JPS5862616A - Optical coupler - Google Patents

Abstract

PURPOSE:To obtain a small-sized and high-coupling efficiency optical coupler, by using a polarizing filter where the refractive index is different in directions of polarization. CONSTITUTION:A polarizing filter 9 where the refractive index is different in directions of polarization is interposed between glass substrates 81 and 82 and is arranged at 45 deg. to parallel beams of semiconductor lasers 11 and 12 which pass through colimator lenses 51 and 52. The refractive index, etc. of the polarizing filter 9 are so set that the incident polarized light parallel to the plane of the figure goes straight and the incident polarized light vertical to the plane of the figure is total reflected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a light combiner suitable for use as an element of an optical communication device. In particular, it relates to an optical coupler that combines optical power sent out from two light sources such as semiconductor lasers and couples them into one optical waveguide.

As shown in FIG. 1, a conventional device of this kind first couples the light emitted from two semiconductor lasers 11.12 to separate sub-optical waveguides 21.2z, and then connects the two sub-optical waveguides 21. .2z is further coupled to one optical waveguide 3. In such a configuration, two sub optical waveguides 21.2
2. It is necessary to increase the mechanical height of the part where one optical waveguide 3 is connected, and the manufacturing process is far apart. This part becomes a discontinuous part of the optical waveguide, so the sub optical waveguide 21 is connected there.
．． There are six drawbacks, such as the light propagating through the optical waveguide 22 being reflected and scattered, not being completely coupled to the optical waveguide 3, and leaking out of the optical waveguide 3.

A conventional device as shown in FIG. 2 is also known. Second
In the figure, 11.12 is a semiconductor laser, 41.42 is a single mode elliptical fiber, 5t and 52 are parallel lenses, 6 is an anisotropic crystal, 7 is a focusing lens, and 3 is an optical waveguide.

Hitoshi's device: Utilizing the phenomenon of an anisotropic crystal in which two orthogonal polarized lights lead to different optical paths, the polarized lights emitted by the two semiconductor lasers 11.1ffi are made orthogonal to each other and incident on the anisotropic crystal. and combine them into one leading wavepath 3. However, in this device, the length of the anisotropic crystal 6 must be made considerably longer in order to place the integrated laser 11.12 directly in front of the collimating lens 51.51. This is because it is necessary to largely separate the optical paths of orthogonal polarized light in the anisotropic crystal 6 due to the size constraints of the drive circuit of the semiconductor laser 11.1g. However, if the anisotropic crystal 6 is lengthened, the insertion loss will increase due to the combination of the parallel lens 51.5 g and the focusing lens 7)
, Eru. To avoid this, anisotropic crystal 6t! 11. Another known technique is to guide the optical output of the semiconductor laser 11.12 into a single mode ellipse 77 (/<41.42) that preserves the plane of polarization and guide it to the collimating lens 51.52. Even in the case, the coupling efficiency between the single mode elliptical fiber 41.42 and the semiconductor laser 1.12 and the coupling efficiency between the single mode elliptic fiber 41.42 and the optical waveguide 3 are as follows. It gets worse than when not in use.

The present invention is an improvement on this, and aims to provide an optical coupler that is small, easy to manufacture, has low reflection and scattering, and has high coupling efficiency.

The present invention uses two light sources that emit single polarized light and whose polarizations are orthogonal to each other, and the polarized light of one light source is made to travel in a straight line, while the polarized light of the other light source is made to be perpendicular to the polarizing filter passing through the optical path. l'11., which combines the polarized light transmitted through a multilayer filter serving as a polarizing filter and the polarized light totally reflected, into one optical waveguide. .

□.

The embodiment drawings will be described in detail below.

FIG. 5 is a structural diagram of an apparatus according to an embodiment of the present invention.

81 and 82 are glass substrates, 9 is a polarizing filter, and a multilayer filter is used here. Other symbols are the same as in FIG. Nine polarizing filters are arranged so as to form an inclination of 45 WIL with respect to the parallel beams of semiconductor lasers F and '12 that have passed through parallel lenses 5z and St, respectively, and are sandwiched between glass substrates 81 and 810. Further, the polarizing filter 9tj is arranged so that when polarized light parallel to the plane of the paper in FIG.

In such a device, a light beam having a polarization parallel to the plane of paper that is emitted from a semiconductor laser 11 is converted into parallel light by a parallel lens 51, enters a β-las substrate 81, passes through a polarizing filter 9, and travels straight. do. On the other hand, the light beam having polarization on the paper surface KfllW1fk which is emitted from the semiconductor -f12 is converted into parallel light by the parallelizing lens 5, enters the glass substrate 8zK, and is totally reflected by the polarizing filter 9.This light mu polarizing filter 9 , is combined with the nine lights on the surface of this polarizing filter 90 , is focused by the focusing lens 7 , and is coupled to the optical waveguide 3 .

In a device with such a configuration, the semiconductor rate t'<.

To realize an optical coupler with extremely low loss, since there are no restrictions on the size of the drive circuit 12, etc., and the light emitted from the semiconductor lasers 11 and 12 is directly converted into parallel light by the collimating lanes 51 and 52. I can do it.

FIG. 4 is another embodiment of the optical coupler according to the present invention;
be. In this example, the half-wave plate 10 is the parallel lens 5.
2 and the glass substrate 82. The conductor lasers 11 and 12 are arranged so that their polarization is parallel to the paper 1. The other □ structures are the same as the example shown in FIG.

In this structure, polarized light parallel to the paper surface emitted from the semiconductor laser 12 is converted into parallel light by the parallel lens 52,
Further, the light is converted into polarized light perpendicular to the plane of the paper by a half-wave plate 1''0, and is incident on a glass substrate 8.

Therefore, regarding the light beam incident on the glass substrate 82, □
The semiconductor laser 12 is similar to the example in FIG.
It has the same effect as placing . Furthermore, in the embodiment shown in FIG. 4 of Jin, since the polarized light of the two semiconductor lasers is directed in the same direction, the electrode arrangement of the two semiconductor lasers is the same, which has the advantage of facilitating fabrication.

In the above example, a multilayer filter is used as the polarizing filter, but the present invention can be similarly applied to a polarizing filter whose refractive index differs depending on the polarization direction.

As described above, according to the present invention, a small optical coupler can be obtained which combines the optical outputs of two semiconductor lasers and couples them into one optical waveguide with low loss.

This device is easy to manufacture and requires little precision machining. The device of the present invention is suitable for use in a submarine repeater for submarine optical overconfidence. In other words, since semiconductor lasers have lower reliability than other devices, it is necessary to install them in duplicate and guide their output light to one optical waveguide, but the device of the present invention It is ideal for this purpose because it is small, has low loss, and does not contain any mechanically moving parts.

[Brief explanation of the drawing]

FIGS. 1 and 2 are configuration diagrams of a conventional optical coupler. 3 and 4 are structural diagrams of an optical coupler according to an embodiment of the present invention. 11.12...Semiconductor laser, 21.22...Sub optical waveguide, 3...-optical waveguide, 41.42...Single mode elliptical fiber, 51.52...Parallel lens, 6・
... Anisotropic crystal, 7... Focusing lens, 81.82.
・・Glass substrate, 9・−・Polarizing filter, 10−2 minutes 1
Wave plate. Patent Applicant Nippon Telegraph and Telephone Public Corporation Agent Patent Attorney Ide Nao Takashi

Claims (2)

[Claims] (1) Equipped with a polarizing filter with a refractive index that differs by 5 depending on the polarization direction, the first person enters from one side of this polarizing filter, and the polarizing filter and this light are connected so that the incident light is totally reflected by this polarizing filter. The angle of the incident light and the refractive index of this polarizing filter are set, and the second incident light that is incident from the other surface of the first incident light and has a different polarization from the first incident light is this polarized light. The 20th incident light beam that passes through the filter and the angle of the incident light beam are set so that the optical path of the transmitted light coincides with the optical path of the first incident light that is totally reflected. is configured, and is a nine-party combiner. (2) A half-wave plate is arranged in the optical path of one of the first incident light or the second incident light, and the polarization direction of the second incident light source and the polarization direction of the light source of the second incident light are The optical coupler according to claim 1, wherein the optical coupler is configured such that the directions are the same.