PWM fronthauling in reflective PON

Pulse width modulation (PWM) has recently been proposed for analog optical fronthauling in centralized radio access networks (CRANs) to avoid the bandwidth expansion of digital fronthauling (e.g., common public radio interface protocol, CPRI). At the transmitter, the radio-signal is mapped onto the duration of an on/off keyed optical signal, while at the fiber receiving-end each PW optical modulated sample is digitized so that the overall analog communication link is transparent. In this framework, we propose a new architecture for optical transmission of PW modulated signals, based on the reflection at the remotized antennas of a seeding signal originated at the baseband unit (BBU). Pros and cons of PWM fronthauling in reflective passive optical network (PON) are evaluated by investigating the outcomes of an in-lab experiment that implements a CRAN fronthauling of 100-MHz RF signals with single-carrier 64QAM modulation up to 20-km standard single mode fiber. Experimental results provide some room for discussion on PWM fronthauling technique.