A complete fronthaul CWDM single fiber solution including improved monitoring scheme

Fronthaul is a network segment between Remote Radio Head (RRH) situated on the antenna site, and the Base Band Unit (BBU) localized in the Central Office. It uses the Common Public Radio Interface protocol (CPRI). A point to point physical topology can be used, but the deployment of this configuration uses a lot of optical resources. Coarse Wavelength Division Multiplexing (CWDM) dual fiber and single fiber links can be used to reduce the number of optical fibers. This paper focuses on the single fiber links because in addition to others advantages of this system, it uses less fiber than the CWDM dual fiber system. The difficulty to build a complete fronthaul single fiber solution is to provide a monitoring system in addition to CPRI data transport. We propose to characterize, in terms of Bit Error Rate (BER) CPRI requirements, a fronthaul CWDM single fiber link up to 4.9 Gbits/s. Furthermore, an innovative single fiber monitoring scheme, based on the reduction of Rayleigh Backscattering light in the fiber is illustrated. This reduction is carried out due to the combination of a Polarization Beam Combiner and a Faraday Rotator Mirror. This reduction allows improving the capacity of failure detection of the fiber in the CWDM single fiber technology.