Low power and inexpensive microstructured fiber Mach Zehnder interferometer as temperature insensitive mechanical sensor

Microstructured fibres (MSFs) reveal unique properties including endlessly single-mode operation from ultraviolet to infrared wavelengths, very high birefringence or nonlinearity, very large or very small effective mode field area, and many others. The size, shape and the location of the air holes allow for tailoring MSF parameters in a very wide range, way beyond the classical fibres, what opens up the possibilities for various applications. Due to their advantages MSFs obtain growing attention for their perspectives in sensing applications. Different MSF sensors have already been investigated, including interferometric transducers for diverse physical parameters. Until now, there have not been any publications reporting on the sensing applications of MSF Mach-Zehnder interferometers, targeting the mechanical measurements of vibrations, dynamic or static pressure, strain, bending and lateral force. Moreover, a critical feature opening the prospective of optical fibre transducer to successfully accomplish a particular sensing task remains its cross-sensitivity to temperature. Studied MSF is made of pure silica glass in the entire cross-section with a hexagonal structure of the holes. Consequently, there is no thermal stress induced by the difference in thermal expansion coefficients between the doped core region and the pure silica glass cladding, in contrast to standard fibres. In this paper we present the experimental comparison of mechanical and temperature sensitivities of Mach- Zehnder interferometer with replaceable FC connectorized sensing fibre arm, such as: off-the-shelf endlessly single mode MSF or standard telecom single mode fibre. Experimental results clearly show very low cross-sensitivity to temperature of studied MSF compared with standard fibre. Additionally, microstructured fibre Mach-Zehnder interferometer with standard FC receptacles allows using different fibres as sensors with the same device. Moreover, investigated interferometer consumes in total extremely low electric power (< 20 mW) due to the implementation of exceptionally effective data analysis electronics and VCSEL as the light source.

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