US Patent 9025963 Processing data in a coherent optical communication system

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.