Iterative Block Decision Feedback Equalization for IM/DD-Based OCDM to Compensate Chromatic-Dispersion-Induced Power Fading

Orthogonal chirp-division multiplexing (OCDM) has recently been proposed as an attractive modulation technique for high-speed fiber-optic systems in virtue of its resilience against system impairments. In this paper, we propose an iterative block (IB) decision feedback equalization (DFE) algorithm for the intensity-modulation and direct-detection (IM/DD) based OCDM system to effectively mitigate the chromatic-dispersion (CD) induced power fading in the fiber. An efficient algorithm is derived to simplify the IB-DFE at the receiver. Analysis is provided to show that the fading effect is compensated by recovering the noisy signals in the vicinity of frequency notches. Simulations were carried out to study the performance of the proposed system. The results show that the proposed system with IB-DFE is able to compensate severe fading effects and improves the bit error rate (BER) by several orders of magnitude. An experiment was implemented to realize 30.3-Gb/s IM/DD-OCDM signal over 50-km fiber, in which power fading due to CD over 20 dB was observed. The experiment results show that the proposed system further reduced the required optical signal-to-noise ratio by 8 dB to achieve a BER of 3 × 10
^-5
.