Zhengyu Huang

Intrinsic Fabry-Pe/spl acute/rot fiber sensor for temperature and strain measurements

This letter presents an intrinsic Fabry-Pe/spl acute/rot interferometric sensor fabricated by splicing a section of multimode fiber in between two single-mode fibers. The fabrication process only involves fusion splicing and cleaving. The sensor is analyzed and the issues in sensor fabrication are discussed. The sensor temperature and strain measurement performance is evaluated. The sensor may find its application in quasi-distributed sensing due to its low insertion loss.

Sapphire-fiber-based white-light interferometric sensor for high-temperature measurements.

We present a fiber-optic temperature sensor with a single-crystal sapphire fiber as the light guide and a sapphire wafer as the sensing element. Temperature is determined by measurement of the thermal dependence of the wafers optical thickness by use of white-light interferometry. We applied digital signal processing techniques to analyze the sensors spectrum. A prototype sensor was tested to 1600 degrees C and demonstrated excellent reproducibility. An accuracy of +/- 0.2% full scale was obtained. The sensor is simple, small, and flexible, with potential advantages of batch fabrication and easy calibration.

Fiber optic pressure and temperature sensors for oil down hole application

Detailed studies on fiber optic pressure and temperature sensors for oil down-hole applications are described in this paper. The sensor head is an interferometric based fiber optic senor in which the air-gap will change with the pressure or temperature. For high-speed applications, a novel self-calibrating interferometric/intensity-based (SCIIB) scheme, which realizes compensations for both the light source drift and the fiber loss variation, was used to demodulate the pressure (or temperature) signals. An improved white light system was developed for sensor fabrication. This system is also used as the signal demodulation system providing very high resolution. Experiment results show that the SCIIB system achieves 0.1% accuracy with a 0-8000psi working range for the pressure sensor and a 0-600 degree(s)C working range for the temperature sensor. The resolution of the white light system is about +/- 0.5 nm with a dynamic range up to 10 micrometers. The long -term testing results in the oil site are also presented in this paper.

Fiber temperature sensor for high-pressure environment

We describe a fiber optic extrinsic Fabry-Perot interferometer EFPI based temperature sensor that incorporates a pressure isolation fixture. The sensor has high temperature sensitivity and low pressure- induced crosstalk. The detailed analysis and discussion of the sensor design, the signal demodulation algorithm, and the sensor fabrication as well as the sensor performance are presented.

Double‐Tubing Encapsulated Fiber Optic Temperature Sensor

Increasing the efficiency of oil production operations requires improved sensors to supply critical information such as mixed‐phase fluid flow, pressure and temperature measurements within the down‐hole oil environment. In order to provide robust and reliable fiber optic temperature sensors capable of operating in the harsh down‐hole oil environment, where temperatures might exceed 250 °C and pressures might reach 20,000 psi (140 Mpa), a novel type of fiber optic temperature sensor has been developed. This temperature sensor functions as an EFPI (extrinsic Fabry‐Perot interferometric) sensor. One unique contribution of this work is that the glass tubing used is a borosilicate glass with a relatively high coefficient of thermal expansion (CTE) and long gauge length, allowing a much higher sensitivity to be achieved, without hysteresis. The sensor structure utilizes a dual tubing design (tubing within a tubing) to allow pressure isolation. An LED light beam is used as the signal interrogation source to remo...

Sapphire temperature sensor coal gasifier field test

This paper describes the effort in developing a sapphire temperature prototype sensor for coal gasifier applications. The sensor is tested in laboratory to 1600 degree C and demonstrated 0.47% accuracy with respect to full measurement range. The efforts on sensor prototype development ranging from sensor probe packaging at each level, sensor electronics, LED modulation to remote data access are addressed.

Frequency-Division-Multiplexed Fabry-Perot Interferometric Fiber Sensors for Temperature Monitoring in a Selective Catalytic Reduction Unit

We present the quasi-distributed temperature measurement results in a selective catalytic reduction unit of a power plant by using a frequency-division-multiplexing optical fiber measurement system with eight intrinsic Fabry-Perot interferometric fiber sensors along a single fiber. The sensor was constructed by splicing a section of multimode fiber between single mode fibers. A high resolution swept laser interrogator was used to measure the spectrogram of the reflected light from the sensors, which contains multiple frequency components in wave number domain corresponding to sensors with different cavity lengths. The temperatures were measured by estimating the optical path length of each Fabry-Perot interferometer. Field test results show that the proposed technology can potentially be used in applications of multi-point high temperature sensing.

Wavefront splitting intrinsic Fabry-Perot fiber optic sensor

We present the principle, fabrication, and characterization of a novel wavefront splitting intrinsic Fabry-Perot fiber temperature sensor. The sensor is made by splicing a section of fused silica tubing to the tip of a single-mode fiber. The completed sensor has the same diameter as the fiber and the sensor length is less than 0.5 mm.

Penetration rate of water in sapphire and silica optical fibers at elevated temperature and pressure

We compare the penetration rate of water in sapphire and silica optical fibers at elevated temperature and pressure, which are usually the conditions in harsh environment sensing applications. The water penetration rate is studied by measuring the transmission attenuation rate at 1390 nm for both fibers. The experimental result shows sapphire fiber is much more water-resistant in such an environment compared to silica fiber, which suggests that it is a strong candidate for harsh environment fiber sensing.

Novel single-phase fiber optic flow sensor system

In this paper, we present a novel design of a fiber optic flow sensor system for single-phase fluid flow detection. This new system is based on the principle of broadband interferometry and cantilever beam bending. The fiber optic sensor system utilizes two fiber ferrule sensors that are bonded on both sides of a cantilever beam. The flow rate can be determined by monitoring the air gap changes caused by bending of the cantilever beam. Cross-sensitivity of the temperature and pressure dependence of the sensor can be compensated for automatically. The prototype sensor system was fabricated and tested on the lab-scale with preliminary evaluations completed. Field-testing was performed in the indoor and outdoor flow loops of Tulsa University in Tulsa, Okalahoma. Both the lab-scale and field-testing results verified that the designed flow sensor system could measure the single-phase fluid flow rate with high resolution and repeatability by compensating the thermal and pressure effects of the environment. The outdoor field-testing demonstrated the feasibility of the designed fiber optic flow sensor for single-phase fluid flow rate measurements in the oil fields.