Impulse response of weakly-coupled multicore fiber measured by using high-dynamic-range linear optical sampling

Abstract

Abstract We report the impulse response measurement of weakly-coupled homogeneous multicore fiber accomplished by coherence-recovered linear optical sampling, which simultaneously realizes a picosecond-level time resolution and a dynamic range of over 70 dB. The observed core-by-core impulse responses include a directly transmitted pulse and plateaus that are yielded by inter-core couplings. A consideration of the observed results suggests that the group velocities are perturbed, and the core with the slowest group velocity alters along the fiber. We also found that the polarization states of the plateaus alter in the time axis of the impulse response chart, with a correlation width as short as the pulse width: we presume that this phenomenon is observed because the polarization change that occurs during propagation is transferred to the coupled signals with the shrinkage of the time axis. Next, we selected a 100 m-long piece of fiber, and measured the group delay of each core. We found that the variation of the core-by-core group delays was not similar to that of the long fiber, and it may change considerably with bending induced in the fiber. These results also suggest a variation in the local group delays over the length of the fiber.