Remote Seeding Scheme for Colorless Optical Network Units (ONUs) in Ultra-Dense Wavelength Division Multiplexing (UDWDM) Networks
Abstract
This paper addresses the need for spectrally efficient and cost-effective optical access networks by investigating a remotely seeded, colorless optical network unit (ONU) architecture for bidirectional ultra-dense wavelength division multiplexing passive optical networks (UDWDM-PONs). The practical contribution of the work is the integrated evaluation of a full bidirectional architecture that combines remote seeding, colorless ONU operation, and odd/even downstream-upstream wavelength allocation to mitigate Rayleigh backscattering and back-reflection while preserving high spectral efficiency. The system was implemented in OptiSystem and first evaluated for 8 users over a 20 km optical link at 25 GHz channel spacing and 10 Gbps in both directions, then extended to narrower channel spacing and reduced bit-rate cases of 12.5 GHz/5 Gbps, 6.25 GHz/2.5 Gbps, and 3.125 GHz/1.25 Gbps to assess scalability. The results show reliable operation across all investigated cases, with BER values below the 10-8 criterion; receiver sensitivities of -22.22 to -26.56 dBm for downstream and -22.02 to -26.37 dBm for upstream transmission; and aggregate full C-band support up to 960 Gbps. The investigated transmitted-power window of -8 to 8 dBm provides the most useful operating range for balancing BER improvement, Q-factor enhancement, and system margin.