Optical transmitter, optical receiver and optical transmission apparatus and control method of optical receiver

摘要

A unipolar original electrical signal is encoded by alternate mark inversion and combined with a DC bias current for injection of a semiconductor laser to produce a bipolar FSK optical signal that is transmitted to a receiver. At the receiver, the received signal is coupled with optical local power and fed to an optical/electrical transducer, preferably a semiconductor, to produce an electrical signal that is demodulated to produce the original unipolar signal. The demodulator may be of different types, for example employing delaying part of the amplified electrical signal and mixing the delayed part with the original signal for passage of the combined signal through a low pass filter; with proper selection of the delay, an AMI decoder is not needed. The demodulator may also be of the type that has one or more band pass filters to respectively separate the positive mark, space and negative mark signals that may thereafter be added. Filtering and polarization beam splitting may also be used in the demodulator for improving the signal-to-noise ratio and preventing other types of degradation.