Refractive index sensor based on the diamond like carbon diffraction grating

In this work we present an optical refractive index (RI) sensor based on the spectral analysis of anomalies in the optical response from the diffraction grating employing polarized polychromatic light. The sensor consists of holographic diffraction grating (period 423.5 nm) coated with a thin (110 nm) SiO_x doped diamond like carbon film (DLC) that defines sensitivity of the sensor as well as the range of the spectral analysis. The deposition of the DLC film (synthesized by the direct ion beam deposition from the hydrocarbon source) has influence on the shape but not on the position of the anomalies observed in the specular reflection spectrum. From the reflection spectra the RI dispersion curve of liquid analyte-water was obtained.     

Pointwise fiber Bragg grating displacement sensor system for dynamic measurements

A method for setting up a fiber Bragg grating (FBG) sensor which can measure the pointwise, out-of-plane or in-plane dynamic displacement is proposed. The proposed FBG sensor is reusable. A multiplexing demodulation system based on a single long-period fiber grating is used in this study. The experimental results of the steady-state motion for a multilayer piezoelectric actuator and the dynamic response of a cantilever beam subjected to impact loadings are presented. These results indicate that the proposed displacement sensor has the ability to measure the out-of-plane dynamic displacement with high sensitivity. Measurements for a piezoceramic plate excited by high frequency show that the proposed displacement sensor also has the ability to provide the in-plane dynamic displacement up to 20 kHz.     

Transducing mechanical force by use of a diffraction grating sensor

A novel means of transducing mechanical force by using a polymeric-based diffractive grating sensor is presented. The diffraction gratings are successfully fabricated upon poly(dimethyl siloxane) polymer substrates by holographic interference and micromolding. A micromaterial tensile test incorporated into the surface diffraction grating experiment showed that a relationship between the load and the observed diffraction-pattern shift could be obtained. The results show an excellent correlation between the optical measurement and load, with a sensitivity of 0.05 N.     

Multimodulation displacement sensor based on a multielement photocell

Translated from Izmeritel'naya Tekhnika, No. 7, pp. 4–5, July, 1991.     

Refractometric sensor based on a phase-shifted long-period fiber grating

A refractometric sensor based on a phase-shifted long-period fiber grating written by electric-arc discharges is presented. Transmission and reflective configurations for refractive index measurements are studied. It is observed that the reflective topology permits better performance compared with the transmission one, which is the approach normally utilized in the context of long-period fiber sensing. The resolution achieved in the measurement of refractive index enables the application of this sensing head structure in demanding situations, such as the measurement of the level of salinity of water.     

Fiber Bragg grating displacement sensor for movement measurement of tendons and ligaments

Biomechanical studies often involve measurements of the strains developed in tendons or ligaments in posture or locomotion. Fiber-optic sensors present an attractive option for the measurement of strains in tendons and ligaments because of their low cost, ease of implementation, and increased accuracy compared with other implantable transducers. A new displacement sensor based on a fiber Bragg grating and shape memory alloy technology is proposed for the monitoring of tendon and ligament strains in different postures and in locomotion. After sensor calibration in the laboratory, a comparison of the fiber sensors and traditional camera displacement sensors was carried out to evaluate the performance of the fiber sensor during the application of tension to the Achilles tendon. Additional experiments were performed in cadaver knees to assess the suitability of these fiber sensors to measure ligament deformation in a variety of simulated postures. The results demonstrate that the proposed fiber Bragg grating sensor is a highly accurate, easily implantable, and minimally invasive method of measuring tendon and ligament displacement.     

基于双折射效应的光纤光栅称重方法研究

与通常的光纤光栅传感器原理不同,本文基于光纤在外界径向载荷作用下产生的双折射效应为原理,建立了一套简单的称重实验装置,并对其检测原理进行了详细的分析。实验表明,这种光纤光栅称重传感器适合大载荷情况的重量检测问题,特别适合于公路计重收费系统中对车辆载重的监测领域,其称重灵敏度可达5kg。     

光纤Bragg光栅位移和温度双参量传感实验研究

采用一种新颖的等强度梁光纤光栅（FBG）传感结构,将光纤光栅沿梁轴向粘贴在传感梁上,并确保光栅的一半粘贴在梁上,另一半则沿梁的轴向呈自由状态,通过两部分光栅对梁自由端位移和环境温度的不同响应,实现温度和位移的同时测量,测量误差不大于4％。通过多次实验验证,所得结果与理论分析相符合。     

应变、温度、位移测量光纤光栅传感器的研究

本文介绍了集成式Bragg光纤光栅(FBGI)传感器的结构及其应用该传感器测量应变、温度、位移的基本原理.利用FBGI和相干性干涉信号解调方法实现了用一个传感器同时测量三个参量.实验结果表明温度精度达±1℃,应变精度为±30u ε,位移分辨率达1nm,测量重复性好.     

基于光栅传感器的空间靶标定位技术研究

由于太空环境的特殊性,空间靶标定位相对复杂,给武器的精度评估测试增加困难。针对现有定位技术在精度和使用寿命等方面都存在不足的问题,提出一种基于光栅传感阵列的空间靶标精确定位的方法。模拟靶标受子弹冲击的全过程,并通过力学仿真分析该过程中靶标应力应变的分布情况。搭建数据采集系统,由光栅传感阵列测得靶标各个位置的应变值,通过质心算法进行解算,最终确定射击中心点的位置。经过测试分析,该方法的定位误差在±0.5%以内,可实现空间靶标的精确定位。     

Polarization-selective beam splitter based on a highly efficient simple binary diffraction grating

A polarization beam splitter (PBS) based on a giant-reflection to zero-order (GIRO) grating is presented. The GIRO grating is a simple binary diffraction grating with parameters chosen such that the excited optical modes in the grating interfere constructively and destructively at the respective interfaces. This interference results in high-zero-order reflection (>99%) with a high polarization-selective extinction ratio (+/-30 dB). The grating shows a low aspect ratio. The GIRO PBS is theoretically and experimentally shown to be an adequate PBS for use as an optical isolator in combination with a quarter-wave plate in a CO2-laser system.     

Optimal implementation of a microspectrometer based on a single flat diffraction grating

An analytical model has been developed and applied to explore the limits in the design of a highly miniaturized planar optical microspectrometer based on an imaging diffraction grating. This design tool has been validated as providing the smallest possible dimensions while maintaining acceptable spectral resolution. The resulting planar spectrometer is composed of two parallel glass plates, which contain all components of the device, including a reflective slit and an imaging diffraction grating. Fabrication is based on microelectromechanical system technology and starts with a single glass wafer; IC-compatible deposition and lithography are applied to realize the parts in aluminum, which makes the microspectrometer highly tolerant for component mismatch. The fabricated spectrometer was mounted directly on top of an image sensor and takes up a volume of only 50 mm(3). The measured spectral resolution of 6 nm (FWHM) in the 100 nm operating wavelength range (600-700 nm) is in agreement with a model calculation.     

基于FBG轴向拉力的液位测量传感器

根据光纤布喇格光栅(fiber Bragg grating,FBG)的传感原理,提出了一种基于波纹管结构的FBG液位传感器,利用补偿FBG(FBG1)与液位FBG(FBG2)具有相同的温度灵敏度进行温度补偿,将FBG2固定在波纹管内,液压产生的张力可以使波纹管的自由端产生位移,从而使固定在里面的FBG2产生轴向应变进而影响布喇格中心波长的改变.通过布喇格中心波长的改变来监测液位的变化,在40~340mm的液位变化范围内进行了实验研究.结果表明,光纤布喇格光栅中心反射波长漂移对液位呈现良好的线性关系,线性拟合度大于0.998,灵敏度为15.7pm/cm,理论测量范围可达到3m.说明通过改变波纹管的波纹数目和其他参数,可实现对传感器测量范围和灵敏度的调整,以满足各种应用场合.     

基于质心寻峰的调频连续波激光干涉位移传感器

调频连续波激光干涉技术在精密测量领域中应用广泛,针对其高精度位移解调问题,本文将质心法应用于其拍频信号的解调中,提出了一种基于质心寻峰法的相位解调算法并进行实验与分析。提出的算法在对截取的拍频信号进行平滑滤波与分峰截幅等处理基础上,通过质心坐标公式得到拍频信号的质心,质心横坐标即为峰值位置,最后通过相位鉴别算法解调出位移。在仿真中设置信噪比(SNR)为15 dB,算法的相位误差为0.016 rad,位移误差为2.04 nm。搭建调频连续波激光干涉位移测量系统进行实验验证,实验结果表明：当固定距离为44 mm时,位移随机误差标准差为2.18 nm。与常规的过零点检测法进行对比分析,结果表明该算法的测量误差降低了49%,分辨率获得了提高,具有广泛的应用前景。

     

Tunable external-cavity diode laser at 650 nm based on a transmission diffraction grating

A tunable external-cavity diode laser (ECDL) based on a transmission diffraction grating in a Littrow mount has been developed and characterized. A single-transverse-mode diode laser at 650 nm is used in an external-cavity configuration in which the transmission grating is used as a dispersive element to select the single longitudinal mode. The transmission diffraction grating is made with electron-beam lithography. A tunable true single-mode cw output power of >20 mW is obtained from the ECDL. The total wavelength tuning range is 12 nm, and the mode-hop-free continuous tunability is >20 GHz.     

Tracking control of a multilayer piezoelectric actuator using a fiber bragg grating displacement sensor system

This paper provides a fiber Bragg grating (FBG) sensor system which can measure the point-wise, out-of-plane displacement to examine the position-tracking control problem of a multilayer piezoelectric actuator (MPA). An FBG filter-based wavelength-optical intensity modulation technique is used in this study. A nominal system model is identified experimentally from the responses excited by random signals measured by an FBG displacement sensor that are simultaneously compared with those obtained from a laser Doppler vibrometer. To further investigate the sensing ability of the proposed system in a feedback control problem, control strategies including robust Hα control, proportional-integralderivative control, and pseudoderivative feedback control are implemented. The characteristics of the step responses for each controller are examined. The experimental results show that the proposed sensor system is capable of performing the system identification and can serve as a feedback control sensor which has a displacement sensitivity of 5 mV/nm.     

Multi-measurement scheme for a fiber-optic sensor based on a single long-period grating

In this paper, we present and discuss a scheme to perform simultaneous measurement of multi-perturbations using a single Long-Period Grating (LPG). It was shown that different spectral shifts in the resonant bands of the transmitted spectrum of an LPG sensor can be used for measuring concurrent perturbations. The functioning mechanism of this multi-parameter sensing scheme is discussed and used to perform simultaneous sensing of temperature, mechanical strain and refractive index variations.     

Wavefront sensor based on the Talbot effect with the precorrected holographic grating

A holographic wavefront sensor based on the Talbot effect is proposed. Optical wavefronts are measured by sampling the light amplitude distribution with a two-dimensional (2D) precorrected holographic grating. The factors that allow changing an angular measurement range and a spatial resolution of the sensor are discussed. A comparative analysis with the Shack-Hartmann sensor is illustrated with some experimental results.