a plurality of photodiodes operable to receive at least a portion of a modulated optical signal including a first optical subcarrier having a first frequency, a second optical subcarrier having a second frequency, and a third optical subcarrier having a third frequency, such that the second optical frequency is greater than the first optical frequency, and the third optical frequency is greater than the second optical frequency, the modulated optical signal including the first, second, and third optical subcarriers that are output from a transmitter, wherein the second optical subcarrier carries clock information;

analog-to-digital converter circuitry operable to receive analog signals indicative of outputs from the photodiodes, the analog-to-digital converters circuitry outputting digital samples;

a digital signal processor operable to receive the digital samples; and

a clock recovery circuit operable to provide a clock signal based on the digital samples, the digital signal processor being operable to output data based on the clock signal.