Demonstration of record sensitivity in an optically pre-amplified receiver by combining PDM-QPSK and 16-PPM with pilot-assisted digital coherent detection

Abstract

We propose a power-efficient modulation/detection scheme that combines PDM-QPSK and 16-ary-pulse-position-modulation. A record sensitivity of 3.5 photons per bit at BER=10−3 is experimentally demonstrated at 2.5 Gb/s with digital coherent-detection, outperforming PDM-QPSK by >3 dB.