Complex-valued decision feedback equalizer for optical IMDD signals with adaptive manipulations in time and amplitude domains

Abstract

In this work, we innovatively equalize optical intensity-modulated and directly detected (IMDD) four-level pulse amplitude modulation (PAM-4) signals using a complex-valued decision feedback equalizer (CDFE). Through mapping adjacent symbols of PAM-4 signals onto the complex domain, the influence of strongest inter-symbol interference (ISI) can be alleviated during the decision process in a decision feedback equalizer (DFE), effectively combating burst-error propagation when signals are noisy. Moreover, signal-adaptive manipulations of DFE parameters in both the time and the amplitude domain are performed by using an ultra-stable timing recovery and level-adaptive decision. Performance evaluations are made on vertical cavity surface emitting laser (VCSEL) modulated and multimode fiber (MMF) transmitted 100-Gbit/s optical PAM-4 signals. Based on experimental results of the short-reach optical communication, the proposed DFE outperforms the traditional DFE with a 0.5-dB system power budget gain at the 7% overhead (OH) forward error correction (FEC) bit error rate (BER) threshold.

Integer codes correcting single errors and double adjacent errors

“…The essence of our idea is to replace the IC with integer single-error-correcting-double-adjacent-error-correcting (SEC-DAEC) codes. The use of such codes could significantly improve data transmission between edge routers and end nodes (computers and servers), especially if they are interconnected by optical links (according to [9][10][11][12][13][14][15][16], 87% to 99% of all channel errors, which occur on optical links, are single and double adjacent (DA) errors). In addition, the receiver would not be subject to any hardware changes, since the proposed codes are a generalization of the IC.…”