JP2005300596A - Composite optical fiber, optical connector, and optical fiber with optical connector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate the manufacture of a thermal-diffusion expanded core (TEC) optical fiber. <P>SOLUTION: A composite optical fiber being a TEC optical fiber is constituted by splicing a plurality of optical fibers 22, 23, 24 and 25 whose core diameters are different in the order in which core diameters become larger gradually. The manufacture of the composite optical fiber is easier than that of the TEC optical fiber in which the core is expanded in a tapered manner. Moreover, when performing an optical connector splicing by attaching an optical connector to the the composite optical fiber 21, since the diameter of the core 25a in the splicing end face 21a is expanded, an influence of deviation in a position is small and splicing loss is small. Moreover, since energy per an unit area of light emitted from the end face becomes small, a problem in which scratched parts and dust of the end face are burned by strong light and the state of the end face is deteriorated can be avoided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a composite optical fiber used for optical connection such as optical connector connection, an optical connector using the same, and an optical fiber with an optical connector.

In an optical communication system, as a connection part between optical fibers, connection by an optical connector is adopted at many places. It is extremely important to reduce the connection loss of the optical connector connection part.
In particular, when the optical fiber is a single mode optical fiber, the core diameter is as small as 5 to 10 [mu] m, so that even if the optical fiber cores are slightly misaligned, the light coupling efficiency with the optical fiber on the other side can be improved. The connection loss is increased.
As an optical fiber that can reduce the connection loss due to the misalignment of the core in the optical connector connecting portion, as shown in FIG. 8, one end side of the microlens 2 is bonded to the end face of the optical fiber 1. There is a microlens optical fiber 4 having a structure in which a multimode cylindrical GI optical fiber (graded index optical fiber) 3 is bonded to the other end. 5 is a clad.
FIG. 8C is a perspective view when the ferrule 6 is attached to the tip of the microlens optical fiber 4 described above.

Similarly, as an optical fiber that can reduce the connection loss caused by the misalignment of the core, as shown in FIGS. 9 (b) and 10 (b), the core diameter is enlarged in the vicinity of the connection end face of the optical fiber. There are also core expansion optical fibers 9 and 10 having different structures.
The core expansion optical fiber 9 shown in FIG. 9 (b) is obtained by heating and stretching the preform (glass base material before drawing) 11 of FIG. 9 (b) as shown in FIG. 9 (b). This is a core-expanding optical fiber of the heat-stretching method in which the core diameter is increased in a tapered shape. In FIG. 2B, 12 is a core and 13 is a clad. A tapered enlarged portion of the core 12 is indicated by 12a. Further, the core-corresponding portion of the preform 11 is indicated by reference numeral 12 ', and the cladding-corresponding portion is indicated by reference numeral 13'.

The core expansion optical fiber 10 shown in FIG. 10B is distributedly heated in the vicinity of the connection end face of the single mode optical fiber 15 shown in FIG. 10A, and the doping agent added to the core 16 is diffused. This is a distributed heating type core expansion optical fiber in which the core diameter is increased in a tapered shape as shown in FIG. This type of core-expanded optical fiber is called a TEC fiber (Thermally-diffused Expanded Core Fiber). A tapered enlarged portion of the core 16 in the TEC fiber 10 is indicated by 16a.
Paragraph number [0009] of JP-A-11-109185, etc. Paragraph number [0029] of Japanese Patent Laid-Open No. 5-119235

  In the case of the microlens optical fiber 4 shown in FIG. 8, it is difficult to manufacture the microlens 2 that requires high accuracy. In particular, there is a problem that the spot size of the microlens is likely to vary and the reproducibility in manufacturing is low. Further, the connection between the microlens 2 and the single mode optical fiber 1 or the GI optical fiber (which is a multimode optical fiber) 3 is complicated, and this is not easy to manufacture. Therefore, there is a problem that the cost becomes high.

In the case of the heat-expanded core expanding optical fiber 9 shown in FIG. Therefore, the cost is also increased.
Moreover, since the diameter of the clad 13 changes, there is also a problem that it is difficult to assemble with a normal ferrule.

  In the case of the TEC fiber 10 shown in FIG. 10, it is difficult to control the tension of the gripped optical fiber, to adjust the burner for the optical fiber, and to accurately control the fuel gas to be supplied.

  The composite optical fiber according to the first aspect of the present invention for solving the above-mentioned problems is characterized in that a plurality of optical fibers having different core diameters are connected in the order of increasing core diameters.

  The optical connector according to claim 2 is characterized in that a short optical fiber in which a plurality of optical fibers having different core diameters are connected in order of increasing core diameter is internally fixed in the optical fiber hole of the ferrule and end face polishing is performed. Features.

  The optical fiber with an optical connector according to claim 3 is prepared in advance with a ferrule in which a short multimode optical fiber is internally fixed in an optical fiber hole and subjected to end surface polishing, and the end of the long single mode optical fiber has the same cladding diameter. In the optical fiber hole, a portion having a different core diameter on the tip side in a composite optical fiber in which a plurality of optical fibers having different core diameters are connected in the order of increasing core diameter is inserted into the optical fiber hole of the ferrule. It is characterized in that it is connected to the short multimode optical fiber that is fixed in the interior.

According to the composite optical fiber of the present invention, the core diameter at the optically connected end face is enlarged. Therefore, compared with the case of optically connecting a single-mode optical fiber having a constant core diameter, the influence of the positional deviation is exerted. Less connection loss can be achieved.
In addition, although the diameter of the core changes in stages, the part of each stage has a cylindrical shape and does not expand in a tapered shape. Therefore, a conventional microlens optical fiber, or a heating drawing method or distributed heating is used. Unlike the core-expanded optical fiber of the system, the difficulty of precisely controlling the core diameter does not occur, and the manufacturing is easy.

In addition, since the energy per unit area of the light emitted from the end face is reduced, even if the end face is scratched or dust is attached, the scratched part or dust is burned with strong light, and the end face condition deteriorates. Can be avoided. Therefore, it is suitable to be applied to an optical fiber compatible with a high output laser such as video transmission.
In addition, since it is less affected by scratches and dust as described above, it is suitable for application to an optical communication line having many optical connector connections in the optical line, such as FTTH (Fiber To The Home).

  Hereinafter, a composite optical fiber, an optical connector, and an optical fiber with an optical connector embodying the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a composite optical fiber 21 according to an embodiment of the present invention. This composite optical fiber 21 (hereinafter simply referred to as “optical fiber 21” in some cases) includes a second optical fiber 23 having a larger core diameter than the first optical fiber 22 that is a single mode optical fiber, and a core diameter. The third optical fiber 24 having a larger diameter and the fourth optical fiber 25 having a larger core diameter are fusion-spliced in order. The diameter of the core 22a of the first optical fiber 22 which is a single mode optical fiber is 10 μm, the diameter of the core 23a of the second optical fiber 23 is 30 μm, the diameter of the core 24a of the third optical fiber 24 is 50 μm, The diameter of the core 25a of the fourth optical fiber 25 is 62.5 μm. Each of the cores 22a, 23a, 24a, and 25a is a cylindrical core having a uniform refractive index. The three short optical fibers 23, 24, 25 on the distal end side are provided with claddings 23 b, 24 b, 25 b having the same outer diameter as the outer diameter 125 μm of the cladding 22 b of the single mode optical fiber 22. A manufactured optical fiber is cut short.
The vicinity of the distal end of the single mode optical fiber (first optical fiber) 22 and the portions of the three optical fibers 23, 24, 25 ahead are fixed internally to the ferrule of the optical connector. For this reason, when an ordinary optical connector having a length of ten to ten and several millimeters is attached, for example, the length of the second optical fiber 23 is 3 mm, the length of the third optical fiber 24 is 3 mm, and the fourth optical fiber. The length of the fiber 25 is 4 mm or the like. The single-mode optical fiber 22 in the illustrated optical fiber 21 is a portion that forms an optical line and is long.

  The composite optical fiber 26 shown in FIG. 2 (hereinafter simply referred to as the optical fiber 26 in some cases) is a shortened portion of the first optical fiber (single mode optical fiber) 22 in the optical fiber 21 of FIG. The entire length is fixed internally to the ferrule of the optical connector. The optical fiber 21 is the same as the optical fiber 21 in FIG. 1 except for the short first optical fiber 22 '.

In the composite optical fiber 21 or 26 described above, the end surfaces 21a and 26a on the larger core diameter side serve as connection end surfaces for other optical fibers or optical components, but the diameter of the core 25a at the connection end surfaces 21a and 26a is increased. Therefore, compared to a case where a single-mode optical fiber having a constant core diameter is optically connected, the influence of the positional shift is less and the connection loss can be reduced.
In addition, although the diameter of the core changes in stages, the part of each stage has a cylindrical shape and does not expand in a tapered shape. Therefore, a conventional microlens optical fiber, or a heating drawing method or distributed heating is used. Unlike the core-expanded optical fiber of the system, the difficulty of precisely controlling the core diameter does not occur, and the manufacturing is easy.
In addition, since the energy per unit area of the light emitted from the end face is reduced, even if the end face is scratched or dust is attached, the scratched part or dust is burned with strong light, and the end face condition deteriorates. Can be avoided. Therefore, it is suitable to be applied to an optical fiber compatible with a high output laser such as video transmission.
In addition, since it is less affected by scratches and dust as described above, it is suitable for application to an optical communication line having many optical connector connections in the optical line, such as FTTH (Fiber To The Home).
When light enters the composite optical fibers 21 and 26 from the optical fiber on the other side to be connected, a difference in the core diameter will cause a slight connection loss. Therefore, the effect of connection loss is not particularly problematic.

  FIG. 3 shows the bare fiber 27a of the single mode optical fiber 27 having an outer diameter of 250 μm as the first optical fiber 22 in the optical fiber 21 of FIG. 1 (that is, the bare fiber 27a = the first optical fiber 22). ). In this case, the coating 27b at the tip of the single mode optical fiber 27 is removed, and the exposed bare fiber (first optical fiber 22) is replaced with the second optical fiber 23 and the third optical fiber 24. The fifth optical fiber 25 is fused and connected in order, and the optical fiber strand 28 in which the core diameter of the tip portion is gradually increased is configured.

  FIG. 4 shows an embodiment in which an optical fiber 41 with an optical connector is configured by attaching an optical connector 30 to the optical fiber strand 28 of FIG. 3 in which the core diameter of the tip is gradually increased. This optical connector 30 is a so-called MT optical connector corresponding to an F12 type multi-core optical fiber connector specified in JIS C 5981. The exposed bare fiber, that is, the end portion of the optical fiber 21 described above (a portion where the core diameter gradually increases and its vicinity) is inserted and fixed and subjected to end face polishing. In addition, before end face polishing, the optical fiber is fixed by filling the adhesive from the adhesive filling window 31b. A boot 29 for protection is inserted in advance into the optical fiber 28.

  FIG. 5 shows an optical connector 34 for installation on the spot, in which the short optical fiber 26 whose core diameter is gradually increased as shown in FIG. 2 is inserted and fixed in advance into the optical fiber hole 31a of the ferrule 31 and subjected to end face polishing. Is. In this case, the bare fiber 27a exposed by removing the coating 27b at the tip of the ordinary single mode optical fiber 27 is inserted into the optical fiber hole 31a of the ferrule 31, and the optical fiber 26, which is a built-in optical fiber. The optical fiber 42 with an optical connector is configured by fixing the optical fiber by filling the adhesive from the adhesive filling window 31b. A butt connection portion of the optical fiber is indicated by a.

  In FIG. 6, a short multimode optical fiber 35 is inserted and fixed in advance into the optical fiber hole 31a of the ferrule 31 and subjected to end surface polishing to form an optical connector 36 for installation on the site. In this case, the bare fiber of the optical fiber 28 in FIG. 3 whose core diameter at the tip is gradually increased, that is, the tip of the optical fiber 21 is inserted into the optical fiber hole 31a, and the built-in optical fiber is used. The optical fiber 43 with an optical connector is configured by matching with a certain multimode optical fiber 35 and filling the adhesive from the adhesive filling window 31b to fix the optical fiber. An optical fiber butt connection is indicated by b.

  The optical fiber 28 in FIG. 3 in which the core diameter of the tip is gradually increased can also be used for connection to an optical element 37 such as a light emitting element or a light receiving element as shown in FIG. It can also be used for connection with optical elements such as lenses and filters, and other optical components.

A single mode optical fiber is usually used as the one with the smallest core diameter among the plurality of optical fibers connected in order of increasing core diameter, but the one with the smallest core diameter should be a multimode optical fiber. Is also possible.
In addition, a plurality of optical fibers connected in order of increasing core diameters usually have the same cladding diameter, but the cladding diameters are not necessarily the same.

It is sectional drawing of the principal part of the composite optical fiber of one Example of this invention. It is sectional drawing of the composite optical fiber of the other Example of this invention. It is a longitudinal cross-sectional view which shows the optical fiber strand 28 which has a coating | cover on the outer periphery of the composite optical fiber 21 of FIG. It is a longitudinal cross-sectional view which shows the Example which attached the optical connector to the optical fiber strand 28 of FIG. It is a longitudinal cross-sectional view which shows the Example which used the composite optical fiber 26 of FIG. 2 as a built-in optical fiber of an on-site optical connector. It is a longitudinal cross-sectional view which shows the Example which attached the field attachment optical connector which used the multimode optical fiber as a built-in optical fiber to the optical fiber strand 28 of FIG. It is a figure which shows the Example which connects the optical fiber strand of FIG. 3 to an optical component. 1 shows a conventional microlens optical fiber in which a microlens is connected to the end face of an optical fiber. (A) is a longitudinal sectional view, (b) is a right side view of (a), and (c). FIG. The core diameter-expanded optical fiber manufactured by the heat drawing method, which is another conventional example, will be described. (A) is a longitudinal sectional view before processing, and (B) is a longitudinal sectional view after processing. Further, a core expansion optical fiber manufactured by a distributed heating method, which is another conventional example, will be described. (A) is a longitudinal sectional view before processing, and (B) is a longitudinal sectional view after processing.

Explanation of symbols

21, 26 Composite optical fibers 21a, 26a Connection end faces 22, 22 ′ First optical fiber (single mode optical fiber)
23 second optical fiber 24 third optical fiber,
25 4th optical fiber 22a, 22'a, 23a, 24a, 25a Core 22b, 22'b, 23b, 24b, 25b Clad 27 Single mode optical fiber strand 27a Bare fiber (= 1st optical fiber 22)
27b Coated 28 Optical fiber 30 Optical connector 31 Ferrule 31a Optical fiber hole 31b Adhesive filling window 34, 36 On-site optical connector 35 Multimode optical fiber (built-in optical fiber)
37 Optical elements (optical components)
41, 42, 43 Optical fiber with optical connector

Claims (3)

  A composite optical fiber comprising a plurality of optical fibers having different core diameters connected in the order of increasing core diameters.   An optical connector characterized in that a short optical fiber in which a plurality of optical fibers having different core diameters are connected in order of increasing core diameter is internally fixed in an optical fiber hole of a ferrule and subjected to end face polishing.   Prepare a ferrule in which a short multimode optical fiber is fixed internally in the optical fiber hole and end-face polished, and a plurality of optical fibers with the same cladding diameter but different core diameter are cored at the end of the long singlemode optical fiber. Short multi-mode optical fibers in which the core diameters on the distal end side of the composite optical fibers connected in order of increasing diameter are inserted into the optical fiber hole of the ferrule, and are fixed internally in the optical fiber hole. An optical fiber with an optical connector, characterized in that it is butt-connected.

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