Fabry-Perot Pressure Sensor Research Articles

Fiber fabry-pero micro pressure sensor

A new fiber fabry-perot pressure sensor is designed. It is made by photolithography, silicon wafer etching, anode bonding, microelectromechanical system technology and so on. It is suitable for the pressure measurement of micro-pressure environment under harsh environment and small space. The structure of the transmitter and the way to make it are described in detail. The design smartly uses the Fiber optic flange, the optical fiber end face is parallel to the sensitive film, thus a high-quality Fabry-Pero-cavity is formed. The structure also contributes to the stability of the initial cavity, the sensor error is reduced. The experimental demodulation system is established, the pressure, temperature and other characteristics are tested in detail. The experiment result shows that within the pressure range of 0~0.1MPa, the sensor has a good linearity, high repeatability and a sensitivity of 61.6 μm/MPa.

Silk fibroin diaphragm-based fiber-tip Fabry-Perot pressure sensor.

A miniature fiber-optic Fabry-Perot is built on the tip of a single mode fiber with a thin silk fibroin film as the diaphragm for pressure measurement. The silk fibroin film is regenerated from aqueous silk fibroin solution obtained by an environmentally benign fabrication process, which exhibits excellent optical and physicochemical properties, such as transparency in visible and near infrared region, membrane-forming ability, good adhesion, and high mechanical strength. The resulted Fabry-Perot pressure sensor is therefore highly biocompatible and shows good airtightness with a response of 12.3 nm/kPa in terms of cavity length change.

Fiber optic Fabry–Perot pressure sensor based on lensed fiber and polymeric diaphragm

A novel optical fiber-based Fabry–Perot pressure sensor fabricated with a lensed fiber and a polymeric diaphragm is proposed for application in the medical field. The lensed fiber was constructed at the tip of a single mode fiber, for use with a deformable flexible polymeric diaphragm. The sensor can reduce the loss of optical power of the back-reflected light, and the flexible diaphragm can increase deformation sensitivity. The lensed fiber was fabricated from a coreless silica fiber attached to a single mode fiber by splicing using a fusion splicing method, and arc discharge. The polymeric diaphragm consists of layered PDMS, parylene and gold mirror. The intermediate parylene layer is helpful to prevent cracking of the mirror when the diaphragm is deformed by external pressure. The polymeric diaphragm was fabricated by MEMS processing including spin-coating, vaporization, and sputtering. The deformation of the polymeric diaphragm was evaluated through numerical simulation. The change in cavity length between the lensed fiber and the polymeric diaphragm with external pressure was estimated using the interference generated from two reflected lights. Experimental results showed that the proposed pressure sensor has a sensitivity of 1.41μm/kPa over a pressure range from 0kPa to 4kPa with good linearity, and its minimum detection resolution is less than 0.03kPa. The proposed sensor could be used for reliable low-pressure measurement, especially in medical applications.

热应力和残余气压对光纤法布里-珀罗压力传感器温度性能的影响

热应力和残余气压对光纤法布里-珀罗压力传感器温度性能的影响

Optical Fibers: The Optical Fiber Tip: An Inherently Light‐Coupled Microscopic Platform for Micro‐ and Nanotechnologies (Adv. Mater. 23/2014)

The flat tip of an optical fibre is illustrated as an inherently light-coupled platform for micro- and nanostructures. The diversity of these structures includes metallic nanoarrays for SERS and plasmonics, MEMS for Fabry–Perot pressure sensors and AFM probes, and entirely selfcontained silicon-photonic circuits. This broad field is reviewed in detail by G Kostovski and co-workers on page 3798.

Low-cost and miniature all-silica Fabry–Perot pressure sensor for intracranial pressure measurement

The monitoring of increased intracranial pressure (ICP) is necessary in the diagnosis and treatment of patients with neurological disease because it can provide an insight into the mechanism of the head injury. In this letter, we develop a novel miniature Fabry-Perot (F-P) sensor for ICP measurement. The proposed sensor is fabricated by using a commercially available fusion splicer and a fiber cleaver, by which many difficult art problems involved in fabrication are solved and the online monitoring of the F-P cavity is actualized. The sensor exhibits a linear response to the applied pressure over the range of 0-25 kPa (ample for ICP measurement), with a sensitivity of 10.18 nm/kPa, a resolution of 0.1 kPa, and a reduced thermal sensitivity of 0.068 nm/°C, which shows it can meet the requirements of ICP measurement.

Spectral eigendecomposition‐based algorithm for cavity estimation in fibre‐optic Fabry‐Pérot pressure sensors

A novel signal processing-based approach for the real-time estimation of air-gap length in fibre optic extrinsic Fabry-Perot pressure sensors is presented; the algorithm is based on eigendecomposition of the spectrum mutual correlation matrix. A pressure accuracy of 6.1 Pa (0.045 mmHg) is achieved in a pressure probe with 1.13 nm/kPa sensitivity, highlighting a 6.4 times improvement over standard quadrature point amplitude tracking by just acting on signal processing.

Birefringence dispersion compensation demodulation algorithm for polarized low-coherence interferometry

A demodulation algorithm based on the birefringence dispersion characteristics for a polarized low-coherence interferometer is proposed. With the birefringence dispersion parameter taken into account, the mathematical model of the polarized low-coherence interference fringes is established and used to extract phase shift information between the measured coherence envelope center and the zero-order fringe, which eliminates the interferometric 2 π ambiguity of locating the zero-order fringe. A pressure measurement experiment using an optical fiber Fabry-Perot pressure sensor was carried out to verify the effectiveness of the proposed algorithm. The experiment result showed that the demodulation precision was 0.077 kPa in the range of 210 kPa, which was improved by 23 times compared to the traditional envelope detection method.

Sensitivity Characteristics of Fabry-Perot Pressure Sensors Based on Hollow-Core Microstructured Fibers

In this paper, the sensitivity characteristics of Fabry-Perot (F-P) hydrostatic pressure sensor based on two different hollow-core (HC) microstructured optical fibers are experimentally and theoretically investigated. The sensors are fabricated by simply splicing a length of HC fiber to singlemode fibers. Hydrostatic pressure is measured by monitoring the wavelength shifts of the interferometric fringes as a result of the two reflection beams at the splicing points. The measured pressure sensitivities of F-P sensors fabricated on the simplified HC microstructured fiber and hollow-core photonic bandgap fiber (HC-PBGF) are - 17.3 and - 23.4 pm/MPa, respectively. Theoretical investigation is then carried out based on the analysis of elastic properties for the individual fibers. The calculated result suggests that the pressure sensitivities are dominantly determined by the induced changes in cavity length. In comparison, the contribution of mode-index change is slight. The mechanisms behind the mode-index changes for the two fibers are clarified by analyzing the deformation of the fiber structure under pressure. The holey microstructure is highly deformable compared to the solid fiber, which provide another dimension for the implementation of tunable photonic devices.

Miniature Fabry-Perot pressure sensor created by using UV-molding process with an optical fiber based mold

We present a miniature Fabry-Perot pressure sensor fabricated at the tip of an optical fiber with a pre-written Bragg grating by using UV-molding polymer process. The mold is constructed by integrating an optical fiber of 80 μm diameter with a zirconia ferrule. The optical fiber based mold makes it possible to use optical aligning method to monitor the coupled intensity between the mold-side and replica-side fibers, rendering a maskless alignment process with a submicrometer accuracy. A polymer-metal composite thin diaphragm is employed as the pressure transducer. The overall sensor size is around 200 μm in diameter. Experimental study shows that the sensor exhibits a good linearity over a pressure range of 1.9-7.9 psi, with a sensitivity of 0.0106 μm/psi. The fiber Bragg grating is exploited for simultaneous temperature measurements or compensation for temperature effects in pressure readings. The sensor is expected to benefit many fronts that require miniature and inexpensive sensors for reliable pressure measurement, especially biomedical applications.

Application of Fiber Bragg Grating Level Sensor and Fabry-Pérot Pressure Sensor to Simultaneous Measurement of Liquid Level and Specific Gravity

This study is proposed for obtaining simultaneous measurements of the level and specific gravity of a liquid using a dual-optical-fiber-sensor system comprising a fiber Bragg grating (FBG) level sensor and a Fabry-Perot (FP) pressure sensor. In the FBG level sensor, the liquid level is derived from the FBG wavelength shift induced when the buoyancy is applied on a cantilever beam. Meanwhile, in the FP sensor, the pressure is calculated from the change in cavity length which takes place when the sensor is immersed. The experimental results show that the FBG level and FP pressure sensors have sensitivities of 0.01491 nm/cm and 0.1569 μm/kPa, respectively. Analytical formulae are derived for the level and specific gravity of the liquid in terms of the Bragg wavelength shift, the change in cavity length, and the vertical separation distance between the two sensors. The average measurement errors of the liquid level and specific gravity are found to be 0.0323 and 0.0528 m, respectively.

Miniature Temperature Compensated Fabry-Perot Pressure Sensors Created with Self-aligned Polymer Photolithography Process

We present a cross-axial and a co-axial miniature Fabry-Perot pressure sensor fabricated at the tip of an optical fiber with a prewritten Bragg grating by using maskless photolithography process and UV curing polymer process. The optical fiber serves as an intrinsic mask for sensor fabrication as well as a waveguide for sensor interrogation. A polymer-metal composite thin diaphragm is employed as the pressure transducer. The overall sensor size is almost the same as that of a standard single mode optical fiber. Experimental study shows that the sensors exhibit good linearity over a pressure range of 1.9- 9.4 psi , with sensitivities of and psi for the cross-axial and co-axial sensors, respectively. The fiber Bragg grating is exploited for simultaneous temperature measurements or to compensate for temperature effects in pressure readings. The dynamic response of the sensors is also evaluated and discussed. These sensors are expected to impact many fronts that require miniature and inexpensive sensors for reliable static and transient pressure measurements of fluids.

Miniature surface-mountable Fabry–Perot pressure sensor constructed with a 45° angled fiber

We present a surface-mountable miniature Fabry-Perot (FP) pressure sensor that utilizes the total internal reflection at a 45 degrees angled fiber end face to steer the optical axis by 90 degrees . By using the fiber as a waveguide, as well as a natural mask in photolithography, an FP cavity is constructed on the sidewall of the fiber. A polymer-metal composite diaphragm is employed as the pressure transducer. The sensor exhibits a good linearity over the pressure range of 1.9-14.2 psi, with a sensitivity of 0.009 microm/psi and a hysteresis of 2.7%. This sensor is expected to impact many fronts that require reliable static pressure measurements of fluids.

Fiber optic Fabry–Perot pressure sensor with low sensitivity to temperature changes for downhole application

Pressure and temperature are two important parameters in reservoir engineering. The fiber optic sensors can be used for permanent downhole monitoring. In this paper, we propose an extrinsic fiber Fabry–Perot interferometer (EFPI) sensor for pressure measurement with low sensitivity variation. The pressure sensitivity of EFPI sensor and of the fiber Bragg grating (FBG) sensors have been measured. The experimental pressure sensitivity for EFPI and FBG sensors are measured to be 2.75×10−81/kPa and 1.52×10−81/kPa, respectively. The temperature cross-sensitivity problem of the EFPI sensor has been solved by a new technique. The temperature sensitivity of EFPI sensor has been decreased to 1.2×10−6/°C, while the temperature sensitivity of non-compensated EFPI sensor has been measured to be 16.4×10−6/°C. The results show that the EFPI sensor has a higher pressure sensitivity and good capability to decrease temperature sensitivity in comparison to FBG sensor.

Laser-machined fibers as Fabry-Perot pressure sensors

Cavities have been laser ablated in the ends of single-mode optical fibers and sealed by aluminized polycarbonate diaphragms to produce Fabry-Perot pressure sensors. Both conventional fibers and novel, multicore fibers were used, demonstrating the possibility of producing compact arrays of sensors and multiple sensors on an individual fiber 125 microm in diameter. This high spatial resolution can be combined with high temporal resolution by simultaneously interrogating the sensors by using separate laser sources at three wavelengths. Shock tube tests showed a sensor response time of 3 micros to a step increase in pressure.

Design and Optimization of Dual Optical Fiber MEMS Pressure Sensor For Biomedical Applications

A novel Single Deeply Corrugated Diaphragm (SDCD) based dual optical fiber Fabry-Perot pressure sensor for blood pressure measurement is proposed. Both mechanical and optical simulations are performed to demonstrate the feasibility and superior performance of the proposed sensor. Result shows that less than 2% nonlinearity can be achieved for the proposed sensor using optimal Fabry-Perot microcavity. Also, the fabrication process of the proposed sensor is given, instead of complicated fusion bonding process, only bulk and surface micromachining techniques are required which facilitate the mass production of such biocompatible and disposable pressure sensors.

All-fiber high-sensitivity pressure sensor with SiO_2 diaphragm

The design and fabrication of a miniature fiber Fabry-Perot pressure sensor with a diameter of 125 microm are presented. The essential element in the process is a thin SiO2 diaphragm that is fusion spliced at the hollow end of an optical fiber. Good repeatability and high sensitivity of the sensor are achieved by on-line tuning of the diaphragm thickness during the sensor fabrication process. Various sensor prototypes were fabricated, demonstrating pressure ranges of from 0 to 40 kPa to 0 to 1 MPa. The maximum achieved sensitivity was 1.1 rad/40 kPa at 1550 nm, and a pressure resolution of 300 Pa was demonstrated in practice. The presented design and fabrication technique offers a means of simple and low-cost disposable pressure sensor production.

Theoretical analysis and measurement of the temperature dependence of a micromachined Fabry–Perot pressure sensor

In this study an analytical model that takes into account the coupled photoelastic and thermo-optical effects is established to evaluate the temperature dependence of a single-chip silicon micromachined Fabry-Perot pressure sensor. The results show that temperature variation has a significant effect on the performance of a micromachined Fabry-Perot pressure sensor with a conventional flat diaphragm. A new membrane-type silicon micromachined Fabry-Perot pressure sensor with a novel deeply corrugated diaphragm is then proposed. The sensor is fabricated on a single-chip by use of both surface- and bulk-micromachining techniques. Both analytical and experimental results show that the cross sensitivity of Fabry-Perot pressure sensors to temperature can be substantially alleviated by use of the proposed single deeply corrugated diaphragm.

Modelling and optimization of a Fabry–Perot microcavity for sensing applications

In this work, a generalized study has been carried out on the transmission characteristics of a Fabry–Perot microcavity illuminated by a laser beam. The analytical expressions are obtained based on Gaussian beam optics and Smith's method. A novel Fabry–Perot microcavity optimization model is then established to achieve both the best sensing performance and least measurement tolerance for high yield of sensors during batch fabrication. The perturbations of Fabry–Perot pressure sensor performance induced by other common issues, such as non-normal incidence angle and microcavity mirror imperfections, are also discussed.

A single-chip diaphragm-type miniature Fabry–Perot pressure sensor with improved cross-sensitivity to temperature

We present a new micromachined Fabry–Perot (FP) cavity with a novel single deeply corrugated diaphragm for pressure-sensing applications. An approximate expression was obtained to evaluate the stress-releasing factor of the proposed diaphragm. Various factors such as the variations of film thickness and stress due to temperature increase were considered to evaluate the temperature dependence of the FP pressure sensor. A temperature controlled sensor chamber was developed to measure the optical response of the proposed FP pressure sensor. Both analytical and experimental results have shown that cross-sensitivity to temperature of a Fabry–Perot cavity-based pressure sensor can reasonably be alleviated by the proposed technique.