Characterization of FBGs written in HiBi IEC fibre for multiparameter sensors

Multiparameter sensors have several applications in engineering, (biomedics, mechanics, civil), where the determination of the strain along three axis and the measurement of the temperature are required. Fibre Bragg gratings (FBG) written in high birefringence (HiBi) fibres have been described as high efficiency sensors for the simultaneous determination of these parameters. There are several commercial designs of HiBi fibres, of which the most common are the internal elliptical cladding (IEC), PANDA and bow tie fibres. Those designs differ in the transversal profile of the refractive index due to stress applying elements inserted in the cladding of the fibre optic. The stress profile leads to different responses of the induced birefringence when strain and/or temperature are present. The characterisation of a sensor based on Bragg gratings written in HiBi fibres thus requires the knowledge about the fibre properties and about the characteristics of the obtained Bragg grating. In this paper, the characterization of HiBi FBGs by experimental and simulation analyses is presented.