JPS61231521A - Photocoupler - Google Patents

Abstract

PURPOSE:To form a photocoupler which does not depends upon the polarization state of incident light by separating different polarized light that the incident light contains temporarily by a polarized light separating film, converting it into a circular polarized wave by a lambda/4-wavelength plate, and then dividing the wave equally by a coupler film. CONSTITUTION:The incident light Po consisting of a P wave and an S wave which differ in polarization dependency is separated by a polarized wave separating film 1 into the P and S waves. Namely, the polarized light separating film 1 made of a multilayered film transmits the P wave and reflects the S wave. The reflected S wave is reflected by a total reflecting film 2, and the P wave transmitted through the polarized wave separating film 1 and the S wave reflected by the total reflecting film 2 are converted into circular polarized waves by the lambda/4-wavelength late 3. The P wave between those P and S waves converted into the circular polarized waves is reflected by a total reflecting film 4, and split into Po/2 and projected by the coupler film made of a dielectric multilayered film formed so that the light is divided by 50% each.

Description

[Detailed Description of the Invention] [Summary] An optical coupler with no polarization dependence, which separates incident light Po into a coupler film into P waves and S waves, and passes each polarized light through a λ/4 wavelength plate. After converting the light into circularly polarized light, it is split using a fog film.

[Industrial application field]

The present invention relates to an optical coupler.1. In particular, it relates to a polarization-independent optical coupler having a structure that does not depend on the polarization state of incident light.

In optical communication equipment, optical equipment, etc., optical multiplexers/demultiplexers,
Optical devices such as optical splitters and couplers are often used. When light enters the optical branching membrane in such an optical device, the branching ratio changes depending on the polarization state of the incident light, and the incident light is split at one end and converted into circularly polarized waves. There is a demand for an optical coupler that does not depend on polarization and branches.

[Conventional technology]

Conventional optical couplers have adopted a method of reducing polarization dependence by constructing a multilayer film that splits incident light.

FIG. 2 is a curve diagram showing the polarization dependence of a conventional coupler film.

In the figure, the vertical axis (Y axis) represents transmittance (%), and the horizontal axis (X
If we take the wavelength on the axis), there will be a difference in polarization dependence between P waves and S waves, as shown in the figure.

[Problem that the invention seeks to solve]

The above-mentioned conventional cobra with low polarization dependence has the problem that the polarization dependence cannot be removed by the multilayer film that constitutes it.
In addition, if the coupler film that splits the incident light is made of a metal film,
Each had the problem of absorption loss.

[Means for solving problems]

The present invention provides an optical coupler that solves the above problems. In other words, the incident light Po consisting of a combination of P waves and S waves incident from a single mode fiber is separated into P waves and S waves, and these P waves and S waves are converted into circularly polarized waves using a λ/4 wavelength plate. When the wave and S wave are input to the coupler film, 50%15
It is made to divide into 0%.

[Effect]

The above optical coupler has a structure in which the different polarized lights contained in the incident light are first separated by a polarization separation film, each is converted into circularly polarized light by a λ/4 wavelength plate, and then divided into equal parts by a coupler film. This is what I did.

〔Example〕

FIG. 1 is a block diagram for explaining the present invention in detail.

In the figure, an incident light Po consisting of a combination of P waves and S waves with different polarization dependencies is separated into P waves and S waves by a polarization separation film 1. That is, the deflection separation film 1 made of a multilayer film transmits P waves and S waves.
The reflected S wave is reflected by the total reflection film 2, and the P wave transmitted through the deflection separation film 1 and the total reflection II! ! The S wave reflected by the wavelength plate 2 is converted into a circularly polarized wave by the λ/4 wavelength plate 3. Of the P waves and S waves converted into circularly polarized waves, the P waves are reflected by the total reflection film 4 and are 50% 150%
In the coupler film 4 made of a dielectric multilayer film configured to be divided into P o /2, each is divided into P o /2 and emitted.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to provide an optical coupler that does not depend on the polarization state of incident light, and it is extremely effective when applied to various optical devices.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining the present invention in detail, and FIG. 2 is a curve diagram showing the polarization dependence of a conventional coupler film.

Claims (1)

[Claims] Incident light P_0 consisting of a combination of P waves and S waves incident from a single mode fiber is separated by a light separation film (1) that transmits P waves and reflects S waves, and the reflected The S wave is reflected by the total reflection film (2), and the reflected S wave and the transmitted P
After converting the wave into a circularly polarized wave with a λ/4 wavelength plate (3), the P wave converted to the circularly polarized wave is reflected by a total reflection film (4), and the P wave and the S wave are transferred to a coupler film. (5) An optical coupler characterized in that the optical coupler is made to enter and split.