Fiber Refractive Index Sensor Research Articles

Enhanced Spectrum Resolution of Optical Fiber Refractive Index Sensors Based on Single-Arm Fiber-Optic Tapered Probe

Enhanced Spectrum Resolution of Optical Fiber Refractive Index Sensors Based on Single-Arm Fiber-Optic Tapered Probe

A D-type photonic crystal fiber refractive index sensor based on Bloch surface waves

A D-type photonic crystal fiber refractive index sensor based on Bloch surface waves

Advances in dispersion turning point enhanced ultrasensitive optical fiber refractive index sensors

Optical fiber sensor operating at the dispersion turning point (DTP) has become a promising building block for future development in biosensing application due to its ultrahigh sensitivity. In this paper, we comprehensively review the fundamentals of various optical fiber sensors under the turning point condition, together with the basic definition, classification, design, fabrication and applications. Three main methods for DTP implementation are introduced and highlighted: i) phase matching condition in long period grating, ii) refractive index (RI) matching to the effective refractive index of the waveguide in modal interferometer, and iii) mode coupling via diameter regulation in modal interferometer, optical microfiber coupler and polarization interferometer. The aim here is to provide reliable and effective methods to achieve the superior performance on turning point-enhanced optical fiber RI sensors, accelerating the development of transduction technology for the research of novel biomedical sensors.

Experimental study on ultra-high sensitivity gold-based SPR sensor for refractive index and temperature measurement

We have experimentally demonstrated an ultra-high sensitivity gold-based fiber refractive index (RI) sensor whose main structure is composed of multimode fiber (MMF) and photonic crystal fiber (PCF). The gold film is deposited on V-shaped PCF by magnetron sputtering, and sensing experiments are performed based on the principle of surface plasmon resonance (SPR). Numerical simulation results indicate that the cladding mode of the V-shaped PCF is more capable of stimulating the SPR effect than the core mode. The experimental results show that the RI measurement range of the sensor is 1.333–1.421, with a maximum sensitivity of 10015 nm/RIU. In addition to RI sensing, sensing probes can be coated with polydimethylsiloxane (PDMS) on a gold film for temperature sensing. For temperature detection, the range is from 10 to 100 °C and the maximum sensitivity is 3.5 nm/℃. Besides high sensitivity in RI measurement, the proposed sensor also has good sensing performance in temperature sensing. With the advantages of high sensitivity, good stability, and easy preparation, this sensor has become an important reference in the field of high-performance sensing.

D-type photonic crystal fiber refractive index sensor with ultra-high fabrication stability and ultra-wide detection range

D-type photonic crystal fiber refractive index sensor with ultra-high fabrication stability and ultra-wide detection range

Design and analysis of surface-plasmon-resonance-based dual-cladding micro-structured fiber temperature and refractive index sensor

Combining the surface plasmon resonance(SPR) effect and the characteristics of dual-cladding micro-structured fiber(DC-MF), this study presents the design and analysis of a temperature and refractive index sensor. The performance of the sensor is analyzed by using the full-vector finite element method, and the structure parameters of the DC-MF and the thickness of the plasmonic material (ITO film), is optimized to achieve high sensitivity measurements of temperature and refractive index. Theoretical analysis results indicate that its maximal temperature and refractive index sensitivity can reach to 25.4 nm/°C and 46559.8 nm/RIU in −40 °C to −40 °C. Its average temperature and refractive index sensitivity is 22.53 nm/°C and 38292.3 nm/RIU in the temperature range from −40 °C to 0 °C, and the value is 7.03 nm/°C and 12591.7 nm/RIU in the temperature range from 0 °C to 40 °C. Besides, its operating wavelength shifts toward a long wavelength region (about 1.05 μm–2.25 μm) as the refractive index of analyte increases from 1.424 to 1.471.

High Resolution and Sensitivity Negative Curvature Hollow Core Fiber Refractive Index Sensor Based on LSPR

High Resolution and Sensitivity Negative Curvature Hollow Core Fiber Refractive Index Sensor Based on LSPR

Design of a New Type of In-Hole Gold-Coated High-Performance Quasi-PCF Sensor Enhanced with Surface Plasmon Resonance

With the development of aerospace, deep-sea exploration and other technologies, the demand for anti-electromagnetic, high-sensitivity and miniaturized sensors is increasingly urgent. In this paper, a model of a quasi-photonic crystal fiber (Q-PCF) refractive index (RI) sensor enhanced with surface plasmon resonance (SPR) is proposed. A stable gold film with a significant SPR effect is applied to the two identically sized and oppositely positioned air holes of the proposed sensor, and all air holes are filled with analyte. A detailed analysis of the mode characteristics, structural parameters and RI sensing performance of the sensor has been carried out using the finite element method. It has been shown that the maximum sensitivity (S) is 4977.59 nm/RIU in the RI range of 1.35–1.40, corresponding to a resolution (R) of 2.01 × 10−5 RIU and a figure of merit (FOM) of 160.36 RIU−1. The proposed Q-PCF sensor has unique fabrication advantages and outstanding sensing properties, providing a new idea for biosensing, complex environment monitoring and long-range measurement, and is of great practical value in the field of highly integrated sensing.

Distributed Refractive Index Sensing Based on Etched Ge-Doped SMF in Optical Frequency Domain Reflectometry.

A distributed optical fiber refractive index sensor based on etched Ge-doped SMF in optical frequency domain reflection (OFDR) was proposed and demonstrated. The etched Ge-doped SMF was obtained by only using wet-etching, i.e., hydrofluoric acid solution. The distributed refractive index sensing is achieved by measuring the spectral shift of the local RBS spectra using OFDR. The sensing length of 10 cm and the spatial resolution of 5.25 mm are achieved in the experiment. The refractive index sensing range is as wide as 1.33-1.44 refractive index units (RIU), where the average sensitivity was about 757 GHz/RIU. Moreover, the maximum sensitivity of 2396.9 GHZ/RIU is obtained between 1.43 and 1.44 RIU.

High sensitivity photonic crystal fiber temperature and refractive index sensor based on surface plasmon resonance

High sensitivity photonic crystal fiber temperature and refractive index sensor based on surface plasmon resonance

Ultrasensitive refractive index fiber sensor based on high-order harmonic Vernier effect and a cascaded FPI.

This paper proposes and demonstrates an ultrasensitive refractive index (RI) sensor based on harmonic Vernier effect (HEV) and a cascaded Fabry-Perot interferometer (FPI). The sensor is fabricated by sandwiching a hollow-core fiber (HCF) segment between a lead-in single-mode fiber (SMF) pigtail and a reflection SMF segment with an offset of 37 µm between two fiber centers to form a cascaded FPI structure, where the HCF is the sensing FPI, and the reflection SMF is the reference FPI. To excite the HEV, the optical path of the reference FPI must be multiple times (>1) that of the sensing FPI. Several sensors have been made to conduct RI measurements of gas and liquid. The sensor's ultrahigh RI sensitivity of up to ∼378000 nm/RIU can be achieved by reducing the detuning ratio of the optical path and increasing the harmonic order. This paper also proved that the proposed sensor with a harmonic order of up to 12 can increase the fabricated tolerances while achieving high sensitivity. The large fabrication tolerances greatly increase the manufacturing repeatability, reduce production costs, and make it easier to achieve high sensitivity. In addition, the proposed RI sensor has advantages of ultrahigh sensitivity, compactness, low production cost (large fabrication tolerances), and capability to detect gas and liquid samples. This sensor has promising potentials for biochemical sensing, gas or liquid concentration sensing, and environmental monitoring.

Design and numerical investigation of a dual-core photonic crystal fiber refractive index sensor for cancer cells detection

Design and numerical investigation of a dual-core photonic crystal fiber refractive index sensor for cancer cells detection

Portable Multihole Plastic Optical Fiber Sensor for Liquid-Level and Refractive Index Monitoring

In this article, we report a low-cost method to fabricate plastic optical fiber (POF) liquid-level and refractive index (RI) sensors integrated with smartphones by molds and drilling microholes in side-growing POFs (SGPOFs) with high-temperature metal wire. These sensors can be used for real-time liquid-level and RI monitoring, especially under situations requiring portability and illumination. When the liquid level changes, the change of the RI around the microholes leads to a change in the light intensity transmitted in the fiber, enabling us to measure the liquid level and RI. Utilizing one sensor with six holes (0.45 mm radius and 15 mm spacing) in 2.0-mm SGPOF, the results of level and RI measuring are in good agreement with the theory. The liquid-level measurement of the sensor is carried out for water with an RI of 1.333, the level sensitivity is 0.29%/cm ± 0.02%/cm. In the RI measurement, the RI sensitivity of the sensor is −22.8%/RIU ± 0.6%/RIU in the measurement range from 1.333 to 1.475.

Refractive index sensor based on a gradually hot-pressed flatted plastic optical fiber

This paper proposes a gradually hot-pressure plastic optical fiber (POF) refractive index (RI) sensor with a flatted structure to detect the glucose concentration, and experimentally investigates the performance of RI sensor with straight and micro-bending POFs. The sensor is fabricated by a temperature-controllable metal rod to form the hot-pressed end face of POF which can increase signal-to-noise ratio (SNR) of the sensor. The experimental results show that the proposed sensor, utilizing a flatted structure POF with thickness of 0.5 mm and diameter of 0.4 cm, achieves maximum intensity sensitivity of up to 1748.91 %/RIU and resolution of up to 5.97 × 10−4 RIU in the RI range of 1.33 to 1.382. Furthermore, its simple design and manufacturing process shows potential for application, especially in biochemistry and environmental safety.

Photonic crystal fiber refractive index sensor based on SPR

Photonic crystal fiber refractive index sensor based on SPR

Simulation study of a temperature-calibrated double-sided polished optical fiber SPR refractive index sensor.

The temperature of the environment directly affects the accuracy of refractive index (RI) measurement. Therefore, we propose a double-sided polished surface plasmon resonance (SPR) RI fiber sensor, which is available for simultaneous measurement of the RI and temperature in real time. The proposed sensor uses single-mode fiber as a special double-sided polishing structure. The double-sided polishing regions are coated with a gold-silver hybrid film; one side is additionally coated with graphene layers to increase detection sensitivity, and the other side is coated with polydimethylsiloxane on the metal layer for temperature sensing. The simulation result shows that in the range from 1.33 to 1.35, RI sensitivity reaches as high as 2600nm/RIU. In the range from 15°C to 85°C, temperature sensitivity reaches as high as -3.5n m/∘ C. The full width at half maximum is 65nm. Compared with previous studies, the sensitivity is slightly improved, and an excellent temperature compensation effect can be achieved. It is suitable for high-precision measurement of the environment and biochemical aspects.

D-shaped optic fiber temperature and refractive index sensor assisted by tilted fiber bragg grating and PDMS film

A sensor combining a polydimethylsiloxane-coated Mach-Zehnder interferometer with a tilted fiber Bragg grating is proposed for dual-parameter sensing of liquid temperature and refractive index. Mach Zehnder interference is used for high sensitivity temperature sensing while the core mode of tilted fiber Bragg grating is used to distinguish the temperature range and avoid spectral overlap. Meanwhile, the cut-off mode of tilted fiber Bragg grating is used for refractive index sensing, which can effectively eliminate crosstalk between temperature and refractive index. The average temperature sensitivity of the sensor can reach 4.88, 5.15, 4.53 and 4.38 nm/°C over the range of 20, 30, 40 and 50 °C, respectively. The refractive index is in the range of 1.3330–1.3614, and the sensing sensitivity can reach 521.92 nm/RIU. Compared with other optical fiber sensors, the sensor proposed in this paper has the advantages of simple fabrication, compact structure, stable mechanical structure and high sensitivity, which is expected to be applied in the sensing field where refractive index and temperature need to be detected simultaneously.

D-shaped optical fiber refractive index sensor for application in fuel oil mixtures and leakage detection

D-shaped optical fiber refractive index sensor for application in fuel oil mixtures and leakage detection

Design and analysis of surface plasmon resonance sensor based on multi-core photonic crystal fiber

A three-core photonic crystal fiber refractive index sensor based on the surface plasmon resonance effect is proposed. The three cores of this sensor are symmetrical about the center. The gold film deposited outside the fiber structure makes this sensor contact with the analyte directly, which not only reduces the complexity of the fabrication but also makes the limiting loss very low. The sensing performance of the proposed sensor is investigated by using the finite element method. Numerical results show that the loss spectra of the x-polarized core mode are consistent with the y-polarized core mode. The sensor realizes the sensing detection of the analyte refractive index ranging from 1.37 to 1.42. When the analyte’s refractive index is 1.42, the maximum wavelength sensitivity of 2427 nm/RIU for x and y polarization, the corresponding maximum resolution can reach 4.12 × 10−5 RIU.

Sensitivity of a tapered fiber refractive index sensor at diameters comparable to wavelength

While there is an established literature on the effect of geometric parameters and material properties on the sensitivity of tapered fiber refractive index sensors, the impact of these parameters has been largely overlooked at sensor at diameters comparable to wavelength. Here, we investigate the effect of geometric parameters and materials properties at dimensions comparable to wavelength using full-wave solutions of Maxwell’s equations. Our results indicate that to achieve the maximum sensitivity for the tapered fiber sensors, the diameter should be closer to operational wavelength. For diameters less than the operational wavelength, sensitivity reduces instead of further increasing, a phenomenon opposite to what was predicted by ray-tracing based tapered fiber models. Another important finding of this study is the effect of optical loss constant on the sensitivity, a parameter often overlooked in the literature. As the optical loss constant was varied from 0 to 0.04 for each iteration of RI variation range, a linear decrease in sensitivity from 0.12 trans. (A.U)/RIU to 0.05 trans. (A.U)/RIU.