Guiling Huang

Temperature-insensitive fiber Bragg grating liquid-level sensor based on bending cantilever beam

A temperature insensitive fiber Bragg grating (FBG) liquid level sensor based on bending cantilever beam (BCB) is proposed and demonstrated. The BCB induces axial strain gradient along the sensing FBG, resulting in a Bragg bandwidth modulation. The broadening of FBG spectrum bandwidth and the reflection optical power change with the liquid level and they are insensitive to spatially uniform temperature variations. For a liquid level variation of 500 mm and a temperature range from 0/spl deg/C to 80/spl deg/C, the measured liquid level fluctuates less than 2% without any temperature compensation. By optical power detection via a pin photodiode, the liquid-level sensor avoids complex demodulation process and potentially costs low.

Temperature-insensitive fiber Bragg grating dynamic pressure sensing system

Temperature-insensitive dynamic pressure measurement using a single fiber Bragg grating (FBG) based on reflection spectrum bandwidth modulation and optical power detection is proposed. A specifically designed double-hole cantilever beam is used to provide a pressure-induced axial strain gradient along the sensing FBG and is also used to modulate the reflection bandwidth of the grating. The bandwidth modulation is immune to spatially uniform temperature effects, and the pressure can be unambiguously determined by measuring the reflected optical power, avoiding the complex wavelength interrogation system. The system acquisition time is up to 85 Hz for dynamic pressure measurement, and the thermal fluctuation is kept less than 1.2% full-scale for a temperature range of -10 degrees C to 80 degrees C.

Simultaneous measurement of stress and temperature with a fiber Bragg grating based on a loop thin-wall section beam.

We designed and demonstrated what we believe to be a novel sensor for simultaneous measurement of stress and temperature. A fiber Bragg grating is flatly adhered to the surface of a loop thin-wall section beam. The theoretical analyses and the experimental results show that both the central wavelength shift and the chirped bandwidth of the grating reflection spectrum have a linear relationship with the stress and the temperature, respectively, and the slopes of them are different. Therefore, the temperature and stress can be discriminated by interrogating the chirped fiber grating. Moreover, we also investigated the strain of the loop thin-wall section beam, and the results show that the strain is cosine proportional to the double positional angle.

Force sensing with temperature self-compensated based on a loop thin-wall section beam

A novel method about force sensing with temperature self-compensated based on a loop thin-wall section beam is proposed and demonstrated. Two identical fiber Bragg gratings are rigidly affixed on the outer surface of the beam with the positional angle difference between the two gratings of 90/spl deg/. The wavelength space between the two reflected peaks of the gratings is proportional to the force and insensitive to temperature when the direction of the force and one of the two gratings are located along a diameter; therefore, the force sensing with temperature self-compensated can be achieved.

Tunable Chirped Fiber Bragg Grating Filter Based on Special Strain Function Modulation and Its Application in Fiber Sensor

A novel technique for chirp control of a uniform fiber Bragg grating (FBG) based on the special strain function modulation is presented. A cylinder taper cantilever beam (CTCB) is specially designed and capable of providing special position-dependent strain function gradients along an originally uniform FBG, which allows tunable quasi-triangular and quasi-Gauss-gradient FBG filter. Furthermore, the feasibility of the tunable chirped FBG based on the strain function modulation as sensor is validated. This state-of-art technique is expected to be applied in fiber filter, FBG sensor and multiwavelength fiber laser.

A novel method for independent tuning of the center wavelength and the bandwidth of fiber Bragg grating

A novel method for independent tuning of the center wavelength and the bandwidth of a fiber Bragg grating (FBG) was proposed and demonstrated. An FBG was adhered to the outer surface of a loop thin-wall section beam. The center wavelength and the bandwidth of the FBG can be tuned independently through changing the force while the fiber grating locates at different special positions. Quasi-chirp-free wavelength tuning with 6.706 nm and bandwidth tuning with 5.368 nm under quasi-shift-free center wavelength were obtained experimentally. The experimental results are in good agreement with the theoretical analyses.

Temperature-independent fiber Bragg grating micro-displacement sensor

Temperature-independent micro-displacement measurement using a single fiber Bragg grating based on broadened reflection spectrum is proposed and experimentally demonstrated. The structure of specially designed bending cantilever beam (BCB) is proposed. The BCB induces axial strain gradient along the sensing FBG, resulting in a Bragg bandwidth modulation. The broadening of FBG spectrum bandwidth and the reflected optical power correspond to micro-displacement changes, insensitive to spatially uniform temperature variations. For a displacement variation of 20mm and a temperature change from 20°C to 100°C, the micro-displacement measurement deviation error is ±0.12mm without any temperature compensation. Through optical power detecting by a pin photodiode (PD), the micro-displacement sensor avoids complex demodulation process and potentially costs little.

Synthesis of fiber Bragg grating parameters from reflectivity with probabilistic global search Lausanne

A simple and accurate new method for synthesis of fiber gratings with advanced characteristics is proposed. By combining a new direct stochastic algorithm for global search called probabilistic global search Lausanne (PGSL) and transfer matrix method, we obtain a promising method synthesizing the physical parameters of a fiber Bragg grating (FBG) structure from its reflectivity. The method can be applied over uniform and nonuniform FBGs, and would be useful for other inverse problems. To demonstrate the effectiveness of the method, the synthesis of a fiber Bragg grating with triangular spectrum is presented.

A novel high-birefringence fiber loop mirror electric current sensor

A novel electric current sensor based on a high-birefringence fiber loop mirror(HBFLM) and a kind of magnetostrictive material rod(MMR) is demonstrated theoretically and experimentally. Part of the high-birefringence fiber(HBF) is pasted onto the MMR which is placed in the central part of a solenoid. The HBFLM is used as the sensor head and the linear filter simultaneously. Part of the high-birefringence fiber(HBF) is pasted onto the MMR which is placed in the central part of a solenoid. The rod will have elastic lengthening along the direction of the magnetic field when the uniform magnetic field changes, which will lead to a change of transmission intensity of the HBFLM filter, thus the variation of the electric current can be determined via the laser wavelength within the quasi-linear transmission range of the HBFLM filter. The sensitivity reaches 0.0153/100mA, the resolution reaches 10mA. Comparing with the previous fiber-optic electric current sensor, it has nothing with the linear birefringence based on Faraday effects in the previous fiber-optic electric current sensor. Comparing with the expensive and complex FBG electric current, the sensing signal can be directly detected by a photodiode(PD) and complicated demodulation devices are avoidable. The advantages of the electric current include optical power detection, simple and smart structure, high sensitivity, low cost, and good repeatability, etc.

Temperature-independent fiber Bragg grating liquid-level sensor based on reflection optical power detection

Design and construction of temperature-insensitive fiber Bragg grating (FBG) liquid level sensor based on bending cantilever beam (BCB) is proposed and demonstrated. The BCB induces spatially gradient strain on the unique sensing FBG, resulting in a Bragg bandwidth modulation. The broadening of FBG spectrum bandwidth and the reflected optical power are corresponded to liquid level changes, insensitive to spatially uniform temperature variations. In the liquid-level range of 500 mm and temperature change from 20oC to 80oC, the liquid level measurement fluctuates less than 2% without any temperature compensation. By a pin-photodiode (PD) optical power detecting, the liquid-level sensor avoids expensive and complex demodulation techniques and potentially costs low.