A FBG sensor multiplexing system based on the combination of wavelength- and time- division multiplexing technique is proposed. In this paper, A semiconductor optical amplifier (SOA) connected
in a ring cavity is used to serve as a gain medium and switch. The sensor array is consisted of four groups of sensors and the nominal wavelength of the sensors in the same group is different. The SOA is
driven by a pulse generator which switch on the SOA at different periods, as a switch to select the reflected pulses from a particular group. Using low reflectivity (3%~5%) sensors the number of the groups can achieved 50, the bandwidth of each group used in this system is 40 nm (1525-1565nm), the system permits the interrogation of up to 1000 FBG sensors. With this technique, the FBG sensors system avoid using optical switch to expand channels, it improved the response speed and reduced cost in the application of structural health monitoring where large numbers of sensors are required.
The measurement of pressure is essential for the design and flying controlling of aircraft. In order to measure the surface
pressures of the aircraft, the common pressure tube method and Pressure sensitive paint measurement method have their
own disadvantages, and are not applicable to all aircraft structures and real time pressure monitoring. In this paper, a
novel thin film pressure sensor based on Fiber Bragg Grating (FBG) is proposed, using FBG measuring the tangential
strain of the disk sensing film. Theoretical circle strain of the disk sensing film of the pressure sensor under pressure and
temperature variation are analyzed, and the linear relationship between FBG center wavelength shift and pressure,
temperature variation is gotten. The pressure and temperature calibration experiments prove the theoretical analysis. But
the calibration sensing parameters are small than the calculating ones, which is caused by the constraint of optical fibre
to the thin sensing film.
A systematic method of tunable dispersion compensation based on chirped fiber Bragg gratings (CFBGs) using
electroactive polymer (EAP) as drive device will be proposed. The EAP offer attractive properties of energy transduction
from the electrical to the mechanical form for actuator with high active stresses (up to order of 1MPa), low response
times, high reliability, high stability and low costs. The special tune device is consisted of a straight beam and two EAP
actuators, the CFBG is surface-mounted on one side of the beam. The midpoint of the grating is consistent with the
center of the beam. When the EAP is imposed on voltage, the specially designed mechanical device can control the
chirping ratio along the fiber gratings and consequently the group delay. The group delay can be linearly controllable
since the device induce the linear strain gradient with the input voltage. The dispersion value can be effectively
controlled in corresponding to the input voltage. The resonant wavelength shift of CFBG is less than 0.05 nm over the
dispersion tuning range.
A novel fiber Bragg grating (FBG) sensor system for Structure Health Monitoring (SHM) is proposed
in this paper. The proposed sensor technique is based on time division multiplexing (TDM). This
technique utilizes semiconductor optical amplifier (SOA) as a gain medium and switch. The SOA is
driven by a pulse generator which switch on the SOA at different periods, as a switch to select the
reflected pulses from a particular sensor. The FBG sensors have identical center wavelengths and can
be deployed along the same fiber. This technique relieves the spectral bandwidth issue and permits the
interrogation of up to 100 FBGs along a fiber. The sensor system has a fast signal process and control
unit, which have a typical scan frequency in 50 Hz and self-adaptive measurement for simple sensor
array installation.
A novel fiber Bragg grating (FBG) sensor system for measurement of strain and temperature is proposed in this paper.
The proposed sensor technique is based on time division multiplexing (TDM). A semiconductor optical amplifier (SOA)
connected in a ring cavity is used to serve as a gain medium and switch. The SOA is driven by a pulse generator which
switch on the SOA at different periods, as a switch to select the reflected pulses from a particular sensor. The FBG
sensors have identical center wavelengths and can be deployed along the same fiber. This technique relieves the spectral
bandwidth issue and permits the interrogation of up to 100 FBGs along a fiber. The sensor system has a fast signal
process and control unit, which have a typical scan frequency in 1 kHz and self-adaptive measurement for simple sensor
array installation.
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