Offset double sideband carrier assisted differential detection with field recovery at low carrier-to-signal power ratio

Abstract

Four system frameworks based on carrier assisted differential detection (CADD) receivers for offset double sideband (DSB) signal transmission, including offset DSB asymmetric CADD (offset DSB A-CADD), offset DSB symmetric CADD (offset DSB S-CADD), offset DSB parallel double delay asymmetric CADD (offset DSB PDD-A-CADD), and offset DSB parallel double delay symmetric CADD (offset DSB PDD-S-CADD) are proposed to reduce the requirement for carrier-to-signal power ratio (CSPR) and improve the spectral efficiency (SE) of the self-coherent detection. These frameworks accommodate signal-signal beat interference (SSBI) and efficiently solve the noise enhancement by placing a frequency gap as wide as the signal bandwidth in the middle of the left and right sideband signal. Massive theoretical derivation and simulation verification illustrated that compared with previous interleaved A-CADD, our system achieve field recovery under the condition of 0 dB CSPR with the improvement of SE by 5%, and the OSNR sensitivity is improved by 4.5 dB with 20% forward error correction (FEC) threshold. In addition, due to the devices’ limited bandwidth (BW), the information-bearing signal is attenuated at the high-frequency region. And since SSBI has less influence on the signal in the high-frequency region, the frequency gap of the four offset DSB CADD schemes are compressed to utilize as much low-frequency resource as possible and improve the SE. Efficient compression of the frequency gap from 50% to 32.3% with 20% FEC threshold and 50% to 37.7% with 7% FEC threshold at 0 dB CSPR is achieved, and only a slight performance degradation is observed. At this time, the SE is improved by 22.7% and 17.3% with different FEC thresholds, respectively, compared with the 5% frequency gap interleaved A-CADD.

Machine Learning for Self-Coherent Detection Short-Reach Optical Communications

“…As a result, single-sideband (SSB) modulation systems without vestigial components have been developed as an alternative [14][15][16][17], which can be achieved using IQ modulators or optical frequency shifters. To further improve the electrical SE and transmission capacity beyond the SSB systems, single-polarization phase retrieval (PR) receiver [18][19][20][21], carrier-assisted differential detection (CADD) receiver [10,22,23], and asymmetric self-coherent detection (ASCD) receiver [24] have been proposed to achieve linear detection of complex-valued DSB signals, effectively doubling the electrical SE with respect to SSB and IM-DD systems. Additionally, polarization-division-multiplexing can double the capacity and SE of single-polarization direct detection systems.…”