Measurements of the chromatic refractive index signature of wine models using a fibre long period gratings

A novel optical fibre device is proposed for real-time measurements of near infrared chromatic refractive index signature of a liquid medium in the 1100-1700 nm range. This inline optical fibre chromatic refractive index analyser is based upon collocated fibre long period gratings written adjacently in the core by femtosecond laser inscription yielding 8 attenuation bands associated with different cladding modes, yielding 8 independent measurements across the entire wavelength range. This fibre device is tested on a series of chemical compounds associated with wines. The results for each compound yielded distinctive chromatic responses. The limits of detection for this fibre devices ranged from 1×10⁻³ to 6×10⁻⁵ mol/L for the compounds associated with wines. This demonstrates a potential usefulness of such an optical fibre sensor capable of monitoring in real-time effective chromatic refractive index signatures that is not offered by any current technology.