Suspended-core fibres as optical gas sensing cells: study and implementation

Abstract

We have thoroughly studied and modelled many important aspects for the realization of gas-light interactions in suspended-core fibres. The fraction of the optical field propagating in holes could be calculated from the fibre geometry to predict the total absorption for a given molecular absorption line and fibre length. In addition, the gas diffusion into the fibre holes could be modelled to precisely anticipate the filling time for a given fibre geometry and length. This was experimentally validated by preparing several samples of suspended-core fibres showing various lengths. These samples were filled with acetylene at low pressure (< 50 mbar) and were hermetically and permanently sealed by fusion splicing each fibre end to a plain single-mode silica fibre. The adequacy between the modelling and the experimental results turned out to be excellent. Several physical parameters essential for the fibre characterization could be extracted from a set of measurements, sketching a specific metrological approach dedicated to this type of fibre. Finally, applications and advanced experiments that can be specifically carried out using these fibres are discussed.

Interrogation of a Suspended-Core Fabry–Perot Temperature Sensor Through a Dual Wavelength Raman Fiber Laser

“…Later on, a simple technique for fabrication of these structures as well as its application as a gas sensor was demonstrated [4]. More recently, the geometry of the fiber cross section was exploited to maximize the interaction of light and sample for evanescent field sensing [5] or for optical gas sensing cells [6]. Other authors took advantage of the fact that suspended-core fibers can be made of a single material, in such case silica, and use a four hole SC-MOF for strain and temperature sensing based in a Sagnac interferometer [7] or to construct a Fabry-Perot cavity using a section of SC-MOF between two single mode fibers (SMFs) in order to obtain a refractive index sensor [8].…”