Optical Receiver and Method of Receiving an Optical Communications Signal

An optical receiver comprising:

• an input arranged to receive a subcarrier multiplexing (SCM) optical signal comprising an optical carrier and an optical subcarrier, each having a respective optical power;
• a carrier suppression element arranged to receive the SCM optical signal and having a rejection band that is tunable in frequency to partially suppress the optical carrier by a variable amount;
• an optical amplifier having a variable gain, the optical amplifier being arranged to receive the SCM optical signal output from the carrier suppression element and being arranged to amplify the optical carrier and the optical subcarrier;
• a photoreceiver arranged to receive the SCM optical signal output from the optical amplifier;
• and
• a controller arranged to cause frequency tuning of the rejection band and variation of the gain of the optical amplifier so as to adjust a ratio of the optical power of the optical carrier at the photoreceiver to the optical power of the optical subcarrier at the photoreceiver based on an indication of performance of the SCM optical signal.

A method of receiving an optical communications signal, the method comprising the steps of:

• A. receiving a subcarrier multiplexing (SCM) optical signal comprising an optical carrier and an optical subcarrier, each having a respective optical power;
• B. filtering the optical carrier using a carrier suppression element having a rejection band that is tunable in frequency to partially suppress the optical carrier by a variable amount;
• C. amplifying the optical carrier and the optical subcarrier by a variable amount by applying a variable optical gain;
• D. receiving and photodetecting the amplified SCM optical signal;
• and
• E. tuning the frequency of the rejection band and varying the applied optical gain so as to adjust a ratio of the optical power of the optical carrier at the photoreceiver to the optical power of the optical subcarrier at the photoreceiver based on an indication of performance of the SCM optical signal.

A non-transitory computer-readable medium comprising, stored thereupon, a computer program comprising instructions configured so as to cause a processor executing the instructions to:

• A. receive a subcarrier multiplexing (SCM) optical signal comprising an optical carrier and an optical subcarrier, each having a respective optical power;
• B. filter the optical carrier using a carrier suppression element having a rejection band that is tunable in frequency to partially suppress the optical carrier by a variable amount;
• C. amplify the optical carrier and the optical subcarrier by a variable amount by applying a variable optical gain;
• D. receive and photodetect the amplified SCM optical signal;
• and
• E. tune the frequency of the rejection band and varying the applied optical gain so as to adjust a ratio of the optical power of the optical carrier at the photoreceiver to the optical power of the optical subcarrier at the photoreceiver based on an indication of performance of the SCM optical signal.