Optical transmission system, optical transmitter for optical transmission system, and optical receiver for optical transmission system

Abstract

An optical transmission system is provided in which the optimum operating point of a Mach-Zehnder interferometer, matched to the optical frequency of the light source on the transmitting side, can be set. The optical receiver () has an infinitesimal-modulated signal component detection circuit (), which uses the signal train output from a balanced detection circuit () to detect the infinitesimal-modulated signal component applied to the phase adjustment terminal () of an MZI () by an infinitesimal-modulated signal oscillation circuit (); a synchronous detection circuit (), which synchronously detects the infinitesimal-modulated signals output from the infinitesimal-modulated signal component detection circuit () and infinitesimal-modulated signal oscillation circuit () and detects the error signal component arising from the shift between the optical signal carrier frequency and the optical frequency characteristic of the MZI (); and a controller (), which outputs a control signal to adjust the phase difference between two split optical signals output from the MZI () so as to correct the shift amount.