An all optical fiber gas sensor of NH3 and CO based on based on the spectral absorption and harmonic detection

An all optical fiber gas sensor is presented to detect the concentration of NH3 and CO. Based on the spectral absorption, The wideband light source is used to reflect two narrowband spectra by fiber grating of different duty. and piezoelectric ceramics to obtain narrowband output light. The high sensitivity detection can be measured from the second harmonic signal. The two narrowband spectra are corresponding to the absorption spectra of NH3 and CO. Concentration detection are realized by the detection of variety of light intensity. Sensitivity is proved and cost is reduced.

High-resolution tumor marker detection based on microwave photonics demodulated dual wavelength fiber laser sensor

The specific detection of tumor markers is crucial in early tumor screening and subsequent treatment processes.To ac-curately distinguish the signal response caused by trace markers,the high demodulation resolution of the sensor is nec-essary.In this paper,we propose a dual-wavelength fiber laser sensing system enhanced with microwave photonics de-modulation technology to achieve high-resolution tumor marker detection.This sensing system can simultaneously per-form spectral wavelength-domain and frequency-domain analyses.Experimental results demonstrate that this system's refractive index(RI)sensitivity reaches 1083 nm/RIU by wavelength analysis and-1902 GHz/RIU by frequency analysis,with ideal detection resolutions of 1.85×10^(-5)RIU and 5.26×10^(-8)RIU,respectively.Compared with traditional wavelength domain analysis,the demodulation resolution is improved by three orders of magnitude,based on the same sensing structure.To validate its biosensing performance,carcinoembryonic antigen-related cell adhesion molecule 5(CEACAM5)is selected as the detection target.Experimental results show that the improved sensing system has a limit of detection(LOD)of 0.076 ng/mL and a detection resolution of 0.008 ng/mL.Experimental results obtained from human serum samples are consistent with clinical data,highlighting the strong clinical application potential of the proposed sens-ing system and analysis method.

NOVEL SPECTRUM ABSORPTION OPTICAL FIBER METHANE SENSOR

Based on spectrum principle and analyzing the infrared absorption spectrum ofmethane, a kind of optical fiber methane gas sensor and its system are developed. DFBLD(Distributedfeedback laser diode) in 1 300 nm waveband is used as illuminant and phase-detecting technology isused to carry out harmonic wave detecting the concentration of methane. The sensitivity can arriveat 10^(-5). Experiments results show that the performance targets of the sensor such as sensitivitycan basically satisfy the requests of methane detection.

Distributed optical fiber acoustic sensor for in situ monitoring of marine natural gas hydrates production for the first time in the Shenhu Area,China

The distributed acoustic sensor(DAS)uses a single optical cable as the sensing unit,which can capture the acoustic and vibration signals along the optical cable in real-time.So it is suitable for monitoring downhole production activities in the process of oil and gas development.The authors applied the DAS system in a gas production well in the South China Sea for in situ monitoring of the whole wellbore for the first time and obtained the distributed acoustic signals along the whole wellbore.These signals can clearly distinguish the vertical section,curve section,and horizontal production section.The collected acoustic signal with the frequency of approximately 50 Hz caused by the electric submersible pump exhibit a signal-to-noise ratio higher than 27 dB.By analyzing the acoustic signals in the production section,it can be located the layers with high gas production rates.Once an accurate physical model is built in the future,the gas production profile will be obtained.In addition,the DAS system can track the trajectory of downhole tools in the wellbore to guide the operation.Through the velocity analysis of the typical signals,the type of fluids in the wellbore can be distinguished.The successful application of the system provides a promising whole wellbore acoustic monitoring tool for the production of marine gas hydrate,with a good application prospect.

Evaluation of fiber optic methane sensor using a smoke chamber

This report presents the results of experiments to evaluate a prototype fiber optic methane monitor exposed to smoke using a smoke chamber to simulate atmospheric conditions in an underground coal mine after a fire or explosion. The experiments were conducted using test fires of different combustible sources commonly found in mines —douglas-fir wood, SBR belt, and Pittsburgh seam coal. The experiments were designed to assess the response of the fiber optic methane sensor to different contaminants,different contaminant levels and different contaminant durations produced from the test fires. Since the prototype methane monitor detects methane by measuring absorption at a specific wavelength, optical power at the absorption wavelength(1650 nm) was measured as a function of smoke concentration and duration. The other sensor response parameter-methane response times-were measured between smoke tests to assess the impact of soot accumulation on the sensor. Results indicate that the sensor screen effectively prevented smoke from obscuring the optical beam within the sensor head, with minimal impact on the system optical power budget. Methane response times increased with smoke exposure duration, attributed to soot loading on the protective screen.

PLASMA RESONANCE FIBER OPTIC SENSOR FOR CURE MONITORING OF EPOXY COMPOSITE

The plasma resonance fiber optic sensor has a research values in theory and is widely used in engineering because of its simple structure and high sensitivity. It is a simple and sensitive method to measure the refractive index with optical fiber plasma wave. We make use of this characteristic to manufacture the plasma resonance fiber optic sensor which can detect the cure of epoxy compo site. We study the method of testing the solutions which have different refractive index with plasma resonance fiber optic sensor. A fiber optic sensing probe which has reliable performance and convenient operation for detecting the refractive index has been designed. The system for detecting the solution refractive index is developed and used to measure the refractive index of epoxy during the different phases in the cure process. Result shows that this system is credible and stable, the parameters tested are in accord with the facts.

Remote structural health monitoring with serially multiplexed fiber optic acoustic emission sensors

Development and testing of a serially multiplexed fiber optic sensor system is described.The sensor differs from conventional fiber optic acoustic systems,as it is capable of sensing AE emissions at several points along the length of a single fiber.Multiplexing provides for single channel detection of cracks and their locations in large structural systems. An algorithm was developed for signal recognition and tagging of the AE waveforms for detection of' crack locations,Labora- tory experiments on plain concrete beams and post-tensioned FRP tendons were pcrlormed to evaluate the crack detection capability of the sensor system.The acoustic emission sensor was able to detect initiation,growth and location of the cracks in concrete as well as in the FRP tendons.The AE system is potentially suitable lot applications involving health monitoring of structures following an earthquake.

DISTRIBUTED OPTICAL FIBER SENSOR FOR LONG-DISTANCE OIL PIPELINE HEALTH

A fully distributed optical fiber sensor （DOFS） for monitoring long-distance oil pipeline health is proposed based on optical time domain reflectometry （OTDR）. A smart and sensitive optical fiber cable is installed along the pipeline acting as a sensor, The experiments show that the cable swells when exposed to oil and induced additional bending losses inside the fiber, and the optical attenuation of the fiber coated by a thin skin with periodical hardness is sensitive to deformation and vibration caused by oil leakage, tampering, or mechanical impact. The region where the additional attenuation occurred is detected and located by DOFS based on OTDR, the types of pipeline accidents are identified according to the characteristics of transmitted optical power received by an optical power meter, Another prototype of DOFS based on a forward traveling frequency-modulated continuous-wave （FMCW） is also proposed to monitor pipeline. The advantages and disadvantages of DOFSs based on OTDR and FMCW are discussed. The experiments show that DOFSs are capable of detecting and locating distant oil pipeline leakages and damages in real time with an estimated precision of ten meters over tens of kilometers.

Optically Powered Pressure Sensor with Optical Fiber Link

An optically powered sensor for measuring pressure which is linked by optical fiber is developed in new scheme. Its pulse position modulation (PPM) optical signal and optical supply power for electronics in probe are transmitted via a single optical fiber. The optical power is carried by a 1 300 nm laser diode (LD) and the sensing data are carried by a 850 nm LED. The remote probe uses all CMOS chips and particular modulations (PPM and PWM). Its electrical consumption including signal manipulation and LED driven current from optically converted is less than 100 μW. The laser diode supplies 5 mW optical power into the fiber. A photodetector converts sufficiently this power into electrical power to drive the whole probe operation. The optically powered distance gets up to 500 m. The novel sensor combines optical fiber and electronics technology into a system. Because of using the principle of ratio measurement between measured and reference signals, as well as light feedback,the system is available with high reliable, outstanding accuracy and repeatability.

Intra-Cavity Absorption Sensors for Gas Detection Using Wavelength Sweep Technique

Wavelength sweep technique （WST） is introduced into intra-cavity fiber laser （ICFL） for low concentration gas detection. The limitation induced by noise can be eliminated using this method, and the performance of the system is improved. The sensitivity of the system is reduced to less than 300 ppm. With WST, sweeping characteristic of the ICFL can be described according to known gas absorption spectra.

Intra-Cavity Absorption Gas Sensors Using Wavelength Modulation and Wavelength Sweep

Wavelength modulation technique （WMT） and wavelength sweep technique （WST） are introduced into intra-cavity absorption gas sensors （ICAGS） for low concentration gas detection. The optimized parameters of the system maximizing the signal-to-noise ratio （SNR） are found. Calibration of acetylene concentration and gas recognition are both realized.

Development and Application of Methane Leakage Monitoring System for Gas Transmission Pipeline

Oil and gas pipeline transportation,as a relatively safe way of oil and gas transportation,undertakes most of the transportation tasks of crude oil and natural gas.Oil and gas pipeline accidents affect a wide range of consequences.Therefore,the oil and gas pipeline leakage detection is paid more and more attention.In this paper,ultra-low power methane gas sensor is selected to collect methane gas concentration in the air,and wireless network technology is used to build a wireless network sensor system with 4G function.Through the sensor distribution along the pipeline,it can intuitively and accurately judge whether there is a micro-leakage in the pipeline,and understand the diffusion situation after the leakage.The sensor system has high reliability and stability,and has high value of popularization and application.

An optical fiber methane gas sensing film sensor based on core diameter mismatch

An optical fiber evanescent wave methane gas sensor based on core diameter mismatch is reported.The sensor consists of a multimode fiber in which a short section of standard single-mode fiber,coated with the inclusion of cryptophane molecules E in a transparent polysiloxane film,is inserted.The sensing principle is analyzed by optical waveguide theory.For different sensing film thicknesses and interaction lengths,the sensor signal is investigated within the methane concentration range of 0-14.5%（v/v）.It is shown that the sensor signal with the thickness of 5μm and the interaction length of 3 mm strengthens linearly with the increasing concentration of methane,with a slope of 0.0186.The best detection limit of the sensor for methane is 2.2%（v/v） with a response time of 90 s.This sensor is suitable for the detection of methane concentration below the critical value of 5%.

Realization of Rapid Debugging for Detection Circuit of Optical Fiber Gas Sensor： Using an Analog Signal Source

An optical fiber gas sensor mainly consists of two parts： optical part and detection circuit. In the debugging for the detection circuit, the optical part usually serves as a signal source. However, in the debugging condition, the optical part can be easily influenced by many factors, such as the fluctuation of ambient temperature or driving current resulting in instability of the wavelength and intensity for the laser; for dual-beam sensor, the different bends and stresses of^the optical fiber will lead to the fluctuation of the intensity and phase; the intensity noise from the collimator, coupler, and other optical devices in the system will also result in the impurity of the optical part based signal source. In order to dramatically improve the debugging efficiency of the detection circuit and shorten the period of research and development, this paper describes an analog signal source, consisting of a single chip microcomputer （SCM）, an amplifier circuit, and a voltage-to-current conversion circuit. It can be used to realize the rapid debugging detection circuit of the optical fiber gas sensor instead of optical part based signal source. This analog signal source performs well with many other advantages, such as the simple operation, small size, and light weight.

OVMD-MF算法用于漏电流光纤传感

针对船舶电力网络漏电流光纤传感测量响应度低、测量能力弱等问题,提出了一种基于最优变分模态分解与形态学滤波组合的降噪方法,以提升微弱电流测量能力。以希尔伯特谱熵为适应度函数,利用捕食者优化算法搜寻分解模式数及二次惩罚因子的最优组合,并完成变分模态分解获取本征模态函数分量。设置相关系数阈值确定有效模态函数分量,完成信号重构。以信噪比为适应度函数,通过捕食者优化算法确定形态学滤波的结构因子及比例系数,对重构后的信号进行时域降噪处理,实现对漏电流信号进一步降噪。通过仿真分析以及实验验证,确定该方法相对于现有的滤波方法,改善了信号的信噪比,降低了最小均方误差,泄漏电流的分辨力可提升至3mA。

Optical fiber sensors for heavy metal ion sensing

The ecological environment suffers from multiple pollution from many aspects,and the heavy metal ions(HMI)pose a significant threat to human health.Detecting these ions is challenging due to their trace amounts and diverse types.Optical fiber sensors offer numerous advantages over conventional techniques in HMI sensing,including small size,quick response,resistance to electromagnetic interference,and long-range monitoring capabilities.In this paper,several optical methods for HMI detection have been described,namely fluorescence,fiber grating,fiber modal interference,surface plasmon resonance,and optical absorbance.The principles,structures,and sensitive materials of these methods are discussed in detail.The advantages and disadvantages of each approach are illustrated to facilitate a better comparison.Furthermore,the current status and future directions for the development of HMI optical fiber sensors are also discussed,which could enlighten the future HMI sensor design.

On-Line Defect Detection of Aluminum Coating Using Fiber Optic Sensor

Aluminum metallization using the sprayed coating for exhaust mild steel （MS） pipes of tractors is a standard practice for avoiding rusting. Patches of thin metal coats are prone to rusting and are thus considered as defects in the surface coating. This paper reports a novel configuration of the fiber optic sensor for on-line checking the aluminum metaUization uniformity and hence for defect detection. An optimally chosen high bright 440 nm BLUE LED （light-emitting diode） launches light into a transmitting fiber inclined at the angle of 60° to the surface under inspection placed adequately. The reflected light is transported by a receiving fiber to a blue enhanced photo detector. The metallization thickness on the coated surface results in visually observable variation in the gray shades. The coated pipe is spirally inspected by a combination of linear and rotary motions. The sensor output is the signal conditioned and monitored with RISHUBH DAS. Experimental results show the good repeatability in the defect detection and coating non-uniformity measurement.

Optical fiber methane sensor based on SAN film containing cryptophane-E-(OEt)_6

A novel long-period fiber grating （LPFG） film methane sensor is designed and applied successfully. The sensor is constructed by depositing a thin styrene-acrylonitrile （SAN） film containing the new compound cryptophane-E-（OEt）6 onto the cladding surface of the LPFG. This film is sensitive to methane gas. Methane causes a change in the refractive index of the sensing film, which can be measured by shifting the resonance wavelength. Experimental results show that the resonant wavelength shifts to the longer wavelength, with increasing methane concentration at a range of 0.0%–3.5% （v/v）. A linear relationship is obtained within the test range. Detection limit is estimated at 0.2%, and response time is 60 s. No significant interference is detected from dry air, O2 , CO, CO2 , and H2 . This novel methane sensing material has great application potential due to its advantages.

微分散液滴的光纤检测研究

微分散是微化工技术的重要组成部分,传统利用显微摄像分析和统计微分散液滴的方法成本高,不易推广。提出了一种基于光纤传感的微分散液滴在线检测技术,该方法基于漫反射光纤、光纤传感器、数据采集卡和LabVIEW程序实现了微通道内液滴生成频率和长度的在线检测,满足0.21 mm以上直径液滴的检测,检测频率上限为500 Hz,当液滴通过光纤时间超过15 ms时,还可检测液滴长度。研究结果表明光纤直径和光纤传感器响应时间是影响该方法检测性能的主要因素,与相似平台对比,以较低的成本实现了较高检测性能。

一种新型二氧化硅多孔材料固定化酶光纤葡萄糖传感器的研究

目的 研制一种新型的基于氧敏感指示剂Ru(bpy)3Cl2和固定化葡萄糖氧化酶(GOD)的复合敏感膜光纤传感器,用于实时检测葡萄糖溶液质量浓度。方法 以多孔SiO_(2)纳米粒子为载体固定GOD,并采用溶胶-凝胶法同时加入Ru(bpy)_(3)Cl_(2)制备葡萄糖敏感膜,通过提拉法在光纤端面沉积敏感膜制成光纤传感探头,搭建光纤传感器用于实时检测葡萄糖溶液质量浓度。结果 光纤传感器检测葡萄糖溶液质量浓度为50~900mg/dL(2.78~50.00mmol/L),在用于实时监测葡萄糖溶液质量浓度变化时响应时间短,测试标准曲线线性良好。结论 SiO_(2)多孔材料固定化酶光纤葡萄糖传感器具有灵敏度高、响应速度快、检测范围大等优点,未来可以检测人体血液中的葡萄糖质量浓度。