AUTOMATIC INTENSITY CONTROL OF AN OPTICAL-TRANSMISSION LINE USING ENHANCED GAIN SATURATION IN CASCADED OPTICAL AMPLIFIERS

The output characteristics through an optical transmission system with multiple-optical amplifiers which operates in the gain-saturation regime have been studied in both a uniformly-pumped laser amplifier and an erbium-doped fiber amplifier with pump absorption. It has been shown that the output intensity becomes almost constant in the optical system if the input intensity changes within the gain-saturation regime of the amplifiers. The stabilization of the output intensity is greatly enhanced by cascading the saturated-optical amplifiers. There is a characteristic input intensity which causes no intensity changes at the output end of the transmission line. This technique is applicable to soliton transmission as well as ordinary pulse communications.