OPTICAL AMPLIFIER, AND OPTICAL TRANSMISSION SYSTEM

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PROBLEM TO BE SOLVED : To provide an optical amplifier capable of improving an SBS threshold by optically amplifying signal light and widening the spectrum width of signal light. SOLUTION : Excitation light with a wavelength capable of exciting a rare earth element added to a fiber 11 for optical amplification is output from an excitation portion 61, is passed through a WDM coupler 31, and is supplied, in the forward direction, to the fiber 11 for optical amplifier. Signal light input to an input end 1A is passed through a branch coupler 21, an optical isolator 41 and the WDM coupler 31, is input to the fiber 11 for optical amplification, and optically amplified by the fiber 11 for optical amplification. The optically amplified signal light is passed through the optical isolator 42 and a branch coupler 22, and is output from an output end 1B. At the excitation portion 61, a driving signal including a modulation frequency component of higher than or equal to 40 MHz and lower than 76 MHz is supplied to an excitation light source and the excitation light from the excitation light source is modulated according to the driving signal. COPYRIGHT : (C)2011, JPO&INPIT