Nonlinear distortion evaluation of MZM with equivalent mathematical model calculation in IM/DD OOFDM transmission system

We propose an approach by reducing the distortion to signal ratio (DSR) of Mach-Zehnder modulator (MZM) to improve the bit error rate (BER) performance in intensity modulated and direct detected (IM/DD) optical orthogonal frequency division multiplexing (OOFDM) system. The DSR of the MZM, which is a measurement of nonlinear distortions induced by MZM, can be correctly evaluated by building an equivalent polynomial model, and then minimized with partial transmit sequence (PTS) technique without over-sampling. Experimental results demonstrate that compared to the original scheme and peak to average power ratio (PAPR) reduction with PTS scheme, the improvement of the receive sensitivity by the proposed scheme is 2.8 dB and 1.2 dB, respectively, at the BER of 1×10−3 after transmission over 100 km standard single-mode fiber. The theory analysis also shows the proposed scheme can reduce computational complexity significantly compared to the PAPR-PTS scheme.