Pulse Width Modulation for Fronthaul in a Broadband-Seeded RSOA WDM PON

Pulse width modulation (PWM) can support centralized radio access networks in analog optical fronthaul, avoiding the bandwidth expansion of the digital fronthaul. The PWM encodes the analog samples at the transmitter onto the duration of the on-off-keyed optical signal, splitting the sampling and quantization of the radio signal between remote radio units (RRUs) and baseband units (BBU). In-between the PWM encoded signal is transmitted over a novel wavelength-division-multiplexed passive optical network (WDM PON) architecture, exploiting broadband-seeded reflective semiconductor optical amplifiers in a polarization retracing circuit, which is resilient to Rayleigh scattering impairments. Multiple RRU-to-BBU links are supported through virtual point-to-point connections based on the wavelength resource. We demonstrate the performance of the proposed PWM-based colorless self-tuning WDM PON supporting the fronthaul of 100-MHz RF signals up to 20-km transmission over standard single mode fiber for 30 WDM channels.