Temperature- and strain-independent curvature sensor based on multimode interference
S. Silva, O. Frazão, L. A. Ferreira, F. M. Araújo, INESC Porto - Institute for Systems and Computers Engineering of Porto (Portugal); F. X. Malcata, ISMAI - Maia Higher Institute University (Portugal); J. L. Santos, INESC Porto - Institute for Systems and Computers Engineering of Porto (Portugal)
This work describes a fibre optic sensing structure that is sensitive to curvature, and features a low temperature- and strain cross-sensitivity. It is based on multimode interference, and relies on a single mode – step index multimode – single mode fibre configuration. It was observed that the transmitted optical power in such layout becomes highly sensitive to the wavelength of operation and to the length of the multimode fibre. The optical spectrum entertains two dominant loss bands, at wavelengths that have similar responses both to temperature and strain, and different responses to curvature. Based on this result, an interrogation approach is proposed that permits substantial sensitivity to curvature (8.7±0.1 nm.m) and residual sensitivities to temperature and strain (0.3±0.1 pm/ºC and -0.06±0.01 pm/με, respectively).
