JP2008046178A - Holder for connecting optical fiber and connecting method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably hold the ends of a pair of optical fibers to be connected by a self-forming optical waveguide technique, in a state in which axial shift and angular deviation are hardly caused, and to facilitate connection without requiring any fine adjustment. <P>SOLUTION: Simple connection of a pair of optical fibers by a self-forming optical waveguide technique is made possible by using a holder 10 for connecting optical fibers, without requiring any fine adjustment. This holder 10 is composed of a transparent material that transmits light with a wavelength for curing a photosetting resin, and provided with: a through hole 11 which has a fitting tolerance capable of limiting, within a specific range, the axial shift and angular deviation of a pair of optical fibers, with each end inserted from both sides of the holder; and a resin pouring hole 12 which is arranged so as to cross the through hole 11, and has a size capable of retaining a mixed liquid of the photosetting resin by a quantity to such an extent that a self-forming optical waveguide can be formed between the ends of the optical fibers. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for connecting optical fibers by a self-forming optical waveguide technique.

  In the self-forming optical waveguide technology, a core part and a clad part are formed between first ends of a pair of optical fibers to be connected by first and second photocurable resins having different refractive indexes after curing. Simple optical connection is possible (see Patent Documents 1, 2, and 3).

  Specifically, a mixed solution of the first and second photocurable resins is filled between one end of each optical fiber opposed to each other with a predetermined gap, and the second end of at least one optical fiber is filled with the first. A light having a wavelength for curing the photocurable resin of 1 is incident to form a core portion, and then the second photocurable resin is cured near one end of each optical fiber filled with the mixed solution. At least one of the optical fibers is filled with a first photo-curing resin solution between one end of each of the optical fibers facing each other with a predetermined gap. The light of the wavelength for hardening of the first photocurable resin is incident from the other end of the optical fiber to form the core portion, and then the first photocurable resin solution is removed from between the ends of the optical fibers. And filling the second photocurable resin solution with the second photocurable resin. There is for forming a clad portion by irradiating light having a wavelength for curing the second light curing resin in the vicinity of one ends of the optical fibers filled.

Conventionally, when optical fibers are connected to each other by the self-forming optical waveguide technique described above, one end of a pair of optical fibers to be connected is held by a holding means including a V-groove substrate and a pressing plate for fixing the optical fiber to the substrate. Each solution or mixed solution of the first and second photocurable resins is held in a liquid reservoir portion that is held at a position where one end of the optical fiber of the substrate is opposed to each other with a predetermined gap therebetween. The solution of each of the first and second photocurable resins or the mixed solution was filled between the one ends.
Japanese Patent Laid-Open No. 5-127028 Japanese Patent Laid-Open No. 9-5544 JP 2006-106472 A

  However, in the case of the holding means using the above-described V-groove substrate, the position of the optical fiber pressed by the pressing plate is outside the above-described liquid reservoir, that is, slightly away from one end to which the optical fiber is to be connected. It is difficult to stably hold one end of the optical fiber in a state in which almost no axial deviation or angular deviation that causes connection loss occurs (particularly when the solution is dropped or injected) The optical fiber may float up and cause an axis deviation or an angle deviation.) When connecting, it was necessary to make fine adjustments many times.

  The object of the present invention is to stably hold one end of a pair of optical fibers to be connected by self-forming optical waveguide technology in a state in which almost no axial deviation and angular deviation occur, and requires some fine adjustment. It is an object of the present invention to provide an optical fiber holding means that can be easily connected without using a connection method, and a connection method using the optical fiber holding means.

  In the present invention, in order to solve the above-described problem, at least a pair of transparent materials that can sufficiently transmit light having a wavelength for curing the second photocurable resin for forming the clad portion and that are to be connected from both sides. A through-hole having a fitting tolerance capable of inserting an axial deviation and an angular deviation between the pair of optical fibers within a certain range in a state where one end of each of the optical fibers is inserted and opposed with a predetermined gap therebetween. And a first photo-curable resin for forming a core part, which is provided at a portion where the ends of the pair of optical fibers of the through hole face each other so as to intersect the through hole, and has a different refractive index after curing, and Hold the mixed solution of the second photo-curing resin for forming the clad part in such an amount that a self-forming optical waveguide can be formed between the ends of the pair of optical fibers facing each other with the predetermined gap therebetween. Has a possible size Using an optical fiber connection holder, characterized in that a resin injection hole.

  The optical fiber connection using the optical fiber connection holder described above is performed by inserting one end of a pair of optical fibers to be connected from both sides of the through hole of the optical fiber connection holder. 2 is injected into the resin injection hole of the optical fiber connection holder, and light having a wavelength for curing the first photocurable resin is incident from the other end of at least one of the optical fibers. The core portion is formed, and the cladding portion is formed by irradiating light having a wavelength for curing the second photocurable resin in the vicinity of the resin injection hole of the optical fiber connection holder.

  At this time, after injecting the mixed solution of the first and second photocurable resins into the resin injection hole of the optical fiber connection holder, one end of the pair of optical fibers to be connected is connected to the optical fiber connection respectively. You may make it insert from both sides of the through-hole of a holder.

  According to the present invention, by inserting one end of each of the pair of optical fibers to be connected from both sides of the through hole of the optical fiber connection holder and facing each other with a predetermined gap therebetween, Since it is possible to stably hold the shaft deviation and angle deviation within a certain range, no fine adjustment is required for connection. Further, in this state, only by injecting into the resin injection hole a mixed solution of the first photocurable resin for forming the core portion and the second photocurable resin for forming the clad portion having different refractive indexes after curing, The mixed solution of the first and second photocurable resins can be filled between the one ends, and thereafter the photocurable resin is cured similarly to the case of connection by the conventional self-forming optical waveguide technology. A pair of optical fibers can be easily connected by forming the core part and the clad part using light of a wavelength for the purpose.

  Further, as the resin injection hole of the optical fiber connection holder, a bottomed hole having an inner diameter substantially the same as the predetermined gap and a depth exceeding at least the through hole, or an inner diameter substantially the same as the predetermined gap Or a slit having a width substantially the same as the predetermined gap and at least a depth reaching the through hole, and a pair of optical fibers than in the case of a holding means using a V-groove substrate. Can be connected by a small amount of photo-curing resin, and the overall size can be reduced.

  1A and 1B show a first embodiment of an optical fiber connecting holder according to the present invention. FIG. 1A is a front view, and FIG. 1B is a side view (end view).

  The optical fiber connection holder of the present embodiment, for example, 10 is made of a transparent material having a substantially cylindrical shape that can sufficiently transmit at least light having a wavelength for curing the second photocurable resin for forming the cladding part. It has a through hole 11 and a resin injection hole 12.

  Here, the wavelength for curing the photocurable resin varies depending on the composition of the photocurable resin, but the wavelength for curing the first photocurable resin for forming the core part is about 406 nm, Ultraviolet rays having a wavelength of about 360 nm are used as the wavelength for curing the second photocurable resin for forming the clad portion, and examples of the transparent material that sufficiently transmits light having these wavelengths include quartz glass and ultraviolet transmissive acrylic. It is done.

  The through-hole 11 is opposed to the outer diameter of the optical fiber to be connected (strictly speaking, the optical fiber strand from which the coating has been removed) by inserting one end of each of the pair of optical fibers from both sides with a predetermined gap therebetween. In this state, the holder 10 is provided along the central axis of the holder 10 so as to have an inner diameter of a fitting tolerance capable of keeping the axial deviation and the angular deviation between the pair of optical fibers within a certain range.

  The resin injection hole 12 is orthogonal to the through hole 11 at a portion where the ends of the pair of optical fibers of the through hole 11 face each other, here, in the vicinity of the center of the optical fiber connecting holder 10 in the longitudinal direction. The provided mixed solution of the first photocurable resin for forming the core part and the second photocurable resin for forming the clad part having different refractive indexes after curing is opposed to each other with the predetermined gap therebetween. A hole having a size capable of holding an amount capable of forming a self-forming optical waveguide between one end of a pair of optical fibers in a closed state, here, an inner diameter substantially similar to the predetermined gap, and the through hole 11 It consists of a bottomed hole with a depth that is slightly over.

  Next, the above-mentioned “fitting tolerance capable of keeping the axial deviation and the angular deviation within a certain range” will be examined.

The relationship between the amount of axial deviation d and the connection loss α in the optical fiber connection is as follows.
α = -10 log (T) (1)
However, T = exp [−d ² / w ² ]
As shown in FIG. 2 (for example, D. MARCUSE, “Loss Analysis of Single-Mode Fiber Splices”, THE BELL SYSTEM TECHNICAL JOURNAL, Vol. 56, No. 5, 1977, American Telephone and Telegraph Company, pp.703-718).

  Currently, single-mode fiber connection methods used include fusion, connector, and mechanical splice, all of which achieve a connection loss of 0.5 dB or less. In order to realize the connection loss of 0.5 dB or less, it can be seen from FIG. 2 that the axis deviation d needs to be suppressed to 1.6 μm or less.

In addition, one end of a pair of optical fibers to be connected from both sides is inserted into the through hole 11 of the optical fiber connection holder 10, and the insertion length for one of the optical fibers is L. Then, when the inner diameter of the through hole 11 has the above-described axis deviation amount (axial deviation tolerance d), the maximum angle deviation amount θ generated in the inserted optical fiber is understood from FIG. θ = arctan (d / L) (2)
It becomes.

The relationship between the connection loss angle shift amount θ in the optical fiber connection α is, n ₂ the refractive index of the cladding, when the communication wavelength and lambda,
α = -10log (T) (3)
However, T = exp [− (wπn ₂ θ) ² / λ ² ]
(See, for example, D. MARCUSE, "Loss Analysis of Single-Mode Fiber Splices", THE BELL SYSTEM TECHNICAL JOURNAL, Vol. 56, No. 5, 1977, American Telephone and Telegraph Company, pp.703-718.) ).

  From the above formulas (2) and (3), the amount of angular deviation θ when the optical fiber is inserted into the through-hole 11 having an axis deviation amount (allowable axis deviation) d of 1.6 μm and an insertion length L of 3 mm is 0. .0005 °, and when the insertion length L is 10 mm, the angle deviation amount θ is 0.00016 °, which is twice the maximum between a pair of optical fibers to be connected. In connection, the amount of angular deviation that achieves a connection loss of 0.5 dB or less is 0.0074 ° or less, and the above-described angle deviation amount is a value that can be sufficiently ignored in consideration of the connection loss.

  Therefore, when the outer diameter of the optical fiber (optical fiber strand) to be connected is 125 μm, if the inner diameter of the through-hole 11 of the optical fiber connection holder 10 is 125 μm or more and 126.6 μm, the axis deviation and angle It is possible to keep the loss due to the shift to 0.5 dB or less.

  FIG. 4 shows an optical fiber connection process using the optical fiber connection holder of FIG. 1, and hereinafter, an example of connecting single mode fibers (SMF) to each other as an example, the optical fiber connection method of the present invention. Will be described. In addition, here, for easy understanding, the optical fiber connection holder is represented by its cross section.

  First, as shown in FIG. 4 (a), one end of a pair of SMFs (optical fiber cores) 20 and 30 from which the coating is removed and the optical fiber strands 21 and 31 are exposed is held for optical fiber connection. It inserts from the both sides of the through-hole 11 of the tool 10, and opposes it through the resin injection hole 12 with a predetermined gap. At this time, if the length for removing the coating of each of the SMFs 20 and 30 is set to approximately ½ of the length obtained by subtracting the predetermined gap from the total length of the optical fiber connecting holder 10, the strand portion is penetrated. Positioning is possible only by inserting from both sides of the hole 11 and bringing the core portion into contact with the end face of the optical fiber connecting holder 10.

  Although the through hole 11 of the optical fiber connection holder 10 and the SMFs 20 and 30 (the optical fiber strands 21 and 31) are actually in close contact with each other with little gap, it is easy to understand in FIG. In order to do so, both are drawn apart.

  Next, as shown in FIG. 4B, two types of photocurable resins prepared in advance and adjusted in refractive index after curing and curing start wavelength (reaction wavelength), that is, a first for forming a core part. A mixed solution 40 containing a photocurable resin and a second photocurable resin for forming a cladding portion is injected into the resin injection hole 12 of the optical fiber connection holder 10, and between the ends of the SMFs 20 and 30. To fill.

Examples of resin materials for the first and second photocurable resins include acrylic, epoxy, oxetane, and vinyl ether. Here, the adjustment of the refractive index after curing may be any value before the curing, but the refractive index n1 after curing of the first photocurable resin and the curing of the second photocurable resin. The subsequent refractive index n2 is
n1> n2
It means to adjust to meet the condition of. Further, the adjustment of the curing start wavelength means that only the first curable resin starts the curing reaction by the light having the wavelength for forming the core part, and only the second curable resin is made by the light having the wavelength for forming the cladding part. It refers to selecting the resin materials of the first and second photocurable resins so as to start the curing reaction.

  After injecting the mixed solution 40 of the first and second photocurable resins into the resin injection hole 12 of the optical fiber connection holder 10, one end of the SMF 20, 30 (the optical fiber strands 21, 31) is connected. It is also possible to connect by inserting from both sides of the through hole 11 of the optical fiber connecting holder 10 respectively.

  Next, in this state, a light source (not shown) for forming a core part connected to the other end of either or both of the SMFs 20 and 30 is operated, and light having a wavelength for forming the core part is emitted from the other end. Make it incident. Then, light having a wavelength for forming a core part is emitted from one or both ends of the SMFs 20 and 30 (optical fiber strands 21 and 31 thereof) into the mixed solution 40, thereby the first in the mixed solution 40. As shown in the enlarged view of FIG. 4C, a waveguide having a substantially uniform core diameter between the end faces of the optical fiber strands 21 and 31 of the SMFs 20 and 30 is obtained. Core portion) 41 is formed.

  Next, after confirming that the core portion 41 is reliably formed between the end faces of the SMFs 20 and 30 (the optical fiber strands 21 and 31), a light source for forming a cladding portion (not shown) is operated, and FIG. As shown in (d), light having a wavelength for forming a cladding portion is irradiated in the vicinity of the resin injection hole 12 of the optical fiber connection holder 10. Then, only the second photocurable resin in the mixed solution 40 reacts and cures, and a clad portion 42 is formed around the core portion 41 as shown in an enlarged view in FIG.

  4E shows a state in which a clad portion 42 having the same thickness as that of the optical fiber strands 21 and 31 is formed, but actually, in the mixed solution 40 in the resin injection hole 12. In the mixed solution 40 in the resin injection hole 12 depending on the irradiation direction and irradiation range of the irradiation light, the entire portion irradiated with the light having the wavelength for forming the cladding portion is cured. A part or all of the second photocurable resin is cured to form the clad portion 42.

  Thus, one end of the pair of optical fibers to be connected is inserted from both sides of the through hole of the optical fiber connection holder, and the mixed solution of the first and second photocurable resins is injected into the resin injection hole. As a result, a simple connection by the self-forming optical waveguide technique is possible without any fine adjustment.

  FIGS. 5A and 5B show a second embodiment of the optical fiber connecting holder of the present invention. FIG. 5A is a front view, and FIG. 5B is a side view (end view).

  The optical fiber connection holder according to the present embodiment, for example, 10B, is the resin injection hole 13 including a through hole having an inner diameter substantially similar to a predetermined gap in the optical fiber connection holder according to the first embodiment. It has.

  According to the present embodiment, the viscosity or surface tension of the mixed solution of the first and second photocurable resins is high, and the bottomed resin injection hole cannot be sufficiently filled between the ends of the optical fiber. It is effective for.

  FIGS. 6A and 6B show a third embodiment of the optical fiber connecting holder of the present invention. FIG. 6A is a front view, and FIG. 6B is a side view (end view).

  The optical fiber connection holder according to the present embodiment, for example, 10C has the same width as the predetermined gap and at least the depth reaching the through hole in the fiber connection holder according to the first embodiment. The resin injection hole 14 which consists of a slit which has is provided.

  According to the present embodiment, it is not necessary to consider the position of the through hole 11 when the resin injection hole 14 is provided, and the production thereof becomes easy.

  In addition, the connection method of the optical fiber at the time of using the optical fiber connection holder which concerns on 2nd and 3rd embodiment is also the case where the optical fiber connection holder which concerns on 1st Embodiment is used. The same is good.

The block diagram which shows 1st Embodiment of the holder for optical fiber connection of this invention Graph showing the relationship between the amount of misalignment and connection loss in optical fiber connection Explanatory drawing which shows angle deviation | shift amount (theta) at the time of inserting optical fiber only by length L in the through-hole of axial deviation | shift tolerance d Process diagram of optical fiber connection using optical fiber connection holder of FIG. The block diagram which shows 2nd Embodiment of the holder for optical fiber connection of this invention The block diagram which shows 3rd Embodiment of the holder for optical fiber connection of this invention

Explanation of symbols

  10, 10B, 10C: optical fiber connection holder, 11: through hole, 12, 13, 14: resin injection hole, 20, 30: optical fiber, 21, 31: optical fiber, 40: photocurable resin 41: waveguide (core part), 42: clad part.

Claims (6)

One end of the pair of optical fibers is formed by using a first photo-curing resin for forming a core part and a second photo-curing resin for forming a clad part, which have different refractive indexes after curing, and self-forming light between them. An optical fiber connecting holder used when forming and connecting a waveguide,
It is made of a transparent material that can sufficiently transmit light having a wavelength for curing at least the second photocurable resin for forming the cladding part,
One end of the pair of optical fibers is inserted from both sides, and a fitting tolerance capable of keeping the axial deviation and angular deviation between the pair of optical fibers within a certain range in a state of facing each other with a predetermined gap therebetween. A through-hole having
The one end of the pair of optical fibers of the through hole is provided at a portion where the ends of the pair of optical fibers face each other, and the mixed solution of the first and second photocurable resins is separated with the predetermined gap therebetween. An optical fiber connector holder comprising: a resin injection hole having a size capable of holding a self-forming optical waveguide between ends of a pair of optical fibers in a state of being opposed to each other. . The optical fiber connecting holder according to claim 1,
The resin injection hole comprises a bottomed hole having an inner diameter substantially the same as the predetermined gap and at least a depth exceeding the through hole. The optical fiber connecting holder according to claim 1,
The resin injection hole is a through hole having an inner diameter substantially the same as the predetermined gap. An optical fiber connection holder. The optical fiber connecting holder according to claim 1,
The resin injection hole comprises a slit having substantially the same width as the predetermined gap and at least a depth reaching the through hole. In the optical fiber connection method of connecting one end of a pair of optical fibers using the optical fiber connection holder according to any one of claims 1 to 4,
Insert one end of a pair of optical fibers to be connected from both sides of the through hole of the optical fiber connection holder,
Injecting a mixed solution of the first photocurable resin for forming the core part and the second photocurable resin for forming the clad part with different refractive indexes after curing into the resin injection hole of the optical fiber connection holder,
Forming a core part by entering light having a wavelength for curing the first photocurable resin from the other end of at least one optical fiber;
A method for connecting optical fibers, comprising forming a clad portion by irradiating light having a wavelength for curing the second photocurable resin in the vicinity of a resin injection hole of an optical fiber connection holder. The optical fiber connection method according to claim 5,
After injecting a mixed solution of a first photocurable resin for forming a core part and a second photocurable resin for forming a clad part having different refractive indexes after curing into a resin injection hole of an optical fiber connection holder One end of a pair of optical fibers to be connected is inserted from both sides of the through hole of the optical fiber connecting holder, respectively.

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