High-Capacity Carrierless Amplitude and Phase Modulation for WDM Long-Reach PON Featuring High Loss Budget

This paper utilizes spectrally efficient carrierless amplitude and phase (CAP) modulation and four wavelength division multiplexing channels in formulation of a high-capacity transmission system. The dispersion and loss associated with a single-mode fiber of 60 km can result in severe power fading and insufficient loss budget, respectively. This study employed high launch power to overcome these issues and thereby achieve long-reach transmission without the need for dispersion compensation or an optical inline amplifier. Modified Volterra filtering is used to deal with the linear and nonlinear distortions within the system. This allowed for the inclusion of cost-effective 10-GHz-class electro-absorption modulators and p-i-n detectors for 4-<inline-formula> <tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> 224-Gb/s 32-CAP 60-km transmission with a loss budget of 26 dB/channel. The proposed system provides support for the 64 optical network units (ONUs) with downstream transmission of <inline-formula><tex-math notation="LaTeX">$>$</tex-math></inline-formula> 3 Gb/s/ONU for future long-reach passive optical networks. We also examined the transmission performance of each channel under various launch powers. Increasing launch power from 9  to 18 dBm/channel increases the loss budget by 9 dB and expands the total capacity by 42%.