Signal Processing Algorithms for Down-Stream Traffic in Next Generation 10 Gbit/s Fixed-Grid Passive Optical Networks

Abstract

We have analyzed the impact of digital and optical signal processing algorithms, that is, Volterra equalization (VE), digital backpropagation (BP), and optical phase conjugation with nonlinearity module (OPC-NM), in next generation 10 Gbit/s (also referred to as XG) DP-QPSK long haul WDM (fixed-grid) passive optical network (PON) without midspan repeaters over 120 km standard single mode fiber (SMF) link for downstream signals. Due to the compensation of optical Kerr effects, the sensitivity penalty is improved by 2 dB by implementing BP algorithm, 1.5 dB by VE algorithm, and 2.69 dB by OPC-NM. Moreover, with the implementation of NL equalization technique, we are able to get the transmission distance of 126.6 km SMF for the 1 : 1024 split ratio at 5 GHz channel spacing in the nonlinear region.

Low Complexity Multichannel Nonlinear Predistortion for Passive Optical Networks

“…Fiber nonlinearity will have an impact on these channels due to self phase modulation (SPM) but, additionally, due to cross phase modulation (XPM). SPM could be compensated at the ONU using digital back propagation (DBP) [2], however the sensitivity gain is limited by the noise introduced in the receiver (i.e., shot noise) [3], and the tolerable ONU complexity. To overcome this issue, DBP could be applied as a signal predistortion at the optical line terminal (OLT), exploiting the high transmitted signal-to-noise ratio (SNR) 1 , while moving complexity away from the ONU.…”

“…For a high transmitted SNR, transmitter-side DBP will effectively linearize the transmission channel in a single span transmission system 2. Nyquist pulse shaping of channels has the additional benefit of crosstalk mitigation at the ONU[6,7], and would likely be used regardless of the method of channel generation.…”