Simultaneous measurement of displacement and temperature using a balloon-like hybrid fiber sensor

Abstract

A fiber sensor based on a silica capillary in a balloon-like shape for simultaneous measurement of displacement and temperature is proposed and experimentally demonstrated. The sensor is fabricated by splicing a segment of a hollow-core fiber between two single-mode fibers (SMF) and by creating a balloon shape with the capillary at the top-center position. The SMF–capillary–SMF configuration excites an antiresonant (AR) guidance, and the balloon shape enhances the Mach–Zehnder interferometer (MZI). Experimental results show that, for a balloon length of 4.0 cm and a capillary length of 1.2 cm, the AR is insensitive to displacement and its sensitivity to temperature is 14.3 pm/°C, while the MZI has a sensitivity to displacement of 1.68 nm/mm in the range between 0 and 5 mm and a sensitivity to temperature of 28.6 pm/°C, twice the value of the AR. The proposed fiber sensor has only one sensing element in one configuration, which makes it simple to fabricate as well as low cost.

Simultaneous Measurement of Microdisplacement and Temperature Based on Balloon-Shaped Structure

“…The sensitivity of our sensor is much higher than that of the same type of temperature and displacement dual-parameter measurement sensor with a balloon shape. Our work's displacement sensitivity is 182.14 times higher than its displacement sensitivity and 5.77 times higher than its sensitivity to temperature [22]. In addition, the sensor benefits from an easy construction, high reproducibility, and excellent stability.…”

“…We use spectral drift to calculate the microdisplacement. The RI distribution in the COJ-based balloon-shaped SMF structure can be expressed as [22]:…”

“…The findings demonstrate the significant potential of the core offset structure in the creation of optical fiber sensors for biological detection. The optical fiber's bending structure can also increase the sensitivity of the optical fiber sensor [22]. This method is extensively used to measure physical parameters, such as the refractive index [23][24][25], magnetic field [26], curvature [27], temperature [28], and salinity [29].…”

Highly Sensitive Balloon-like Fiber Interferometer Based on Ethanol Coated for Temperature Measurement

“…When light passes through the bending region, some of the cladding modes are recoupled back to the fiber core ( Figure 1 d). The intensity of light transmission through the balloon-like structure can be expressed as [ 33 ] where and represent the intensities of the cladding and core modes, and φ denotes the phase difference between them, which can be expressed as where represents the wavelength of the light signal in free space, refers to the effective RI difference between the cladding and core modes, and is the effective bending length of the balloon-like area. An interference dip occurs at specific wavelengths when the condition of , = 0, 1, 2,....…”

“…), bent fibers are simple in structure, high in mechanical strength, and easy to fabricate. Due to the growing popularity of optical fiber communication networks worldwide, FOTSs based on bent optical fibers have been published, and the bending loss characteristics of optical fibers have also been extensively investigated [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. In 2009, Ginu et al [ 27 ] exposed a layer of material outside the cladding by removing the original coating layer, which was used to eliminate the whispering-gallery mode (WGM), thus effectively reducing the influence of other factors when performing temperature measurements.…”