Methods and systems for optical receivers

摘要

Broadband access networks are driving the upgrade of DWDM networks from 10 Gb/s per channel to more spectrally-efficient 40 Gb/s or 100 Gb/s. Signal quality degradation due to linear and non-linear impairments are significant and error control coding and signal processing solutions play increasingly key roles in meeting increasing demand, providing improved quality of service, and reduced cost. It would be beneficial to reduce the power consumption of optical receivers for optical links exploiting for example LPDC encoding. Accordingly, the inventors have established a low complexity soft-decision front-end compatible with deployable LDPC codes in next-generation optical transmission systems. Beneficially the optical receiver design can be retro-fitted into deployed hard-decision based optical systems and replaces the 3-to-2 encoder of the prior art in the electrical portion of the receiver with a single gate design. Further, the design may act as a 2-bit Flash ADC in multimode fiber based optical receivers.

主权项

1. A circuit comprising:
a photodetector receiving an optical signal comprising data encoded according to a predetermined standard; an amplifier receiving a converted optical signal from the photodetector and generating an amplified received signal; a fan-out buffer for receiving the amplified received signal and generating a plurality of buffered signals, each buffered signal representative of the amplified received signal; a plurality of first comparators, each first comparator receiving a buffered signal of the plurality of buffered signals and generating a confidence level in dependence upon the buffered signal of the plurality of buffered signals and a predetermined threshold value; a logic circuit receiving a plurality of confidence levels from the plurality of first comparators and generating a result in dependence thereof; an optical splitter to receive the optical signal and to split the optical signal into a first predetermined portion for coupling to the photodetector and a second predetermined portion for coupling to a hard decision circuit; the hard decision circuit comprising:
a second photodetector for receiving the second predetermined portion of the optical signal;a second amplifier receiving a converted optical signal from the second photodetector and generating a second amplified received signal;a second comparator for generating a decision in dependence upon the second amplified received signal and a predetermined decision threshold;a delay line for delaying an output of the second comparator by a predetermined time delay; and an output decision circuit for receiving the result from the logic circuit and the delayed output of the comparator within the hard decision circuit.