Optical polar OFDM: on the effect of time-domain power allocation under power and dynamic-range constraints

Polar OFDM (P-OFDM) is an OFDM format that can double the spectral efficiency of existing real-valued and unipolar optical OFDM intensity-modulation with direct detection (IM/DD) optical communication systems. P-OFDM modulates the amplitude and phase of a complex OFDM signal to allow a real unipolar signal. In this paper, we investigate the effect of power allocation to the phase and the amplitude components of P-OFDM time-domain signal on (1) the effective signal-to-noise ratio (SNR) at the receiver (2) the peak-to-average power ratio (PAPR) under transmit power constraint and (3) the induced clipping noise under optical-source's dynamic-range and transmit power constraints. In addition to a 4 dB reduction in PAPR from ACO-OFDM, we demonstrate the improvement of throughput for P-OFDM over other optical OFDM methods when the signal power is limited.