Patent ID: 6396051
Filing Date: 2002-05-28
Classification: G02B,H04B

Abstract:
An apparatus for measuring the optical-signal-to-noise-ratio (OSNR) of an optical signal having an optical spectrum and at least one channel, each channel having a center frequency, said apparatus comprising:a splitter to split said optical signal into first and second paths; in said first path, a narrow-band optical notch filter centered on one center frequency of said at least one channel receiving a first optical signal on said first path and outputting a notch filtered optical signal to a first detector to provide a first electrical signal indicating an optical noise power of said notch filtered optical signal; in said second path, a second optical signal from said splitter is provided to a second detector that provides a second electrical signal indicating an optical channel and noise power of said second optical signal; a tunable bandpass filter disposed before said splitter, wherein said tunable bandpass filter is operative to be tuned to at least one center frequency of said at least one channel, and wherein said narrow-band notch filter is a cascaded narrow-band notch filter having a plurality of notches each notch centered on a center frequency of said at least one channel; and a processor to calculate OSNR based on said first and said second electrical signals wherein said processor is further operative to select said center frequency of said tunable bandpass filter.