Power Efficient Communications Employing Phase Sensitive Pre-Amplified Receiver

The receiver sensitivity is a very important metric in optical communication links operating at low received signal powers. Phase sensitive optical amplifiers (PSAs) can amplify optical signals without excess noise, thus providing a fundamental sensitivity improvement of 3 dB when employed as a pre-amplifier compared to conventional erbium doped fiber amplifiers (EDFA). In this letter, we investigate, both theoretically and experimentally, the sensitivities achieved using power efficient multi-dimensional modulation formats such as M-ary pulse position modulation format (M-PPM) and M-PPM combined with quadrature phase shift keying (QPSK) along with a near-noiseless PSA pre-amplified coherent intradyne receiver. We find that at high signal to noise ratios (SNRs) corresponding to low bit-error-rates (BER), M-PPM+QPSK results in the hest sensitivity, which is improved with the order M, while at low SNRs corresponding to high BER (similar to 14% where 100% overhead forward error correction codes (FEC) would he needed to recover the data), QPSK is the most sensitive format, while at the same time providing the best spectral efficiency. We report experimental sensitivities of 2.1 photons per information bit (PPB) at a pre-FEC BER = 10(-3) using 64-PPM+QPSK and assuming 7% FEC, and 0.8 PPB at a pre-FEC BER = 0.14 using QPSK and assuming 100% FEC.

Automated summary

This letter investigates the sensitivities achieved using power efficient multi-dimensional modulation formats and a near-noiseless PSA pre-amplified coherent intradyne receiver. The results show that M-PPM+QPSK has the highest sensitivity at high SNRs, while QPSK has the highest sensitivity and best spectral efficiency at low SNRs.