Low-complexity single-feedback SSBI cancellation for independent dual-SSB direct detection systems

This article proposes a low-complexity single-feedback reconstruction and cancellation (SFRC) algorithm for signal-signal beat interference (SSBI) suppression in independent dual single-sideband (dual-SSB) direct detection systems. SFRC combines a Hilbert-transform-based preliminary estimate with a single feedback loop to cancel the complete SSBI (including self-beating and mutual-beating terms) in a single pass, achieving superior suppression accuracy with lower DSP overhead. Simulations over 90 km standard single-mode fiber (SSMF) show that, at the hard-decision forward error correction (HD-FEC) threshold, SFRC achieves an upper sideband (USB) received optical power (ROP) gain of 1.3 dB and 1 dB carrier-to-signal power ratio (CSPR) tolerance improvement over the two-iteration iterative SSBI cancellation (ISSBIC) algorithm, with consistent improvement also observed on the lower sideband (LSB). At 16 GBaud, SFRC effectively suppresses the bit error rate (BER) upturn at high ROP exhibited by conventional algorithms, demonstrating robustness for high-speed, low-cost short-reach optical interconnects.