In this paper we present the simulative analysis of a 200 Gbps per wavelength (λ) 8-level pulse amplitude modulation (PAM-8) downstream communication over up to 20 km single mode fiber (SMF) in C-band based on direct detection (DD) achieving at least a 29 dB link power budget in a PON environment. We use chromatic dispersion digital pre-compensation (CD-DPC) and a dual-arm in-phase and quadrature Mach–Zehnder modulator (IQ-MZM) at the optical line termination (OLT) side, while preserving DD in the optical network unit (ONU). Three receiver digital-signal-processing (DSP) options are analyzed and compared: square-root-like technique (SQRT) in combination with a feed forward equalizer (FFE) and a decision feedback equalizer (DFE), the Volterra nonlinear equalizer (VNLE), and the SQRT in combination with the VNLE. The SQRT can be applied in combination with the VNLE to decrease the receiver DSP complexity while maintaining the required system performance. We show that PAM-8 with CD-DPC and the SQRT in combination with the VNLE is a feasible solution for 200 Gbps per λ downstream C-band transmission for PON.
In the scenario of downstream Passive Optical Networks (PON), we analyze through simulations and experiments a 100 Gbps/λ link using digital signal processing (DSP) over up to 50 km single mode fiber (SMF) in C-band. In particular, we propose chromatic dispersion digital pre-compensation (CD-DPC) and quaternary pulse amplitude modulation (PAM-4) levels optimization at the transmitter side (TX), and simple non-linear compensation (NLC) in combination with adaptive equalization (AEQ) at the receiver side (RX). Regarding NLC, we compare two approaches: a quadratic polynomial function and a square-root-like function respectively. In this paper, we analyze in detail the performances of four proposed options, namely equispaced PAM-4 levels without NLC (baseline case), equispaced PAM-4 levels in combination with NLC, optimized PAM-4 levels without NLC, and optimized PAM-4 levels in combination with NLC. We demonstrate through simulations and experiments that optimized PAM-4 levels can only offer limited enhancement when NLC is applied, and up to 3.3 dB sensitivity gain can be obtained thanks to NLC at RX when setting the optimum parameters, with respect to the baseline case.
In this paper we present an experimental analysis of several modulation formats (pulse amplitude modulation (PAM-2), quaternary pulse amplitude modulation (PAM-4) and electrical duobinary (EDB)) for passive optical network (PON) applications at 25 Gbps bit rate in a C-band 10G-class directly modulated lasers (DML) and avalanche photodiode (APD) intensity modulation and direct detection (IM-DD) system over a single mode fiber (SMF) of up to 25 km, optimizing DML operations and demonstrating that PAM-2 is a promising choice. We also theoretically and experimentally analyzed the channel frequency response of DML and SMF affected by DML chirp and SMF chromatic dispersion.
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