Study on the possibility of Φ-OTDR sensing in hollow-core fibres

The backscattering process in hollow core fibres shows a large similarity with Rayleigh scattering, offering the potential to be exploited for distributed sensing. A classical Φ-OTDR implementation is used to observe the backscattering signal from the surface roughness at the silica-air interface in hollow-core photonic bandgap fibres. In contrast with standard single mode silica-core fibres, the hollow core photonic bandgap fibre shows a chaotic response when the temperature is slightly changed, but stable results under strictly constant temperature conditions. Another temperature-dependent effect is highly perturbing the coherent scattering response, and it is believed that higher-order guided modes cause detrimental interferences totally jamming the response. By using single-mode hollow core fibres it should be in principle possible to obtain the relevant temperature measurement pattern, though as anticipated the extreme weakness of the signal certainly represents an insurmountable challenge.