Semi-passive optical front-haul supporting channel monitoring and link protection for the cloud radio access network.

To accommodate the extremely large traffic load on the front-haul of a cloud radio access network, optical fibres along with wavelength division multiplexing (WDM) technology have become the de facto solution. In this study, the authors propose the model of a semi-passive front-haul device that can overcome the vulnerability of the optical fibre by using duplicated optical fibres and optical power monitoring for each WDM channel. Experiments conducted on the implemented prototype demonstrate that the link protection mechanism satisfies the regulation imposed by the international standard and that the optical power monitoring results are accurate. Thus, the proposed semi-passive front-haul device provides a high link reliability, fault reporting capability, and low operating cost.