Study of LPG-assisted fibre modal Michelson interferometers with coherence addressing and heterodyne interrogation

Abstract

In this work, the LPG-assisted fibre Michelson modal interferometer is studied as a sensing structure for environmental refractive index, temperature and liquid level when coherence addressing and heterodyne interrogation are considered. The effects on measurand sensitivity of the order of the cladding mode excited by the LPG, of the degree of etching of the sensing fibre and of the fibre type used are investigated.

Sensing characteristics of hollow-core photonic crystal fibre modal interferometers

“…After an adequate electronic filtering, this signal has the form of an electric carrier (90 Hz) with a phase that mirrors the optical phase of the tandem interferometric system. This pseudo-heterodyne processing technique is known to provide sensitive interferometric phase reading [9]. Figure 6 shows the phase changes associated with strain and temperature variations applied to the sensing head, now with L≈40 cm.…”

“…On the other hand, concerning curvature, no measurable sensitivity was noticed. To measure the phase changes in the fibre modal interferometer, a second interferometer was built to implement coherence reading [9]. Figure 5 shows the setup implemented.…”

Controlling the sensitivity of a non-adiabatic tapered optical fiber for measuring the refractive index using all fiber Sagnac loop interferometer

“…In many areas of biophysics, biochemistry and biomedicine measurements are based on two fundamental concepts, namely spectroscopy (fluorescence and absorption) and evanescent field interaction [1][2][3]. The second concept is based on the partial overlap of the evanescent guided electromagnetic wave with a medium whose refractive index (RI) is measured.…”