Probabilistic Amplitude Shaping for a 64-QAM OFDM W-Band RoF System

In this letter, probabilistic amplitude shaping (PAS) is performed in the case of orthogonal frequency division multiplexing (OFDM) by combining with orthogonal circulant matrix transform (OCT) precoding. Thanks to the precoding method, one optimized probabilistic distribution is globally implemented across 240 subcarriers by merely one distribution matcher (DM). The proposed probabilistic shaping scheme for OFDM is experimentally demonstrated in a 64-ary quadrature amplitude modulation (QAM) W-band radio-over-fiber (RoF) system using direct-detection (DD), with 20-km single-mode fiber (SMF), and 0.5-m free-space transmission. The experimental results show that, compared to the uniform 64-QAM, there is 1.07-dB shaping gain for system sensitivity at BER of 10
^-4
. Meanwhile, it inherits the advantage of flexible capacity granularity from the conventional single-carrier PAS.