Optical amplifier

An optical amplifier comprising:

• a rare-earth doped optical fiber produced by doping an optical fiber material with rare-earth elements;
• a first photodetector element for converting an optical input signal to a first electrical signal;
• a wavelength multiplexer for inputting said optical input signal into one end of said rare-earth doped optical fiber, and for inputting a leakage signal emitted from said one end of said rare-earth doped optical fiber into said first photodetector element;
• a monitor-equipped excitation light source for generating an excitation light, and for generating a monitor signal in proportion to a light intensity of said excitation light;
• an optical coupler for guiding an optical signal outputted from other end of said rare-earth doped optical fiber to an optical output terminal, and for inputting said excitation light into said other end of said rare-earth doped optical fiber;
• an excitation light source driving circuit for driving said monitor-equipped excitation light source in accordance with said monitor signal and said first electrical signal so as to amplify said optical input signal by a process of accumulating excitation energy within said rare-earth doped optical fiber by transforming light energy, supplied by said excitation light injected into said other end of said rare-earth doped optical fiber, to excitation energy and converting said excitation energy to an optical signal having wavelength and phase characteristics identical to the wavelength and phase characteristics of said input optical signal inputted into said one end of said rare-earth doped optical fiber;
• wherein said optical amplifier is provided with an optical splitter for splitting an incoming optical signal to be amplified into a first split signal and a second split signal;
• a second photodetector element for converting said first split signal produced by said optical splitter to a second electrical signal;
• a correction signal generation circuit for generating a correction signal in accordance with said second electrical signal;
• and an optical delay circuit for delaying said second split signal for a specific duration of time prior to inputting into said wavelength multiplexer;
• and
• wherein said excitation light source driving circuit regulates operation of said monitor-equipped excitation source in accordance with said monitor signal, said first electrical signal and said correction signal.