OPTICAL DIRECT AMPLIFIER FOR WAVELENGTH DIVISION MULTIPLEXING SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide an optical direct amplifier for wavelength division multiplexing system which detects light input decline or disconnection without recource to the number of wavelength channels and enables the optical direct amplifier to perform shut-down operation. SOLUTION: Part of an output light is branched by an optical coupler 11 and photoelectrically converted by a photodiode 21 by way of a wavelength variable light band pass filter 19. An output of an optical direct amplifier 2 is controlled at a constant level by having an output constant control circuit 17 and a driving circuit 18 control an output light power so that this photoelectrically converted valve becomes constant.