Patent ID: 8849125

Claim:
A method comprising: receiving, by an optical receiver, traffic that includes four-bit symbols, the four-bit symbols being encoded using a four-bit phase modulation scheme; processing, by the optical receiver, the traffic to recover a four-bit symbol of the four-bit symbols; decoding, by the optical receiver, the recovered four-bit symbol to obtain a three-bit symbol, the three-bit symbol being associated with a three-quadrature amplitude modulation (3QAM) scheme, the decoding being performed without creating an error, within the traffic, when cycle slip occurs, the cycle slip occurring when the recovered four-bit symbol includes a first state, of a set of modulation states associated with the four-bit phase modulation scheme, that is different than a second state, of the set of modulation states, that exists before the recovered four-bit symbol is transmitted to the optical receiver; and outputting, by the optical receiver, the traffic based on the three-bit symbol.