Measurement and system impact of multipath interference from dispersion compensating fiber modules

Dispersion compensating modules (DCM) are key components in long distance and high-speed fiber-optic transmission systems. However, many types of DCMs exhibit multipath interference (MPI) that acts as noise in transmission and degrades the bit error rate of the system. Further, MPI generated in DCMs is mostly due to forward scattering and mostly of the coherent type. This type of MPI cannot be correctly measured using conventional measurement techniques that use electrical spectrum analysis to measure post-detection noise. We demonstrate an accurate and simple method of MPI measurement using a swept wavelength system apparatus. We discuss the strengths and limitations of this measurement method and show system results of Q penalty due to MPI from concatenated DCMs.