Optical 90 degree hybrid circuit and light receiver using same

Abstract

An object of the present invention is to provide an optical 90 degree hybrid circuit that is capable of adjusting an optical power ratio between a signal light and a local oscillator light with ease and inhibits an optical system related to a light receiver from becoming complex, and a light receiver using same. In the optical 90 degree hybrid circuit, light waves of a predetermined plane of polarization which is included in the signal light are combined with the local oscillator light which is adjusted by a circularly polarized light at the same wavelength as the signal light, and multiplexed light is polarization-separated so as to demodulate a multi-level phase modulated signal corresponding to each polarized wave. The present invention comprises polarized wave separation means (polarized wave separation) that extracts the light waves of the predetermined plane of polarization from the signal light, a polarized wave conversion element that rotates the plane of polarization extracted from the polarized wave separation means, and a polarizer that defines the plane of polarization of the signal light before the combination with the local oscillator light. The polarized wave separation means works in cooperation with the polarized wave conversion element and the polarizer so as to adjust the optical intensity (VOA function) of the signal light.

Description

technical field [0001] The present invention relates to an optical 90-degree hybrid circuit and an optical receiver using the optical 90-degree hybrid circuit, in particular to combining the light wave of the predetermined polarization plane of the signal light with the local oscillation light and separating the polarization of the combined light to coordinate with each polarization An optical 90-degree hybrid circuit for demodulating corresponding multi-valued phase modulation signals and an optical receiver using the optical 90-degree hybrid circuit. Background technique [0002] There are optical communication technologies using quadrature phase shift modulation (QPSK) signals, multi-polarization quadrature phase shift modulation (DP-QPSK) signals, quadrature amplitude modulation (QAM) signals, and the like. In these modulation methods, when the received signal is obtained, such as figure 1 As shown, signal light such as phase-modulated light and quadrature amplitude-mod...

AI Technical Summary

Problems solved by technology

In this case, it is impossible to receive an optical signal (signal light) with a certain power or more due to the limitation of the input specification of the above-mentioned TIA.

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