Novel twist measurement method based on TFBG and fully optical ratiometric interrogation

In this paper we present a novel twist measurement technique based on the influence of changes in the input light polarization state on the tilted Bragg grating. In the proposed sensor with the interrogation method, changes in the amplitudes of high-order cladding modes are measured by wavelength-matched fiber Bragg grating filters working in reflection mode. The key element of the method is the use of parameters of two selected parts of one cladding mode that are in close proximity to each other. Application of appropriate technological parameters to the manufactured photonic structures of the sensor and interrogation filter elements allows to obtain high-resolution measurement with simultaneous immunity to temperature fluctuations. The differential character of the proposed method also provides independence from changes in the optical power of the illuminating light source.