Kisała Piotr, Cięszczyk Sławomir
Appl Opt. 2015 Apr 1;54(10):2677-87. doi: 10.1364/AO.54.002677.
This paper presents a method for measuring two components of bending force and temperature using one sensor head. Indirect inference based on the spectra of two fiber Bragg gratings (FBGs) placed on a cantilever beam is used. The method was developed during work on the inverse problem of determining a nonuniform stress distribution based on FBG spectra. A gradient in the FBG stress profile results in a characteristic shape of its reflective spectrum. The simultaneous measurements of force and temperature were possible through the use of an appropriate layout of the sensor head. The spectral characteristics of the sensor's gratings do not retain full symmetry, which is due to the geometry of the sensor's head and the related difference in the distribution of the axial stress of the gratings. In the proposed approach, the change in width of the sum of the normalized transmission spectra was used to determine the value of the applied force. In the presented method, an increase in the sensitivity of this change to the force is obtained relative to the other known systems. A change in the spectral width was observed for an increase in bending forces from 0 to 150 N. The sensitivity coefficient of the spectral width to force, defined as the ratio of the change of the spectral half-width to the change in force was 2.6e-3 nm/N for the first grating and 1.2e-3 nm/N for the second grating. However, the sensitivity of the whole sensor system was 5.8e-3 nm/N, which is greater than the sum of the sensitivities of the individual gratings. For the purpose of this work, a station with a thermal chamber has been designed with a bracket on which fiber optic transducers have been mounted for use in further measurements. The sensor head in this experiment is considered to be a universal device with potential applications in other types of optical sensors, and it can be treated as a module for development through its multiplication on a single optical fiber.
本文提出了一种使用单个传感头测量弯曲力和温度两个分量的方法。该方法基于放置在悬臂梁上的两个光纤布拉格光栅（FBG）的光谱进行间接推断。此方法是在基于FBG光谱确定非均匀应力分布的反问题研究过程中开发的。FBG应力分布中的梯度会导致其反射光谱呈现出特征形状。通过采用传感头的适当布局，可以同时测量力和温度。传感器光栅的光谱特性并不完全保持对称，这是由于传感头的几何形状以及光栅轴向应力分布的相关差异所致。在所提出的方法中，利用归一化透射光谱总和的宽度变化来确定所施加力的值。与其他已知系统相比，在本方法中，这种变化对力的灵敏度有所提高。当弯曲力从0增加到150 N时，观察到光谱宽度发生了变化。光谱宽度对力的灵敏度系数，定义为光谱半高宽变化与力变化的比值，对于第一个光栅为2.6e - 3 nm/N，对于第二个光栅为1.2e - 3 nm/N。然而，整个传感器系统的灵敏度为5.8e - 3 nm/N，大于各个光栅灵敏度之和。为了开展这项工作，设计了一个带有热室的实验站，该实验站带有一个支架，光纤传感器安装在该支架上以供进一步测量使用。本实验中的传感头被认为是一种通用设备，在其他类型的光学传感器中具有潜在应用，并且通过在单根光纤上进行复用，它可以被视为一个用于开发的模块。
