Relationship Between Mode Coupling and Fiber Characteristics in Few-Mode Fibers Analyzed Using Impulse Response Measurements Technique

Abstract

When few-mode fibers are employed in mode-division multiplexing (MDM), mode coupling between the propagation modes must be suppressed. In this study, the impulse response for a two-mode fiber (TMF) is theoretically described to estimate the mode coupling in the fiber and at a splice point. We then propose a technique for measuring the mode-coupling coefficient in a TMF based on the impulse response technique. The mode-coupling behavior in a fiber and at splice points is measured experimentally using the proposed technique for several fabricated TMFs. We clarify the relationship between the effective-index difference $\Delta n_{{\rm{eff}}}$ between ${\text{LP}}_{{01}}$ and ${\text{LP}}_{{11}}$ modes and the mode-coupling coefficient h for our fabricated TMFs.