Mingshun Jiang

Novel FBG vibration sensor based on matching filter demodulation

A novel fiber Bragg grating (FBG) vibration sensor is designed based on optical fiber sensing technology. The principle of vibration detection using optical fiber Bragg grating is analyzed. At the same time, both the theories of matching grating demodulation technology and optical fiber grating tuning technology based on constant strength cantilever are adopted. As a result, the sensitivity of sensor and the stability of the detecting signal are all improved by employing additionally electromagnetic damping. Good results are obtained from vibration detecting experiments using vibrator standard signal, then Fourier analysis is applied. Frequency detection ability of the vibration sensor is favorable. The frequency detection precision is ± 0.5 Hz, and frequency measuring scope is up to 200 Hz. In addition, the detecting signal has high signal to noise ratio. From shock vibration experiment, it can be seen that free vibration frequency of the sensor is about 250 Hz. Above all, the vibration sensor has extensive application prospects in practical engineering.

Development of Distributed Temperature Sensor Based on Single-mode Fiber

The distributed optical fiber temperature measurement system (DTS) is a kind of sensing system, which is applied to the real-time measurement of the temperature field in space. It is widely used in monitoring of production process: fire alarm of coal mine and fuel depots, heat detection and temperature monitor of underground cable, seepage and leakage of dam. Through analyzing temperature effect of optical fiber Raman backscattering theoretically, a distributed temperature sensor based on single-mode fiber was designed, which overcame the inadequacies of multimode fiber. The narrow pulse width laser, excellent InGaAS PIN, low noise precision difet operational amplifier and high speed data acquisition card in order to improve the stability of this system were selected. The demodulation method based on ratio of Anti-Stokes and Stokes Raman backscattering intensity was adopted. Both hardware composition and software implementation of the system were introduced in detail. It is proved that its distinguishing ability of temperature and space are 1 m and 2 m, respectively. The system response time is about 180 s, with a sensing range of 5 km and the temperature measurement range 0~100 °C.

Tunable chirped fiber Bragg grating based on two-fixed-end compressive bar without central wavelength shift

A novel method of tuning chirped fiber Bragg gratings (CFBGs) without a center wavelength shift is proposed. The designed structure can flexibly control the chirp ratio of the CFBG. The proposed tuning technique has potential applications in the optical communication and fiber sensor field.

Study of chirped fiber Bragg gratings apodized with different apodization length ratios

Symmetrical apodization technique of the chirped fiber Bragg grating has the advantages of suppressing the sidelobes of reflection spectra and smoothing the curves of group delay. However, it shortens the bandwidth of the reflection spectrum markedly. Compared with symmetrical apodization method, the asymmetric method can increase the 3dB bandwidth by 64.08% without the change of group delay curves. The apodization simulation is implemented by using a rised cosine function with different apodization length ratios at both ends of the grating. There is a compromise between the bandwidth and the group delay ripple. The result shows that the grating with 30% apodization at the long wavelength end and 20% apodization at the short wavelength side can improve the reflection bandwidth effectively and depress the group delay ripple within the range of ±2 ps.

Design of a multi-channel mechanically induced long period fiber gratings module

A multi-channel tunable mechanically induced long-period fiber gratings (LPFGs) scheme is presented, which can induce several LPFGs with different resonance wavelengths simultaneously. LPFGs spectra characteristics are simulated to find the influence of these parameters such as grating length, tilt angle and the pressure on the fiber. The simulation results show that the transmission loss peak mainly depends on both the grating length and the pressure, while tilt angle factor dominates the resonant wavelength. The infuence of the pressure and tilt angles on the transmission spectra is experimentally studied. This multi-channel LPFGs module will have great potential applications in the fiber sensing field and flexible filter design region.