Impulse Response Characterization of a Commercial Multimode Fiber using Superconducting Nanowire Single-Photon Detectors

TL;DR

This paper demonstrates the use of superconducting nanowire single-photon detectors to accurately measure impulse responses in multimode fibers, revealing mode coupling and group delay effects with high sensitivity, enabling advanced applications like quantum communications.

Contribution

It introduces a novel application of SNSPDs for detailed impulse response characterization of multimode fibers, surpassing limitations of traditional photodetectors.

Findings

Quantified distributed mode coupling and DMDG in MMF

Detected cladding modes as pulse pedestals

Enabled potential quantum communication applications

Abstract

Time-of-flight measurements are key to study distributed mode coupling and differential mode group delay (DMDG) in multimode fibers (MMFs). However, current approaches using regular photodetectors with limited sensitivity preclude the detection of weak modal interactions in such fibers masking interesting physical effects. Here we demonstrate the use of high-sensitivity superconducting nanowire single-photon detectors (SNSPDs) to measure the mode transfer matrix of a commercial graded-index multimode fiber. Two high performance 45-mode multi-plane light conversion (MPLC) devices served as the mode multiplexer/demultiplexer. Distributed mode coupling and DMDG among different mode groups are accurately quantified from the impulse response measurement. We also observed cladding modes of the MMF as a pedestal of the pulse in the measurement. This work paves way for applications such as quantum communications using many spatial modes of the fiber.