expanded. Thus, FIG. As in C, the optical waveguide OWG has a thick portion L ₁ on the left side of the transflective mirror M ₂ and a thick portion L ₂ on the lower side, and the left and lower cores of the transflective mirror M ₂ are It will have continuity. Thus, the mirror M ₂ by using the total reflection wavelength light, when connecting the optical fiber OF1 and the optical fiber OF2 through the core C1 and C2, the optical loss is reduced. Thus, the four-way core can be highly continuous.

  A branched optical waveguide was created as follows, and the effect of the present invention was confirmed. First, a wavelength selective mirror 30 shown in FIG. 3 was prepared. Incidentally, this is when a light beam having a full width at half maximum of FFP of 32 degrees is incident on the wavelength selective mirror from the direction of 45 degrees, and is an average value of transmittance for each of S waves and P waves. The wavelength-selective mirror 30 has a transmittance of 10% or less at a visible portion having a wavelength of 480 nm or more and 660 nm or less, and a transmittance of 90% or more at a near infrared portion having a wavelength of 750 nm or more. Further, of the respective curing wavelengths of the two photocurable resin liquids shown below, the transmittance at 457 nm is 44% (that is, the reflectance is 56%), and the transmittance at 488 nm is 3% (that is, the reflectance is). 97%).

First, FIG. As shown in A, a plastic with a core diameter of 1 mm is provided so that a wavelength-selective mirror 30 is erected inside a transparent acrylic casing 10 and light is irradiated from a direction of 45 degrees to the surface of the wavelength-selective mirror 30. The optical fiber 20 was inserted into the side wall of the housing 10. The core end of the optical fiber 20 is defined as an optical port P1. As the optical fiber 20, Eska-MEGA manufactured by Mitsubishi Rayon was used. Next, the case 10 was filled with a photocurable resin liquid 40. As the photocurable resin liquid 40, 100 parts of Toagosei acrylic monomer M-210 and 0.5 part of Ciba Specialty Chemicals IRGACURE819 as a photopolymerization initiator were used. Next, FIG. As in B, the core 41 was formed by irradiating the photocurable resin liquid 40 with laser light λ _w having a central wavelength of 457 nm through the optical fiber 20 and curing it in a self-condensing manner. The core 41 grows and reaches the wavelength selective mirror 30, partly along the reflected light as the core 41 rf in the lower direction in the drawing, and partly along the transmitted light as the core 41 th in the right direction on the drawing. Continued to grow. Here, FIG. The positions indicated by B as optical ports P2 and P3 are the design growth end points that the cores 41rf and 41th should reach.

Here, before the core 41th reaches the optical port P3, the laser light λ _w having a wavelength of 457 nm was also introduced from the optical port P3 toward the optical port P1. In this way, the growth of the core was started also from the optical port P3, and was combined with the core 41th that passed through the wavelength selective mirror 30. Thus, the laser irradiation was stopped when the core 41rf reached the optical port P2. The cured product of the photocurable resin includes a core 41 reaching the wavelength selective mirror 30 from the optical port P1, a core 42 reaching the optical port P2 from the wavelength selective mirror 30, and a core connecting the wavelength selective mirror 30 and the optical port P3. 43 and a core 43rf extending from the wavelength selective mirror 30 in the upward direction in the drawing along the light partially reflected by the wavelength selective mirror 30 from the optical port P3. These four cores were formed with good continuity. Three such optical modules are prepared, and a laser having a wavelength of 780 nm that is transmitted through the wavelength selective mirror 30 by 90% or more is irradiated from the optical port P3, and the optical intensity at the other end of the optical fiber 20 connected to the optical port P1. The optical loss was as good as 0.6 dBm to 0.9 dBm and an average of 0.7 dBm. The optical loss at the connection point between the core grown from the optical port P3 and the core 41th transmitted through the wavelength selective mirror 30 was 0.3 dB or less.

[Comparative example]
In the examples, optical modules were similarly prepared with a curing wavelength of 488 nm and 20 mW. Since the transmittance of the wavelength selective mirror 30 is 3% at the wavelength of 488 nm, the core 41th is not formed, and the core 43 is formed only by the curing light from the optical port P3. Three optical modules according to such a comparative example are prepared, and a laser having a wavelength of 780 nm that transmits 90% or more of the wavelength selective mirror 30 is irradiated from the optical port P3, and the other optical fiber 20 connected to the optical port P1. When the light intensity was measured at the end, the optical loss was 1.7 dBm to 2.9 dBm, and the average was 2.5 dBm. That is, compared to the example in which the core is formed by using the wavelength selective mirror that is semitransparent and semi-reflective with respect to the curing light, in the comparative example, the continuity of the core is poor. It was found that optical loss occurred before and after.

[Modification]
In the above embodiment, a configuration in which three optical ports are perpendicular to each surface (side in the sectional view) with respect to the casing 10 having a square section is shown in FIG. It may be an oblique direction such as A. In the above embodiment, the curing light is irradiated from the optical ports P1 and P3. However, the curing light may be irradiated from the optical ports P1 and P2, or the curing light may be irradiated from the optical ports P1, P2, and P3 (FIG. 5). B). The above is an optical module having one branch and three ports, but the present application can be applied to an optical module having an arbitrary number of optical ports, number of branches, or input / output. For example, FIG. Like C, it is good also as a structure which irradiates hardening light from 2 ports or more of the optical module which has two branch points (wavelength selective mirrors 31 and 32) and 4 ports (P1, P2, P3, P4). When light is irradiated from all four ports, a hardened core is formed by the light transmitted through the wavelength selective mirrors 31 and 32 from the optical ports P2 and P3, such as 42th and 43th, but as shown above, The optical loss due to the useless core part is very small.

The conceptual diagram which shows the effect of this invention. The another conceptual diagram which shows the effect of this invention. The graph which shows the wavelength transmittance characteristic of the wavelength selective mirror used for the Example. Sectional drawing which shows the process of an Example. Sectional drawing which shows a modification.

Explanation of symbols

10: Housing 20: Optical fiber 30, 31, 32, M, M ₂ : Wavelength selective mirror 40: Uncured photocurable resin liquid 41, 41rf, 41th, 42, 43: Photocured resin cured product Core P1, P2, P3: Optical port

Claims (2)

An optical waveguide having a photocuring resin cured in a self-collecting manner, and a method of manufacturing an optical module having a branch using at least one wavelength selective mirror,
The wavelength selective mirror is:
90% or more reflectivity for at least one communication wavelength,
The transmittance is 90% or more with respect to at least one other communication wavelength,
For the curing wavelength of the photocurable resin for forming the optical waveguide, the transmittance and the reflectance are each 20% or more,
Of the three or more optical ports that the optical module should have,
From the planned formation position of two or more optical ports,
The light having the curing wavelength is incident on the photocurable resin,
A method for producing an optical module, wherein the cured photocurable resin that grows in a self-collecting manner is formed so as to be integrated in the vicinity of the wavelength selective mirror. The optical module manufacturing method according to claim 1, wherein at least one of the optical ports that the optical module should have is realized by bringing a core end of an optical fiber into contact with the photocurable resin. Method.

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