Patent ID: 8180228

Claim:
In a direct-detection receiver having an analog-to-digital converter (ADC) for sampling a received optical signal including data symbols modulated thereon, a sequence estimator for recovering data symbols from a multi-bit sample stream generated by the ADC, and a clock recovery block for recovering a clock signal synchronous with a timing of the data symbols, a method of acquiring a channel lock condition of the clock recovery block, the method comprising: preliminarily providing a plurality of sets of channel statistics, each set of channel statistics optimizing performance of the sequence estimator for a respective predetermined combination of channel chromatic dispersion and polarization mode dispersion, and wherein there is at least one set of channel statistics which, when installed in the sequence estimator, will yield symbol estimates having residual distortions that are within an acquisition range of the clock recovery block, and storing the plurality of sets of channel statistics in a memory of the receiver; and during start-up of the receiver: a controller selecting one of the sets of channel statistics from the memory and installing the selected set of channel statistics in the Sequence Estimator; and if a channel lock condition is not detected by the clock recovery block within a predetermined time interval, the controller repeating the step of selecting one of the sets of channel statistics from the memory and installing the selected set of channel statistics in the Sequence Estimator until a channel lock condition is detected.