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A sensor for measuring of respiration of patients based on the high sensitivity of the speckle patterns obtained by multimode optical fibers is presented. The transducer consists of a small piece of optical fiber U-shaped adherent in the central region of an elastic band and placed around the patient's chest. The prototype achieved consists of the multimode plastic optical fiber step-index of 240/250 µm diameter core/cladding. Experimental results show a high correspondence with breathing signal. In this paper prototype and experimental results conducted on a population of 20 people are presented. By end components used can be considered as an alternative to the proposed low-cost system. [ABSTRACT FROM AUTHOR]

Raman Distributed Temperature Sensors (RDTS) are attractive for the monitoring of coolant loop systems in nuclear power plants and monitoring of overhead power transmission lines. This paper discusses deployment of RDTS on double walled pipelines of primary sodium circuits in Fast Breeder Reactors (FBR). It is demonstrated as a proof-of-concept on a test loop with water as the leaking medium. Path delay multiplexing is adopted to improve the spatial resolution from 1.02 m to 0.5 m. A second application focuses on the influence of environmental factors on the detectability of defects in the ACSR cables using RDTS. [ABSTRACT FROM PUBLISHER]

In order to fast, accurate and reliable obtain the state of charge of battery, the reflection of light in solution was studied. A function of relation of the solution concentration and battery capacity was established. In this paper introduced a new method of on-line detection of battery capacity, and the detection system was designed based on virtual instrument. It can automatically to test the concentration of battery electrolytic liquid by using the reflection type optical fiber sensor. The data acquired was processed utilized the neural network technology, eliminating the temperature influence. The parameters of battery capacity was obtained. The experimental results show that the method is feasible. The batteries are mostly through the plate and the solution for electronic exchange chemistry complete electrical energy storage and release, therefore, the method proposed has an important application value. [ABSTRACT FROM PUBLISHER]

We report a novel-principle fiber-laser intra-cavity sensor for measuring refractive index and solute concentration of aqueous solutions. The sensor operation is based on a variation of the laser oscillation relaxation frequency (RF, the measured parameter), sensitive to the intra-cavity loss. As the loss includes the reflection coefficient on the frontier aqueous solution—silica fiber cleaved cut, being the laser output coupler and simultaneously the sensor head, the RF becomes affected by the changes in refractive index of the aqueous solution; in turn, because the solution index is proportional to the solute concentration in water, the RF becomes also a function of the latter. The sensor capacity is demonstrated on the example of measurements of sugar concentration in water. A modeling of the sensor operation is presented, allowing its performance optimization. [ABSTRACT FROM AUTHOR]

We report an optical twisting alert sensor using beat frequency from a short cavity polarization-maintaining erbium-doped fiber (PM-EDF) based distributed Bragg reflector (DBR) laser. A DBR fiber laser with an effective cavity length of ∼ 1 cm formed by a pair of fiber Bragg gratings (FBGs) inscribed on a portion of PM-EDF was developed for demonstrated. This fiber laser exhibited stable operation in dual-polarization single-longitudinal-mode. The amplitude of the beat frequency generated by two orthogonal polarizations of the cavity is twist dependence. It is shown that the beat frequency signal can be completely “turned off” at ∼ 180° twist angle. This type of single mode DBR fiber laser can be used as optical twisting alert sensors for remotely interrogated systems and multi-parameter monitoring systems. [ABSTRACT FROM PUBLISHER]

The numerous potential applications of UV-induced fiber Bragg gratings (FBGs) in fiber optic sensing and telecommunication have generated a significant interest in this field in recent years. However, two major factors—the photosensitivity of the fiber in which the grating is written and the thermal stability of the grating—are of prime importance in terms of choosing the most appropriate fiber to use and of the long-term functionality of the grating over a wide range of temperatures. Based on the plasma chemical vapor deposition (PCVD) process and high speed drawing process, the high Ge (Germanium) doped photosensitive fiber were developed. It is mature technique that to precise control the dopant quantity by PCVD process and fiber defects control by the drawing process. The photosensitive fibers with same doping process and drawing process have been studied. Based on the experimental results obtained from studies of several kinds of photosensitive fiber on both the photosensitivity and the temperature sustainability of the FBGs written into them, the experimental results exhibit that the drawing temperature and drawing tension influence on the FBG's high-temperature sustainability. The drawing tension would influence the FBG's high-temperature sustainability greater than the drawing temperature. [ABSTRACT FROM PUBLISHER]

The phase generated carrier (PGC) modulation-demodulation technique is the main demodulation technique for fiber interferometric sensors. There are two methods to realize PGC modulation. One method is inner modulation, and the other is external modulation. However, there is less study on the PGC external modulation than the PGC inner modulation. In this paper, we focus on the PGC external modulation to analyze its characteristics. The experiment results indicate that the external demodulation performs well. Furthermore, its cost is much lower than that of inner modulation. [ABSTRACT FROM PUBLISHER]

We describe the fabrication of a double-layer silicon photonic crystal using self-aligned CMOS-compatible processes and its assembly on a single mode fiber using a wafer template and epoxy bonding. The fiber sensor has sharper resonances and higher temperature sensitivity than the previously-reported single-layer sensor. The new assembly method facilitates batch-production of the sensor and allows for extension to high temperature measurement. [ABSTRACT FROM PUBLISHER]