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Temperature performance of Raman scattering in data fiber and its application in distributed temperature fiber-optic sensor
Deming LIU, Shuang LIU, Hairong LIU
Front Optoelec Chin. 2009, 2 (2): 159-162.
https://doi.org/10.1007/s12200-009-0023-y
A wavelength division multiplexer (WDM) was used to extract the Raman scattering signal from a data fiber. The temperature performance of Raman scattering spectrum was studied theoretically and experimentally. On the base of this study, a distributed fiber-optic temperature sensor (DFTS) system was developed. The sensing distance was 4?km. The temperature accuracy and the distance resolution reached to±1°C and±1?m, respectively. The system is stable and adequate for commercial usage, such as the power industry, the underground tunnel, the subway, and the pipe laying, and also for the mission applications, such as the warship and the airplane.
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Photonic crystal fiber with novel dispersion properties
Shuqin LOU, Shujie LOU, Tieying GUO, Liwen WANG, Weiguo CHEN, Honglei LI, Shuisheng JIAN
Front Optoelec Chin. 2009, 2 (2): 170-177.
https://doi.org/10.1007/s12200-009-0022-z
Our recent research on designing microstructured fiber with novel dispersion properties is reported in this paper. Two kinds of photonic crystal fibers (PCFs) are introduced first. One is the highly nonlinear PCF with broadband nearly zero flatten dispersion. With introducing the germanium-doped (Ge-doped) core into highly nonlinear PCF and optimizing the diameters of the first two inner rings of air holes, a new structure of highly nonlinear PCF was designed with the nonlinear coefficient up to 47 W-1·km-1 at the wavelength 1.55 μm and nearly zero flattened dispersion of ±0.5 ps/(km·nm) in telecommunication window (1460-1625 nm). Another is the highly negative PCF with a ring of fluorin-doped (F-doped) rods to form its outer ring core while pure silica rods to form its inner core. The peak dispersion -1064 ps/(km·nm) in 8 nm full width at half maximum (FWHM) wavelength range and -365 ps/(km·nm) in 20 nm (FWHM) wavelength range can be reached by adjusting the structure parameters. Then, our recent research on the fabrication of PCFs is reported. Effects of draw parameters such as drawing temperature, feed speed, and furnace temperature on the geometry of the final photonic crystal fiber are investigated.
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High-power EDFA applied in distributed optical fiber Raman temperature sensor system
Xu ZHANG, Deming LIU, Hairong LIU, Qizhen SUN, Zhifeng SUN, Ziheng XU, Wengang WANG
Front Optoelec Chin. 2009, 2 (2): 210-214.
https://doi.org/10.1007/s12200-009-0033-9
In this paper, a high-power erbium-doped fiber amplifier (EDFA) for the temperature sensor system is theoretically designed and experimentally demonstrated. It consists of an erbium-doped fiber that is pumped bidirectionally with two 980-nm high-power laser diodes (LDs). At the EDFA input, an optical isolator (ISO) is used to ensure that the signal pulse transmits forward only. After that, a wavelength division multiplexer (WDM) is employed to combine the forward pump laser (980 nm) and incident optical pulse (1550 nm) into the erbium-doped fiber for direct amplification in the optical domain. At the EDFA output, another WDM couples the backward pump laser (980 nm) into the erbium-doped fiber and outputs the amplified optical pulse (1550 nm) with an ISO followed to isolate the backscattering light. According to this structure, we carried out the experiment in the condition as follows. For 980 nm pump LD, the operating current is 590 mA, and the setting temperature is 25°C. For EDFA, the length of erbium-doped fiber is 12.5 m, and the power of 1550 nm input signal is 1.5 mW. As a result, the power of pump LD is 330 mW, and the power uncertainty is 0.5%. The power of EDFA output at 1550 nm is 300 mW, and the power uncertainty is±3 mW.
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Design of distributed Raman temperature sensing system based on single-mode optical fiber
Ziheng XU, Deming LIU, Hairong LIU, Qizhen SUN, Zhifeng SUN, Xu ZHANG, Wengang WANG
Front Optoelec Chin. 2009, 2 (2): 215-218.
https://doi.org/10.1007/s12200-009-0043-7
The distributed optical fiber temperature sensor system based on Raman scattering has developed rapidly since it was invented in 1970s. The optical wavelengths used in most of the distributed temperature optical fiber sensor system based on the Raman scattering are around from 840 to 1330?nm, and the system operates with multimode optical fibers. However, this wavelength range is not suitable for long-distance transmission due to the high attenuation and dispersion of the transmission optical fiber. A novel distributed optical fiber Raman temperature sensor system based on standard single-mode optical fiber is proposed. The system employs the wavelength of 1550?nm as the probe light and the standard communication optical fiber as the sensing medium to increase the sensing distance. This system mainly includes three modules: the probe light transmitting module, the light magnifying and transmission module, and the signal acquisition module.
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Distributed optical fiber perturbation sensing system based on Mach-Zehnder interferometer
Wengang WANG, Deming LIU, Hairong LIU, Qizhen SUN, Zhifeng SUN, Xu ZHANG, Ziheng XU
Front Optoelec Chin. 2009, 2 (2): 229-232.
https://doi.org/10.1007/s12200-009-0025-9
A novel distributed optical fiber vibration-sensing system based on Mach-Zehnder interferometer has been designed and experimentally demonstrated. Firstly, the principle of Mach-Zehnder optical path interferometer technique is clarified. The output of the Mach-Zehnder interferometer is proportional to the phase shift induced by the perturbation. Secondly, the system consists of the laser diode (LD) as the light source, fiber, Mach-Zehnder optical interferometers as the sensing units, a 1×N star fiber-optic coupler, an N×1 fiber-optic coupler, a photodiode (PD) detector, and a computer used in signal processing. The entire monitoring region of this system is divided into several small zones, and each small monitoring zone is independent from each other. All of the small monitoring zones have their own sensing unit, which is defined by Mach-Zehnder optical interferometer. A series of sensing units are connected by the star fiber-optic couplers to form a whole sensing net. Thirdly, signal-processing techniques are subsequently used to calculate the phase shift to estimate whether intruders appear. The sensing system is able to locate the vibration signal simultaneously, including multiple vibrations at different positions, by employing the time-division multiplexed (TDM) technique. Finally, the operation performance of the proposed system is tested in the experiment lab with the conditions as follows: the number of the sensing units is 3, the length of the sensing fiber is 50 m, and the wavelength of the light diode is 1550 nm. Based on these investigations, the fiber surrounding alert system is achieved. We have experimentally demonstrated that the sensing system can measure both the frequency and position of the vibration in real time, with a spatial positional resolution better than 50 m in an area of 1 km2.
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FBG sensing temperature characteristic and application in oil/gas down-hole measurement
Shaomin LI, Xiaoying LIU, Chong LIU
Front Optoelec Chin. 2009, 2 (2): 233-238.
https://doi.org/10.1007/s12200-009-0042-8
Fiber Bragg gratings (FBGs) have been used to sense numerous parameters such as strain, temperature, and pressure. Cost-effective multipoint measurements have been achieved by connecting FBGs in parallel, serial, and other topologies as well as by using spatial, wavelength, and time-domain multiplexing techniques. This paper presents a method of measuring temperature of the oil/gas down-hole. Detailed contents include the basic theory and characteristics of fiber gratings, analysis of the sensing mechanism of fiber-optic gratings, and the cross-sensitivity effect between temperature and strain; the method of making the light-source of the fiber-optic gratings and the technology of measuring wavelength shift, building an experimental system of the temperature measurement, and dealing with the experimental data. The paper makes a comparison of several kinds of FBG sensing systems used in oil/gas down-hole to measure temperature and the analysis of the experimental results of building the temperature measurement system. It demonstrates that the fiber-optic grating sensing method is the best choice in all methods of measuring temperature in oil/gas down-hole, which has a brilliant applied prospect.
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