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A liquid surface deformation sensor with high sensitivity based on a Mach–Zehnder interferometer (MZI) was demonstrated. The MZI was constructed by cascading two Bowknot Type Tapers (BTTs) with an ...

A sensitivity-enhanced strain sensor constructed by a 7-mm-long thin-core fiber (TCF) splicing with a 10-mm-long tilted fiber Bragg grating (TFBG) was proposed. The modal interferometer formed by the TCF will interact with the spectrum of the TFBG to form an overlapped spectrum, which will extremely increase the axial strain sensitivity of the TFBG. Experimental results showed that the wavelength shifts of the resonant dip in the overlapped spectra for the applied axial strain have a high sensitivity of 0.67 pm/ $\mu \varepsilon $ . Meanwhile, the proposed sensor has the temperature self-compensation function for the variation of the external temperature simply by measuring the relative wavelength shifts of the Bragg mode of the TFBG.

A ferromagnetic material equipment internal defect detection system based on low-frequency (20–50 Hz) electromagnetic technique was proposed. Direct current magnetization was used to make the ferromagnetic material sample (20# steel for instance) be in a saturation magnetization state to decrease its permeability, which is beneficial for increasing the skin depth of the sample and strengthening the signal of the magnetic flux leakage. A low-frequency alternating current source was used to excite the spatial alternating electromagnetic field and a Hall sensor was used to collect the signal of the spatial magnetic field. Experimental results showed that the 6-mm buried depth internal defect with the sensitivity of 0.05 mm can be detected in the 12-mm thick 20# steel plate or pipeline, which is almost 1.5 times higher than that of the current similar sensors.

In microfluidic chip applications, the flow rate plays an important role. Here we proposed a simple liquid flow rate sensor by using two cascaded bowknot-type tapers (BTTs) to form a Mach–Zehnder interferometer (MZI) as the sensing element. As the water flows in the vicinity of the BTT, the cascaded BTTs based MZI’s interference spectrum changes due to its contact with water. By comparing the time-swept spectra of the cascaded BTTs MZI from the state of one BTT in water to that of another BTT in water as the water flowing over it, the flow rate can be detected. The proposed sensor has a detectable range from 0.66 mm/s to 10.6 mm/s.

A highly sensitive surface plasmon resonance (SPR) sensor for glucose detection has been proposed by using self-assembled p-mercaptophenylboronic acid (PMBA) monolayer on Au coated tilted fiber Bragg grating. Au nanoparticles (Au NPs) were modified with 2-aminoethanethiol (AET) and PMBA for signal amplification. It exhibits high sensitivity and selective response to glucose over fructose and galactose within the range of 1μM–500μM and the sensitivity is up to 2.61dB/μM.

A compact and low-power consuming fiber-optic anemometer based on single-walled carbon nanotubes (SWCNTs) coated tilted fiber Bragg grating (TFBG) is presented. TFBG as a near infrared in-fiber sensing element is able to excite a number of cladding modes and radiation modes in the fiber and effectively couple light in the core to interact with the fiber surrounding mediums. It is an ideal in-fiber device used in a fiber hot-wire anemometer (HWA) as both coupling and sensing elements to simplify the sensing head structure. The fabricated TFBG was immobilized with an SWCNT film on the fiber surface. SWCNTs, a kind of innovative nanomaterial, were utilized as light-heat conversion medium instead of traditional metallic materials, due to its excellent infrared light absorption ability and competitive thermal conductivity. When the SWCNT film strongly absorbs the light in the fiber, the sensor head can be heated and form a “hot wire”. As the sensor is put into wind field, the wind will take away the heat on the sensor resulting in a temperature variation that is then accurately measured by the TFBG. Benefited from the high coupling and absorption efficiency, the heating and sensing light source was shared with only one broadband light source (BBS) without any extra pumping laser complicating the system. This not only significantly reduces power consumption, but also simplifies the whole sensing system with lower cost. In experiments, the key parameters of the sensor, such as the film thickness and the inherent angle of the TFBG, were fully investigated. It was demonstrated that, under a very low BBS input power of 9.87 mW, a 0.100 nm wavelength response can still be detected as the wind speed changed from 0 to 2 m/s. In addition, the sensitivity was found to be −0.0346 nm/(m/s) under the wind speed of 1 m/s. The proposed simple and low-power-consumption wind speed sensing system exhibits promising potential for future long-term remote monitoring and on-chip sensing in practical applications.

A two-dimension magnetic flux density distribution of the ferromagnetic metal was simulated by using finite element analysis method. From the magnetic flux density distribution, the crack in ferromagnetic metal can be detected through the magnetic flux leakage. Experimental results showed that the magnetic flux density decreased gradually with the increasing of the width and depth of the crack under the width range of 1 to 5 mm and depth range of 0 to 6 mm, respectively.

In this paper, we fully investigate a nonlinear device based on a tilted fiber Bragg grating (TFBG) coated with single-walled carbon nanotubes (SWCNTs). We found that the non-linear optical properties were significantly effective in 6 degree tilted fiber Bragg grating and ∼1.3um thickness. The signal noise to ratio (SNR) of the FWM is up to 10.11dB.

The electrochemistry (EC) method was used to synthesize graphene oxide-nickel (GO-Ni) metal organic framework (MOF) that has the thickness of μm-level. The MOF's thermal stability and hydrogen adsorption and desorption capacity were measured by using an optical fiber Mach-Zehnder interferometer (MZI) sensor. This MZI was fabricated by core-offset fusion splicing one section of single mode fiber (SMF) between two SMFs. Experimental results showed that the GO-Ni MOF could be stabilized, even as the environmental temperature reached 125 °C. The MOF showed good hydrogen adsorption ability for the the MOF and hydrogen molecules's interactions.