Abstract
We propose a novel zero guard band (ZGB) multi-twin-SSB bidirectional passive optical network system which combines the multiband carrier-less amplitude phase and twin single sideband (SSB) modulation techniques. The multi-twin-SSB signal is generated at the downlink transmitter side with zero guard band between the left-sideband and right-sideband. A weak local oscillator which is extracted from the uplink optical source aids the downstream signal detection. Kramers-Kronig algorithm is used at both downlink and uplink receiver sides to reconstruct the SSB signal and eliminate the signal-signal beat interference. The downstream and upstream signals are transmitted in a single fiber without any spectral overlap between them and the Rayleigh backscattering noise is removed by the optical band-pass filter. The proposed scheme is extensively investigated and analyzed with four sub-bands using 50 Gbps 16-QAM modulation for each sub-band over a bidirectional 50 km transmission. The results show that, compared with the conventional multi-twin-SSB scheme, the proposed ZGB multi-twin-SSB scheme can improve the spectral efficiency by about 11%. The required optical signal to noise ratio (OSNR) and the required received optical power (ROP) can be reduced by more than 15 dB and 7 dB respectively at the 7% hard decision forward error correction (HD-FEC) threshold (bit error rate of $3.8\times 10^{-3}$ ), respectively. For the uplink transmission, the required ROPs for the inner and outer sub-bands at 7% HD-FEC are about −10 dBm and −11 dBm, respectively. And the signal to noise ratio to the corresponding ROPs for the inner and outer sub-bands are 15.4 dB and 15.3 dB, respectively.
Highlights
With the continuous growing number of network users and the emergence of new network business applications such as live-streaming of high definition video multimedia and cloud computing using remote data storage, the potential capacity demand imposes challenging burdens on passive optical networks (PONs) [1]–[10]
Digital chromatic dispersion (CD) compensation is conducted in the frequency domain and the data stream corresponding to i-th optical network units (ONUs) was digitally filtered by a matched filter (MF)
KK algorithm is adopted at the receiver side digital signal processing (DSP) to reduce the required carrier to signal power ratio (CSPR) as well as eliminate the signal-signal beat interference (SSBI) induced by the square-law detection
Summary
With the continuous growing number of network users and the emergence of new network business applications such as live-streaming of high definition video multimedia and cloud computing using remote data storage, the potential capacity demand imposes challenging burdens on passive optical networks (PONs) [1]–[10]. Some key advantages of the proposed ZGB multi-twin-SSB scheme are listed as follow: 1) No guard band is needed between the LSB and RSB signals so the SE is higher than that of conventional twin-SSB scheme; 2) The required optical signal to noise ratio (OSNR) for the downlink transmission is reduced and the receiver sensitivity is improved due to the optical carrier suppressed transmission and the heterodyne detection; 3) The SSBI is eliminated and the required optical LO power from the uplink laser is reduced because of the application of the KK algorithm. The KK algorithm can greatly reduce this distributary power because required CSPR for the KK receiver is much lower than the conventional receiver
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