Yutian Wang

Optically powered hydrostatic tank gauging system with optical fiber link

In this paper, a practical optically powered hydrostatic tank gauging system with optical fiber is presented. It combines the advantages of optical fibers with the micro power consumption sensor. Two multimode fibers are connected between the readout and the sensor, so it has external optical attributes. Optical energy transmitted from the readout is converted to electricity at the sensor. Digital data from the sensor is transmitted over the fiber to the readout. The parameters measured include the liquid level. the interface between water and oil, the tank storage.The paper gives results measured above parameters by means of the semiconductor strain gauges.

New optically powered ultravoltage current transformer

In this paper an electron-optic current transformer (CT) is described which is used in measuring the super-voltage stations line current. The measurement system uses a conventional CT as the sensing probe whose electronics is optically powered. The paper describes the principle of measurement system, including the system design, optically powered sensing probe, the data link, measurement signal processing and result showing current measurement by means of CT.

Capsule pressure sensor with optical fiber coupling

A new type of optical fiber pressure sensor is introduced in this paper. The ratio measurement by means of the sensing optical fiber and the reference fiber with different beginning positions and the technique to improve the stability of the sensor are first discussed. Then the ability to restrain and compensate the interference of the same nature through the double channel ratio measurement is illustrated. Finally, the performance of sensor and its engineering design are discussed.

Improving the temperature resolution and response speed of distributed optical fiber temperature sensor with Wavelet

Distributed optical fiber temperature sensor system can sense the temperature changes along the optical fiber by the continuous form of distance. For the characteristics of insulation and resistance to electromagnetic interference, it has a wide using prospect in the field of petroleum and gas pipeline, tunnel and mine. The distributed temperature measurement is realized by using single channel anti-Stokes light, and the temperature and space resolution of the system can be assured. But the anti-Stokes signal will be submerged by noise because of the weakness of anti-Stokes light signal, the loss of scattering light and the system noise. In order to reduce the influence of various noises in distributed temperature measurement, the method of increasing the times of signal accumulating is used to increase temperature resolution. But this will lengthen the period of temperature measurement and influence the practical application of the system. By using the multi-resolution analysis of Wavelet to handle the distributed temperature signal, we can shorten the period of temperature measurement and enhance the response speed of system on the basis of the assurance of time and space resolutions.

New optically powered pressure sensor with optical fiber link

An optically powered sensor for measuring pressure which linked by optical fiber is developed in a new scheme. Its pulse position modulation (PPM) optical signal and optical supply power for electronics in probe are transmitted to and fro via a single optical fiber. The optical power is carried by a laser diode (LD) source with 1300 nm wavelength and the sensing data are carried by LED 850 nm source. The remote probe uses all CMOS chips and particular modulations (PPM and PWM). Its electrical consumption including signal manipulation and LED driven current from optical conversion is less than 100 (mu) W. The laser diode supplies 5 mW of optical power into the fiber. An advanced photodetector converts sufficiently the section of this power into electrical power to drive the whole probe operation. The optically powered distance gets up to 500 m. The novel sensor combines advanced optical fiber and electronics technology into a system. It continuously measures pressure in real time. Because of using the principle of ratio measurement between mesurand and reference signals, as well as light feedback for light source stability, the system is available with high reliability, outstanding accuracy, and repeatability.

A method for displacement measurement based on reciprocal interferometry with spectrum analysis techniques

A nanometer range displacement measurement system is presented where a reciprocal interferometer is employed whose configuration is similar to Michelson interferometer. Although the reciprocal interferometer is very simple and insensitive to environmental perturbations, we concluded that the spectrum analysis techniques could also be used to process the interference fringes and increase the measurement precision of reciprocal interferometry. Fast-Fourier transform and filter are used to eliminate the noises in fringes. The reconstructed fringes are very clear, which location can be measured accurately. Theoretical analysis is presented. Experimentally, the displacement of a nanopositioner-driven target was measured by using a reciprocal interferometer, a CCD camera, picture card and computer. The system has demonstrated a minimum resolution is 1.5 nm when the number of sample point is 512.

Design of pulsed light source in distributed optical fiber temperature sensing system

Distributed optical fiber temperature sensor use the principle of temperature effect of spontaneous Raman scattering in fiber and optical domain time reflection (OTDR) to detect the temperature field in space and its changing with time. It can sense the temperature changes along the fiber length by the continuous form of distance in a fiber of several kilometers length. Theoretically, the minimal discernible space length of fiber in the distributed optical fiber temperature sensor system is proportional to the width of incident light pulse, that is, the narrower the width of incident light pulse, the higher the space resolution of fiber. The width, power and edge quality of incident light pulse can directly influence the space and temperature resolution of distributed optical fiber temperature sensing system. This paper focused on the optimum design of light pulse producing based on the use of LD light source. A high power light pulse of narrower width is produced by designing reasonable circuit of increasing voltage, discharging control and making full use of LD, which makes sure to improve the space and temperature resolution of the system.

Fluoroptic temperature detection by using a microprobe with optical fiber

This paper presents a monitoring temperature system in real time. The fluoroptic temperature could be detected quantitatively by the signals of PSD. When the optical fiber is 2 m long, the real-time temperature sensitivity is 0.1 degrees Celsius and the accuracy is 1%. The high sensitivity and high accuracy are partly due to the operation of the light source feedback, and partly due to the ratio of measurement and reference signals. This fluorescence temperature measuring system finds wide application fields where conventional techniques either cannot be used, or have proven to be unsatisfactory. It is especially useful for measurements in electrically hostile environments.

Optical fiber underwater fluorometer for measuring chlorophyll-a concentration

This paper describes an efficient method for in-situ measurement of chlorophyll-a concentration in the seawater with fluorescence method and optical fiber techniques. The instrument uses the pulsed xenon lamp as the excited light resources. Both the exciting light and the fluorescence from algae chlorophyll-a are transmitted along two fiber bundles. The fluorescent signal is detected by using the relevant pulsed detecting technology. The minimal detecting concentration of chlorophyll-a in the ocean can reach 1x10-5mg/cm3. The system has advantages of simple structure, passive sensor head and high sensitivity. The experimental results show that this measurement method is realizable.

Novel method for improving the space resolution of distributed optical fiber temperature sensing system using decoupling technique

The distributed optical fiber temperature sensing system based on the Raman back scattering has been widely used. By using the optical time domain reflection (OTDR) technique, the high intensity light pulse is coupled into optical fiber. By detecting and recording the variation of back scattering signal related to optical fiber temperature along with the time, the distribution measurement of environmental temperature is carried out. In order to ensure a certain intensity of the light pulse, it must have a certain width. In the meanwhile, the responding rate of the photoelectric components and the bandwidth of the digital collection systems cause the reduction of the space resolution. The signal coupling brought by the pulse width can be reduced and the space resolution of distributed optical fiber temperature sensing system can be improved by using self-adaptive wavelet nerve network which has a stronger ability of function approach and tolerant fault to process the data.