A
transmitter comprising a programmable optical vector modulator and method for coherent optical
signal communication. The
transmitter includes a
transmitter laser whose output is coupled by way of an
optical fiber to an amplitude modulator. The output of the amplitude modulator is coupled by way of a length of
optical fiber to a phase modulator. The phase modulator generates a modulated light output from the transmitter.
Amplitude modulation is achieved by inputting data and a data
clock signal to amplitude
symbol mapping logic whose outputs are selectively weighted, summed, amplified and input to the amplitude modulator to amplitude modulate the output of the transmitter
laser.
Phase modulation is achieved by inputting the modulating data and the data
clock signal to
phase angle symbol mapping logic whose outputs are selectively weighted, summed, amplified, delayed to synchronize with the arrival of the light from the amplitude modulator, and input to the phase modulator to phase modulate the amplitude modulated output of the transmitter
laser. The programmability of the vector modulator allows the transmission of an M-ary modulation format that maximizes the
data transmission for a given optical
dynamic range and
bit error rate target. Also, the programmability allows for rapid change in modulation format to maximize
data transmission for changes in optical
dynamic range and
bit error rate target. The M-ary
constellation may be predistorted to compensate for equipment piece part variation and
fiber nonlinear effects; in particular the effect commonly known as “self-
phase modulation”.