Photonic system with marker tone

An apparatus, comprising:

• a laser;
• an optical splitter coupled to the laser;
• a first optical pathway coupled to the optical splitter, the first optical pathway comprising a first modulator, the first optical pathway coupled to an optical combiner;
• a second optical pathway coupled to the optical splitter, the second optical pathway comprising a second modulator coupled to the optical splitter, a phase tuner coupled to the second modulator, and a polarization rotator coupled to the phase tuner and to the optical combiner;
• and
• an optical coupler coupled to the optical combiner.

An apparatus, comprising:

• an optical coupler;
• a phase splitter coupled to the optical coupler;
• a first optical pathway coupled to the phase splitter and coupled to an interferometer;
• a second optical pathway coupled to the phase splitter and to the interferometer;
• a first photodiode coupled to the interferometer;
• and
• a second photodiode coupled to the interferometer.