JPS58117515A - Optical demultiplexer - Google Patents

Abstract

PURPOSE:To reduce incident-mode dependency, etc., by inserting a columnar optical material between a onvergent type optical fiber and a taper fiber which has clad layer of optical fibers put together in one body at least at a tapered tip part. CONSTITUTION:The incidence-side convergent type fiber 11 is connected to the columnar optical material 22 which has a diameter nearly equal to the core diameter of an optical fiber in a faying surface. The columnar optical material 22 is connected to the tapered part 23 in a faying surface 19 and the tapered part 23 is obtained by heat-sealing a bundle of optical fibers 12-18 partially, drawing both ends of the optical fibers, and cutting the tapered part where a diameter nearly equal to the core diameter of the optical fiber 11 is obtained. In the faying surface 19, a nearly uniform light intensity distribution is obtained to demultiplex light to optical fibers 12-18 at nearly equal rates.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical splitter for use in optical fiber communications.

Prior Art and its Problems A conventional tapered fiber type optical splitter having one input port is shown in FIG. 1. In Figure 1, (2), (2), (41, (5), [6
), (7), +8) are optical fibers that are tapered and fused to the core of the optical fiber (1) at the joint surface (9). The tapered part (11
heats the optical fiber.

It can be obtained by pulling out both ends of an optical fiber and cutting it at an appropriate point. This optical splitter is an optical fiber (1
), the optical fiber (2
) to (8) are combined and distributed to the cores. Since the cladding mode light that cannot be coupled to the core at the joint surface (9) is converted to the core mode by propagating through the taper part aI, it is an extremely low-loss optical distributor. Moreover, when light is incident on the optical fibers (2) to (8), it is also possible to use them as a light combiner.

In the optical splitter shown in Figure 1, if the optical fiber (1) is a stepped optical fiber and the diameter of the taper tip and the core diameter of the optical fiber (1) are approximately equal, the variation in the distribution ratio will be affected by the incidence of the distribution ratio. The mode dependence can be made quite small, making it a good optical splitter, but when the optical fiber (1) is a focusing type optical fiber, there is a drawback that the incident mode dependence increases due to variations in the distribution ratio. The reason for this is that in the case of a focusing optical fiber, the light is concentrated at the center of the core, and the state of this light concentration is mode dependent, with lower-order modes tending to center around the core. Therefore, the optical fiber (8) connected to the center of the core of the optical fiber (1) is connected to the other optical fibers (2) to (
7) A large amount of optical power is distributed. However, there is a drawback that the difference in distribution increases as the mode incident on the optical fiber (1) becomes a lower-order mode.

OBJECTS OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks and to provide an optical splitter in which the dependence on the incident mode and the variation in the distribution ratio are reduced even when the input optical fiber is a focusing optical fiber.

Summary of the Invention That is, the optical distributor according to the present invention inserts a columnar optical material between an input focusing optical fiber and a tapered fiber.

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

@2 Figure is an embodiment of the optical distributor according to the present invention. αυ
is a focusing optical fiber on the input side, and the joint surface Q11 of the columnar optical material has a diameter almost equal to the core diameter of optical fiber 01).
connected with. The columnar optical material (2z is connected to the taper part ■ and the joint surface (1'J). The taper part ■ is connected to the optical fiber (12, (131,0, It is obtained by heating and fusing, tightening both ends of the optical fiber, and cutting the tapered portion at a diameter approximately equal to the core diameter of the optical fiber (Iυ).

Since the core of a focusing optical fiber has a refractive index distribution that decreases approximately as the square of the distance from the center, light is concentrated at the center of the core. On the other hand, if the columnar optical material has a substantially uniform refractive index, the light incident on the columnar optical material from the optical fiber a1) will be diffused and have a substantially uniform light intensity distribution at the joint surface aI. Become. In order to obtain such a substantially uniform light intensity distribution, the length of the columnar optical material must be at least 20 times the diameter. At the junction surface O9, the optical fibers (13-(
11, the light is distributed in approximately equal proportions. Moreover, even if light is incident on the optical fiber (11) in a low-order mode, it is diffused by the columnar optical material so as to have a substantially uniform light intensity distribution, so that the dependence on the incident mode is also reduced.

Note that a stepped refractive index gradient optical fiber may be used as the columnar optical material as shown in Figure @3. In this case, the core diameter of the optical fiber should be approximately equal to that of the focusing optical fiber 6υ, and the numerical aperture of the optical fiber (O) may be larger than that of the optical fiber C(1).

As described in detail, according to the present invention, even if the input optical fiber is a focusing type fiber, an optical splitter with small dependence on the incident mode can be obtained even if the distribution is uneven.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a conventional optical distributor, Figure 2 is a perspective view showing one embodiment of the optical distributor according to the present invention, and Figure 3 is a perspective view showing another embodiment of the present invention. at+, Oυ... Focusing optical fiber (221... Columnar optical material (43... Stepped refractive index distribution optical fiber n';!J,
(131, αi, as, ae, a'n, αs, oz,
cn, cw, ca, m, cm, m... Optical fiber ■, -... Taper part QD, Ql, (41), (31/W Joint agent Patent attorney Nori Chika Kensuke (1 other person)

Claims (1)

[Scope of Claims] (1) A plurality of optical fibers are tapered and thin, and at least at the tip of the taper, the cladding layers of the plurality of optical fibers are fused and integrated, and the tapered tip is 1. An optical splitter having a structure connected to an end face of a single focusing optical waveguide, characterized in that a columnar optical material is inserted between the focusing optical fiber and the tapered fiber. (The optical distributor according to claim 1, characterized in that the core diameter of the 2+i1 bundle type optical fiber, the outer diameter of the columnar optical material, and the outer diameter of the tapered tip are approximately equal. (3) Column-shaped 2. The optical distributor according to claim 1, wherein a stepped refractive index gradient optical fiber having a core diameter substantially equal to the core diameter of the focusing optical fiber is used as the optical material.