Patent ID: 7453628
Filing Date: 2008-11-18
Classification: H01S,H04B

Abstract:
1. An optical amplifier comprising: an input port and an output port; a first optical amplification unit configured to amplify a wavelength division multiplexing light inputted to said input port; a first optical attenuation unit configured to attenuate the wavelength division multiplexing light amplified by said first optical amplification unit; a second optical amplification unit configured to amplify the wavelength division multiplexing light attenuated by said first optical attenuation unit, and outputs the wavelength division multiplexing light to said output port; an input monitor unit configured to detect power of the wavelength division multiplexing light inputted to said input port; an output monitor unit configured to detect the power of the wavelength division multiplexing light outputted from said output port; and a control unit configured to control said first and second optical amplification units based on the detection results of said input monitor unit and said output monitor unit such that a gain of each optical amplification unit is kept constant, and configured to control an attenuation amount of said first optical attenuation unit such that the signal light level per one wavelength outputted from said output port is kept constant, even if the signal light level per one wavelength of the wavelength division multiplexing light inputted to said input port is changed, wherein the optical amplifier includes a second optical attenuation unit which is provided between said second optical amplification unit and said output port, and when a signal light input level per one wavelength computed based on the detection result of said input monitor unit is lower than a predetermined first base point level, said control unit is configured to minimize the attenuation amount of said first optical attenuation unit and said control unit is configured to control the attenuation amount of said second optical attenuation unit according to said signal light input level, when said signal light input level is higher than said first base point level, said control unit is configured to control the attenuation amounts of both said first and second optical attenuation unit according to said signal light input level, wherein said first base point level is higher than a lower limit level of an effective input dynamic range, and said first base point level is lower than an intermediate level of said input dynamic range.