Processing data in a coherent optical communication system

摘要

This disclosure describes techniques to sample electrical data streams in coherent receivers. For instance, an analog-to-digital converter (ADC) samples the received electrical data stream at a sampling rate that is nominally twice or greater than twice the symbol rate of the electrical data stream that the ADC receives. A digital filter receives the digital data stream from the ADC, and digitally filters the digital data streams to output a filtered digital electrical data stream at an effective sampling rate that is less than the sampling rate and less than twice the symbol rate, and greater than or equal to the symbol rate.

主权项

1. A method comprising:
receiving a first analog electrical data stream transmitted by a photonics module in a coherent optical communication system, and a second analog electrical data stream transmitted by the photonics module that together represent a portion of an optical signal received by the photonics module; sampling the first analog electrical data stream and the second analog electrical data stream at a sampling rate that is approximately twice or greater than twice a symbol rate of the first and second analog electrical data streams to convert the first analog electrical data stream to a first digital electrical data stream, and convert the second analog electrical data stream to a second digital electrical data stream; digitally filtering the first digital electrical data stream and the second digital electrical data stream to output a first filtered digital electrical data stream and a second filtered electrical data stream, respectively, at a first effective sampling rate that is less than the sampling rate and less than twice the symbol rate of the first and second analog electrical data streams, and greater than or equal to the symbol rate of the first and second analog electrical data streams; compensating for chromatic dispersion on at least the first and second filtered digital electrical data streams at a rate that is substantially equal to the first effective sampling rate to generate a compensated digital electrical data stream; performing timing recovery using the compensated digital electrical data stream to generate a timing recovered digital electrical data stream; digitally filtering the timing recovered digital electrical data stream at a second effective sampling rate, different than the first effective sampling rate, that is less than the sampling rate and less than twice the symbol rate of the first and second analog electrical data streams and greater than or equal to the symbol rate of the first and second analog electrical data streams; and processing the digitally filtered timing recovered digital electrical data stream at a rate that is substantially equal to the second effective sampling rate to recover data in the optical signal received by the photonics module.