Joint Bandwidth Limitation and Electrical Dispersion Pre-Compensation in Cost-Sensitive IM/DD Transmission Systems

The modified Gerchberg-Saxton (GS) algorithm provides an effective solution for electrical dispersion pre-compensation (pre-EDC) in short reach intensity modulation and direct detection (IM/DD) optical fiber transmission systems. To further enhance its performance under bandwidth-limited IM/DD systems, a joint bandwidth limitation and electrical dispersion pre-compensation (pre-BL-EDC) scheme is proposed. In this scheme, an equalization filter for bandwidth limitation (BL) is integrated into the modified GS pre-EDC, and a 2-tap finite impulse response (FIR) filter is introduced to improve the pre-compensation performance. In this way, simultaneous pre-compensation of BL and chromatic dispersion (CD) can be achieved at the transmitter, eliminating the need for any post-equalization at the receiver. Simulation results in a C-band 56 Gbit/s on-off keying (OOK) system demonstrate that the pre-BL-EDC can improve the bit error ratio (BER) performance and reduce device bandwidth requirements. Under back-to-back (BTB) transmission, bandwidth limitation pre-compensation (pre-BLC) improves receiver sensitivity by 2.2 dB, 1.8 dB, and 1.4 dB at the hard-decision forward error correction (HD-FEC) threshold for 24 GHz, 32 GHz, and 40 GHz bandwidths, respectively, compared to without pre-compensation. Under 80 km transmission, the receiver sensitivity of pre-BL-EDC is 3.2 dB, 2.8 dB and 1.0 dB higher than that of modified GS pre-EDC for the above corresponding bandwidths. Moreover, pre-BL-EDC allows for longer transmission distances in bandwidth-limited systems. Taking 32 GHz bandwidth as an example, for transmission distances ranging from 10 km to 100 km, the BER can be below the HD-FEC threshold using pre-BL-EDC, whereas it cannot be achieved using modified GS pre-EDC. The proposed scheme is further validated by an experimental system with 3-dB bandwidth of 9 GHz at different baud rates over a 50 km transmission. For OOK signals at 20 Gbit/s, 28 Gbit/s and 32 Gbit/s, the receiver sensitivity gains of pre-BL-EDC compared to modified GS pre-EDC are 1.0 dB, 1.0 dB and 2.0 dB at the HD-FEC threshold, respectively.