Semi-Active Wavelength Division Multiplexing System Based on Pilot-Tone Relay Detection for 5G Centralized Front-Haul Network

Abstract

A semi-active wavelength division multiplexing (WDM) system based on pilot-tone relay detection is proposed and experimentally demonstrated for 5G centralized front-haul network, which is composed of a passive WDM multiplexer at active antenna unit (AAU) side, an active WDM equipment at distributed unit (DU) side, and several WDM optical modules in AAU and DU, respectively. In this semiactive WDM scheme, WDM technology is applied as an optical transport layer to save fibers and the semiactive architecture based on pilot-tone modulation is capable of flexible deployment with lite operation, administration and maintenance (OAM) functions. The experimental results show that the sensitivity penalty is lower than 0.3 dB and the extinction ratio is still higher than 4.2 dB by using 4 % amplitude depth of pilot-tone modulation. The bit rate of the OAM signal is 1024 bps to reuse the existing microcontroller unit in the optical modules for generating and detecting OAM signals. The robustness of the pilot-tone signals is further demonstrated as the sensitivities of the 25-Gbps eCPRI signals and the 1024-bps OAM signals are -16 dBm and -23 dBm, respectively. Compared with the OAM demodulation both in upstream and downstream direction for the active WDM equipment, the number of OAM demodulation unit can be reduced by 50% and the sensitivity requirement of OAM demodulation can be improved by 11.5 dB by using only downstream OAM demodulation unit. Error-free 24-hour transmission of real-time 12-channel 25-Gbps eCPRI signals combined with 1024-bps pilot-tone OAM signals over 10-km single mode fiber is obtained.

Interoperable pilot tone technology applied in 100Gb/s multichannel IM-DD optical modules

“…Currently, pilot tone technology has been applied in some 25Gb/s semi-active systems at wireless fronthaul field [6], it is predicable that this technology may be used for other higher rate modules in future especially between those cross domain optical networks nodes. The pilot tone signal transmission protocol has universality and expansibility, and it is also can be regarded as important reference to suit for other IM-DD optical modules with different bit rate and transmission distance, including beyond 400G silicon photonics based transceivers in the future.…”