Bi-directional optical communication system

A bi-directional optical communication system, comprising:

• a first optical data processing unit, the first optical data processing unit comprising:
• a first transmitter, the first transmitter comprising:
• a first channel configured to provide a first electrical signal at a first data rate;
• a second channel configured to provide a second electrical signal at the first data rate;
• a differential quadrature phase shift keying (DQPSK) encoder configured to encode the first electrical signal and the second electrical signal to provide at least two differentially encoded electrical signals at the first data rate;
• a Gaussian pulse generator configured to generate an optical pulsed signal centered at a wavelength with a pulse duration;
• an optical power splitter configured to split the optical pulsed signal into at least two optical pulsed signals;
• at least two Mach-Zehnder modulators (MZM) configured to phase modulate the at least two optical pulsed signals using the at least two differentially encoded electrical signals to provide a first phase modulated optical pulsed signal and a second phase modulated optical pulsed signal;
• a phase shifter configured to phase shift the first phase modulated optical pulsed signal to generate a phase shifted phase modulated optical pulsed signal;
• an optical combiner configured to combine the second phase modulated optical pulsed signal and the phase shifted phase modulated optical pulsed signal to generate a processed optical pulsed signal at a second data rate;
• a third channel configured to provide a third electrical signal at the first data rate;
• an Electro-absorption Modulator (EAM) configured to amplitude modulate the processed optical pulsed signal using the third electrical signal to provide a phase-amplitude modulated optical pulsed signal at a third data rate;
• an optical amplifier configured to amplify the pulse-amplitude modulated optical pulsed signal and generate a transmitter optical pulsed signal for transmission;
• and
• wherein the transmitter optical pulsed signal is transmitted as a first free space optical link through a first transmitter telescope;
• and
• a second optical data processing unit, the second optical data processing unit comprising:
• a first receiver, the first receiver comprising:
• a first receiver telescope configured to receive an optical pulsed signal, wherein the receiver optical pulsed signal is an attenuated version of the transmitter optical pulsed signal;
• a first optical splitter configured split the optical pulsed signal into a receiver optical pulsed signal and a reuse optical pulsed signal;
• a second optical splitter configured to split the receiver optical pulsed signal into a first optical pulsed signal, a second optical pulsed signal and a third optical pulsed signal;
• a photodetector configured to convert the first optical pulsed signal into a first electrical signal with two amplitude levels corresponding the third channel in the first transmitter;
• a differential quadrature phase shift keying (DQPSK) demodulator configured to demodulate the second optical pulsed signal and the third optical pulsed signal into a first amplitude-modulated electrical signal and a second amplitude-modulated electrical signal;
• at least three low-pass filters configured to remove harmonics from the first electrical signal, the first amplitude-modulated electrical signal and the second amplitude-modulated electrical signal to provide three filtered electrical signals;
• and
• at least three bit-error rate analyzers configured to estimate a bit error rate of each of the three filtered electrical signals.