Multiple spatial and wavelength conversion operations based on a frequency-degenerated intermodal four-wave-mixing process in a graded-index 6-LP few mode fiber

TL;DR

This paper demonstrates a novel experimental process in a graded-index few-mode fiber that enables simultaneous spatial and wavelength conversion using phase-matched intermodal four-wave mixing, with implications for telecom bandwidth.

Contribution

It introduces a new method for concurrent spatial and wavelength conversion in a few-mode fiber via phase-matched intermodal four-wave mixing involving multiple modes.

Findings

Successful experimental observation of simultaneous threefold wavelength and spatial conversion.

Identification of the impact of differential modal group delay on conversion bandwidth.

Demonstration of phase-matched intermodal four-wave mixing in a graded-index few-mode fiber.

Abstract

We report on the experimental observation of a simultaneous threefold wavelength and spatial conversion process at telecommunication wavelengths taking place in a 6-LP-mode graded-index few-mode fiber. The physical mechanism is based on parallel and phase-matched frequency-degenerated intermodal four-wave mixing (FD-IFWM) phenomena occurring between the fundamental mode and higher-order spatial modes. More precisely, a single high-power frequency-degenerated pump wave is simultaneously injected in the four spatial modes LP01, LP11, LP02 and LP31 of a 1.8-km long graded-index few-mode fiber together with three independent signals in the fundamental mode. By means of three parallel phase-matched FD-IFWM interactions, these initial signals are then simultaneously spatially and frequency converted from the fundamental mode to specific high-order modes. The influence of the differential modal group delay is also investigated and shows that the walk-off between the spatially multiplexed signals significantly limits the bandwidth of the conversion process for telecom applications.