Tapered Fiber Optic Sensor Research Articles

Tapered fiber optic sensor for arterial pulse wave monitoring

Arterial pulse wave monitoring has been recognized as an effective medical diagnostic tool for various cardiovascular diseases. To overcome the barriers in traditional, complex, and expensive detection configurations, new electronic and optical sensors have been developed with their unique advantages. Particularly, various configurations of fiber-optic sensors have been proposed. This paper demonstrates the use of a tapered optical fiber structure to create a sensitive sensor that can detect carotid arterial pulse waves on the skin surface. The demonstrated fiber sensor probe utilizes an in-line Mach-Zehnder interferometer configuration and liquid-gold film coating on the sensor tip to enhance its sensitivity and demonstrate its use by encapsulating the sensor with a flexible elastomer material for detecting arterial pulse waves with a simple testing configuration. Considering the simple fabrication and high sensitivity without a complex demodulation scheme, the proposed sensor has broad implementation in biomedical health monitoring systems.

Enhanced Magnetic Field Sensing Using a Magnetic Graphene Oxide-Coated Tapered Fiber Optic Sensor

Enhanced Magnetic Field Sensing Using a Magnetic Graphene Oxide-Coated Tapered Fiber Optic Sensor

"DISCRIMINATION OF TEMPERATURE AND STRAIN INTERFERENCE IN FBG SENSORS USING TAPERED OPTICAL FIBER SENSOR "

"The optical fiber industry has progressed a lot in recent years. Earlier, they were used as a bed to carry light and image for medical applications, especially in endoscopy. In the mid-1960s, calls were widely used to transmit information. So far, optical fiber technology has been a worthy subject for research. Low loss rate, high bandwidth, electromagnetic reliability, small size, light weight, safety, relatively cheap price, low need for reconstruction and maintenance are the reasons for the attractiveness of optical fibers. In recent years, optical sensors, including FBG, are widely used in the field. Different methods have been used. Among these applications, we can refer to imaging in the fields of civil engineering, aerospace, marine sciences, oil and gas, composites and smart structures. Fiber Bragg Grating (FBG) sensors have found more usages in the industry to diagnose the safety of mechanical structures due to their high sensitivity, non-exposure to the electromagnetic field, linearity, and lightness. A limitation of the application of FBG sensors is the Inability to distinguish the effects of temperature and strain in the simultaneous measurement. For this purpose, we must somehow discriminate the effect of temperature from the strain. In this Article, by designing a tapered fiber-FBG composite sensor we have provided a solution for this problem. Studies performed on the designed composite sensor show that no sensitivity interference will occur in the sensor. In the composite sensor, a tapered fiber optic sensor with a temperature sensitivity of and a FBG sensor with the temperature and strain sensitivity of and, respectively, are used. Keywords: Tapered fiber, Temperature sensor, FBG sensor, Strain health monitor, Structural health monitor, Interferences. "

Label-Free Tapered Fiber Optic Sensor for Real-Time In Situ Detection of Cell Activity

Label-Free Tapered Fiber Optic Sensor for Real-Time In Situ Detection of Cell Activity

Study on Determination of Lead Ion Concentration by Chelating Agent Modified Tapered Fiber Optic Sensor

Study on Determination of Lead Ion Concentration by Chelating Agent Modified Tapered Fiber Optic Sensor

Lossy mode resonance-based uniform core tapered fiber optic sensor for sensitivity enhancement

A lossy mode resonance (LMR)-supported fiber optic sensor in which a uniform fiber core is placed among two identical tapered regions, is investigated numerically. Indium tin oxide (ITO) and aluminum-doped zinc oxide (AZO) are considered as LMR active materials used to excite several lossy modes and gold and silver are used as surface plasmon resonance (SPR) active materials. In this probe design, a central uniform core coated with ITO/AZO is the active sensing region, whereas tapered regions are meant for bringing the incident angle close to the critical angle. The sensitivity of the present fiber optic bio-sensor is evaluated for first two LMRs utilizing both ITO and AZO separately, along with its variation with the taper ratio (TR). For ITO, the maximum sensitivity values are observed to be 18.425 μm RIU−1 (refractive index unit) and 0.825 μm RIU−1, corresponding to the first and second LMRs, respectively, at a TR of 1.6 and for AZO, equivalent values are 0.79 μm RIU−1 and 0.35 μm RIU−1, respectively, at a TR of 2.0. The results illustrate that the first LMR is more sensitive than the second LMR and the ITO-coated probe possesses greater sensitivity than the AZO-coated probe for both LMRs. Similarly, for the fiber optic SPR sensor, the maximum value of sensitivity is 5.6425 μm RIU−1, in the case of gold and 5.0615 μm RIU−1 in the case of silver, at a TR of 1.6. Hence, the result shows that the sensor with the present fiber optic probe design has around a 3-fold enhancement in sensitivity compared with conventional SPR sensors. This study will have applications in many sensing schemes where the requirement of large sensitivity is vital.

Design considerations of a surface plasmon resonance (SPR) based tapered fiber optic bio-sensing probe with graphene-MoS2 over layers

In this paper, we have reported the design considerations of a surface plasmon resonance (SPR) based tapered fiber optic sensor by coating a thin film of platinum on a tapered fiber core followed by graphene-molybdenum disulphide (MoS2) monolayers. The theoretical study is based on five-layer matrix model. To see the effect of graphene-MoS2 over layers, performance parameters in terms of sensitivity and detection accuracy are evaluated for four taper profiles viz. exponential-linear, linear, parabolic and quadratic along with the taper ratio. From results, we inferred that with increase in taper ratio sensitivity also increases while detection accuracy decreases monotonically. For the proposed sensor configuration, maximum sensitivity value is found to be 7.04 μm/RIU at taper ratio 2.0 for exponential-linear taper profile while maximum detection accuracy obtained is 16.7623μm−1, at taper ratio 1.0. Thus, the results show that by introducing additional graphene-MoS2 monolayers, the sensitivity of the proposed sensing probe is enhanced by more than 44% at taper ratio 2 as compared to the conventionally used SPR based fiber optic sensors coated with platinum only. Also, the effect of increasing number of layers of graphene and MoS2 on the performance parameters is evaluated and compared. The advantageous features of the graphene and MoS2 layers have also been discussed for bio-sensing applications.

Study of surface plasmon resonance sensors based on silver–gold nanostructure alloy film coated tapered optical fibers

Surface plasmon resonance (SPR) based tapered fiber optic sensor having nanostructure film with different particle sizes and volume fractions are analyzed and compared. Using ray-tracing model change in resonance wavelength, propagation length and penetration depth in metal of coupled light are obtained for proposed sensor configuration. The sensitivity of the sensor has been estimated with volume fraction and particle size of nanostructure materials. The sensitivity of the sensor increases with raise in volume fraction along with decline in taper ratio. In addition, the particle size of nanostructure film only affects the detection accuracy. Among all proposed configurations the nanostructures allow film of 2 nm particle size over tapered fiber, shows better detection accuracy and better sensitivity for larger volume fraction of silver.

Sensitivity enhancement of a lossy mode resonance based tapered fiber optic sensor with an optimum taper profile

In this study, we have presented the design considerations of lossy mode resonance (LMR) based tapered fiber optic sensors for sensitivity enhancement. The study includes the effect of the taper ratio and the taper profile, i.e. exponential-linear, linear, parabolic, gaussian and quadratic, on the sensitivity. Also, we have analyzed the effect of various coating materials on the sensitivity. It is revealed from the analysis that with an increase in the taper ratio, the sensitivity increases. The effect of the taper profile shows that among five profiles considered for comparison, the exponential-linear profile has the maximum sensitivity value whereas the quadratic profile has the lowest value. For indium tin oxide (ITO), for the exponential-linear taper profile, the sensitivity corresponding to the first and second lossy modes is 12.005 µm/RIU (refractive index unit) and 0.8 µm/RIU, respectively, at the taper ratio 1.7; whereas for aluminum doped zinc oxide (AZO), the corresponding values are 0.515 µm/RIU and 0.235 µm/RIU, respectively, at the taper ratio 2.0. For surface plasmon resonance (SPR) based tapered fiber optic sensors, the maximum sensitivity value for the exponential-linear taper profile for platinum is 6.39 µm/RIU at the taper ratio 2.0, whereas for copper its value is 3.665 µm/RIU. At the taper ratio 1.0, i.e. the uniform core, the sensitivity of the LMR based tapered fiber optic sensors using an ITO coating is two times greater than the platinum-coated SPR based fiber optic sensor. Increasing the taper ratio further enhances the sensitivity around 40% when compared to the uniform core fiber optic sensor. Therefore, LMR based tapered fiber optic sensors with the considered optimum design parameters demonstrate around a 2.5-fold enhancement in sensitivity compared with conventionally used SPR based fiber optic sensors, giving an optimum structure for sensitivity enhancement. We believe that this study will find suitable applications in research/industry for those working in the area of chemical and biological sensing.

Long Range Surface Plasmon Resonance Based Taper Fiber Optic Sensor with Enhanced Sensitivity using Au Nano-Layer through Radially Polarized Light

A new theoretical approach towards the sensitivity enhancement of tapered fiber optic sensor based on the long range surface plasmon (LRSP) resonance technique in Teflonmetal coated tapered fiber structure using radially polarized is proposed, designed and simulated within Kretschmann-Raether geometry. The configuration comprising a fiber core coated with 690 nm and 70 nm thin Teflon layer and Au layer respectively where the uniform taper waist having diameter 330 µm and 350 µm with taper ratio of 1.7 (NA: 0.25, 10 mm long waist region) and a sensing layer having varying refractive index from 1.333 to 1.353. With the increase in refractive index the observed results indicates a 1.7 times better sensitive tapered fiber sensor as compared to the existing LRSP based fibre optic sensors using intensity interrogation technique. To the best of our knowledge several articles have been devoted in the field of LRSP based fibre optic sensor with p-polarized light whereas no such article has yet been reported with Teflonused as a dielectric between metal coated taper fiber optic sensors using radially polarized light with better sensitivity. Here sensitivity also analysed w.r.t wavelength interrogation technique where the sensitivity enhancement is about 1.7 times than the existing fiber optic sensors.

Analysis of surface plasmon resonance based bimetal coated tapered fiber optic sensor with enhanced sensitivity through radially polarized light

The presented proposal of surface plasmon resonance (SPR) configuration with tapered fiber structure and radially polarized light beam is a new and different analysis towards the sensitivity enhancement in the field of SPR based fiber optic sensors. Here the taper waist region of optical fiber having diameter around 330μm is deposited with 40nm thin Ag layer, 10nm thin Au layer and the sensing layer with refractive index 1.333–1.353 respectively for achieving the bimetal coated taper fiber optic sensor with SPR configuration. The cylindrical symmetry and special radial field distribution of radially polarized light make its more interesting SPR study and leads to the enhanced excitation of surface plasmon wave. This results 10 times better sensitivity of fiber optic sensor output response as compared to p-polarized light beam with wavelength interrogation technique and 2.307 times better sensitivity with intensity interrogation technique. Also including the temperature effect in proposed taper bimetallic structure, this sensitivity analysis provides an evidence, for exploring a new idea towards the enhanced excitation of SPR which expedites the new avenues in the field of sensor applications with radially polarized light.

Theoretical investigation of absorption and sensitivity of nano-plasmonic tapered fiber optic sensors

In this paper, a theoretical investigation for the performance a tapered fiber optic sensor based on surface plasmon resonance (SPR) is proposed. The tapered fiber optic sensor is considered for three different taper profiles, namely, linear, parabolic, and exponential-linear. The tapered fiber optic sensor is coated with thin nanoparticle metallic films. The nanoparticle metallic film consists of spherical metallic nanoparticles embedded in a host material. The performance has been analyzed in terms of sensitivity and absorption of the sensor. It is shown that sensitivity and absorption of sensors depends on parameters such as taper ratio, taper profile, nanoparticle film thickness, nanoparticle radius, sensing region length, fiber core diameter, and concentration of sensing layer.

Theoretical analysis of tapered fiber optic surface plasmon resonance sensor for voltage sensitivity

The geometry dependent reflecting spectrum, resonance wavelength and sensitivity of surface plasmon resonance (SPR)-based tapered fiber optic sensor have been investigated. It is observed that as the tip end diameter decreases, the refractive index sensitivity of proposed sensor monotonically increases. However, the voltage sensitivity increases with the tip end diameter decreasing to a certain value. The relationship between the tip end diameter and refractive index sensitivity, voltage sensitivity present here gives a guideline to use tapered fiber optic SPR sensor targeting specific applications.

Surface Plasmon Resonance-Based Tapered Fiber Optic Sensor: Sensitivity Enhancement by Introducing a Teflon Layer Between Core and Metal Layer

Surface plasmon resonance (SPR)-based tapered fiber optic sensor with Teflon as a dielectric sandwiched between metal and tapered fiber core is proposed. The sensitivity of the sensor has been maximized using different combinations of metal and Teflon layer thicknesses for a given taper ratio. The study shows that the sensitivity of the sensor with the introduction of dielectric (Teflon) increases with the increase in the taper ratio. The maximum sensitivity achieved for a given taper ratio is around 15 times higher than the general SPR-based fiber optic sensor.

Surface plasmon resonance based tapered fiber optic sensor with different taper profiles

A theoretical model for surface plasmon resonance (SPR) based tapered fiber optic sensor is proposed with three different taper profiles, namely, linear, parabolic, and exponential-linear. The effect of taper ratio and taper profiles on the sensor’s performance is studied in detail and the design considerations for significantly enhanced sensitivity are reported. The study shows that the exponential-linear taper profile with high taper ratio provides the best performance. The physical reasons behind sensitivity enhancement due to taper ratio and taper profile are given, wherever required.