Optical transport system for two-carrier signals

An apparatus, comprising:

• an optical transmitter, wherein the optical transmitter comprises:
• an optical modulator configured to modulate an optical carrier with data to generate a first modulated optical signal;
• and
• a nonlinear optical device configured to optically mix, via a phase-conjugation (PC) process, the first modulated optical signal, a first optical-pump signal, and a second optical-pump signal to generate a second modulated optical signal, wherein the nonlinear optical device comprises an optical filter configured to separate the first and second modulated optical signals from the first and second optical-pump signals and apply the separated first and second modulated optical signals to an output port of the optical transmitter;
• and
• an optical-transport link coupled to the output port of the optical transmitter and configured to subject the first and second modulated optical signals applied thereto to phase-sensitive amplification, wherein:
• the optical-transport link is configured to generate, via said phase-sensitive amplification, a third modulated optical signal and a fourth modulated optical signal at a remote end of the optical-transport link;
• each of the first and third modulated optical signals has a first carrier frequency;
• and
• each of the second and fourth modulated optical signals has a second carrier frequency different from the first carrier frequency.

An apparatus, comprising:

• a nonlinear optical device configured to optically mix, via a first nonlinear optical process, a first modulated optical signal and a second modulated optical signal to generate a first mixed signal and a second mixed signal;
• an optical detector configured to generate a first measure and a second measure, said first measure being a measure of the first mixed signal and said second measure being a measure of the second mixed signal;
• and
• a signal processor configured to:
• determine a constellation symbol based on the first and second measures;
• and
• decode the constellation symbol to determine a corresponding bit word carried by the first and second modulated optical signals;
• and
• wherein the optical detector comprises:
• a first optical mixer configured to optically mix the first mixed signal with a first local-oscillator (LO) signal to generate first and second optical interference signals, wherein the first LO signal has a carrier frequency corresponding to a carrier frequency of the first modulated optical signal;
• a second optical mixer configured to optically mix the second mixed signal with a second LO signal to generate third and fourth optical interference signals, wherein the second LO signal has a carrier frequency corresponding to a carrier frequency of the second modulated optical signal and different from the carrier frequency of the first LO signal;
• and
• an optical-to-electrical converter configured to convert (i) the first and second optical interference signals into the first measure and (ii) the third and fourth interference signals into the second measure.