Abstract

We experimentally demonstrate digital signal processing (DSP)-free 8 × 10 Gb/s 4-level pulse-amplitude modulation (PAM-4) transmission for cost-effective coherent wavelength division multiplexing passive optical network (WDM-PON) with 20 GHz channel spacing over the C-band. The polarization-independent coherent receiver at optical network unit (ONU) including a 3 × 3 fiber coupler and a polarization beam splitter (PBS) followed by three single-ended photodiodes (PDs), is simple and cost-effective, because neither DSP nor phase/frequency locking is necessary for the coherent detection of PAM-4 signal. We numerically compare the performance between the transmitted signal diversity and the local oscillator (LO) signal diversity schemes, and optimize the parameters of heterodyne detection, in order to enhance the power budget. Based on the LO signal diversity scheme, we can achieve an average receiver sensitivity of −26 dBm for eight wavelength channels at a bit error ratio (BER) below the hard-decision forward error correction (HD-FEC) threshold (i.e., 3.8 × 10⁻³), leading to a power budget of 29 dB after 25 km standard single-mode fiber (SSMF) transmission. Moreover, we verify an unequally spaced PAM-4 signaling, leading to contribution of 1 dB receiver sensitivity improvement for 10 Gb/s/λ PON.

Unequally spaced PAM-4 signaling enabled sensitivity enhancement of a simplified coherent receiver applied in a UDWDM-PON

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200 Gbit/s/λ PDM-PAM-4 PON system based on intensity modulation and coherent detection

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Direct DPSK modulation of chirp-managed laser as cost-effective downstream transmitter for symmetrical 10-Gbit/s WDM PONs

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Ultra-dense WDM-PON 6.25 GHz spaced 8×1 Gb/s based on a simplified coherent-detection scheme

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Low-complexity equalizer with a hybrid decision scheme for 50 Gb/s/λ PAM4-PON using a low-cost 10 G receiver

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Opt. Lett. 45(22) 6278-6281 (2020)