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To solve the problem of near-field measurement of aeroengines a novel large-range high-precision Fabry–Perot interferometer (FPI) is developed, which is verified by a high-temperature experiment. Based on the principle of FPI wavelength drift and frequency spectrum drift, a double-beam-interference FPI is designed. Through an analysis of the optical path difference between the two beams, the conclusion that the spectrum drifts to the long-wave direction with the increase of temperature is obtained. Moreover, through frequency spectrum analysis, the measurement error caused by the distortion of the spectrum is avoided, and it is found that the increase in temperature will cause the change in frequency spectrum. The temperature sensitivity of the glass-type FPI is only 0.0011 nm °C−1. A ceramic material with a higher thermal expansion coefficient is selected as the collimating tube to make the sensitivity of the temperature sensor as high as 0.691 nm °C−1 from normal temperature to 100 °C. To meet the needs of a wide range of measurements from room temperature to 1000 °C the frequency drift method is utilized. A field experiment is carried out on the ceramic FPI at the tail spray of the aeroengine simulation platform. The temperature response test from normal temperature to 1000 °C is completed, and the accuracy of the sensor reached 0.043%. In this study, the principle, design, production, and testing of optical fiber sensors are carried out. The developed optical fiber sensor has significance for high temperature monitoring.

A single-beam spin-exchange relaxation-free (SERF) atomic magnetometer can extract vector magnetic field information by detecting the transmission intensity of a resonant circularly polarized pumping beam, which depends sensitively on the atomic density of the alkali metal. We present a novel scheme to determine atomic density based on zero-field magnetic resonance. The resonance linewidth under different transverse DC magnetic fields is fitted by means of a quadratic function. The atomic density can be extracted from the quadratic coefficients of the fitted function. The experimental results indicate that the deviation of measured density is less than two times compared with the theoretical values between 378 K and 403 K. Furthermore, the influence of modulation field on resonance linewidth is investigated experimentally and theoretically. A miniature single-beam SERF atomic magnetometer with a sensor head volume of only 16.2 cm3 and the measuring sensitivity of 40 fT/ Hz1/2 has been achieved. These results should be beneficial for guiding the development of a chip-scale atomic magnetometer with high sensitivity and spatial resolution for bio-magnetic field imaging applications.

In this paper, a novel optical fiber surface plasmon resonance (SPR) magnetic field sensor is proposed and experimentally demonstrated. The structure is fabricated by splicing a section of photonic crystal fiber between two multimode fibers. After the structure is coated with 10 nm Cr and 50 nm Au, the high refractive index (RI) sensitivity, from 1973.72 nm RIU−1 to 3223.32 nm RIU−1 in the range of 1.3326–1.3680, verifies the SPR sensor, which is higher than the structure based on single mode fiber with the same coating. In addition, the microscopic mechanism of the tunable characteristics of magnetic fluid RI with the ambient magnetic field is simulated by the molecular dynamics method. To measure the external magnetic field, the sensing region of the SPR sensor is fully inserted in a capillary tube, which is filled with magnetic fluid and sealed with UV glue. A maximum sensitivity of 4.42 nm mT−1 is achieved in the range of 0–24 mT, experimentally. Due to high sensitivity, simple manufacturing and compact size, the proposed sensor possesses attractive application prospects in environmental monitoring, power transmission and biomedical applications.

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 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/µe. 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.