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A novel fiber sensor based on photonic crystal fiber (PCF) for simultaneous measurement of temperature and humidity is proposed. The PCF is filled with alcohol, which is sensitive to temperature. A...

A temperature-compensated MZI-based optical sensor using few-mode concentric multilayer-core fiber (CMCF) was designed, and surrounding refractive index (SRI) sensing via interference spectra was successfully proposed and experimentally demonstrated. This sensor with sandwich structure generated lots of resonance dips in the interference spectra, which had differentiated sensitivities to SRI and temperature. The homemade CMCF only supported few mode groups, and variability of the resonance drift could be influenced by different mode excitation and sensitivity. For the two selected dips of this proposed sensor, the SRI sensitivities experimentally achieved were −76.88 and −50.51 nm per refractive index unit (RIU), and the temperature ones were 80.2 and 50.1 pm/°C, respectively. The experimental mechanism and results have been analyzed in brief. The standard matrix inversion method could be used for simultaneous two parameter determination. Therefore, the SRI detection could show good accuracy and sensitivity by temperature compensation.

In this paper we investigate the fiber Bragg grating (FBG) arrays selectively inscribed in a multicore fiber for a different sensor and laser applications. Particularly, wavelength-switchable and tunable fiber laser was realized based on uniform and non-uniform FBGs precisely positioned in the selected cores. A quasi-distributed 3D shape sensor based on FBG array inscribed in a multicore fiber with helically twisted side cores was fabricated and applied for shape reconstruction of papillotome.

A robust fiber sensor for salinity measurement based on encapsulated long-period grating in microfiber is proposed. The long-period grating is fabricated in microfiber by inducing periodical deformation with CO2 laser, which is then encapsulated in a holey capillary tube. The encapsulation tube is designed to effectively protect the microfiber from external interference, but does not change the optical properties of the fiber and the response speed of the sensor, which makes the sensor more robust for real applications. Experimental results show that the sensor can achieve a sensitivity of 2.16 nm/% with a good linearity for concentration from 0% to 20%. It is theoretically proved that the sensitivity can be further improved by optimizing the diameter parameters. Such structure may be used as low loss evanescent-wave-coupled optical absorption, fluorescent and gain cells, photoacoustic cells, and etc.

In the chain and rope hoist systems of large cranes, instant and monitoring of the strain caused by different loads is of great importance. Strain is a size that cannot be measured directly and whose effect can be measured. Strain can be measured point by point with the help of electronic sensors. However, increasing the number of measuring points causes complexity in electronic systems. Thanks to distributed fiber sensors, this problem has been overcome and standard SMF has been used as tens of thousands of measuring points. In this study, a model of the pulley system used in large cranes is created and the strain occurring at a certain point of a SMF was experimentally measured using the BOTDA technique. SNR was improved by using the wavelet noise reduction technique in the processing of the received signals. In order to monitor the measured strain, a user-friendly interface was designed.

This paper proposed a fiber sensor based on a Silicon core fiber incorporated with a fused silica grating design. The proposed structure is a nice sensitive in refractive index and temperature variation through theoretical calculation and finite element method simulation. The sensitivities of the refractive index in different polarization directions are 1838.7 and 1949.8 nm/RIU, respectively, within the index range from 1.28 to 1.38 RIU. The temperature range within 15 to 40 oC has the sensitivity up to 1.6 nm/oC by using ethanol analyte. The proposed fiber sensor can provide a method or a solution for intelligent sensing systems.

Liquid level measurement in microfluidics is challenging, where a sensor with ultra-high sensitivity but miniature in nature is demanded. In this paper, we propose for the first time a microsized fiber sensor structure in both diameter and length for microfluidics applications, which is capable of sub-micrometer scale liquid level measurement. The sensor is simply fabricated by fusion splicing a short section of a hollow core fiber (HCF) between two singlemode fibers (SMFs). HCFs with different air core diameters (10 µm, 20 µm, 30 µm) were investigated and it is found that for a given length of HCF stronger resonant dips were excited in transmission for the HCF with a smaller air core diameter. Thus the HCF structure with an air core diameter of 10 µm (HCF-10) was used for demonstration of high sensitivity liquid level measurement in microfluidics. Simultaneous excitation of both Anti-Resonant Reflecting Optical Waveguide (ARROW) guiding mechanism and Mach-Zehnder interferometer (MZI) in transmission is demonstrated in such an HCF-10 structure when HCF-10 is longer than the critical length. A maximum sensitivity of 0.042 dB/µm (corresponding to a calculated liquid level resolution of ~0.23 µm) was experimentally achieved with an HCF-10 length of ~867 µm, which is three times higher than that of the previous reported to date of the most sensitive fiber optic liquid level sensors based on intensity modulation. In addition, the proposed sensor shows good repeatability of measurement and a very low cross sensitivity to changes in the surrounding refractive index.

Surface plasmon sensors offer high sensitivity and real time measurement and are used in a wide range of fields such as environment, plant, biology, chemistry, medicine and physics. In order to realize high sensitivity and remote sensing of the fiber type device, we analyzed the structure dependence of the sensitivity at the communication wavelength of 1500 nm band for the device with a fiber tip and gold particles attached. Actualy we fabricated the sensors and achieved fundamental sensing operation with high sensitivity.

In this article, a method to improve refractive index (RI) sensitivity of single‐mode–no core–single‐mode fiber (SNS) sensor structure is addressed by optimization of geometric parameters of no-core fiber (NCF), which could be used to accurately measure the irreversible deformation of the battery expansion state caused by temperature change. From the perspective of temperature changing RI of the electrolyte solution, the impacts of diameter, length, and waveband on the performance of the fiber sensor have been discussed as RI measurement range is 1.340–1.390. After optimization, RI sensitivity can reach approximately 2,252.7 and 2037.3 nm/RIU with the length of 6.55 and 6.75 mm when the RI is from 1.380 to 1.390.

Long-range surface plasmon resonance (LRSPR), generated from a coupled plasmon polariton in a thin metal slab sandwiched by two dielectrics, has attracted more and more attention due to its merits, such as longer propagation and deeper penetration than conventional single-interface surface plasmon resonance. Many useful applications related to light–medium interaction have been demonstrated based on the LRSPR effect, especially in the sensing area. Here, we propose and demonstrate an LRSPR-based refractive index sensor by using a SiO2-Au-TiO2 heterostructure, in which a D-shaped honeycomb-microstructure optical fiber (MOF) is designed as the silica substrate and then deposited with a gold film and thin-layer titanium dioxide (TiO2). By using the full-vector finite-element method (FEM), this heterostructure is numerically investigated and demonstrated to excite LRSPR without a buffer layer, which is usually necessary in previous LRSPR devices. Through comprehensive discussion about the influence of structural parameters on the resonant wavelength, the excitation of the LRSPR in the proposed heterostructure is revealed to be highly related to the effective refractive index of MOF’s fundamental core mode, which is mainly determined by the MOF’s pitch, the thicknesses of the silica web and the planar-layer silica. Moreover, the thin-layer TiO2 plays an important role in significantly enhancing the resonance and the sensitivity to analyte’s refractive index as well, when it is coated on the top of the Au film rather than between the metal and waveguide. Finally, the proposed LRSPR sensor based on SiO2-Au-TiO2 heterostructure shows an ultra-high wavelength sensitivity of 20,100 nm/RIU and the corresponding minimum resolution is as low as 4.98×10−7 RIU. Thus, the proposed LRSPR device offers considerable potential for sensing applications in biomedical and biochemical areas.

Resonant waveguide gratings (RWG) are widely used as on-chip refractometers due to their relatively high sensitivity to ambient refractive index changes, their possibility of parallel high-throughput detection and their easy fabrication. In the last two decades, efforts have been made to integrate RWG sensors onto fiber facets, although practical application is still hindered by the limited resonant peak intensity caused by the low coupling efficiency between the reflected beam and the fiber mode. In this work, we propose a new compact RWG fiber-optic sensor with an additional Fabry-Pérot cavity, which is directly integrated onto the tip of a single-mode fiber. By introducing such a resonant structure, a strongly enhanced peak reflectance and improved figure of merit are achieved, while, at the same time, the grating size can be greatly reduced, thus allowing for spatial multiplexing of many sensors on a tip of a single multi-core fiber. This paves the way for the development of probe-like reflective fiber-tip RWG sensors, which are of great interest for multi-channel biochemical sensing and for real-time medical diagnostics.

A graphene oxide-coated in-fiber Mach-Zehnder interferometer (MZI) formed with a multimode fiber-thin core fiber-multimode fiber (MMF-TCF-MMF) is proposed and experimentally demonstrated for ammonia gas (NH3) sensing. The MZI structure is composed of two segments of MMF of length 2 mm, with a flame-tapered TCF between them as the sensing arm. The MMFs act as mode couplers to split and recombine light owing to the core diameter mismatch with the other fibers. A tapered TCF is formed by the flame melting taper method, resulting in evanescent wave leakage. A layer of graphene oxide (GO) is applied to the tapered region of the TCF to achieve gas adsorption. The sensor operates on the principle of changing the effective refractive index of the cladding mode of a fiber through changing the conductivity of the GO coating by adsorbed NH3 molecules, which gives rise to a phase shift and shows as the resonant dip shifts in the transmission spectrum. So the concentration of the ammonia gas can be obtained by measuring the dip shift. A wavelength-shift sensitivity of 4.97 pm/ppm with a linear fit coefficient of 98.9% is achieved for ammonia gas concentrations in the range of 0 to 151 ppm. In addition, we performed a repetitive dynamic response test on the sensor by charging/releasing NH3 at concentration of 200 ppm and a relative humidity test in a relative humidity range of 35% to 70%, which demonstrates the reusability and stability of the sensor.

Simulated transmission spectra for tapered fibers with no taper, one taper and two tapers in the near infrared wavelength range, calculated by Finite-Difference-Time-Domain method are currently presented. Transmission peak positions tend to shift to the shorter wavelength when the taper deformation is added to the fiber or the taper width gets narrower. The thickness sensitivity for the tapered structures with different taper thicknesses is about 2.28e-3 nm·µm−1. There is an interference structure in the electric field distribution images, which reveals in the fiber structures. The transmission spectra for the fiber without taper, one taper and two-tapered structures were simulated in near infrared wavelength by FDTD. The transmission spectra for tlated in near infrared wavelength by FDTD. The sensitivity of the fiber was about 50 nm × RIU−1 and it had better refractive index detection. The tapered fiber can be applied to the bio-chemical sensors and physical deformation testing.

Novel textile moisture sensors based on multi-layered braiding constructions offer attractive monitoring possibilities for many application fields of e-textiles (electronic textiles), especially for ambient air, which is the main focus of this work. In this paper the theoretical foundations and the production, as well as the procedural, mechanical and humidity tests on newly developed, textile-based sensors for moisture measurement are described. The sensor, which is based on a capacitive measurement principle, was tested in environments ranging from 22% to 94% relative humidity. Within this range, the electrical capacitance of the sensors changed up to 135% of the base capacitance, giving it a very high sensitivity.

Based on the large evanescent field of microfibers, a novel fiber sensor composed of a microfiber knot resonator and a fiber Bragg grating is proposed for the simultaneous measurement of temperature and refractive index of solutions. Due to the different responses of the microfiber knot resonator and fiber Bragg grating to temperature and refractive index variations, the fiber sensor can measure temperature and refractive index simultaneously by utilizing the sensitivity matrix. The experimental measurement results show that the sensitivities of the microfiber knot resonator and the fiber Bragg grating to temperature are 12.1 pm/°C and 11.6 pm/°C, respectively. The sensitivity of the microfiber knot resonator to the refractive index of solutions is 315 nm/RIU. It is indicated that microfiber knot resonators have a high sensitivity to the refractive index variation of solutions. Considering its small size, low cost, and high stability, the sensor proposed has a prospect in the fields of chemistry and biology.

A cascaded fiber sensor for measuring different curvature ranges based on the cladding mode resonance in double-cladding fiber is proposed. It is formed by double-cladding fiber and single-mode fiber. Based on the evanescent wave coupling principle, the cladding mode resonance phenomenon in double-cladding fiber is illustrated. The transmission spectrum with different length are also analyzed. The experimental results show that the resonance wavelength changes with the length of double-cladding fiber. When the fiber length is 22 mm, the transmission spectrum is blue-shifted as the curvature increases in minor range of 0–0.204 m−1, the corresponding curvature sensitivity can be up to −19376.48 pm/m−1. When the fiber length is 20 mm, the corresponding curvature sensitivity can be up to −4161.73 pm/m−1 as the curvature increases in large range of 0–1.06 m−1. The proposed curvature sensor has the characteristics of simple structure and high sensitivity, so it has a good application prospects in large bridges, industrial buildings and other curvature measurement situations.

We have demonstrated a distributed vibration sensor based on phase-sensitive optical time-domain reflectometer (φ-OTDR) system exhibiting immunity to the laser phase noise. Two laser sources with different linewidth and phase noise levels are used in the φ-OTDR system, respectively. Based on the phase noise power spectrum density of both lasers, the laser phase is almost unchanged during an extremely short period of time, hence, the impact of phase noise can be suppressed effectively through phase difference between the Rayleigh scattered light from two adjacent sections of the fiber which define the gauge length. Based on the phase difference method, the external vibration can be located accurately at 41.01 km by the φ-OTDR system incorporating these two lasers. Meanwhile, the average signal-to-noise ratio (SNR) of the retrieved vibration signal by using Laser I is found to be ~37.7 dB, which is comparable to that of ~37.5 dB by using Laser II although the linewidth and the phase noise level of the two lasers are distinct. The obtained results indicate that the phase difference method can enhance the performance of φ-OTDR system with laser phase-noise immunity for distributed vibration sensing, showing potential application in oil-gas pipeline monitoring, perimeter security, and other fields.

First, the temperature effect on the output polarization degree of the fiber Lyot depolarizer was analyzed in this paper theoretically, which shows that when the environment temperature changes from −40℃ to 80℃, the degree of the output light polarization (DOP) of the fiber Lyot depolarizer will increase until about 70℃, then DOP begin to decrease. The further numerical simulations indicate that this result was caused together by thermally induced group birefringence and thermal coefficient of expansion of the polarization fiber. Using our made fiber Lyot depolarizer (DOP≤0.3% when the environment temperature is 20℃), DOP of the fiber Lyot depolarizer was studied at the condition of a variable temperature experimentally, the results are in agreement with the related theoretically results basically, at last, the difference between theoretical and experimental results is discussed, the possible methods to reduce the influence of the temperature on the output DOP of fiber Lyot depolarizer is presented in this paper. It is a good guiding significance to improve the depolarization performance of the fiber Lyot depolarizer in the fields of fiber sensor, fiber gyroscope, fiber Raman amplifier and so on as we believe.

Biometric-based human identification has been investigated and applied in daily life applications, but some of them meet fundamental limitations, e.g., highly sensitive to the ambient light of the image-based recognition and unable to detect wrinkle finger with the fingerprint identification, and therefore, decrease the user experience. Recently, electrocardiogram (ECG) has demonstrated to be a very attractive identification technique against attacks. However, the ECG-based human identification is still not a convenient solution since direct skin-contact and chest/body hair shaving are required for ECG acquisition even with the novel single-lead ECG. We propose and experimentally demonstrate an unobtrusive and continuous ballistocardiogram (BCG)-based human identification system using a microbend fiber sensor, which provides a more convenient way to identify the human who is seating on the chair with leaning back against the specially-designed cushion. To the best of our knowledge, this is the first study that a microbend fiber sensor is exploited for human identification. The results show that the proposed 1D-convolutional neural network (CNN) delivers outstanding performance with an average of 100% and 90% identification rate under 15 subjects and 30 subjects, respectively. We recommend that the BCG-based biometric identification technique has great potential to be an innovative solution in smart, private, and security applications with a small group.

We report the use of a femtosecond infrared (fs-IR) laser to produce random grating structures in optical fibers for fiber sensor and fiber laser applications. The plane-by-plane method of inscribing various gratings is presented. We review our experimental results over the past 5 years of the applications of fiber random gratings for distributed temperature measurements, fiber lasers and fiber laser sensors. The potential applications of fs-IR laser processed optical fibers in structure health monitoring, harsh environment sensing, perimeter intrusion detection and encrypted communication will be discussed., Fiber Optic Sensors and Applications XVII, April 12-17, 2021, Online Only, United States, Series: Proceedings of SPIE

We present the first report on a compact, temperature-insensitive, multi-axial mechanical force sensor based on a single-core antiresonant hollow-core fiber (ARHCF). Single-core antiresonant fibers are inherently few-moded in a short length and show characteristic multimode interference pattern in their transmission spectrum. We report here a simple technique that enhances the interaction between the interfering modes in these fibers, giving rise to up to four-fold increase in the peak-to-peak amplitude of the interference pattern. The enhanced interference pattern is shown to be responsive to external mechanical forces, like longitudinal and transverse strain and curvature, with distinguishable linear responses. Transverse and longitudinal mechanical forces affect different attributes of the interference pattern, making the proposed sensor suitable for their simultaneous sensing. The temperature sensitivity of the sensor is found to be 3.3 pm/°C suggesting negligible thermal crosstalk while measuring the effect of mechanical forces. The sensor has a compact configuration and is inherently insensitive to polarization of light used. National Research Foundation (NRF) Submitted/Accepted version This work was partly supported by National Research Foundation, Singapore, through Quantum Engineering Programme (QEP-P4).

We present the fusion of temperature measurements from different distributed fiber sensing technologies, namely Raman-DTS and DAS based DTGS, and its application. The method yields an improvement of factor 3 in temperature resolution compared to DTS only, revealing temperature features otherwise undetectable.

This paper shows the manufacture of a 300 µm lab-in-fiber sensor integrated in a surgical needle. It includes an air micro-cavity and a Pl-b-Pl FBG, allowing to detect a medium change and the surrounding refractive index.

We discuss the novel concept of harmonics of the Vernier effect for optical fiber sensors as a tool to break the limits of conventional optical Vernier effect currently used. The new effect provides enhancements scalable with the harmonic order.

Distributed fiber optical systems (DFOS) allow deployed optical cables to monitor the ambient environment over wide geographic area. We review recent field trial results, and show how DFOS can be made compatible with passive optical networks (PONs).

We studied the dependence of sensitivity of a biconically tapered optical fiber sensor on the wavelength of light used, and experimentally demonstrated refractive index sensitivity of about 11000 nm/RIU at nearly 1570 nm. Based on our theoretical analysis, we predict that tapered fiber refractive index sensors with sensitivities exceeding 50000 nm/RIU can be developed. We attribute the enhanced sensitivity mainly to the nonlinear variation of the difference in mode propagation constants with wavelength. Such ultrahigh sensitivity combined with low cost and simplicity for tapered fiber refractive index sensors makes them good candidates for numerous sensing applications in medical diagnosis, food safety, environmental monitoring, and biodefense. © 2020 The Author(s)

We demonstrate fiber optic sensing systems in a distributed fiber sensor network built on existing telecom infrastructure to detect temperature, acoustic effects, vehicle traffic, etc. Measurements are also demonstrated with different network topologies and simultaneously sensing four fiber routes with one system.

The paper presents an experimental investigation of frequency modulation of different types of single-frequency lasers. Dependences of frequency modulation coefficients on modulating frequency were obtained experimentally and parasitic intensity modulation was estimated. The work is of an applied nature, and can be useful for interferometric fiber optic sensors engineering.

There is an optical interference noise in the conventional Raman-based fiber-optics distributed sensing, which results in a poor temperature resolution performance. In addition, the traditional whole-fiber demodulation principle complicates the operation steps of the system. In this paper, a novel dynamic difference attenuation recognition (DDAR) principle is operated in the DDP scheme (dual demodulation principle) and the SDP scheme (self-demodulation principle) respectively. It not only helps to eliminate the optical interference noise, but also omits the whole-fiber calibration process. In this experiment, a temperature resolution of 0.30 &deg, C (17.0 km) is achieved through using the DDP scheme based on the DDAR principle, and the measurement time can be shortened to 1.5 s. Meanwhile, a temperature resolution of 0.18 &deg, C (17.0 km) is obtained for the SDP scheme under the DDAR principle. The SNR of DDP and DSP schemes can be optimized to 12.82 dB and 13.32 dB by the proposed DDAR technology. Furthermore, the temperature resolution performance under a large temperature measurement range (0&ndash, 1000 &deg, C) is theoretically analyzed. The results indicate that the temperature responsivity for DDP and SDP schemes are parabolic and linear type respectively, which causes the temperature resolution of the two schemes to show a different trend with the change of temperature. The proposed DDAR method also can improve the temperature resolution in such a large temperature measurement range.

The method of a spatial resolution improvement for common phi-OTDR system is proposed. The suggested method allows to decrease the size of acquisition points in the fiber sensor due to the special arrangement of weak Fiber Bragg Gratings (wFBG). The scheme of phi-OTDR doesn’t need any changes, moreover it does not possess the limitation of an acousto-optic modulator switching frequency.

A temperature sensor was fabricated with a functional conductive poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) coating on a long-period fiber grating (LPFG). The LPFG was fabricated by laser-assisted wet-chemical etching for controlling the grating depth of the LPFG after the treated surface of an optical fiber was inscribed by laser light. The functional conductive polymer acts as a temperature sustained sensing layer and enhances the grating depth of the LPFG sensor as a strain buffer at various temperatures. The sensor was subjected to three cycles of temperature measurement to investigate the sensor&rsquo, s wavelength shift and energy loss when exposed to temperatures between 30 and 100 &deg, C. Results showed that the sensor&rsquo, s average wavelength sensitivity and its linearity were 0.052 nm/&deg, C and 99%, respectively, average transmission sensitivity and linearity were 0.048 (dB/&deg, C) and 95%, respectively.

We propose and demonstrate a hybrid fiber-based sensor combining a multimode interference (MMI) structure and a surface plasmon resonance (SPR) structure for simultaneous measurement of temperature and refractive index (RI) of a liquid sample. We configure the MMI structure by connecting a single-mode fiber, a no-core fiber, and a single-mode fiber sequentially. We set up the SPR structure by coating a gold film with a thickness of 50 nm on the surface of the no-core fiber. We measure the sensitivity of RI and the temperature of the MMI and SPR structure, respectively. Then we obtain the coefficient matrix to simultaneously measure the temperature and RI of a liquid sample and obtain the highest RI sensitivity of 2061.6 nm/RIU and temperature sensitivity of 37.9 pm/°C. We verify the feasibility of the sensor in liquid alcohol. The testing results indicate that the proposed sensor and testing method are feasible, accurate, and convenient.

We demonstrate refractive index (RI) measurement of liquid sample based on RI/RF conversion in fiber comb cavity including multi-mode interference fiber sensor. We further discuss its potential for application bio-sensor.

We proposed a surface plasmon resonance based fiber sensor which was applied for detecting temperature and concentration of ethanol simultaneous. The measured range of the temperature and concentration were 10-40oC and 0-70%, respectively.

In this paper, an all fiber optic sensor based on a Mach-Zehnder interferometer (MZI) has been proposed for the simultaneous measurement of underwater pressure and temperature, utilizing a dual-mode fiber (DMF) which has been specially designed, and supporting only the LP01 and LP02 modes propagating in the fiber. In this design, an in-line MZI sensor that was constructed by splicing a DMF between two pieces of single mode fibers, shows a critical wavelength (CWL) which exists in the transmission spectrum of the LP01-LP02 mode interference. Since the two peaks, located closest to the CWL (and from both lower and higher wavelengths), shift in opposite directions and show different sensitivities under temperature and water pressure variations, the DMF-MZI sensor is capable of measuring both the water pressure and the temperature simultaneously. The CWL-based interference spectrum is stable with the variation of underwater salinity or impurities seen around the fiber surface and independent of the polarization states of the transmission light. As a result, in the operation of the DMF-MZI sensor, underwater pressure and temperature sensitivities increase significantly, when the peak wavelengths are close to that of the CWL. A theoretical analysis has been developed and used to predict that the sensitivities of this specific DMF-MZI structure which can be further improved by increasing the physical length of the DMF and by adjusting the position of the first left/right peak to be closer to the critical wavelength. This co-located, multi-parameter all-fiber sensor developed in this way and showing relatively high sensitivity is easy to implement in the underwater environment. It does not require a complex shell design and the peaks nearest to a CWL are convenient, allowing easy identification and detection, thereby providing a large measurement range to satisfy the requirements of practical marine and fresh water measurements.

Novel textile temperature sensors based on strain-relieved braiding constructions offer attractive monitoring possibilities for numerous application fields involving e-textiles in general, and medical textiles in particular. Thus, the research work presented in this paper focused on theoretical foundations, manufacturing, and procedural, mechanical as well as thermal testing of these newly developed, textile-based sensors for temperature measurements. The median basic resistance of the scalable sensor yarns using a helical stainless steel wire is about 0.81 Ω/mm. Within the temperature range of 22 to 40℃, the developed sensor yarn has a mean linearity deviation of 0.028 K. The measured temperature coefficient is 0.68 × 10−3 K−1, which correlates with the properties of the stainless steel wire.

This paper firstly and experimentally demonstrates an in-fiber axial micro-strain sensing head, combined with a Mach-Zehnder interferometer (MZI) based on the concentric multilayer elliptical-core fiber (CMECF). This MZI with a high extinction ratio (about 15 dB) is successfully achieved with a CMECF-single mode fiber-CMECF (CSC) structure. The MZI sensor theory and the resonance demodulation technology are systematically described in this paper. In this CSC structure, two sections of the CMECF have a role as the mode generator and coupler, respectively. LP01 and LP11 even, which have similar excitation coefficients, are two dominated propagating mode groups supported in the CMECF. On account of the distinct dual-mode property, a good stability of this sensor is realized. The detected resonance in the MZI shifts as the axial micro-strain variated due to the strong interaction between higher order modes. High sensitivity of ∼1.78 pm/με is experimentally achieved within the range of 0 με–1250 με, meanwhile, the intensity fluctuation is below 0.38 dB.

A novel fiber sensor composed by two single mode fibers and long period fiber grating based on a photonic crystal fiber prepared by periodic discharge heating has been experimentally investigated t...

Tungsten disulfide (WS2) nanosheets is a promising two-dimension (2D) material for offering lots opportunities in the development of new biological and chemical sensors and sensing strategies. Fiber SPR sensor is a powerful tool in the field of biology and chemistry. In this work, we simulated the effect of different tickness WS2 nanosheets on the fiber SPR sensor. The result show that, the SPR sensor perform best when WS2 nanosheets is 9.6 nm. Its refractive index sensitivity is 2018.4nm/RIU, the full width at half maximum is 151.4 nm, and the quality factor is 1.333.