Electrical measurements of multipath interference in distributed Raman amplifiers

Measurements of multipath interference (MPI) using an electrical technique have shown that the use of distributed Raman amplification can significantly increase the amount of MPI in a system. The MPI is primarily attributed to double-Rayleigh scattering along the length of the transmission fiber. Analytical expressions for MPI have been developed that give good agreement with measurements and numerical simulations. These can be used to predict the buildup of MPI in a lightwave transmission system. Poor connectors will cause a further increase in MPI by causing back-reflections into the Raman gain cavity.