Fabry-Perot Interferometric Optical Fiber Sensor Research Articles

Effect of temperature change on refractive index of an egg white and yolk: a preliminary study

In this article, the refractive index of an egg white and yolk depending on temperature in range 30 - 47 °C over 1550 nm was determined. The measurement head was constructed as fiber optic Fabry-Perot interferometer with interference between polished fiber end-face and aluminum weighing dish. The measurement setup has been made of an optical spectrum analyzer, a superluminescent diode with a central wevelength of 1550 nm, 2:1 fiber coupler and heat plate. Full Text: PDF ReferencesP. Magdelaine, "Egg and egg product production and consumption in Europe and the rest of the world, Improving the Safety and Quality of Eggs and Egg Products", Egg Chemistry, Production and Consumption, 3 (2011). CrossRef H. Kuang, F. Yang, Y. Zhang, T. Wang, and G. Chen, "The Impact of Egg Nutrient Composition and Its Consumption on Cholesterol Homeostasis", Cholesterol (2018). CrossRef J. Gienger, K. Smuda, R. Müller, M. Bär, and J. Neukammer, "Refractive index of human red blood cells between 290 nm and 1100 nm determined by optical extinction measurements", Sci. Rep. 9, 1 (2019). CrossRef P. Listewnik, M. Hirsch, P. Struk, M. Weber, M. Bechelany, and M. Jędrzejewska-Szczerska, "Preparation and Characterization of Microsphere ZnO ALD Coating Dedicated for the Fiber-Optic Refractive Index Sensor", Nanomaterials 9, 2 (2019) CrossRef Y. Wu, Y. Zhang, J. Wu, and P. Yuan, "Fiber-Optic Hybrid Structured Fabry-Perot Interferometer Based On Large Lateral Offset Splicing for Simultaneous Measurement of Strain and Temperature", J. Lightwave Technol., 35, 19 (2017). CrossRef M. Islam, M. Mahmood, M Lai, K. Lim, and H. Ahmad, "Chronology of Fabry-Perot Interferometer Fiber-Optic Sensors and Their Applications: A Review", Sensors 14, 4 (2014). CrossRef K. Karpienko, M. Wróbel, and M. Jędrzejewska-Szczerska, "Determination of refractive index dispersion using fiber-optic low coherence Fabry-Perot interferometer: implementation and validation", Opt. Eng. 53, 7 (2014). CrossRef M. Kosowska, D. Majchrowicz, K. Sankaran, M. Ficek, K. Haenen, and M. Szczerska, "Doped Nanocrystalline Diamond Films as Reflective Layers for Fiber-Optic Sensors of Refractive Index of Liquids", Materials 12, 13 (2019). CrossRef G. Xiao, A. Adnet, Z. Zhang, F. Sun, and C. Grover, "Monitoring changes in the refractive index of gases by means of a fiber optic Fabry-Perot interferometer sensor", Sensors and Actuators 118, 2 (2005). CrossRef

Fabrication of silicon-tipped fiber-optic temperature sensors using aerogel-assisted glass soldering with precise laser heating.

We demonstrate the fabrication of fiber-optic Fabry-Perot interferometer (FPI) temperature sensors by bonding a small silicon diaphragm to the tip of an optical fiber using low melting point glass powders heated by a 980 nm laser on an aerogel substrate. The heating laser is delivered to the silicon FPI using an optical fiber, while the silicon temperature is being monitored using a 1550 nm white-light system, providing localized heating with precise temperature control. The use of an aerogel substrate greatly improves the heating efficiency by reducing the thermal loss of the bonding parts to the ambient environment. A desirable temperature for bonding can be achieved with relatively small heating laser power. The bonding process is carried out in an open space at room temperature for convenient optical alignment. The precise temperature control ensures minimum perturbation to the optical alignment and no induced thermal damage to the optical parts during the bonding process. For demonstration, we fabricated a low-finesse and high-finesse silicon FPI sensor and characterized their measurement resolution and temperature capability. The results show that the fabrication method has a good potential for high-precision fabrication of fiber-optic sensors.

A Gold Diaphragm-Based Fabry-Perot Interferometer With a Fiber-Optic Collimator for Acoustic Sensing

In this paper, a high sensitive fiber-optic Fabry-Perot interferometer sensor based on gold diaphragm for acoustic detection has been proposed and experimentally demonstrated. The extrinsic Fabry-Perot interferometer (EFPI) comprises a 140-nm-thick gold diaphragm and the end-face of a fiber-optic collimator, both of which are enclosed into a structure made of glass tubes. A fiber-optic collimator is first adopted in acoustic sensing to reduce the light loss and improve the sensitivity. The experimental results show that the proposed sensor has a wide flat response range from 400 Hz to 12 kHz, almost covering the primary frequency component of audible sound. The pressure sensitivity and the minimum detectable acoustic pressure level (MDP) are measured to be −175.7 dB re 1rad/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> Pa@150Hz and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$95.3~\mu $ </tex-math></inline-formula> Pa/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> @2kHz, respectively. The proposed sensor has advantages of high sensitivity, wide flat response, low cost, and simple fabrication, which shows its potential as a fiber optical microphone with high sensitivity and high acoustic quality in practical applications.

Faraday Michelson Interferometers for Signal Demodulation of Fiber-Optic Sensors

We developed an all-fiber-based optical demodulator for the signal interrogation of low-coherence fiber-optic Fabry-Perot interferometric sensors. The optical demodulator consists of a Michelson interferometer implemented by using a 3 × 3 fiber coupler and two fiber-coupled Faraday reflectors with tunable fiber delay lines. The demodulator's output contains two optical interference signals with a constant phase shift and the output shows no sensitivity to the polarization variation in the light source or fibers. A digital phase recovery algorithm is used to extract the measurand information from the phase-shifted signals at high accuracy, high dynamic range, and high stability. The optical demodulator has been applied to the measurement of high-frequency vibrations and strains using fiber-optic sensors.

Pulse Wave Velocity Measurement With Multiplexed Fiber Optic Fabry–Perot Interferometric Sensors

The paper presents an approach to noninvasively measure pulse wave delay and velocity by means of two multiplexed fiber-optic Fabry-Perot interferometric sensors interrogated by means of spectral interferometry. The pulse wave signals were measured with 1 kHz sampling rate. The obtained optical path difference resolutions are on the order of tens picometers, which allowed the pulse wave signal features as small as 100 pm to be clearly observed in the demodulated waveforms. The pulse wave velocity between different arteries was measured, demonstrating good agreement with the known data, where applicable. The paper also presents a mathematical model based on Cramer-Rao approach, describing the fundamental resolution limits of the pulse wave delay measurement. The derived mathematical model is not limited to fiber-optic pulse wave sensors and can be used for estimating the performance of other systems, such as photoplethysmographic and ultrasound. The reported work paves the way to development of novel all-optical non-invasive systems for medical diagnostics and vital signs monitoring, including portable devices.

Quadrature phase-shifted optical demodulator for low-coherence fiber-optic Fabry-Perot interferometric sensors.

We demonstrate a quadrature phase-shifted optical demodulation scheme for low-coherence fiber-optic Fabry-Perot interferometric sensors. The main part of the demodulator is a fiber-optic Mach-Zehnder interferometer (MZI) constructed with a 1 × 2 fiber coupler, a 3× 3 fiber coupler, and fiber delay lines. This configuration allows us to generate quadrature phase-shifted interference signals simultaneously, thus eliminating the problem of ambiguous phase discrimination. The path length difference of the MZI is adjustable to adapt to sensors with arbitrary gaps. A great phase stability of the MZI has been obtained by using identical optical components in its two optical paths. The demodulator has been applied to a fiber-optic vibrometer. Measurement of vibrations with amplitudes from 0.67 nm to 12.3 µm has been demonstrated.

Fiber optic Fabry–Perot interferometer sensor: an efficient and fast approach for ammonia gas sensing

In this work, we propose and demonstrate a Fabry–Perot-interferometer-based polydimethylsiloxane (PDMS) and poly(methyl methacrylate) (PMMA)-composite-coated optical sensor for ammonia and volatile organic compounds (VOCs) detection at room temperature. The principle of sensing is based on change in the cavity length of the FP cavity in the presence of varied concentrations of gases, which results in changes in the total reflectance due to the shift in wavelength of an interference pattern. The sensing composite material was coated on a single-mode optical fiber by using a simple dip-coating technique and explored it for sensing. The ammonia and VOCs measurements were performed for concentrations ranging from 5 to 500 ppm. The corresponding sensitivity and limit of detection of the developed sensor for ammonia gas detection was observed of the order of around 4.16 pm/ppm and 4.8 ppm, respectively. The response and recovery times of the sensor were found to be of the order of 50 s and 10 s, respectively, for the ammonia gas. This sensor provides a simple, cost-effective, highly sensitive, and repeatable approach to measure ammonia gas and other VOCs at room temperature and could fulfill the demands of industrial applications.

Ultrasonic imaging of seismic physical models using a fringe visibility enhanced fiber-optic Fabry-Perot interferometric sensor.

A fringe visibility enhanced fiber-optic Fabry-Perot interferometer based ultrasonic sensor is proposed and experimentally demonstrated for seismic physical model imaging. The sensor consists of a graded index multimode fiber collimator and a PTFE (polytetrafluoroethylene) diaphragm to form a Fabry-Perot interferometer. Owing to the increase of the sensor's spectral sideband slope and the smaller Young's modulus of the PTFE diaphragm, a high response to both continuous and pulsed ultrasound with a high SNR of 42.92 dB in 300 kHz is achieved when the spectral sideband filter technique is used to interrogate the sensor. The ultrasonic reconstructed images can clearly differentiate the shape of models with a high resolution.

Characterization of miniature fiber-optic Fabry-Perot interferometric sensors based on hollow silica tube

Abstract A miniature fiber-optic Fabry-Perot interferometer (MOFPI) fabricated by splicing a hollow silica tube (HST) with inner diameter of 4 µm to the end of a single-mode fiber is investigated and experimentally demonstrated. The theoretical relationship between the free spectrum range and the length of HST is verified by fabricating several MOFPIs with different lengths. We characterize the MOFPIs for temperature, liquid refractive index, and strain. Experimental results show that the sensitivities of the temperature, liquid refractive index, and strain are 16.42 pm/°C,–118.56 dB/RIU, and 1.21 pm/µε, respectively.

광섬유 패치코드를 이용한 Fabry-Perot 간섭계 온도센서

In this paper, we propose and demonstrate a Fabry-Perot interferometer (FPI) optical fiber tip sensor fabricated by a blade-sawing technique using a fiber optic patch cord for high-resolution temperature measurement. The sensor head consists of a short air FP cavity near the tip of a single-mode fiber patch cord tip. The temperature which we can measure is determined through a phase variation of the interference fringes in the reflective spectrum of the sensor. The fiber optic FPI sensor in this work can monitor the environmental temperature very accurately from 40 to <TEX>$120^{\circ}C$</TEX>. As a result, the temperature sensitivity is obtained as <TEX>$38.2pm/^{\circ}C$</TEX>.

Adaptive filter-based interrogation of high-sensitivity fiber optic Fabry-Perot interferometry sensors

A novel method for interrogation of fiber-optic Fabry-Perot interferometric (FPI) sensors arranged in a white-light setup is presented. The proposed approach is based on a recursive least square (RLS) adaptive filtering to estimate the length of the Fabry-Perot cavity. Applied to an extrinsic FPI sensor with 1.6nm/kPa sensitivity, the interrogation method achieves pressure accuracy of 6.1Pa (0.045mmHg), with an improvement of 8.7 times over standard Q-point tracking method at no computational expense. The RLS-based algorithm also exhibits better resilience to low signal-to-noise ratio (SNR) conditions, achieving 0.87mmHg accuracy for SNR=−5.0dB. The proposed approach finds its best application in medical pressure sensors, for sub-mmHg in vivo pressure detection, and is based on a biocompatible FPI design.

通过改进非本征法布里-珀罗干涉型光纤传感器结构实现温度补偿的新方法

通过改进非本征法布里-珀罗干涉型光纤传感器结构实现温度补偿的新方法

Smart Truss for Education

This work discusses a laboratory resource and associated lecture material that are implemented in an interdisciplinary course ‘Smart Structures and Sensors.’ Instruction in structural behavior, sensor systems, and experimental systems issues is supported. The Smart Truss Bridge is a reconfigurable aluminum truss structure that is instrumented with strain sensors. It is designed to be representative of a full-scale steel bridge such that person loads produce reasonable strain levels. This multiple-bay truss can be configured with and without redundant members. Strain instrumentation with extrinsic Fabry-Perot Interferometric fiber optic sensors demonstrates the performance and use of sensor systems. Theoretical analysis and experimental measurement may be correlated for different load placements. Observations include elastic strain behavior as well as practical experimental issues such as noise and non-ideal connections. A smart structures case study shows the use of artificial neural networks in a monitoring application. The weight and location of a load are predicted using different combinations of member strain. The Smart Truss Bridge provides educational opportunities for students with different majors to investigate infrastructure technologies and to interact across the disciplines. The topics are relevant to current infrastructure research and problems.

Refractive index measurement using photonic crystal fiber-based Fabry-Perot interferometer

We have constructed a novel refractive index (RI) sensor based on a fiber optic Fabry-Perot interferometer (FPI) by splicing a section of hollow core fiber between a single-mode fiber and a photonic crystal fiber (PCF). Owing to the air holes in the cladding of the PCF, various substances, such as liquids and gases with different RI, can enter or leave the in-fiber air cavity, which makes the device usable as a refractometer. In this paper, the fiber optic FPI sensor has been used to monitor the RI changes of air with different pressures, and the experimental results show that such a sensor has an RI sensitivity of 805.1 microm/RIU, and hysteresis is not observed. Moreover, the easy fabrication method gives the in-fiber refractometer many potential applications in the sensing field.

Micro Extrinsic Fiber-Optic Fabry-Perot Interferometric Sensor Based on Erbium- and Boron-Doped Fibers

Micro extrinsic Fabry–Perot interferometers (MEFPIs), with cavity lengths of up to ∼ 9 μm and maximum fringe contrast of ∼ 19 dB, are fabricated by chemically etching Er- and B-doped optical fibers and then splicing the etched fiber to a single-mode fiber, for the first time to the best of our knowledge. The strain and temperature responses of the MEFPI sensors are investigated experimentally. Good linearity and high sensitivity are achieved. Such a type of MEFPI sensor is cost-effective and suitable for mass production, indicating its great potential for a wide range of applications.

Diaphragm-based extrinsic Fabry-Perot interferometric optical fiber sensor for acoustic wave detection under high background pressure

A new structure for diaphragm-based extrinsic Fabry-Perot interferometric (EFPI) optical fiber sensors is presented. This structure introduces a through hole in a conventional diaphragm-based EFPI sensor and significantly reduces the effect of operating point drift due to the background pressure and fluctuations. This structure also potentially has high temperature stability.

Parameter design of signal processing for transmission/reflection-type hybrid extrinsicFabry–Perot interferometric optical fiber sensors

A transmission/reflection-type hybrid extrinsic Fabry–Perot interferometric (TRHEFPI)optical fiber sensor presents transmission-type and reflection-type sensor signalssimultaneously, and measurement directions can be robustly distinguished withthe phase lead or lag of the linear combination signal from the original sensorsignal. This sensor principle compensates for the ambiguous distinction of themeasurement directions and direction changes of conventional interferometric optical fibersensors, including extrinsic Fabry–Perot interferometric optical fiber sensors, dueto the exclusive use of fringe counting in signal processing. Designing a sensorcoefficient in the linear combination signal is one of the most important works insignal processing for the TRHEFPI optical fiber sensor because the magnitudeof the phase shifts depends on the sensor coefficient. A design method of thesensor coefficient is presented in this research. The method was verified withexperimental sensor signals and applied to strain measurement experiments. A method ofabsolute measurement using the TRHEFPI optical fiber sensor is also presented.

Monitoring changes in the refractive index of gases by means of a fiber optic Fabry-Perot interferometer sensor

We have developed a simple fiber optic Fabry-Perot interferometer (FPI) sensor that is used to precisely monitor changes in the refractive index of gases. The operating principle of the sensor is discussed in this paper, and it was noticed that the wavelength positions of the FPI reflectance peaks change linearly with the refractive index of gases. Using this unique property of FPI sensors, it is feasible to achieve a resolution of better than 10 −5 in monitoring the changes in the refractive index of gases. The sensor has been successfully used to monitor changes in the refractive index of nitrogen gas as a function of pressure.

A study on the development of transmission-type extrinsic Fabry-Perot interferometric optical fiber sensor

The conventional reflection-type extrinsic Fabry-Perot interferometric (EFPI) optical fiber sensor has good sensitivity and resolution compared with other types of optical fiber sensors. However, they have the disadvantage that the distinction of strain direction of EFPI is difficult because of measurement method by only fringe counting. This paper presents the newly developed transmission-type EFPI (TEFPI) optical fiber sensor, which has been improved by additional functions, and whose measuring system differs from that of the reflection-type EFPI optical fiber sensors using a single-mode fiber (SMF) and multimode (MMF) fibers as light guides and reflectors, respectively. The output signal of the TEFPI optical fiber sensor was analyzed with the uniform plane wave-based model, the SMF power distribution-based model and the splice loss-based model; the analyzed signals were then verified experimentally. Based on the results of analysis, the TEFPI optical fiber sensor was fabricated using two single-mode fibers connected to the light source and optical receiver; this was then used in strain measurement. The strain measured by the TEFPI optical fiber sensor was compared with that measured by the electric strain gauge.

Multiplexed optical fiber sensors using a single Fabry-Perot resonator for phase modulation

This paper describes the use of different optical return paths in a single Fabry-Perot phase modulator to perform coherence division multiplexing, and a combination of coherence and frequency division multiplexing of Fabry-Perot interferometric optical fiber sensors. A path-matched differential interferometry (PMDI) using low finesse Fabry-Perot sensors, one moderate finesse Fabry-Perot read-out resonator, and a broadband light source consisting of amplified spontaneous emission (ASE) from an erbium-doped fiber amplifier (EDFA) is used to illustrate the idea. The first, second and third order of multiple paths in a single Fabry-Perot read-out resonator are used to path-match three Fabry-Perot sensors. These three orders of path-matches provide a single, double and triple depth of modulation (phase-change) when the read-out is used as an optical phase modulator, and therefore provide a single, double and triple carrier frequency when serrodyne demodulation is used. The use of a single moderate finesse read-out Fabry-Perot resonator to simultaneously path-match coherence multiplexed sensors reduces the complexity of the optical system. Experiments and modeling are used to show the existence of the first, second, and third order of interference path-match conditions, and to determine the read-out configuration that enhances the visibility of the higher order path-match conditions. Using the multiple return paths in a single PZT-based Fabry-Perot read-out interferometer and serrodyne demodulation, several multiplexing schemes are investigated, and their relative merits discussed.