JPS6125110A - Optical distributor - Google Patents

Abstract

PURPOSE:To reduce distributing variance among terminals by making an incidence-side optical fiber thin at a prescribed taper ratio, connecting a columnar optical material to its tip, and connecting tapered thin-diameter end part of a plural-fiber bundle to the other end surface. CONSTITUTION:One incidence-side optical fiber 11 has a taper part 12 and is connected to the columnar optical material 14 at a connection part 13-1. Further, this is connected to the taper part of plural optical fibers 16 at a connection part 13-2. The optical distributor converts the light of the incidence-side optical fiber 11 to a clad mode, the columnar optical material 14 mixes the light, and the connection part 13-2 reduce light which is incident directly on a optical fiber core, thereby distributing the light almost uniformly. Then, the taper ratio R of the incidence-side fiber is specified as shown by an inequality to improve the reduction effect of variance of distributing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical splitter that can be used in optical fiber communications.

[Technical background of the invention and its problems]

As an IXn optical splitter using a tapered fiber, for example, the one shown in FIG. 3 is known. In this figure, (3
1) is a plurality of optical fibers, which are twisted to the east and have a tapered portion (32). The tip of the tapered part is approximately equal to the core diameter of one optical fiber (33), and the tip of the connecting part (34
) is optically coupled. To process a plurality of optical fibers into a tapered shape, it is sufficient to heat one side of the optical fiber bundle, stretch out both ends of the optical fibers, and cut them at a predetermined diameter.

FIG. 4 is a sectional view for explaining the operation of this optical distributor. According to Figure 4, the core (4υ
The light that has propagated therein is incident on one of the plurality of optical fiber cores (42), (43), and (44) at the connection portion (34), and the light that has been propagated thereon is present. Ray of light (45
) is directly incident on the original fiber core (43).

Light that is incident on any of the 7C fiber cores (42), (43), and (44), such as light ray (46), is totally reflected at the interface of the cladding of the tapered portion (32) and converted into a lower-order mode. It becomes a waveguide mode of either core.

In such a conventional lXn optical splitter, the connection (34)
Due to the deformation of the optical fiber core due to thermal fusion splicing, light cannot be uniformly incident on the cores of multiple fibers.

In FIG. 4, cores (43) and #(44) are greatly deformed, and less light enters these cores.

As described above, conventional optical distributors are unable to distribute light evenly, and variations in distribution occur between output terminals.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical distributor that improves the above-mentioned problems and reduces distribution variations between terminals.

[Summary of the invention]

That is, the optical distributor according to the present invention tapers the optical fiber on the incident side, connects one end surface of the columnar optical material at its tip, and connects the tapered light beam formed by a plurality of fibers to the other end surface of the columnar optical material. It connects the narrow diameter ends of the fiber bundle.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to extremely reduce variations in distribution and provide a low-loss optical distributor with little dependence on the incident mode.

[Examples of inventions]

The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of an optical splitter according to the present invention.

(11) is a single optical fiber with an input of 4N++1.

It has a tapered portion (12). It is connected to the columnar optical member (14) at the connecting portion (13-1). Also, the connection part (1
3- Tapered part (16) of multiple optical fibers (15) in illusion
It is connected to the.

The optical splitter according to the present invention converts the light from the input optical fiber (11) into a cladding mode at the taper section (12), mixes the light at the columnar optical material (14), and converts the light from the input optical fiber (11) into a cladding mode at the connection section (13-2).
, the amount of light directly incident on the core of the optical fiber (15) is reduced.

FIG. 2 is a cross-sectional view for explaining the S dance of light. Light m (
22) is converted into a cladding mode at the tapered portion (12). However, not all the light is converted into the cladding mode, but the light incident in the low-order mode reaches the connection part (13-1) while remaining in the waveguide mode. The light intensity distribution is not uniform, and the light intensity in the core part is high.The purpose of the columnar optical material is to make this uneven light intensity distribution uniform.The taper part (
The light converted to cladding mode in J, 2) is connected to connection C1.
，? , -2) in %:l! a optical fiber (15
) (Fig. 1), even if it enters either of the cores (2η, C24), C25), it will immediately fly out and the
16] and is converted into a waveguide waveguide of either core. Therefore, the light is distributed almost evenly, regardless of imperfections in the connections (13, -2).

In this way, the method of using tapered optical fibers on both sides and inserting a columnar optical material between them was known for nxm (n, m is 2 or more) optical splitters, as described in Japanese Patent Application No. 57-81. However, in the conventional example, the reason for tapering both sides is different. Namely, the purpose is to reduce packing flux loss and to mix light at the tapered part. Therefore, Considering these two reasons by applying them to the 1×n optical splitter, there is no need to form the input side optical fiber into a tapered shape (it was thought that the conventional example shown in Fig. 3 would suffice.However, the 1×n optical splitter When we investigated the non-uniformity of the light distribution, we found that some of it was due to imperfections in the connections.

It has been discovered that tapering the input side has a great effect on this problem. The present invention is based on this discovery.

It is considered that the taper ratio R of the input fiber should be within the range described below.

In other words, the numerical aperture of one input optical fiber is NA,
The core @/outer diameter is set to , the refractive index of the cladding is set to n, and the numerical aperture of the multiple optical fibers on the output side is NA.

In this case, the numerical aperture at the output end of the input side taper part is NA,
, 1'L-k, so NA, 9k>NA*
It is considered that the effects of the present invention occur when (1) is satisfied.

Further, the maximum value of the taper ratio R1 is determined under the condition that the taper portion (12) does not enter the radiation mode. That is, N A , Rk (fT[1(2)) may be used. From equations (11, 1), the range of the taper ratio R can be obtained.

The optical splitter according to the present invention is effective regardless of the refractive index distribution of the optical fiber used, such as SI, GI, etc., and can be used without making any special distinction between the input side and the output side. It goes without saying that this can be done.

Further, the method of processing a single fiber into a tapered shape may be performed by stretching it by heating or by etching it with chemical chemicals.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the optical distributor according to the present invention, Fig. 2 is an enlarged sectional view of the connection part of the optical distributor shown in Fig. 3, and Fig. 3 shows a conventional example. The configuration diagram and FIG. 4 are enlarged cross-sectional views of the connection parts of the optical distributor shown in FIG.
・Columnar optical material, 15...multiple optical fibers, 16・
...Tapered part.

Claims (2)

[Claims] (1) One optical fiber having a tapered portion, a columnar optical member whose one end face is connected to the tapered end face of this optical fiber, and a plurality of columnar optical members whose tapered end faces are connected to the other end face of the columnar optical member. 1. An optical distributor comprising: a tapered optical fiber bundle made of optical fibers; (2) The optical distributor according to claim 1, wherein the taper ratio R of one optical fiber having a tapered portion is defined by the following formula A. Note NA_2/(NA_1K)<R<√(n^2-1)/K
NA_1...A However, NA_1 is the numerical aperture of one optical fiber having a tapered part, K is the core diameter/outer diameter ratio of one optical fiber having a tapered part, and n is the numerical aperture of one optical fiber having a tapered part. The refractive index of the cladding of one optical fiber, NA_2 is the numerical aperture of the tapered optical fiber bundle consisting of multiple optical fibers.