Xianhui Mao

Tsinghua University, Beijing, Beijing Shi, China

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Publications (5)3.47 Total impact

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    ABSTRACT: In this paper, our present work, which aimed at investigating a novel optical fiber biochemical sensor based on long period grating (LPG), is introduced. Biochemical sensor is one of the most attractive fields of sensor research, especially with the development and occurrence of all kinds of novel theory and technology such as LPG. When there is a refraction index periodic perturbation, the guiding mode and cladding mode in LPG couple with each other. This make the LPG is sensitive to the ambient refractive index. This means it can be a novel bio-chemical sensor when it is applied in the fields of biochemistry. After investigating the principle of coupling in LPG, where the formulas of resonance wave length and band width are induced by 3-layer step index model, we developed an optical fiber biochemical sensor. The structure of its probe is designed by coating some function films whose thickness is between several tens and several hundreds nanometers on the cladding of optical fiber. Experiments of monitoring the saline separateness process of Bovine Serum Albumin (BSA) and Mice-Immunoglobulin G (M-IgG) by using the developed LPG sensor have been done. The monitoring indicated that for the BSA, the saline separateness occurs when the saturation is between 50% and 60%, for the M-IgG, the percentage is between 30%-40%. Besides the monitoring, the experiments could also analyze the effects of protein type (different molecule structure), protein consistency and saline saturation to saline separateness. The experimental results show that the optical fiber biochemical sensor based on LPG has many advantages such as simple structure, high sensitivity and miniature. It has a promising future in many research fields and application fields.
    Proc SPIE 10/2007;
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    ABSTRACT: A long period grating (LPG) coated with hydrogel has been developed for monitoring the relative humidity (RH) levels. The response wavelength of the LPG varies with the changes of the relative humidity. The four-layered step index waveguide model is presented to explain this observation, which is based on the effect of the hydrogel thin film, the index of which increases with the increasing RH. Experiment shows that the hydrogel-coated LPG sensor is highly sensitive between 38.9% and 100% RH, and behaves linearly with humidity with an accuracy of ±2.3% RH. The small-size and low-cost LPG fibre sensor will have extensive applications in various areas, such as remotely measuring RH, building health monitoring, medical facilities and goods' preservation.
    Measurement Science and Technology 09/2007; 18(10):3131. · 1.44 Impact Factor
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    ABSTRACT: The long-period grating (LPG) coated with the hydrogel was investigated for monitoring the relative humidity (RH) levels-the ratio of the amount of water vapor in the air at a specific temperature to the maximum amount that the air could hold at that temperature. The experimental results showed that the resonant wavelength of the hydrogel-coated LPG was shifted when the RH varied from 38.9% to 100%, with a linearity of 99.5% and an accuracy of plusmn2.3% RH
    IEEE Photonics Technology Letters 07/2007; · 2.04 Impact Factor
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    ABSTRACT: A 3-Component fiber-optic accelerometer (FOA) array used in oil-well logging is presented. A novel and general parameter (SB2D-1P) to evaluate the characteristics of the interferometric FOA is brought forward
    10/2006;
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    ABSTRACT: The development of the optic interferometric sensors is partly restricted with the demodulation technique. The Phase Generated Carrier (PGC) modulation scheme is a useful demodulation method for interferometric sensors, for it is simple and accurate. At first, the PGC scheme is demodulated by analog demodulation techniques. Its capability is limited by the electronic devices, and not fit to the large-scale sensors application. In the past few years, a number of digital demodulation processing approaches have been investigated. Another arctangent approach based on digital demodulator exhibits more advantages than the traditional Differentiate and Cross Multiply (DCM) approach, which has a small measurement range and rather complex circuit. In this paper, the arctangent approach on the PGC configuration used in the array of optical fiber interferometer are discussed and emulated. The measurement range, operation complexity, quality of operation, noise performance, and applicability are compared among the variant arctangent approaches and the DCM approach. The variant arctangent approaches and the DCM approach will be influenced by differently factors, such as, the intensity of the light source, the shift of visibility of the interference fringes due to the change of the state of polarization in fiber, the phase delay. The dependence on these influences of these approaches is analyzed in detail. Their
    01/2006;