Patent ID: 7423804

Claim:
A method of monitoring spectral tilt comprising: passing a multiplexed optical signal having a plurality of wavelength channels through a spectral tilt monitor such that an arrayed waveguide grating in the spectral tilt monitor separates the multiplexed optical signal into a plurality of sub-bands, each sub-band including more than one wavelength channel from the plurality of wavelength channels; measuring the optical power in each of the sub-bands; and, calculating spectral tilt of the multiplexed optical signal using the measured optical power in each of the sub-bands, wherein the arrayed waveguide grating includes: an optical waveguide for transmitting the multiplexed optical signal; a waveguide array having a first end optically coupled to a first slab waveguide and a second end optically coupled to a second slab waveguide, the first slab waveguide for receiving the multiplexed optical signal from the optical waveguide, the second slab waveguide for providing demultiplexed sub-signals of the multiplexed optical signal; and a plurality of multi-mode output waveguides optically coupled to the second slab waveguide, each multi-mode output waveguide having a width selected to collect a plurality of the demultiplexed sub-signals and provide one of the sub-bands.