Photonics, Vol. 12, Pages 561: Complete Dispersion Measurement for Few-Mode Fibers with Large Mode Numbers Enabled by Multiplexer-Assisted S2

Photonics doi: 10.3390/photonics12060561

Authors:
Bingyi Zhao
Zhiqun Yang
Zhongze Lv
Huihui Wang
Yaping Liu
Zhanhua Huang
Lin Zhang

With the widespread use and increasing importance of few-mode fibers (FMFs), comprehensive dispersion measurement for FMFs with large mode numbers is in urgent demand. Among existing methods, spatially and spectrally resolved (S2) imaging technique offers distinct advantages for measuring differential mode group delay (DMGD) and chromatic dispersion (CD) parameters. However, it suffers from several limitations such as uncontrollable mode excitation and an inability to measure absolute CD. In this study, we enhance the traditional S2 method, making it possible to effectively measure the complete dispersion for high-mode-count FMFs. By introducing a mode multiplexer (MMUX), selectively and proportionally mode excitation can be realized. Combined with a tunable delay line array, the misalignment of the MMUX’s fiber pigtail lengths is canceled. Additionally, with the help of a reference path capable of generating planar light, the measurement of the absolute CD is enabled. Based on the enhanced MMUX-assisted S2, a simultaneous DMGD and absolute CD measurement for an FMF supporting up to six LP modes is conducted, which has not been previously demonstrated with a single S2-based system. The proposed paradigm significantly expands the mode number of FMF measurable by S2, enriches the parameters that S2 can cover, and even has great inspiration for other measurement methods.

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Bingyi Zhao www.mdpi.com