Nonlinear characteristics of fluorescent optical fiber sensors for low-temperature measurement

Ferrofluid is a novel kind of functional materials, which possesses both the magnetism of solid magnetic material and fluidity of liquid material. Due to its unique optical properties, especially the refractive index tunability under magnetic field, ferrofluid has been widely utilized for magnetic field and current sensing combined with various optical fiber structures. Hence, in this paper, the refractive index tunability of ferrofluid, which is mainly applied into the optical fiber sensors, is first reviewed and illustrated in detail. Then we mainly introduce our work on the applications of ferrofluid in optical fiber sensors based on the refractive index tunability of ferrofluid, including the whole physical configurations, the operating principles, and the performances of these optical fiber sensors. At last, the deficiencies of ferrofluid in the applications of optical fiber sensors as well as valuable potential prospects in further research are analyzed and presented. From all the above reviews and discussions, it can be foreseen that the characteristics of ferrofluid will be improved and the applications of ferrofluid-based optical fiber sensors will be developed rapidly and maturely.

Smart Grid is a promising power delivery infrastructure integrated with communication and information technologies. By incorporating monitoring, analysis, control and communications facilities, it is possible to optimize the performance of the power system, allowing electricity to be delivered more efficiently. In the transmission and distribution sector, online monitoring of transmission lines and primary equipments is of vital importance, which can improve the reliability of power systems effectively. Optical fiber sensors can provide an alternative to conventional electrical sensors for such applications, with high accuracy, long term stability, streamlined installation, and premium performance under harsh environmental conditions. These optical fiber sensors offer immunity to EMI and extraordinary resistance to mechanical fatigue and therefore they will have great potential in on-line monitoring applications in Smart Grid. In this paper, we present a summary of the on-line monitoring needs of Smart Grid and explore the use of optical fiber sensors in Smart Grid. First, the on-line monitoring needs of Smart Grid is summarized. Second, a review on optical fiber sensor technology is given. Third, the application of optical fiber sensors in Smart Grid is discussed, including transmission line monitoring, primary equipment monitoring and substation perimeter intrusion detection. Finally, future research directions of optical fiber sensors for power systems are discussed. Compared to other traditional electrical sensors, the application of optical fiber sensors in Smart Grid has unique advantages.

Partial discharge (PD) is a common phenomenon in high voltage (HV) equipment, which will radiate light signals outward in the process of discharge, by detecting this optical signal, we can judge whether the HV equipment have PDs or not, the conventional detection methods under impulse voltage are very complex due to the interference of electromagnetic (EM) wave, but optical method does not have this problem. Fluorescent optical fiber is not affected by numerical aperture problem, so the sensitivity of fluorescent optical fiber sensor is much higher than that of traditional quartz optical fiber sensor. In this work, the fluorescent optical fiber sensor was manufactured and applied to the PD detection in gas insulated switch (GIS) and transformer, fluorescent optical fiber was used as a probe, which was connected with the transmission optical fiber by coupler, and the photomultiplier tube was used to convert the optical signal into electrical signal for displaying by oscilloscope. The discharge signal can be detected by the sensor when the impulse voltage was applied to the GIS and transformer, and it was less affected by the interference of EM wave signals. As the PD source at different positions in GIS, we found that the optical signal attenuates greatly when the optical was blocked by some internal structures, and the attenuation was increase with the increase of distance between PD source and the sensor. The optical signals of PDs can also be detected by the sensor in the transformer, but the attenuation of the optical signal in the transformer was greater than that in GIS, it was greatly affected by the blocking of windings. The two experiments were verified in the TracePro simulation software, and the average deviations between results of experiments and simulations were less than 10%.

Optical fiber sensors have been used in military and biomedical applications for twenty years. Industrial and civil engineering applications of optical fiber sensors particularly for mechanical measurements require sometimes quite different configurations and parameters of sensors. In addition, a problem of cost effectiveness of the sensor is not so important for military and medical applications as in industrial ones. Hence each design of optical fiber sensor for mechanical parameter measurements is specific and should be tested not only in laboratory. The paper presents a short overview of methods and systems of optical fiber sensors which are used in mechanical measurements. Selected applications of optical fiber sensors are described in detail. Unique and quite new application of polarimetric fiber optic sensor for dynamic strain measurements is given as well. In conclusion, some advantages and disadvantages of optical fiber sensors applications in mechanical measurements are discussed.

The information and the necessity of engineering monitoring of Dongying Yellow River Bridge are briefly introduced firstly. And then the application of optical fiber sensors in construction supervision, loading test and health monitoring of this bridge is illuminated. The distribution of the internal force monitoring sections, strain and temperature monitoring points and the measuring contents are concisely analyzed. The Encapsulation techniques, installation means and protective measures of optical fiber sensors used in this bridge are also clarified. The author emphasizes the comparison between the theoretical results and actual measuring data derived from optical fiber sensors under some load cases of all the three monitoring phases, which shows that the measuring data is accurate and reliable. Considering its other merits, the author proves that the optical fiber sensors fit the monitoring of large bridge. At last, the outline of health monitoring system integration, especially the accessing of sensors to Interrogator, is showed and the mode of date acquisition, display and analysis, through the long range wireless transmission, is specified.

Review on the graphene based optical fiber chemical and biological sensors

Recent development and applications of optical and fiber-optic pH sensors

Experimental study on practical application of optical fiber sensor (OFS) for high-temperature system

A novel fluorescent optical fiber sensor for highly selective detection of antibiotic ciprofloxacin based on replaceable molecularly imprinted nanoparticles composite hydrogel detector

Applications of optical fiber sensor in pavement Engineering: A review

In the field of medical microwave hyperthermia, if the detection of the heating temperature is inaccurate, it will seriously endanger the health of patients. However, the active temperature sensor is severely affected by external electromagnetic interference, and the temperature measurement accuracy cannot reach the desired effect. Therefore, the fluorescent optical fiber temperature sensor has been widely used in the above mentioned complicated fields due to its insulation characteristics. In order to further improve the detection accuracy of the fluorescent fiber temperature sensor, the algorithm for extracting the fluorescence lifetime is a key part of the system to improve the accuracy. In this paper, the accuracy of the fluorescence lifetime extracted by the integral area ratio algorithm, FFT algorithm, and least squares fitting algorithm is verified by simulation and experiments. According to the simulation results, the FFT algorithm and the integral area ratio algorithm are completely unaffected by the DC bias of the system, and the least squares fitting algorithm is more sensitive to the DC bias of the system. Compared with the integral area ratio algorithm and the least squares fitting algorithm, the absolute errors of the fluorescence lifetime extracted by the FFT algorithm are reduced by 31% and 45%, respectively. In addition, the running time of the three data processing algorithms was also tested. The test results show that the processing time of the integral area ratio algorithm is reduced by about 99.55% and 93% respectively compared with the least squares fitting algorithm and the FFT algorithm. In summary, the simulation and experimental test results in this paper can provide an important reference for the data processing implementation of fluorescent optical fiber temperature sensors.

The purpose of this article is to review and further promote the application of optical fiber sensor technology in infrastructure monitoring. Compared with traditional sensors, optical fiber sensors have low maintenance costs and are small in size; consequently, they have gradually become a future development direction of sensors. This paper introduces the basic principles of several commonly used optical fiber sensors and the progress of optical fiber sensors in the monitoring of physical, mechanical, and chemical parameters and demonstrates the applications of optical fiber sensors in infrastructure.

The measurement of water inside a transformer is essential to maintain its reliable operation, as the water content can increase as the transformer ages. This measurement is frequently performed by a utility as a part of its periodic maintenance activities. In this paper, the application of optical fiber sensors as an online method to measure water content of paper inside an operating transformer is presented. There are several advantages of using these sensors, including their size, lightweight, flexibility, multiplexing, no-electromagnetic interference, etc. A unique benefit of fiber optic technology is that sensors can be embedded into the winding structure and operate in areas of high electric field strength. For this work, fiber optic water and temperature sensors are investigated by comparing their measurements to a commercial water activity probe immersed in oil. The study found that the determination of water content by fiber optic sensors compared closely with other techniques, which lead to the conclusion that they can be an effective technology for water measurement in an operational transformer.

Microwave hyperthermia is a new method of treating cancer, where the therapeutic effect is determined by the heating temperature. Traditional active temperature sensors are interfered by high frequency so that the accuracy of temperature measurement cannot be guaranteed. It is of great significance to study the high-precision fluorescent optical fiber temperature sensor with complete insulation. This paper has realized a compact and practical fluorescent optical fiber temperature sensor after studying the optical path, circuit, data processing algorithm. In order to improve the accuracy of the system, the weighted linear least-squares fitting algorithm is improved in this paper. Through experimental tests, compared with the standard linear least-squares fitting algorithm and the unimproved weighted linear least-squares fitting algorithm, the accuracy of the algorithm is improved by about 98% and 65.5%, respectively. In addition, the response time is reduced by about 36.5%, compared with the unimproved weighted linear least-squares fitting algorithm. This algorithm fully meets the precision requirements of microwave hyperthermia.

The online temperature monitoring of high voltage switchgear is of great significance to the safe operation of power system. However, the sensitive signal of the traditional active temperature sensor is electrical signal, which is susceptible to the interference of external electromagnetic signals, resulting in a decrease in accuracy. The sensitive signal of fluorescent optical fiber temperature sensor is optical signal, which is completely insulated from the external electromagnetic signal. In addition, the optical signal is safer than the electrical signal in the high-voltage field. Therefore, the fluorescence optical fiber temperature sensor based on the principle of photoluminescence for high-voltage switchgear is realized in this paper. The Fast Fourier Transform (FFT) algorithm is used by the sensor to calculate the fluorescence lifetime. The experimental data show that when the temperature increases from 29 ℃ to 102 ℃, the fluorescence lifetime decreases from 2.6864 ms to 2.2246 ms, and the temperature sensitivity is about 6 us/℃. The fluorescence lifetime has a good linear relationship with temperature. In summary, the fluorescent optical fiber temperature sensor has application value in the field of high voltage switchgear.