Method for an all fiber optic, polarization insensitive, etalon based optical receiver for coherent signals

An optical system comprising:

• a transmitter that transmits a complex modulated optical signal;
• and
• an optical signal receiver that receives the complex modulated optical signal over the medium, the optical signal receiver including:
• a multimode fiber circulator including a first port, a second port, and a third port;
• a first multimode fiber cable coupled to the first port and having an input configured to receive the complex modulated optical signal and provide the complex modulated optical signal to the first port of the multimode fiber circulator;
• a second multimode fiber cable including a low Quality (Q) factor optical resonator coupled to the second port of the multimode fiber circulator that is configured to receive the complex modulated optical signal from the second port of the multimode circulator;
• and
• a third multimode fiber cable coupled to the third port of the multimode fiber circulator that is configured to receive a reflected optical signal from the third port of the multimode circulator, the reflected optical signal being reflected from the low Q optical resonator;
• wherein the resonator of the receiver accounts for any wavefront distortion for detection without any adaptive optics and any local oscillators or mixers for measuring phase of the complex modulated optical signal.