We present an intrinsic Fabry-Perot interferometric fiber sensor for high density quasi-distributed temperature and strain
measurement. The two internal partial reflection mirrors in such a sensor are formed by a pair of ultra-short fiber Bragg
gratings. We experimentally demonstrate the multiplexing of 56 such sensors in a single fiber using a frequency-division
multiplexing scheme. We show that theoretically as many as 500 sensors can be multiplexed. We demonstrated the experimental results of the multiplexed sensors for quasi-distributed temperature and strain measurement and the temperature compensation of strain sensors.
This paper presents a novel fiber optic Fabry-Perot (FP) structure for direct detection of deoxyribonucleic acid (DNA)
sequences. The capture DNA is immobilized onto the surface of a silica optical fiber tip by means of the layer-by-layer
electrostatic self-assembly (L-b-L ESA) technique. With the FP cavity inside the fiber, the change in optical path length
difference (OPD) caused by the immobilization and hybridization can be demodulated. Experimental results demonstrate
short (~5 min) response time. In addition, the sensor fabrication is simple and low cost. The signal is stable with high
visibility.
A novel partial-discharge positioning system was demonstrated using an acoustic sensor array composed of four fiber acoustic sensors and a signal-processing unit. A hyperbolic position-fixing algorithm was employed to locate partial discharges. Convolution, correlation, and leading edge with finite impulse response filtering were used to determine time differences of arrival (TDOAs). Partial-discharge positioning was demonstrated in a 500-gallon tank. The positioning results showed that the correlation and leading edge methods are more robust and accurate in determining the TDOAs than the convolution method. A positioning accuracy of 3.0% was achieved using the leading edge method with a sensing range of 755 mm. These positioning results also indicated that the best sensor array layout is to spread the sensors in the tank in order to achieve high positioning accuracy.
This paper presents a novel intrinsic fiber optic Fabry-Perot (FP) structure with a micrometric diameter tip. With the FP cavity inside the fiber, the change in optical path length difference (OPD) caused by the environment can be demodulated. With such a tiny protrusion, the sensor can be inserted into micron size cells for intracellular measurements. This label-free detection method is very useful in biological areas such as DNA hybridization detection. It provides a valuable tool for intracellular studies that have applications ranging from medicine to national security. In addition, the fabrication is simple including only cleaving, splicing, and etching. The signal is stable with high visibility. Last but not the least, the structure shows great promise for reduction to nanometric size. Once this goal is achieved, the sensor can be inserted into most cells with minimal invasiveness.
This paper presents a novel fiber optic Fabry-Perot (FP) structure with a micrometric diameter tip. The fabrication of micro scale probes has become essential in intracellular surgery, in cell sensing, manipulation, and injection. It is of great importance in many fields, such as genetics, pathology, criminology, pharmacogenetics, and food safety. With such a tiny protrusion, the sensor can be inserted into micron size cells, say, for DNA analysis. With the FP cavity inside the fiber, the change of optical path difference (OPD) caused by the environment can be demodulated. In addition, the structure is intrinsically capable of temperature compensation. What's more, it is simple, cost-efficient, and compact. Last but not the least, the structure shows promise for nanometric protrusion. Once this goal is achieved, the sensor can be inserted into most cells. The sensor could pave the way for faster, more accurate medical diagnostic tests for countless conditions and may ultimately save lives by allowing earlier disease detection and intervention.
We present UV-induced intrinsic Fabry-Perot interferometric (IFPI) fiber sensors and a frequency-division-multiplexing
(FDM) scheme for quasi-distributed temperature and strain sensing. We present a spectrum-based measurement system
with a swept laser source to measure the fringe patterns of IFPI sensors serially arranged along a single fiber. The FDM
scheme is based on the multiplexing of sub-carrier frequencies generated by the frequency-modulation of a continuouswave
light source. IFPI sensors with different optical path differences (OPD) will have different sub-carrier frequencies.
We use band pass filters to select individual frequency component and use frequency-estimation based signal processing
algorithms to determine the OPD of each sensor. Experimental results for multiplexed temperature and strain sensing
are demonstrated. The performance of the multiplexing system is discussed.
Pressure sensors are the key elements for industrial monitoring and control systems to lower equipment maintenance cost, improve fuel economy, reduce atmospheric pollution, and provide a safer workplace. However, the testing environment is usually harsh. For example, inside the turbine engine, temperatures might exceed 600°C and pressures might exceed 100psi (690kPa), where most current available sensors cannot survive. Moreover, due to the restricted space for installation, miniature size of the sensor is highly desirable. To meet these requirements, a novel type of all fused silica optic fiber tip pressure sensor with a 125μm diameter was developed. It is a diaphragm based pressure sensor in which a Fabry-Perot interferometer is constructed by the end face of an optical fiber and the surface of a diaphragm connected by a short piece of hollow fiber. The FP cavity length and the interference pattern will change according to ambient pressure variation. Its main improvement with respect to previously developed optical sensors, such as those utilizing techniques of wet etching, anodic bonding and sol-gel bonding, is the fact that no chemical method is needed during the cavity fabrication. Its dynamic pressure performance was verified in a turbine engine field test, demonstrating not only that it can safely and reliably function near the fan of a turbine engine for more than two hours, but also that its performance is consistent with that of a commercial Kulite sensor.
A novel Intrinsic Fabry-Perot fiber-optic sensor is presented in this paper. The sensors were made through two simple steps: wet chemical etch and fusion splice. Micro air-gaps were generated inside the fibers and functioned as reflective mirrors. This procedure not only provides a simple and cost effective technology for fabricating intrinsic Fabry-Perot Interferometric (IFPI) fiber sensors, but also provides two possible IFPI structures. Both of the fiber cavity between the air-gaps or the air-gap and cleaved fiber end can be used as sensing elements. With these two structures, this sensor can be used to measure the temperature, strain, pressure, refractive index of chemicals and the thin film thickness by itself. Multi-point measurements can also be achieved by multiplexing. Furthermore, it also can be multiplexed with other sensors such as Long Period Gratings (LPG) to provide compensations for other perturbation sensing. Theoretical and experimental studies of two sensor structures are described. Experimental results show that high resolution and high sensitivity can be obtained with appropriate signal processing.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.