This paper presents an investigation of the sensing properties of long-period gratings (LPGs) written with the electric-arc technique in commonly used standard germanium-doped Corning SMF28 and boron co-doped Fibercore PS1250/1500 fibers. In order to increase the sensitivity of the LPGs, we studied and established for each fiber the writing parameters allowing for the coupling of the highest possible order of cladding modes at a resonance wavelength around λ = 1550 nm. The sensitivity of the LPGs to refractive index, to temperature and to hydrostatic pressure was investigated. The experimental results were supported by extensive numerical simulations. Thanks to the well-established and precisely controlled arc-writing process, we were able to reduce the minimum period of the gratings down to 345 and 221 μm, respectively, for LPGs based on the SMF28 and PS1250/1500 fibers. To the best of our knowledge, these are the shortest periods ever achieved for these fibers using the arc-manufacturing technique. The pressure sensitivities of 13 and 220 pm bar −1 are the highest ever measured for LPGs written in the SMF28 and PS1250/1500 fibers, respectively. Moreover, a reduction in the diameters of the SMF28 fiber induced by the arc was found, which significantly affected the distribution of resonances generated by the coupled cladding modes.

This paper reports on the first application of tapered long-period gratings (TLPGs) written in photonic crystal fibres (PCFs) using a cost-effective computer-assisted precision arc-discharge apparatus for conducting direct measurements of hydrostatic pressure up to 180 bar. The developed TLPG-PCF device displays significant potential as a highly sensitive and cost-effective pressure sensor, with a pressure sensitivity of 11.2 pm bar−1. A negligible temperature sensitivity of about 0.3 pm °C−1 of the sensor output signal was observed within the temperature range from 5 °C to 65 °C.