Clock recovery for optical transmission systems

摘要

A receiver for an optical communications system which corrects distortion of a received signal. A clock recovery system utilizing a feedback and feedforward system are provided. The feedback loop comprises a phase detector and a clock source, while the feedforward loop comprises the phase detector and a delay element for delaying the output of distortion correction system. The feedback loop has a significantly lower bandwidth than the feedforward path. There are also provided methods of optimizing tap weights and of acquiring initial tap weights.

主权项

1. A receiver for receiving at least one input signal from a photodiode in an optical communications system, comprising a feedback path, a feedforward path, and a tap weight centralization system,
the feedback path comprising:
an analog-to-digital converter (ADC) configured to digitize the at least one input signal and output a digital signal;a Finite Impulse Response (FIR) filter to process the digital signal and output a processed signal;a phase detector configured to detect a timing phase of the processed signal and output a signal indicative of the timing phase; anda clock source configured to provide a sampling clock signal to the ADC, the clock source receiving as input the signal indicative of the timing phase of the processed signal to control the sampling clock signal; the feedforward path comprising:
the phase detector; anda delay element configured to delay the processed signal and output a delayed processed signal, the delay of the delay element being controlled by the output of the phase detector; and the tap weight centralization system comprising:
a tap weight phase detector to monitor tap weights of the FIR filter and generate a correction signal indicative of a tap weight center offset; andat least one adder to add the correction signal to the signal output by the phase detector that is indicative of the timing phase.