We designed and manufactured all optical fiber CTD to monitor ocean based on the sensitive characteristics about
optical fiber grating. A series of works have done, including the calibration work for sensor in laboratory, simulated
experiment outside and the local test of ocean parameter. The results we got show that the precision of temperature is
0.01℃ and of pressure is better than 0.1%, both of them overtake the secondary standard of GB/T23246-2009, moreover,
close to the primary standard, and of salinity in laboratory has reached 708 pm/1% closely to the secondary standard. It is
satisfied with the ocean monitoring requirements.
A new fiber Bragg grating (FBG) based accelerometer is developed for monitoring seismic activities induced by moving
vehicles. A theoretical model of the sensor is established, and analytical formulas of describing the sensitivity and
resonant frequency are provided. Sensors of this type are fabricated and tested. The experimental results show that they
have a sensitivity of 162.8 pm/G and a resonant frequency of 242.9Hz. The minimum detectable signal of the whole
sensing system is about 12.1 &mgr;g. A field test is carried out to find out that for tracked vehicles' monitoring, a single sensor
has a detection range of about 300 meters, indicating a promising future in practical use.
This paper describes a high-performance multiplexed vibration sensor system using fiber lasers. A serial vibration sensor
array consists of four short cavity fiber lasers. The system employs a single, polarization-insensitive, unbalanced
Michelson interferometer to translate individual laser wavelength shifts induced by vibration signals into interferometer
phase shifts. A dense wavelength division demultiplexor (DWDM) with high channel isolation is inserted to demultiplex
each laser signal as a wavelength filter. Finally, a digital phase demodulator based on the phase generated carrier
technique is used to achieve high-resolution interrogation. Experimental results show that no observable crosstalk is
measured on the output channels, and the minimal detectable acceleration of this system is ~200ng/&sqrt;Hz at 250Hz, which
is fundamentally limited by the frequency noise of the lasers.