Raman-DFB fibre laser enabled FWM in passive optical fibres

Abstract

Wideband wavelength conversion utilizing four-wave mixing (FWM) in optical fibres has received significant attention in the area of fibre communications and networking, due to the natural low-loss compatibility with the conventional optical transmission systems [ref]. Within a 30cm long centre ð phase-shifted distributed-feedback (DFB) grating, formed in a commercially available germano-silica optical fibre (PS980, from Fibercore Ltd.), we recently experimentally demonstrated up to ~167nm wavelength conversion with a conversion efficiency up to -25dB [1, 2]. The concept of the FWM in that work was the following; firstly, a ~2W single-mode, single polarization Yb-doped fibre laser at 1064nm was used to pump a Raman DFB (R-DFB) grating to generate a narrowband signal at ~1117nm (the Bragg wavelength of the DFB) [3]. This lasing signal with a power of ~80mW subsequently acted as the pump for the FWM process allowing for the wavelength conversion of a low-power probe signal (~10mW) extending from 1040.8nm to 1207.8nm. Evidently, the phase-matching condition must be fulfilled to facilitate the FWM process. Although the wavelength region for the demonstrated FWM process lies entirely within the normal dispersion regime of the fibre, we believe that both the dispersion from the grating itself and the high intensity of the circulating lasing signal within the grating contributed strongly to modify the overall dispersion within the structure, thus enabling the phase-matching for such an efficient and wide-range FWM process.

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ORCID for P. Horak: orcid.org/0000-0002-8710-8764

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