Xiangdong Yu

Reflective long-period fiber grating-based sensor with Sagnac fiber loop mirror for simultaneous measurement of refractive index and temperature

In this paper, we propose a reflective long-period grating-based sensor with a Sagnac fiber loop mirror (SFLM) for simultaneous measurement of refractive index (RI) and temperature. By cascading the SFLM to the end of a long-period fiber grating (LPFG), the LPFG works as a reflection operation, which is convenient in some applications. Further, the SFLM and the LPFG have different sensitivities to RI and temperature. As a result, RI and temperature measurement can be simultaneously achieved by monitoring the wavelength shifts of the LPFG and the SFLMs dips in the reflection spectrum. Experimental results show that the temperature sensitivity can reach 1.533 nm/°C, and the RI sensitivity is from 16.864 nm/RIU (refractive index unit) to 113.142 nm/RIU when the RI range is from 1.333 to 1.430. The application for 40 km long-distance RI and temperature measurement shows that the sensor has potential application in long-distance sensing.

Optimum design of 6-km LD-distributed optical fiber Raman photon sensor (DOFRPS) system

In the 6km DOFRPS system, the 1550nm LD is excited photon source. The spontaneous Raman scattering photon are carriers of temperature signal and the Rayleigh scattering photon are carriers of strain and pressure signal. On the 6km optical fiber, the 3000 point temperature, strain and pressure are measured on time and the position of measured local domain have been determined by OTDR technique. The optimum design of 6km LD DOFRPS system and the configuration of the system are discussed in the paper.

Optimum design of 30-km long-distance distributed optical fiber Raman temperature sensor system

A 30km long distance distributed optical fiber Raman temperature sensor (DOFRTS) system has been made, it use new measuring temperature principle of optical fiber amplified anti-Stokes Raman spontaneous scattering. In the system, 1550nm erbium-doped optical fiber laser, a highness speed data acquisition card and signal processing technique are used. By using these technique, the problem of weak signal detection is resolved and signal to noise ratio is increased. All components of system are put into an intellectualized constant temperature box and work in constant temperature condition. Stability and environment adaptability are improved. By appraisal, performance of the system is listed as follows: length of single mode fiber: 31km, temperature rang:0-100°C (can be expanded), temperature measuring uncertainty:±2°C, temperature resolution:0.1°C, measurement time:432s, spatial resolution :3m.

Distributed optical fiber sensors system and networks

The distributed Rayleigh back scattering fiber optical sensors are investigated. The principle of time-domain distributed fiber sensors are discussed.

Optimum designs of 30-km distributed optical fiber Raman photon temperature sensors and measurement network

The distributed optical fiber Raman Photons Temperature Sensors (DFRS) is a real time, on line and multi-point (30k points) measuring system for multi-parameter measurement of temperature etc. According to temperature effect of optical fiber Raman backscattering, the intensity of anti-stokes Raman backscattering of optical fiber is modulated by the spatial temperature field where the optical fiber is laid. Then after signal processing and demodulation, the information of temperature can be extracted from the noise and can be displayed in real time. It is a typical optical fiber sensors measuring network. In time domain, using the velocity of light wave in optical fiber, the time interval of back-direction light wave and optical fiber OTDR technology, the DFRS can locate the temperature spots. In this case, it is a typical optical fiber laser temperature radar system as well. The backscattering spectrum of optical fiber has been measured by fiber laser and optical spectrum analyzer. Raman backscattering spectrum and ZX band backscattering spectrum has been first observed. The amplification of anti-stokes Raman spontaneous scattering (ARS) and the temperature effect have been first observed and applied to DFRS. The performance of DOFS is following: fiber length : 25.2km;temperature measuring range: 0-1000C(can be expand) temperature uncertainty: ±200C : temperature resolution: 0. 1; spatial resolution: 5m: measurement time: 10mm; Main unit operation temperature range: 0—400C . The optical fiber sensor probes and the software for signal processing are also discussed.

10-km distributed optical fiber sensor system and application

This paper briefly introduces the operation principle and configuration of distributed optical fiber sensor (DOFS) system. A new demodulation method that uses Rayleigh back scattering photon flux to demodulate Raman back scattering photon flux is put forward, and the advantages of this new method are discussed. Methods to measure temperature, strain and pressure at the same time are researched. The performance of DOFS is following: fiber length: 10.2 km; temperature uncertainty: +/- 2 degree(s)C: temperature resolution: 0.1 degree(s)C; spatial resolution: 4m: measurement time: 5 min; Main unit operation temperature range: 0 - 40 degree(s)C. The DOFS system have been applied to coal mine.

Distributed optical fiber temperature sensor (DOFTS) system applied to automatic temperature alarm of coal mine and tunnel

The DOFTS system that has applied to temperature automatically alarm system of coal mine and tunnel has been researched. It is a real-time, on line and multi-point measurement system. The wavelength of LD is 1550 nm, on the 6 km optical fiber, 3000 points temperature signal is sampled and the spatial position is certain. Temperature measured region: -50 degree(s)C--100 degree(s)C; measured uncertain value: +/- 3 degree(s)C; temperature resolution: 0.1 degree(s)C; spatial resolution: <5 cm (optical fiber sensor probe); <8 m (spread optical fiber); measured time: <70 s. In the paper, the operated principles, underground test, test content and practical test results have been discussed.

Recent progress in distributed optical fiber raman sensors

A brief review of recent progress in researches, productions and applications of distributed fiber Raman sensors at China Jiliang University (CJLU) is presented. In order to improve the measurement distance, the accuracy, the space resolution, the ability of multi-parameter measurements, and the intelligence of distributed fiber sensor systems, a new generation fiber sensor technology based on the optical fiber nonlinear scattering fusion principle is proposed. A series of new generation distributed fiber sensors are investigated and designed, which consist of new generation ultra-long distributed fiber Raman and Rayleigh scattering sensors integrated with a fiber Raman amplifier (FRA), auto-correction full distributed fiber Raman temperature sensors based on Raman correlation dual sources, distributed fiber Raman temperature sensors based on a pulse coding source, distributed fiber Raman temperature sensors using a fiber Raman wavelength shifter, a new type of Brillouin optical time domain analyzers (BOTDA) integrated with a fiber Raman amplifier, distributed fiber Raman and Brillouin sensors integrated with a fiber Raman amplifier, and distributed fiber Brillouin sensors integrated with a fiber Brillouin frequency shifter. Sensor networks are important components of the internet of things. The distributed optical fiber sensor network (Rayleigh, Raman, and Brillouin scattering) is a 3S (smart materials, smart structure, and smart skill) system, which is easy to construct smart fiber sensor networks. The distributed optical fiber sensor has been applied to the power grids, railways, bridges, tunnels, roads, constructions, water supply systems, dams, oil and gas pipelines and other facilities, and can be integrated with wireless networks.

Distributed fiber optic Raman high-temperature (1000oC) measurement networks

The temperature effect of fiber optics Raman back-scattering have been researched at high temperature (1000 degree(s)C) condition. A distributed fiber optics Raman and Rayleigh back-scattering sensor measuring network have been design and fabricated. The performance of high temperature measuring network is following: temperature measuring range: 0-1000 degree(s)C; temperature uncertainty: <+/- 30 degree(s)C; temperature resolution: 1 degree(s)C; Spatial resolution: 8<m Measuring time: 40s; Fiber length: 100m-10km (according to user need). The stress change of optical cable can be toke out by the measuring network.

Measurement of performance characters of a 10-km LD distributed optical fiber temperature sensor (LDOFTS) system

The operation principle, technique character and measuring method of 10 km LDOFTS are discussed. The testing result of 10 km LDOFTS is given in this paper.