Multi-Tap Optical Delay Line-Based Optical-Electrical Dispersion Compensation Scheme in High-Speed IM/DD Systems

Digital equalizer-assisted optical signal processors based on optical delay line (ODL) offers an efficient solution for chromatic dispersion (CD) compensation in intensity-modulation/direct-detection (IM/DD) transmission systems. In this paper, a multi-tap ODL-based optical-electrical dispersion compensation scheme is proposed to enhance CD compensation effectiveness. The scheme combines a low-complexity digital equalizer with multi-tap cascaded ODL (C-ODL) and feedforward ODL (F-ODL) based on distinct optical architectures. In addition, the theoretical model derivation reveals that the frequency response of the multi-tap ODL scheme achieves a flat spectrum through the superposition of diverse frequency responses. Verified in a C-band 112 Gb/s 40-km PAM4 system, C-ODL and F-ODL schemes exhibit 3-dB and 2.9-dB received optical power (ROP) gains at 7% forward error correction (FEC) limit over the single-tap ODL scheme, and achieve the KP4-FEC limit at ROPs of −5 dBm and −5.4 dBm with 30 and 53 real-valued multiplications, respectively. Furthermore, C-ODL and F-ODL schemes with optimal parameters can reach the KP4-FEC limit at the maximum CDs of 680 ps/nm and 850 ps/nm. The research results indicate that the proposed multi-tap ODL scheme exhibits significant potential for compensating CD in high-performance and complexity-effective IM/DD optical transmission systems.