Impact of Modulator Bias on the OSNR Requirement of Direct-Detection Optical OFDM

In optical orthogonal frequency-division multiplexing (OFDM) with direct detection, modulator bias voltage has a significant impact on receiver sensitivity. It is a compromise between control of carrier power and nonlinear distortion of the OFDM signal. In this letter, sensitivity improvement due to reduction of carrier power is treated analytically. Its range of validity is examined by simulation. The impact of nonlinearity is identified as the difference in sensitivity between a linear and a nonlinear model.