All-fiber Fabry-Perot Interferometer Research Articles

Ultra-High Sensitivity and Temperature-Insensitive Optical Fiber Strain Sensor Based on Dual Air Cavities.

This study proposed an all-fiber Fabry-Perot interferometer (FPI) strain sensor with two miniature bubble cavities. The device was fabricated by writing two axial, mutually close short-line structures via femtosecond laser pulse illumination to induce a refractive index modified area in the core of a single-mode fiber (SMF). Subsequently, the gap between the two short lines was discharged with a fusion splicer, resulting in the formation of two adjacent bubbles simultaneously in a standard SMF. When measured directly, the strain sensitivity of dual air cavities is 2.4 pm/με, the same as that of a single bubble. The measurement range for a single bubble is 802.14 µε, while the measurement range for a double bubble is 1734.15 µε. Analysis of the envelope shows that the device possesses a strain sensitivity of up to 32.3 pm/με, which is 13.5 times higher than that of a single air cavity. Moreover, with a maximum temperature sensitivity of only 0.91 pm/°C, the temperature cross sensitivity could be neglected. As the device is based on the internal structure inside the optical fiber, its robustness could be guarantee. The device is simple to prepare, highly sensitive, and has wide application prospects in the field of strain measurement.

Real-time displacement reconstruction based on all-fiber Fabry–Perot interferometer

A real-time displacement reconstruction method based on an all-fiber Fabry–Perot interferometer (FPI) is proposed, utilizing the fiber end face and the object surface to form an extrinsic FPI. Using the constant phase difference of 90° between the two output ports of the 2×2 coupler, two-phase orthogonal FPI signals carrying the object motion information can be detected by two invisible photodetectors, and real-time displacement reconstruction can be realized by adopting inverse tangent and unwrapping processing procedures. Results show that the absolute errors of the experiment are below 80 nm.

All-Fiber Fabry-Perot Interferometer Gas Refractive Index Sensor Based on Hole-Assisted One-Core Fiber and Vernier Effect

A novel high sensitivity all-fiber Fabry-Perot interferometer (FPI) gas refractive index (RI) sensor based on hole-assisted one-core fiber (HAOCF) and Vernier effect was proposed and demonstrated. The sensor is fabricated by splicing a section of HAOCF to a section of silica tube (ST) fused with the lead-in single-mode fiber (SMF), ensuring that the sensor is composed of an air-cavity FPI and a silica-cavity FPI. The cascaded dual-cavities generate the Vernier effect due to a similar free spectrum range (FSR), which significantly improve the sensitivity of the sensor. Owing to the air hole in the cladding of the HAOCF, gases with different RI can enter or leave the in-fiber air cavity, which makes the device usable as a gas RI sensor. The sensor was used to monitor the RI changes of air with different pressures and provided a high sensitivity of -9462.4 nm/RIU. The proposed sensor has a potential to find further applications in the fields of gas composition detection, medical diagnostics and environmental monitoring.

Ultrashort all-fiber Fabry-Perot interferometer fabricated by a CO2 laser.

We proposed and demonstrated a method to fabricate ultrashort all-fiber Fabry-Perot interferometers by splicing a standard single-mode fiber and another single-mode fiber with a concave surface constructed by a CO2 laser pulse. The geometric parameters of the concave surface could be controlled flexibly by adjusting the laser pulse and the relative position between the laser beam and the optical fiber. In our experiments, the minimum depth of the concave surfaces is 0.12 µm, which offers a means of fabricating an all-fiber Fabry-Perot interferometer with submicrometer cavity length. Moreover, the ultralow-roughness concave surface fabricated by a CO2 laser pulse is beneficial to improve the fringe visibility of the interferometer. These advantages make it attractive for practical applications.

Hollow-Core Fiber-Based All-Fiber FPI Sensor for Simultaneous Measurement of Air Pressure and Temperature

In paper, an all-fiber Fabry-Perot interferometer (FPI) sensor with cascaded micro-cavities is presented to measure air pressure and temperature simultaneously. The proposed sensor mainly consists of two tiny segments of hollow-core fiber (HCF) located at the end of lead-in single mode fiber (SMF), and there is a misalignment fusion splicing between the two HCFs with different core diameter. The sensor has minor length of about $210~\mu \text{m}$ since the two HCFs lengths are about $80~\mu \text{m}$ and $130~\mu \text{m}$ , respectively. Because the reflection spectrum of the sensor is formed by the fiber cavity, air cavity and their combined cavity, which can be processed by methods of fast Fourier transform (FFT) and Fourier band-pass filter (FBPF), so we can analyze the corresponding responses of every cavity from the reflection spectrum of sensor for temperature and pressure variations. The experiment results show that the sensor has not only two different linear temperature sensitivities but also two different linear pressure sensitivities, which can be used to distinguish air pressure and temperature simultaneously. The validity experiment shows the relative errors of 1.0% and 1.4% are obtained in simultaneous measurements of air pressure and temperature. The advantages of the presented sensor than other structure sensors are miniaturization, easier to manufacture and with lower fabrication cost, which is promising used in the harsh environment monitoring.

High-sensitive all-fiber fabry-perot interferometer gas refractive index sensor based on lateral offset splicing and Vernier effect

A high sensitivity all-fiber open-cavity Fabry-Perot interferometer gas refractive index (RI) sensor based on lateral offset splicing and Vernier effect is proposed and demonstrated. The sensor is fabricated by splicing a short section of single mode fiber (SMF) between the lead-in SMF and a section of SMF with a specific length, ensuring that the sensor consists of an open-cavity FPI and a silica-cavity FPI. The reflection beam from the last end face of the sensor is used to generate the Vernier effect, which significantly improves the sensitivity of the sensor. The sensor was successfully used to monitor changes of air RI as a function of pressure and provided a high sensitivity of -11368.5 nm/RIU with good linearity by tracing the shift of the reflection spectrum envelope caused by Vernier effect. This sensor has potential applications in fields such as gas composition detection, environmental monitoring, and biological sensing.

All-Fiber Fabry–Perot Interferometer for Liquid Refractive Index Measurement

We propose and design an all-fiber Fabry–Perot interferometer (FPI) for liquid refractive index (RI) measurements. The sensor comprises a short section of a single-mode fiber (SMF) fused between the end sections of two longer SMFs with a large intentional lateral offset. The open FPI cavity is obtained by adjusting the lateral offset. Experimental results show that the liquid to be measured can freely enter and leave the cavity without residual bubbles. The RI sensitivity of this sensor is 1,013.8 nm/RIU in the RI range from 1.3464 to 1.3777 with good linearity. Only cleaving and fusion splicing are used in its making; thus the fabrication of the sensor is relatively simple and cost effective. This sensor has potential applications in the chemical and biomedical domains.

Integrated Fiber-Optic Fabry-Pérot Interferometer Sensor for Simultaneous Measurement of Liquid Refractive Index and Temperature

In this paper, an integrated all-fiber Fabry–Perot interferometer (FPI) sensor is proposed and fabricated for the simultaneous measurement of liquid refractive index (RI) and temperature. The sensor structure consists of an open micro-hole and a tiny section of single-mode fiber. Since, the micro-hole that is machined by 193 nm excimer laser, the micro-fiber, and the integrated micro-hole-fiber, respectively, act as different FPI, consequently, the regular interference spectrum is produced and used in simultaneous measurement based on analyzing wavelength shifts of interference fringes with Fourier band-pass filtering method. Experiments indicate the low-frequency interference fringes resulting from micro-hole cavity is sensitive to liquid RI and temperature changes, and the response sensitivities are 1143.0 nm/RIU and −0.1805 nm/°C, respectively. However, the high-frequency interference fringes of micro-fiber cavity is only sensitive to temperature change, and the obtained temperature sensitivity of 0.0115 nm/°C is obviously superior to that of integrated micro-hole-fiber cavity. Utilizing the different response coefficients, we not only construct a measurement matrix to realize simultaneous liquid RI and temperature measurement successfully, but also achieve resolutions of 0.1 °C and $1.4\boldsymbol {\times } 10^{-5}$ RIU. The excellent merits such as all-fiber, miniature size, simple structure, and wavelength-sensing structure make the FPI sensor promise for high precision bio/chemical sensing applications.

Highly stable multi-wavelength erbium-doped fiber linear laser based on modal interference

We report a linear fiber laser cavity based on an all-fiber Fabry–Perot interferometer and bi-tapered optical fiber for multi-wavelength emission generation. Curvature and strain are used to operate the laser system and the number of lines as well, the emission regions are stronger related to the physical effect applied, due to the phase alteration between the multiple fiber optic modes involved. The original laser emissions present zero wavelength variations, minimal power fluctuations and small spacing mode (1 nm). Additionally, a nonlinear fiber was employed trying to improve the performance of the multiple lasing lines. This system offers a low implementation cost, compactness and good laser parameters.

Miniaturized fiber-taper-based Fabry-Perot interferometer for high-temperature sensing.

A microminiaturized all-fiber Fabry-Perot interferometer (FPI) for high-temperature sensing has been proposed and experimentally demonstrated. The FPI is composed of a micro-air bubble and a taper probe with a tip less than 2 μm in diameter as reflected interfaces. A temperature sensitivity of 14.68 pm/°C near the wavelength of 1550 nm is obtained. The sensor, with its miniature size, can work in an ultra-small space with a large range of temperature variation.

Determination of magnetic field using a Fabry–Perot cavity containing novel nanoparticles

ABSTRACTMn0.75Zn0.25Fe2O4 nanoparticles were used to characterize magnetic fields using an all-fiber Fabry–Perot interferometer. The 20-nm nanoparticles were fabricated with citrate and displayed a coercive field of approximately 10 mT. The nanoparticles were dispersed in oleic acid to prepare a magnetic fluid to fill a Fabry–Perot structure fabricated by arc splicing with conventional single-mode and hollow core photonic crystal fibers. This device provided sensitivity and resolution of 0.11 dB/mT and 0.09 mT, respectively. Thermal analysis indicated that the magnetic measurements are weakly depending on temperature (0.7 pm/°C and 7 × 10−3 dB/°C). This device offers low-cost fabrication, simple implementation and may be used in several industrial applications.

Micro-pulse upconversion Doppler lidar for wind and visibility detection in the atmospheric boundary layer.

For the first time, to the best of our knowledge, a compact, eye-safe, and versatile direct detection Doppler lidar is developed using an upconversion single-photon detection method at 1.5 μm. An all-fiber and polarization maintaining architecture is realized to guarantee the high optical coupling efficiency and the robust stability. Using integrated-optic components, the conservation of etendue of the optical receiver is achieved by manufacturing a fiber-coupled periodically poled lithium niobate waveguide and an all-fiber Fabry-Perot interferometer (FPI). The double-edge technique is implemented by using a convert single-channel FPI and a single upconversion detector, incorporating a time-division multiplexing method. The backscatter photons at 1548.1 nm are converted into 863 nm via mixing with a pump laser at 1950 nm. The relative error of the system is less than 0.1% over nine weeks. In experiments, atmospheric wind and visibility over 48 h are detected in the boundary layer. The lidar shows good agreement with the ultrasonic wind sensor, with a standard deviation of 1.04 m/s in speed and 12.3° in direction.

Miniaturized fiber Fabry-Pérot interferometer for strain sensing

A temperature-insensitive miniaturized all-fiber Fabry–Perot interferometer strain sensor was proposed and experimentally studied. This sensor with an air cavity was made by splicing a short section of hollow-core fiber with two standard single mode fibers. The experimental results showed that these sensors have an fringe contrast exceeding 22 and 13 dB for the air cavity with a length of 167.08 and 557.11 μm, and its reflection spectrum shifts linearly to long wavelength by increasing the strain from 0 to 3000 μe with a strain sensitivity of 1.8 and 1.7 pm/μe, respectively. This strain sensor also showed good repeatability and long time stability, while its temperature sensitivity was only about 0.95 pm/°C in the range of 0°C–180°C for the 557.11 μm air cavity, so there is less strain–temperature cross-sensitivity. Moreover, this sensor was easy to be fabricated and there was no requirement for chemical etching, careful cleaving, and special fusion. It may be potentially used for strain sensing applications with high resolution and miniaturized size. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1510–1514, 2016

Modified All-Fiber Fabry–Perot Interferometer and Its Refractive Index, Load, and Temperature Analyses

An all-fiber Fabry–Perot (FP) interferometer is proposed and validated by the arc splicing technique. By using conventional fiber and special hollow-core photonic crystal fiber, several FP cavities were formed at the conventional fiber tip using arc discharges. As a result of the interaction between these cavities, modified FP principle operation was obtained; and temperature, refractive index, and load analyses validated this operation modification. In addition, this all-fiber interferometer presents good resolution and sensitivity in each parameter examined. The structure offers compactness, robustness, high repeatability, and stability measurement.

基于空芯光子晶体光纤的全光纤法布里珀罗干涉式加速度传感器

基于空芯光子晶体光纤的全光纤法布里珀罗干涉式加速度传感器

Long dual‐cavity fiber optic Fabry‐Perot strain sensor with rugate mirrors

An all-fiber Fabry-Perot interferometer using coherence demultiplexing and rugate mirror reflectors grown with electron cyclotron resonance, plasma-enhanced chemical vapor deposition (ECR–PECVD) on the fiber ends is proposed. The interferometer consists of a laser diode source, two optical fiber cavities, three rugate mirrors, an optical phase modulator, and a quadrature phase detection system. Coherence demultiplexing allowed the use of fiber cavities of several meters in length with a partially coherent illuminating light source. Truly inhomogeneous refractive index mirrors were designed, taking into account dispersion and losses of SiOxNy at the required wavelength of 1.3 µm. The reflectance/transmittance ratios during growth were adjustable from 0.05/0.95 to 0.95/0.05 and mirrors used in the experimental interferometer had nominal reflectances of 40, 68, and 40%, respectively. Design and fabrication procedures permitted implementation of window functions and matching layers for flexible control over transmittance and reflectance characteristics. The long-cavity Fabry-Perot sensor was demonstrated for use as a strain gauge. Good agreement was shown with the results obtained by a conventional strain gauge.