OPTICAL RECEIVER, WAVELENGTH MULTIPLE OPTICAL RECEIVER, TIME DIVISION MULTIPLE OPTICAL RECEIVER AND OPTICAL TRANSMISSION SYSTEM USING THEM

摘要

PROBLEM TO BE SOLVED: To improve signal light-to-noise ratio by providing a light source that generates offset light, an optical coupler which combines signal light and the offset light and a saturable absorption type optical element which inputs an optical coupler output and outputs it to a transmission line. SOLUTION: Signal light 11 transmitted from a transmission circuit 2 is transmitted to a transmission line 2 via a saturable absorption type optical element 3, which suppresses the light noise of the light 11. The element 3 has a saturable absorption effect due to the reverse bias voltage application to a semiconductor waveguide and has a nonlinear type transmitted characteristic depending on the input light intensity. Although a data pulse having large light intensity exceeds the absorption capability of the optical element and is transmitted, a noise component having small light intensity receives strong absorption and is reduced. A pulse waveform which includes the noise component and has a peak value that exceeds the threshold levels of the transmitted characteristic and the absorption characteristic can be made to a pulse waveform that reduces the noise component.