Patent ID: 6839131

Claim:
An apparatus, comprising: an emitter for generating an amplified spontaneous emission signal and transmitting the amplified spontaneous emission signal to a reference optical path; at least one fiber bragg grating positioned on the reference optical path downstream of said emitter, said at least one fiber bragg grating transmitting an amplified spontaneous emission signal having at least one reference wavelength by performing at least one of reflecting and absorbing at least a part of the amplified spontaneous emission transmitted from said emitter; an optical switch for receiving a first optical signal corresponding to a wavelength division multiplexed optical signal branched from a main optical path and for receiving a second optical signal corresponding to the amplified spontaneous emission signal having at least one reference wavelength, said optical switch outputting at least one of the first and second signals, the outputting being performed in response to a switching control signal; a tunable optical filter for filtering the optical signals outputted from said optical switch, said filter having a plurality of variable filtering characteristics altered in accordance with a filtering control signal, said filter outputting a filtered optical signal; a photo diode for converting the filtered optical signal to an electrical signal and for outputting the converted signal; and a control unit for analyzing the converted signal in accordance with a predetermined algorithm, said control unit measuring an optical wavelength, an optical power, and an optical signal to noise ratio of the first optical signal, said control unit performing the measuring in accordance with the analyzing of said converted signal; said at least one grating being a tilted fiber bragg grating having a main mode wavelength and a side mode wavelength.