Systems and methods for controlling power of WDM channels in a WDM receiver. A preamplifier is provided prior to a demultiplexer in the WDM receiver chain. The gain of the preamplifier may be controlled based on power measurements made on individual WDM channels. A filter with controllable tilt may be employed to compensate for amplifier gain tilt and assure that all of the WDM channels remain within the dynamic range of the photodetector and receiver electronics. This provides improved bit error rate performance.
Use in an optical communications system of multiple detectors to separately detect respective multiple spectral modes of a received optical signal. The invention also provides for corresponding multi-channel, dispersion-tolerant optical receivers. Embodiments are presented both for direct detection and for coherent detection of optical signals.
An optical performance monitor for accurate monitoring of the OSNR of a WDM optical signal is provided wherein a demultiplexing arrayed waveguide grating (AWG) having a plurality of Vernier input ports is disposed between an optical switch and a photodiode array coupled to the output ports of the AWG. In operation, the optical switch sequentially provides the input optical signal into each of the Vernier ports, and signals detected by photodiodes are stored in a memory unit. The apparatus is capable of monitoring the OSNR of the WDM signal with a frequency step which is M times smaller than a frequency spacing between the AWG transmission bands, while enabling the OSNR monitoring in an enhanced dynamic range by providing accurate noise sampling.
An apparatus for monitoring an input optical signal at a plurality of distinct optical frequencies is disclosed wherein a demultiplexing arrayed waveguide grating (AWG) having a plurality of M>1 Vernier input ports is disposed between an optical switch and a photodiode array coupled to the output ports of the AWG. In operation, the optical switch sequentially provides the input optical signal into each of the Vernier ports, and signals detected by photodiodes are stored in a memory unit. The apparatus is capable of monitoring the input optical signal with a frequency step which is M times smaller than a frequency spacing between the AWG transmission bands, and obtain M frequency-resolved readings from each photodiode.
A method and apparatus for monitoring spectral tilt uses an arrayed waveguide grating (AWG) to separate a multiplexed optical signal having a plurality of wavelength channels into a plurality of sub-bands, where each sub-band spans a different wavelength range and includes more than one wavelength channel. A photodetector array is provided to measure the optical power in each of the sub-bands, while control electronics calculate spectral tilt of the multiplexed optical signal using the measured optical power in each of the sub-bands. The spectral tilt monitor in accordance with the instant invention provides spectral resolution, increased monitoring speeds, and decreased manufacturing costs.
