Coded optical probe pulses in return-to-zero/non-return-to-zero (RZ/NRZ) formats are used for long-range distance sensing based on a differential pulse-width pair Brillouin time-domain analysis (DPP-BOTDA) order to enhance the spatial resolution and measurement accuracy. It is found that using RZ format maintains spectral shape, enhances range leads higher signal-to-noise ratio compared single-pulse analysis. With 512 bit RZ-coded pulse pairs of 60/55 ns DPP-BOTDA, approximately 0.5 m strain...

A diaphragm-free fiber-optic Fabry-Perot (FP) interferometric gas pressure sensor is designed and experimentally verified in this paper. The FP cavity was fabricated by inserting a well-cut fiber Bragg grating (FBG) hollow silica tube (HST) from both sides into casing. length between the ends of SMF HST changes with density. Using temperature decoupling method to improve accuracy high environments. An experimental system for measuring under different temperatures established verify...

The linewidth, the threshold, and frequency shift of stimulated Rayleigh scattering (STRS) in single mode fiber (SMF-28e), large effective area (LEAF) polarization maintaining (PMF) have been studied using heterodyne detection to separate Brillouin with a laser for first time best our knowledge. Experimental results show that linewidth STRS spontaneous are ~9 kHz, ~10 ~11 ~25 ~30 ~27 kHz SMF-28e, LEAF PMF, respectively. threshold power 2 km 7 LEAF, 100 m PMF 11 dBm, 4.5 dBm 16.5 measured...

We realize a scanning-free Brillouin optical time domain analyzer (BOTDA) based on an ultra-fine digital frequency comb (DOFC) with 1.95MHz spacing and 2GHz bandwidth. The DOFC can be used to reconstruct the gain spectrum (BGS) locate shift (BFS) without scanning thus improve measurement speed about 100 times compared conventional BOTDA. This BOTDA scheme has also been demonstrated experimentally 51.2m spatial resolution over 10km standard single mode fiber (SSMF) of 1.5°C for temperature...

In this study, a novel batch-producible fiber-optic Fabry-Perot (FP) pressure sensor based on low-temperature co-fired ceramic technology is proposed and experimentally demonstrated for high-temperature applications. The fabricated by inserting well-cut single-mode fiber (SMF) into zirconia ferrule, followed insertion of the overall structure an alumina head. FP cavity in formed placing end face SMF parallel to diaphragm. external can be detected demodulating length sensor. A theoretical...

Using arc discharge technology, we fabricated a fiber-optic Fabry-Perot (FP) pressure sensor with very low temperature coefficient based on microbubble that can be applied in high-temperature environment. The thin-walled by heating the gas-pressurized hollow silica tube (HST) using commercial fusion splicer. Then, well-cut single-mode fiber (SMF) was inserted into microbubble, and they were fused together. Thus, FP cavity formed between end of SMF inner surface microbubble. diameter up to...

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

A fiber-optic Fabry-Perot pressure sensor based on a micro-electro-mechanical system (MEMS) and CO2 laser fusion technology is developed experimentally demonstrated for high-temperature application. The sensing heads are batch-fabricated by anodically bonding the micromachined Pyrex glass wafer local gold-plated silicon wafer. separated head single-mode fiber fused together to form cavity using laser. In order improve measurement accuracy in environment, Bragg grating used as temperature...

The optical generation of pulsed ultrasound is attractive to nondestructive testing and biological imaging, especially for those involving narrow operation space or strong electro-magnetic interference. However, conventional techniques based on the photoacoustic effect inevitably required an expensive high-energy short laser dedicated preparation optically absorptive composite film. Here, a fiber-optic pulse transmitter continuous-wave (CW) triggered thermo-cavitation was demonstrated....

Brillouin scattering based optical fiber sensors (BOFS) have the unique advantages over other such as long distance, fully distributed, and multi-parameter sensing. The progresses on development of BOFS technology in Nanjing University are reviewed. key technologies to make with ultra-long high spatial resolution, fast measuring speed discussed realized.

We propose and experimentally demonstrate a compact fiber-optic vibration sensor in which tilted Bragg grating is inscribed the core of depressed cladding fiber. The provides resolution up to 2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> m/s xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> linear acceleration response between 0.2 6.0 , together with flat frequency 1 120 Hz. takes advantage cost-effective interrogation scheme by...

Chirped fiber Bragg gratings can straightforwardly and efficiently be fabricated onto microfibers with a uniform phase mask. Due to the variation of propagating constant, which depends on diameter, broadband spectrum grating formed. Depending different responses ambient refractive index in parts grating, bandwidth tuned by changing surrounding solution. In addition, being partly immersed liquid, diameter-chirped act as Fabry-Perot interferometer, whose means controlling liquid level index.

A refractive index sensor by Brillouin scattering in a micro fiber with diameter of 2 μm is experimentally demonstrated. peaks introduced interaction between the fundamental optical mode and axially symmetric radial acoustic modes are identified. We find axial frequency linearly proportional to sodium chloride solution around 1.33. sensitivity approximately 1.6 GHz/RIU achieved. It proposes that candidate for measurement.

In this Letter, a 1-μm-wavelength fiber laser is proposed through the use of ytterbium-doped active and third harmonic Bragg reflectors. Benefiting from ratio below 0.5 between core diameter Talbot length UV fringes, enabling formation secondary-type-In grating, reflector with reflectivity higher than 95% at two-thirds designing wavelength can be fabricated within 2 min. Inherited by lower temperature strain sensitivity has good stability could used as reliable resource. addition, Letter...

A dual-frequency laser Doppler velocimeter implemented by a dual-polarization fiber grating is proposed, with the two frequencies produced orthogonally polarized outputs of laser. The reflected from moving target experience frequency shift, which shown to be linearly related velocity and beat note difference between light. With digital demodulation scheme, high sensitivity 0.64 MHz/(m/s) resolution less than 0.5% for measurement are demonstrated, shows that proposed capable wide range velocity.

A gas pressure sensor based on Brillouin scattering in a microscaled fiber is experimentally demonstrated. The with diameter of 1.9 μm drawn from commercial single-mode fiber. spectrum multipeak structure observed due to the coupling between longitudinal and shear acoustic wave caused by strong index contrast glass air. proposed fact that peak frequency at ~8.5 GHz ~9 shifts when environment air changes. It exhibits sensitivity approximately 0.066 MHz/kPa. This device provides candidate for...

Short-time Fourier transform (STFT) algorithm with Lorentzian fitting is popular in distributed Brillouin optical fiber sensors to acquire frequency. However, STFT often suffers from the tradeoff between frequency measurement resolution and computation complexity. To lower complexity of analysis speedup measurement, a novel method based on instantaneous (IF) proposed. The can be obtained through phase change two adjacent samples time domain. requirement spectral is, therefore, greatly...

As an optical fiber sensing technology based on detecting spontaneous Brillouin scattering, Optical Time Domain Reflectometry (BOTDR) is attracting significant attention due to its immense potential applications in temperature or strain monitoring. To enhance the signal noise ratio (SNR) of BOTDR system, a new Hadamard sequence probe pulse proposed. In pulses are constructed from matrix. The experiment results show that SNR proposed system can be greatly enhanced, and it verified range...

We identify the Brillouin scattering spectrum in both core and cladding of an all-solid photonic bandgap fiber for first time to our knowledge. A multipeak with several frequency shifts particular linewidths is investigated related structural properties accordingly. Because different dependences on surroundings cladding, proposed structure exhibits potential use as simultaneous temperature strain sensors.

Long distance sensing based on Brillouin scattering with centimeter spatial resolution, and yet high strain or temperature resolution requires the optimization of optical electronic system. In domain limiting factors include gain saturation Stokes signal pump depletion induced spectrum distortion, thus a low is desired that power, which sets limit in to noise ratio (SNR). The detection system must have narrow bandwidth reduce noise. coded pulse offers best solution as power long BOTDA...