Influence of the device parameters in ICRBD on SSB-OOFDM signal with reduced guard band

The paper has theoretically evaluated a signal-signal beat interference (SSBI) cancellation receiver with the balanced detection (ICRBD) for single sideband optical orthogonal frequency division multiplexing (SSB-OOFDM) signal, which has an improved spectral efficiency (SE) by reducing the guard band (GB) between the OOFDM signal and the optical carrier. The influences of the parameters of the interleaver (IL), the optical coupler (OC), and the balanced photodiodes (BPD) as well as the connecting optical/electrical paths in the ICRBD on the received OFDM signal performance are studied in detail. The theoretical results show that the received OFDM signal and noise power are dependent on the parameters of the devices and their deviation away from the ideal value degrades the performance greatly. Based on the simulation system, the 40 Gb/s 16QAM SSB-OOFDM signal with 5 GHz GB is converted to the OFDM signal by the ICRBD with the suppressed SSBI. It is observed that (1) the received OFDM signal is insensitive to the deviation of the coupling coefficient of the 3 dB OC; (2) the received signal suffers little degradation from the filter outline of the IL if an IL with the bandwidth over 13 GHz and 6- or higher-order Gaussian filter is used; (3) the polarization deviation and phase shift between the OOFDM signal and the optical carrier caused by the optical paths between IL and OC have smaller influence on the EVM of the received signal; and (4) although the ICRBD is immune to the polarization deviation of the two recombined SSB-OOFDM signals, the relative time delay between the two optical/electrical paths from the OC to the BPD degrades the received signal seriously. By tuning the time delay in optical or electrical domain to reduce the total relative time delay within 10 ps, the EVM maintains below 20%. The simulation results agree well with the theoretical analysis and catch an insight on the mechanism of the ICRBD.