Intra data center optical communication

A network element, the network element comprises a coherent optical receiver, wherein the coherent optical receiver comprises:

• an input that is configured to receive an optical input signal by a coherent optical receiver of a second unit of a data center;
• wherein the input optical
• signal represents a transmitted optical signal that was transmitted by a coherent transmitter of the data center;
• wherein the transmitted optical signal is generated by modulating a transmitter laser signal that is outputted from a laser of the coherent transmitter;
• a processor;
• a controllable laser that is configured to generate a reference signal;
• a processor that is configured to control a frequency of the reference signal independently from a control of the laser of the coherent transmitter;
• optical circuitry that is configured to optically process the reference signal and the optical input signal;
• and
• optical to digital conversion circuitry;
• wherein the processor is also configured to recover data embedded in the optical input signal;
• wherein the controllable laser has a frequency range that is (ii) narrower than a frequency range of a tunable laser, and (ii) limited to a frequency range of a single coarse wavelength division multiplexing (CWDM) link.

A network element, the network element comprises a coherent optical receiver, wherein the coherent optical receiver comprises:

• an input that is configured to receive an optical input signal by a coherent optical receiver of a second unit of a data center;
• wherein the input optical
• signal represents a transmitted optical signal that was transmitted by a coherent transmitter of the data center;
• wherein the transmitted optical signal is generated by modulating a transmitter laser signal that is outputted from a laser of the coherent transmitter;
• a processor;
• a controllable laser that is configured to generate a reference signal;
• a processor that is configured to control a frequency of the reference signal independently from a control of the laser of the coherent transmitter;
• optical circuitry that is configured to optically process the reference signal and the optical input signal;
• and
• optical to digital conversion circuitry;
• wherein the processor is also configured to recover data embedded in the optical input signal;
• wherein the processor is configured to control the frequency of the reference signal while avoiding from requesting an absolute output frequency of the controllable laser.