Patent ID: 8126337

Claim:
A method for optical communications, the method comprising: producing an electrical phase-shaped binary transmission (PSBT) signal with three logical levels to represent a digital data signal to be transmitted; operating an optical Mach-Zehnder modulator to modulate a continuous wave optical beam based on the electrical PSBT signal to produce an optical transmission signal of optical pulses modulated in amplitude and phase to carry the digital data signal; transmitting the optical transmission signal over an optical link; receiving the optical transmission signal from the optical link; splitting the received optical transmission signal into a first optical signal along a first optical path and a second optical signal along a second optical path; controlling a relative phase delay between the first and second optical signals; combining the first and second optical signals to produce an optically constructive signal and an optically destructive signal, said controlling the relative phase delay comprising controlling at least one of the first and second optical paths to set a free spectral range of the optically constructive signal or the optically destructive signal to be between R and 2R, where R is a data rate of the digital signal; operating a first optical detector to convert the optically constructive signal into a first electrical detector output and a second optical detector to convert the optically destructive signal into a second electrical detector output; and obtaining a difference between the first and second electrical detector outputs to produce an electrical signal that carries the digital data signal.