Y.J. Rao

Chongqing University, Chongqing, Chongqing Shi, China

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Publications (47)48.21 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel method for simultaneously measuring displacement and temperature using an in-fibre-Bragg-grating (FBG) based extrinsic Fizeau interferometric sensor is presented. The Fizeau cavity is formed by an FBG with low reflectivity and a highly reflective surface. The FBG acts as both a reflector for the Fizeau interferometer and a temperature sensor, at the same time. Experimental results are provided which demonstrate the feasibility of this sensor design
    Electronics Letters 10/2000; · 1.04 Impact Factor
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    ABSTRACT: A novel method far achieving both large dynamic range and high resolution for static strain measurement is proposed and demonstrated. This method is based on the combination of two in-fibre Bragg gratings (FBG) and an all-fibre Fabry-Perot interferometric sensor (FFPI) formed by the two FBGs. The FFPI is used to carry out high-resolution strain measurement via phase detection of the interferometric signal while the wavelength shift of the two FBGs forming the FFPI is used for determining the fringe number of the interferometric signal
    Electronics Letters 05/2000; · 1.04 Impact Factor
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    ABSTRACT: A novel entirely passive electro-optic electric field sensor is reported. This sensor is based on the intensity change of the diffracted light from an electro-optically induced Bragg grating in a periodically poled LiNbO<sub>3</sub> device. This new type of electric field sensor is simple, inexpensive and capable of achieving high sensitivity, linear operation and very large bandwidth with stable intrinsic biasing
    Electronics Letters 05/1999; · 1.04 Impact Factor
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    ABSTRACT: We describe work on a system able to measure the temperature at a number of points along a single optical fiber probe, designed for in-vivo temperature profile monitoring. The sensing elements are in-fiber Bragg grating sensor and three forms of signal processing have been investigated. System 1 uses interferometric wavelength shift detection with a monochromator providing the WDM. System 2 used a scanning in-line Fabry-Perot filter and system 3 uses a monochromator with a CCD based readout scheme. The performances of the three approaches are compared.
    Proc SPIE 02/1999;
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    Y.J Rao
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    ABSTRACT: In-fibre Bragg grating (FBG) sensor technology has become one of the most rapidly progressing sensing topics of this decade in the field of optical fibre sensors. FBG sensors are currently emerging from the laboratory to find practical applications. Rapid progress has been made in both sensor system developments and applications in recent years. This article presents a systematic review of recent progress in applications of FBG sensors in large composite and concrete structures, the electrical power industry, medicine, and chemical sensing.
    Optics and Lasers in Engineering 01/1999; · 1.92 Impact Factor
  • Proc SPIE 01/1999;
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    ABSTRACT: A novel interferometric wavelength-shift detection system based on the use of two cascaded two-beam interferometers with different optical path differences (OPDs) is developed for static and quasi-static strain measurement with in-fibre Bragg grating (FBG) sensors. These two interferometers are frequency-division-multiplexed and used to provide two sets of interferometric fringes induced by strain. The optical phase output from interferometer 1 with the larger OPD gives a high-resolution measurement whilst the phase output from interferometer 2 with the shorter OPD is used to determine the number of the fringes obtained with interferometer 1. Compared with the detection scheme using a single interferometric scanner, the unambiguous measurement range has been considerably improved. An experimental system with enhancement factors between 11 and 40 in the unambiguous measurement range has been demonstrated for absolute static strain measurement. A large range to resolution ratio of has been achieved. Due to the adjustability of the OPDs in these interferometers, the range to resolution required is also variable, making this system suitable for different applications. On the other hand, a range to resolution of makes FBG strain sensors potentially competitive with traditional strain gauges with the well known benefits of fibre-optic sensors. Therefore, it can be anticipated that after further engineering such a system will find important applications in the field of fibre-optic smart structures.
    Measurement Science and Technology 12/1998; 8(10):1043. · 1.44 Impact Factor
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    ABSTRACT: A sensor multiplexing scheme for the simultaneous monitoring of dynamic strain and temperature is presented. The scheme combines low-coherence and wavelength-division signal processing with a serial array of fibre-Fabry-Pérot (FFP) interferometric sensors defined by in-fibre grating mirrors of matched Bragg wavelength. Heterodyne measurements of signal phase from a 39 cm long FFP interferometer result in a dynamic strain resolution of about at acoustic frequencies. Temperature measurements via the induced changes in Bragg wavelength have a sensitivity of about . The cross-talk between the strain and temperature channels is within the system noise.
    Measurement Science and Technology 12/1998; 9(11):1837. · 1.44 Impact Factor
  • Y J Rao, D A Jackson
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    ABSTRACT: A prototype single-mode fibre-based Fizeau interferometric medical pressure and temperature sensor system using coherence reading signal recovery is demonstrated. These sensors have been designed in such a way that they have similar optical path differences and hence problems associated with multiplexing are greatly reduced. For the pressure sensor, a range to resolution ratio of about 6.7*103:1 and an overall measurement accuracy of better than +or-1% over a pressure range of 0-360 mmHg have been achieved. For the temperature sensor, a measurement resolution of 0.006 degrees C and a 1% span linearity over a temperature range of 27.3-62.5 degrees C have been achieved. The performance of both sensors meets or exceeds established medical requirements, and the dimensions of the probes are compatible with commercial electric probes. Hence this new sensor system is expected to be a practical approach for many medical applications.
    Measurement Science and Technology 12/1998; 5(6):741. · 1.44 Impact Factor
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    ABSTRACT: This paper reports on a novel optical fiber sensor configuration for conducting simultaneous strain and temperature measurements. The sensor consisted of an optical fiber-based extrinsic Fabry-Perot interferometer (EFPI) with an integrated fiber Bragg grating (FBG). The FBG was located within a glass capillary which housed the EFPI sensor and was thus in a strain-free condition. The FBG is primarily sensitive to temperature, while the EFPI was sensitive to both strain and temperature. The integrated FBG/EFPI sensor was embedded in a carbon fiber reinforced composite and evaluated. The standard deviation of strain measurement was 36 (mu) e in the range 0 to 1200 (mu) e, and the temperature measurement had a standard deviation of 3.5 degrees C in the range 30 degrees to 70 degrees C. The thermal expansion of the cross-ply composite was investigated and was found approximately 4.05 X 10-6 degrees C.
    Proc SPIE 07/1998;
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    Proc SPIE 06/1998;
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    ABSTRACT: Two in-fiber Bragg grating (FBG) temperature sensor systems for medical applications are demonstrated: (1) an FBG flow-directed thermodilution catheter based on interferometric detection of wavelength shift that is used for cardiac monitoring; and (2) an FBG sensor system with a tunable Fabry-Perot filter for in vivo temperature profiling in nuclear magnetic resonance (NMR) machines. Preliminary results show that the FBG sensor is in good agreement with electrical sensors that are widely used in practice. A field test shows that the FBG sensor system is suitable for in situ temperature profiling in NMR machines for medical applications. © 1998 Society of Photo-Optical Instrumentation Engineers.
    Journal of Biomedical Optics 01/1998; 3(1):38-44. · 2.75 Impact Factor
  • Yun Jiang Rao
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    ABSTRACT: In-fiber Bragg grating (FBG) sensor technology has become one of the most progressing sensing topics of this decade in the field of optical fiber sensor technologies as FBG sensors are capable of measuring a wide range of parameters and have potential for simultaneous measurement of multi- parameters. In recent years, rapid progress has been made, in particular, in sensor system developments and applications. The fundamental aspects of the FBG sensor technology have been reviewed recently by the author. As a complementary article, this review paper concentrates on the recent progress in applications of FBG sensors for large composite structures, electrical power industry and medicine. Also, recent progress in sensor system developments associated with these applications are addressed.
    Proc SPIE 01/1998;
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    ABSTRACT: A novel technique for simultaneous measurement of static- strain, temperature and vibration for structural health monitoring is demonstrated using a wavelength-multiplexed in-fiber-Bragg-grating (FBG)/fiber-Fabry-Perot- interferometer (FFPI) sensor system, which combines the advantages of both FBGs and fiber-optic low-coherence interferometry. An experimental system, including two 1m long FFPIs with central wavelengths of 1531nm and 1534nm and a FBG with a central wavelength of 1555nm, is demonstrated. A static strain resolution of better than 1 (mu) (epsilon) , a temperature sensitivity of 0.1 degrees C and a vibration amplitude sensitivity of better than 1nm/(root) Hz have been obtained. The system cross-talk measured is less than -50dB.
    Proc SPIE 01/1998;
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    ABSTRACT: A novel technique for simultaneous measurement of static-strain, temperatures and vibration for structural health monitoring is demonstrated using the wavelength-multiplexed in-fibre-Bragg-grating (FBG)/fibre Fabry-Perot interferometer (FFPI) sensor system which combines the advantages of both FBGs and fibre optic low coherence interferometry
    Electronics Letters 12/1997; · 1.04 Impact Factor
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    ABSTRACT: For medical temperature measurements small, reliable and inexpensive thermocouple and thermistor devices have been commercially available for many years and are still widely used in practice. However, as these sensors are electrically active they are not appropriate for use in a number of medical applications, in particular, in high magnetic fields associated with NMR machines in which temperature profiling in the human body is needed to be measured for diagnosis purposes. A range of miniature fibre-optic medical temperature sensors have been reported in recent years and a small number have been successfully commercialised. Generally speaking, these sensors are all point sensors which can only provide temperature readings over a small volume in the body rather than temperature distribution within the body. Although passive multiplexing of these point sensors is possible it is difficult to achieve in practice due to limitations on the probe size.
    Optical Fiber Sensors; 10/1997
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    ABSTRACT: Measurement of the heart’s efficiency plays a key role for cardiac monitoring. Since 1970, doctors have injected patients with cold solution to measure their hearts’ blood output [1]. A flow-directed thermodilution catheter is inserted into the right atrium of the heart. The catheter allows the solution to be injected directly into the heart and enables measurement of the temperature of the blood in the pulmonary artery. By combining temperature readings with pulse rate, doctors can determine how much blood the heart pumps. Such types of catheters with conventional thermistor and thermocouple devices have been commercially available for many years and are still widely used in practice. However, as these sensors are electrically active they are not appropriate for use in a number of medical applications, in particular, in high magnetic fields associated with NMR machines. Fibreoptic sensors can overcome this problem as they are dielectric and hence virtually immune to electromagnetic interference
    Optical Fiber Sensors; 10/1997
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    ABSTRACT: In this paper we describe preliminary experiments to demonstrate the simultaneous measurement of dynamic strain and temperature with a multiplexed serial array of fibre Fabry-Pérot (FFP) interferometric sensors.
    Optical Fiber Sensors; 10/1997
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    ABSTRACT: The detection of impact damage in fiber reinforced composites is of significant concern because such damage can reduce the load-bearing ability of the composite. A number of factors can influence the nature and extent of impact damage development in composites including: (1) the type of reinforcing fiber and resin system; (2) the magnitude of the residual (fabrication) stresses; (3) the lay-up sequence; and (4) other factors such as the nature of the impactor, impact velocity, impact energy, temperature, moisture content in the composites etc.. From a structural health monitoring point of view, it is necessary to investigate the distribution of damage through the thickness of the composite. This paper reports on a simple, partially multiplexed optical fiber strain sensor system for in-situ strain and residual strain measurements in a carbon fiber reinforced epoxy composite. An extrinsic Fabry-Perot interferometric (EFPI) sensor design was used along with single mode fibers. The multiplexing scheme was based on wavelength division via the use of two super luminescent diodes at different wavelengths. A low-cost fiber optic CCD spectrometer was used as the detector. The multiplexing scheme was demonstrated using two EFPI sensors. In principle, a number of EFPI sensors can be multiplexed using the proposed scheme provided that each sensor is illuminated at a specified and different wavelength. The feasibility of detecting the residual strain in the composite was demonstrated successfully at two specified positions within a 16-ply carbon fiber reinforced composite. Preliminary results indicated that the sensor system was also capable of detecting the effects of a 3.2 J impact. Excellent correlation was obtained between the EFPI sensor output and that obtained using surface mounted strain gauges.
    Proc SPIE 01/1997;
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    ABSTRACT: Optical fiber Bragg grating (FBG) sensors have significant potential for use as embedded devices to monitor the structural integrity of engineering materials. The main drawback of the FBG strain sensor is its cross-sensitivity to temperature. This paper reports a simple scheme for multiplexing a FBG and an extrinsic Fabry-Perot interferometric (EFPI) sensor to enable the decoupling of strain from temperature. The EFPI sensor was constructed using a precision bore quartz capillary tube which housed two cleaved optical fibers. The gap between the fiber end- faces served as the Fabry-Perot cavity. Since the coefficients of thermal expansion between the optical fiber and the capillary tube were similar, the EFPI sensor has a very low sensitivity towards temperature. Therefore, when both sensors are placed close together, the EFPI sensor can act as the strain sensor, and temperature can be determined from the FBG wavelength shift after taking out the strain effect. The signal processing for the EFPI sensor was based on a channelled spectrum method using a CCD spectrometer. The same CCD spectrometer was also used to determine the wavelength shift of the FBG. The cross-talk between the EFPI and FBG sensors was evaluated. The feasibility of conducting simultaneous strain and temperature measurements was demonstrated.
    Proc SPIE 01/1997;

Publication Stats

445 Citations
48.21 Total Impact Points

Institutions

  • 2000
    • Chongqing University
      • School of Opto-Electronic Engineering
      Chongqing, Chongqing Shi, China
  • 1993–1999
    • University of Kent
      • School of Physical Sciences
      Canterbury, ENG, United Kingdom
  • 1996–1998
    • Aston University
      • • School of Engineering and Applied Science
      • • Department of Electrical, Electronic and Power Engineering
      Birmingham, ENG, United Kingdom