Cycle slip reduction in coherent optical communications

摘要

Carrier phase estimation techniques are provided for processing a received optical signal having a carrier modulated according to a modulation scheme. First and second carrier phase estimation operations are performed on a digital signal derived from an optical carrier obtained from the received optical signal using coherent optical reception. The first carrier phase estimation operation tracks relatively fast phase variations of the optical carrier of the received optical signal to produce a first carrier phase estimation and the second carrier phase estimation operation tracks relatively slow phase variations of the optical carrier of the received optical signal to produce a second carrier phase estimation. A difference between the first and second carrier phase estimations is computed. Occurrence of a cycle slip is determined when the difference is greater than a threshold. A correction is applied to the first carrier phase estimation when the low pass filtered difference exceeds the threshold.

主权项

1. A method comprising:
receiving an optical signal comprising an optical carrier that has been amplitude and phase modulated according to a modulation scheme and obtaining the optical carrier from the received optical signal using coherent optical reception; converting the optical carrier to an electrical signal; converting the electrical signal to a digital signal in a representation of complex numbers, each complex number being associated with a constellation point of a symbol constellation according to the modulation scheme; performing in parallel first and second carrier phase estimation operations on the digital signal, the first carrier phase estimation operation to track relatively fast phase variations of the optical carrier of the received optical signal to produce a first carrier phase estimation and the second carrier phase estimation operation to track relatively slow phase variations of the optical carrier of the received optical signal to produce a second carrier phase estimation; computing a difference between the first and second carrier phase estimations; and determining occurrence of a cycle slip when the difference is greater than a threshold.