Fiber Bragg gratings (FBGs) have become a promising sensor element for measuring temperature, strain and other parameters. However, there exists a cross-sensitivity between temperature and strain. An all-fiber sensing system composed of gold-plated FBGs and acrylic FBGs has been proposed and fabricated, which can achieve simultaneous measurement of axial strain and temperature. Using a spectrometer to monitor the shift in the transmission spectrum in real time, the strain and ambient temperature applied to the sensor can be measured conveniently. The experimental results show that the temperature sensitivity of a gold-plated FBG is 3.2 times of that of an acrylate-plated FBG, which can distinguish the temperature changes efficiently. In other words, its sensitivity is increased 2.2 times compared with ordinary fiber grating. The strain sensitivity of gold-plated FBG and acrylate-plated FBG is the same, which is 1.19 pm/µ ε . The sensor has the advantages of having a simple structure and high sensitivity and can be used to monitor the running state of rail traffic.

The fiber Bragg grating vibration sensor has received a lot of attention due to its unique performance. However, the natural frequency of the sensor limits its development and application. This paper presents an acceleration sensor with an isosceles triangular cantilever and mass block structure, which has high natural frequency and high sensitivity. The optical fiber sensing system consists of two fiber gratings. One section of the fiber grating is pasted on the cantilever and serves as an accelerometer; the other is used as a reference grating. The first-order natural frequency of the accelerometer is 8356 Hz, and its sensitivity is 0.46 pm g ⁻¹ . A vibration test confirms the reliability of the sensor, and the resonant frequency of the sensor is 8193 Hz. The principle of light intensity demodulation is adopted in the sensor system and its sensitivity is 45.82 mV g ⁻¹ with a linearity of 0.997. The sensor has the advantages of high frequency and sensitivity, and thus can be applied to the rail transit bearing systems

Fiber Bragg grating (FBG) acceleration sensor is an important branch of FBG application and has irreplaceable advantages compared with an electronic accelerometer. An FBG acceleration sensor with high sensitivity and high natural frequency is designed. This sensor adopts a double cantilever structure to sense the vibration perpendicular to the axis. Compared with a single cantilever structure, the natural frequency is increased without reducing the sensing length. Through the above structure design and material selection, the sensor shows a high natural frequency of 8658 Hz and its sensitivity is 0.44 pm/g. After the photoelectric demodulation is used, the sensitivity is 52 mV/g and the linearity is 0.998. Through the experiment and simulation analysis, the sensor performs good anti-interference in the transverse direction and temperature compensation in the process of vibration measurement. The system is very small due to the use of light intensity demodulation technology, which is conducive to application and integration in actual measurement scenarios.

Environmental monitoring plays an important role in the preventive protection of ancient buildings, although it is still in the prototype stage. In order to provide data support for the protection of ancient buildings, an environmental monitoring system with multi-sensor and multi-node for the interior and exterior of ancient buildings is designed and realized, based on ZigBee, TCP/IP, and intranet penetration technology. The new type of indoor node package box and outdoor package device are designed to meet the needs of different types of sensors. The monitoring platform is developed on the strength of the LabView so as to obtain real-time display, storage, and over-limit warning functions for local and remote monitoring data. It also proves that the monitoring system is stable and reliable by monitoring the actual ancient building with a brick (stone) structure.