Ultrasensitive vibration sensor based on an asymmetric multi-core optical fiber

Abstract

We report on a simple, highly sensitive interferometric vibration sensor that operates in reflection mode, which is suitable to monitor low frequencies with low amplitudes. The sensor was fabricated with a short segment of three strongly coupled core optical fiber. The device was protected with capillary tubes and it was placed in cantilever position. The sensor exploits the ultrahigh sensitivity of supermodes to small bending.

Advances in Multicore Fiber Interferometric Sensors

“…In addition to the periodicity of vibration, the amplitude of vibration, which indicates the magnitude of the restoring force, can also be used for acceleration measurement [ 20 ]. It has been widely reported that high-sensitivity vibration measurement can be achieved by using MCF interferometer-based sensors [ 16 , 17 , 20 , 43 , 45 , 70 , 71 , 113 , 114 , 116 , 117 ] because these sensors are sensitive to curvature changes, which will contribute to the high sensitivity of the vibration sensors. Table 2 summarizes various MCF interferometer-based vibration sensors.…”

“…It indicates that an MCF-based interferometric vibration sensor can provide a large frequency-measurement range, varying from 1 mHz [ 20 ] to 12 kHz [ 17 ]. These compact and high-sensitivity sensors can be used in many fields, such as the long-term monitoring of construction and mechanical structures [ 71 ], contactless vital signs monitoring [ 43 ], seismic measurement [ 116 ], accelerometers [ 20 ], etc.…”

“…Thanks to the large spatial distribution of the fiber mode field of supermodes, bending will easily distort the mode field, which can change the mode loss of each supermode and the phase difference between the supermodes. As a result, bending will result in wavelength shifts [ 93 ], light power variation [ 15 ], and fringe visibility changes [ 107 ] in the SMI, which has been widely used for the high-sensitivity measurement of bending/strain-related external perturbations, such as bending [ 15 , 93 , 94 , 95 , 96 , 107 , 108 , 109 , 110 , 111 , 112 ], vibration [ 16 , 18 , 20 , 113 , 114 , 115 , 116 , 117 ], and strain [ 118 , 119 ]. Furthermore, by using an MCF with asymmetrically distributed cores, the SMI can be used to sense the bending direction.…”

“…In addition to the bending and strain sensing applications, supermode interferometers are also capable of sensing the bending-related dynamic parameters, i.e., vibration [ 16 , 18 , 20 , 113 , 114 , 115 , 116 , 117 ]. Due to the large mode spatial distribution of SMIs, bending can easily cause variation in the interference spectrum and the output optical power.…”

“…Due to the large mode spatial distribution of SMIs, bending can easily cause variation in the interference spectrum and the output optical power. Thus, by monitoring the wavelength shift through a high-speed spectrometer [ 18 , 20 , 113 , 114 , 115 , 116 , 117 ] or detecting the output optical power variation [ 16 , 20 ], the vibration frequency can be retrieved through the fast Fourier transform (FFT) of the time domain signal. For example, in 2017, Joel Villatoro et al proposed a cantilever vibration sensor fabricated by a strongly coupled MCF, as shown in Figure 22 a [ 115 ].…”