JPS5913723B2 - fiber optic connector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber connector for bidirectional transmission using optical branching.

Recently, optical transmission technology using optical fibers, including optical communications, has been rapidly put into practical use, and the performance of optical fiber connector technology as well as technology for optical fibers, signal processing, light emitting and light receiving elements, etc. is rapidly increasing. There is an urgent need for practical application in all respects, including structure, cost, etc.

10 Various proposals have been made as conventional general connectors, but all of them involve butting together fibers having cross sections perpendicular to the axis.

In particular, optical splitters are indispensable for bidirectional transmission lines, but the conventional connectors used in this case have large crosstalk as described in detail below, so optical splitters with better performance have not been developed. It is predicted that this defect in connectors will become more serious as time goes on. The present invention is an optical fiber connector that tilts the fiber end face within a certain range and matches 20 fibers with such an end face with high precision with a simple structure. Seed connectors had not been considered.
First, the principle of the present invention will be explained. FIG. 1 is a diagram for explaining the coupling state of optical fibers in a conventional connector, and shows the locus of light rays when the optical fiber connection portion is perpendicular to the optical axis. Now, if we consider light that is incident and propagated at the maximum angle φ at which it is totally reflected on the cladding surface of an optical fiber and propagated, the light ray travels along a trajectory like an arrow.
In this case, the reflected wave is totally reflected again on the modulus line A-A, propagates at the maximum propagation angle φ, and travels in the core in the original direction. This backward traveling light results in crosstalk in the case of a bidirectional transmission path. Next, the coupling state of the optical 35 fibers in the case of the present invention will be explained with reference to FIGS. 2 and 3.

Figure 2 shows the case where the connecting part has a cross section inclined by θ with respect to the optical axis.If we consider light incident and propagating at the maximum angle φ that is totally reflected on the cladding surface as in Figure 1, rays 1 and 2 are It travels as shown by the arrow, and with respect to the normal line A''-N on the inclined surface, the reflected waves travel as 1' and 7, and the refracted waves as 11 and 7. Here, the reflected waves 1' and 2 are the problem. ' is larger than the maximum total reflection angle φ at each cladding surface, so light leaks out of the core.
This condition is satisfied as long as the normal line of the inclined surface exists outside the shaded area shown in FIG. That is, the value of θ may be set as follows when the core refractive index is n1 and the cladding refractive index is N2.

What is shown in FIGS. 4 to 6 is the above fiber end face condition,
This is an example of a connector used for an optical transmission line using an optical branching device.

Reference numerals 3 and 4 designate first holding members, which are made of high-precision sleeves in which holes with a diameter K close to the outer diameter of the clad portions of the optical fibers 5 and 6 are drilled coaxially with respect to the outer peripheries 7 and 8.

The tips 9, 10 of the first holding members 3, 4 are inclined at an angle within the above-mentioned range. For example, the core refractive index n1 is 1.5
45. If the cladding refractive index N2 is 1.531, the angle θ of the tips 9 and 10 is 0.134rad〈θ×1.436
It is sufficient if it is within the range of rad.

In addition, the first holding members 3 and 4 have flanges 11 and 1 at the intermediate part.
In addition, pins 13 and 1 are provided on a part of the outer circumferences 7 and 8.
4 is held upright.

Here, it is preferable that the pins 13 and 14 are attached in the same plane. Next, one first holding member 3 is inserted into the second holding member 15 provided with slits 16 and 17 that engage with the pins 13 and 14, and the flange 11 of this first holding member 3 is inserted.
A press fixing member 19 is placed over the second holding member 15 with a spring 18 interposed between them, and the flange 12 of the other first holding member 4 is attached to the end surface 20 of the second holding member 15.
The pressing fixing member 21 is tightened and coupled to the second holding member 15 so as to press against it.

FIG. 6 is a configuration diagram when the connector of the present invention is used in a bidirectional optical transmission line equipped with an optical splitter, and 22 and 23 are L
ED. A light emitting element such as an LD, and 24 and 25 are light receiving elements such as a PIN photodiode or APD.

Reference numerals 26 and 27 represent optical splitters, and one terminal of each of the four terminals is subjected to anti-reflection treatment.

28 and 29 are connector systems of the present invention.

The light emitted from the 22 light emitting elements is divided into two by the optical splitter 26, and one enters the light receiving element 25 via the connector system 28, 29. Similarly, light emitted from 23 light emitting elements enters the light receiving element 24 via an optical splitter 27 and connector systems 28 and 29. When using a conventional right-angle end face connector as shown in FIG. However, when the connector systems 28 and 29 of the present invention are used, the crosstalk shown in FIG.
As shown in FIG. 3, the reflected light escapes from inside the core to the outside of the cladding or is greatly attenuated, so that the light from the light emitting element 22 is no longer reflected at the connector portion and returned to the light receiving element 24. In particular, in the embodiment shown in FIG. 4, since the positioning pins 13 and 14 are provided at the same position from the tips 9 and 10, the first holding members 3 and 4 can have the same shape, and the tips 9 and 10 It is easy to mold, and is excellent in terms of number of parts and compatibility.

Further, since one first holding member 3 is biased against the other first holding member 4 by the spring 18, the close contact between the two fibers can be maintained extremely well. Furthermore, the pins 13 and 14 have a rotation-preventing effect and a positioning effect around the optical axis, and the movement of the fiber is restricted only in the front-back direction, so the fiber end face is not damaged by rotation, etc., and the fibers are joined together. The accuracy can also be made sufficiently high. As described above, according to the present invention, it is possible to provide an optical fiber connector that can be used particularly in a bidirectional optical transmission line, largely eliminates crosstalk, and has extremely good coupling accuracy and adhesion between optical fibers.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing how optical fibers are coupled in a conventional connector, FIGS. 2 and 3 are diagrams showing how optical fibers are coupled in a connector of the present invention, and FIG. 4 is a diagram showing an embodiment of the present invention. 5 is a perspective view of the same essential parts, and FIG. 6 is an embodiment of a bidirectional optical transmission system using the present invention. 3, 4... First holding member, 5, 6...
Optical fiber 7, 8... outer circumference, 9, 10...
... Tip, 11, 12 ... Flange, 13,
14...pin, 15... ...Second holding member, 16, 17...Slit, 18...
Spring, 19, 21...Press fixing member.

Claims (1)

[Claims] 1. The refractive index of the core portion is n_1, and the refractive index of the cladding portion is n_1.
When _2, the angle θ of the end face with respect to the optical axis is √(n_
1^2-n_2^2)/n_1<θ<π/2-(√[n
_1^2-n_2^2]/n_1), and the end face of the other optical fiber or the end face of another optical element connected to this optical fiber is set at the angle θ.
A pair of first holding members are provided in which the pair of optical fibers or the optical fiber and the optical element are inserted, and the first holding member has its tip portion formed at the same angle as the angle θ. A pin is attached to a part of the outer circumferential surface of the cylinder, and a second holding member is provided that abuts the pair of first holding members so that the two end faces face each other, and the second holding member is provided with a pin on a part of the outer peripheral surface of the cylinder. An optical fiber connector that is provided with a slit that engages with a pin, and that at least one first holding member is held by a pressing fixing member via a spring. 2 A pin disposed on the outer peripheral surface of the first holding member is provided at the same position with respect to the end face of the distal end of the first holding member, while a slit of the second holding member that engages with the pin The optical fiber connector according to claim 1, characterized in that the optical fiber connector is provided symmetrically with respect to the center.