High-speed IM-DD optical interconnect based on low-complexity ISI-reconstructed detection for bandwidth and...

Intensity modulation and direct detection (IM-DD) has been widely adopted in short-reach optical interconnects, owing to its low cost and hardware simplicity. However, as symbol rates scale beyond 100 Gbaud, bandwidth limitations emerge as critical challenges, arising from both link dispersion-induced power fading and transceiver bandwidth constraints. While maximum likelihood sequence detection (MLSD) can address these impairments, its exponential computational complexity hinders practical deployment. In this work, we propose a low-complexity inter-symbol interference reconstructed (ISI-R) detection to mitigate the ISI in bandwidth-limited systems and suppress the equalization-enhanced colored noise. With less than 8 iterations, the decision of the received symbols' coverages, resulting in a reduced BER without using sequence detections. We experimentally demonstrate high baud rate IM-DD transmission with a 128-GSa/s DAC sampling rate. The bandwidth limitation is caused by sub-sampling signal generation and dispersion-induced power fading. In the experiment, up to 152-Gbaud on-off keying (OOK), 112-Gbaud 4-level pulse amplitude modulation (PAM-4), and 92-Gbaud PAM-6 signals are transmitted through 2-km standard single-mode fiber (SSMF), respectively, showing improved BER performances with the help of ISI-R detection. Compared to MLSD, there is an 88% decrease in the number of multiplications for PAM-4 signals. The proposed scheme offers a low-complexity and power-efficient candidate for next-generation optical interconnects.