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 semi-active WDM scheme, WDM technology is applied as an optical transport layer to save fibers and the semi-active 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 micro-controller 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.
Highlights
Centralized radio access network (C-RAN) architecture is a promising way for 5G RAN network [1]–[7], which is capable of decreasing power consumption, saving machine room, promoting collaborative radio, etc
12-channel bidirectional wavelength division multiplexing (WDM) centered from 1267.5 nm to 1374.5 nm is applied as an example of the physical layer. 25-Gbps enhanced common public radio interface (eCPRI) wireless services are transformed from electrical signals to optical signals in the WDM optical modules of the antenna unit (AAU) and distributed unit (DU)
The 25-Gbps eCPRI signals are generated and detected by a service analyzer. 1024-bps OAM signals are modulated onto the 25-Gbps signals simultaneously in the transceivers
Summary
Centralized radio access network (C-RAN) architecture is a promising way for 5G RAN network [1]–[7], which is capable of decreasing power consumption, saving machine room, promoting collaborative radio, etc. The theoretical analysis show that the pilot-tone relay detection can reduce system cost and release sensitivity requirements significantly compared with the OAM demodulation both in upstream and downstream direction for the active WDM equipment.
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