Temperature and strain-independent curvature sensor based on a singlemode/multimode fiber optic structure

Abstract

This work describes a fiber 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 singlemode-step index multimode-singlemode fiber structure. It was observed that the transmitted optical power in such a layout is highly sensitive to the wavelength of operation, and to the length of the multimode fiber. The optical spectrum exhibits two dominant loss bands, at wavelengths that have similar responses both to temperature and strain, but 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 • C −1 and (−0.06 ± 0.01) × 10 −6 m m −1 , respectively). The beam-propagation method was employed for modeling the propagation of light along the optical fiber sensing device proposed.

Applications of Modal Interferences in Optical Fiber Sensors Based on Mismatch Methods

“…Silva et al [17] described a strain and temperature independent optical fiber curvature single-mode-multimode-single-mode sensor. When the temperature and strain changed, two distinct troughs in the spectrum moved in the same direction.…”

Refractive index sensing based on photonic crystal fiber interferometer structure with up-tapered joints

“…Therefore, the in-line optical fiber MZIs which had smaller and simpler structure was proposed. Literatures [1][2][3][4] reported a serious of in-line optical fiber MZI sensors based on multimode interference, which was fabricated by splicing a section of multimode fiber between SMFs. However, the interference spectrum had low contrast because the different patterns of energy between the multimode fiber was large, which reduced the measure precision.…”

Fiber-Optic Bend Sensor Based on Double Cladding Fiber

“…In such a structure, the light interferes after propagation through the core and the cladding, which act like two arms of an interferometer [7,8]. For example, there are studied interferometers with a longperiod fiber grating [4,5], misaligned splicing point [4,9,10], a nonadiabatic taper [11], a photonic crystal fiber having collapsed air holes [5], and splice of fibers with unmatched mode profiles (single-mode/multimode fiber splice) [12][13][14][15]. These structures find application in sensors of strain, temperature [16,17], and bend [18] and also in multiwavelength fiber laser [19].…”