Needle Shape Sensing With Fabry-Perot Interferometers

Advances in Multicore Fiber Interferometric Sensors

“…The reported four different structures of MCF interferometric sensors exhibit their own advantages and disadvantages. For example, MCF-based FPIs are able to achieve a very tiny size of the sensor head (less than 200 μm [ 13 , 14 , 24 , 31 , 32 , 34 ]), and each core can be used to fabricate an individual sensor, which can measure differential responses in distinct cores separately [ 13 , 14 , 24 , 31 , 32 , 33 ]. However, the manipulation of an individual core in the MCF is still a technical challenge, thus it is difficult to fabricate intrinsic FPIs in different cores of MCF.…”

“…On the other hand, since the side cores are usually more sensitive to external disturbances, MCF interferometric sensors have intrinsic advantages in sensing applications that are related to bending and strain, e.g., curvature [ 13 , 19 ], vibration [ 18 , 20 ], twisting angle [ 7 , 21 ], fluid flow [ 19 , 22 ], etc. Particularly, MCF interferometric sensors are able to distinguish the direction of bending [ 15 , 23 ], which has enabled many new sensing applications, e.g., 3D shapes [ 24 ]. In addition, MCF interferometric sensors have also been used to measure other external environmental parameters, e.g., temperature [ 25 , 26 ], gas concentration [ 27 ], refractive index [ 28 , 29 ], and so on.…”

“…In addition, in 2016, Guigen Liu et al proposed a vector flow sensor by analyzing the differential responses between the reflection spectra of multiple extrinsic FPIs that are fabricated at the cleaved-end faces of a seven-core fiber, and the sensor could detect the liquid flow speed and direction simultaneously [ 32 ]. Furthermore, in 2021, Guozhao Wei et al proposed a needle-shaped sensor by etching three individual FPIs on three single-core fibers and then fixing them in a flexible needle parallelly, and the shape of the needle was retrieved with a reconstruction method, which shows potential in medical puncture applications [ 24 ]. In general, by making use of the high sensitivity of FPIs to the cavity length variation, the multiple parallel FPIs that are fabricated in a single MCF allow for bending-direction sensing by analyzing the differential responses between the FPIs, which has great potential in precise shape-sensing applications.…”

Multipoint Bending Measurement Using Multicore Fiber Bragg Grating and Two-Photon Absorption Process in Si-APD

“…The typical fiber optic bending sensors include (i) modulation-based ones that change their output optical power according to the bendinduced transmission loss [1][2][3] and (ii) Bragg-grating-or longperiod-grating-based ones that change their Bragg wavelengths or resonance wavelengths by the applied bending [4][5][6]. The bending sensor based on Brillouin frequency shift in an optical fiber [7,8], Rayleigh backscattering [9], and Fabry-Perot interferometer [10] are also proposed. A sophisticated system using Rayleigh backscattering has achieved distributed sensing with a high spatial resolution and successfully measured a needle shape [9].…”

“…A sophisticated system using Rayleigh backscattering has achieved distributed sensing with a high spatial resolution and successfully measured a needle shape [9]. The Fabry-Perot method is especially useful for measuring small curvature at a single point [10]. In principle, This work was supported in part by the Grant-in-Aid for Scientific Research (JP20H02158) from the Japan Society for the Promotion of Science (JSPS).…”