We demonstrate the distributed measurement of Brillouin dynamic grating spectra in a polarization-maintaining fiber based on time-domain analysis. Local reflection spectra of the Brillouin dynamic grating are acquired by synchronized propagation of the pump and the probe pulses based on the map of the Brillouin frequency distribution. Large temperature sensitivity as high as -50.9 MHz/ degrees C is observed with 2 m spatial resolution in 100 m range.
"The shaping of the optical spectrum of the probe pulse was carried out by controlling the width and the amplitude of the RF pulse, and Fig. 4(b) shows the best obtained spectrum used for the measurement, showing a 3-dB bandwidth of 7 GHz. It should be pointed out that this bandwidth corresponds to the coverage of a C temperature range according to the temperature sensitivity of the BDG spectrum . The reflected signal from the BDG was extracted using a PM circulator and spectrally cleaned up by a tunable grating filter, before being pre-amplified by another EDFA prior to the detection by a 12 GHz photo diode (PD1) and the fast data acquisition (DAQ). "
[Show abstract][Hide abstract] ABSTRACT: We demonstrate an optical time-domain distributed fiber sensor showing the highest spatial resolution ever reported based on Brillouin dynamic grating in a polarization-maintaining fiber. In our scheme, the acoustic gratings containing the information on the local Brillouin frequency are generated by a long pump pulse in one polarization, and read out by a short probe pulse in the orthogonal polarization at a clearly distinct optical frequency from the pump. In the experiment, distributed temperature measurements over a 20 m fiber are performed with 1.2 cm spatial resolution.
[Show abstract][Hide abstract] ABSTRACT: We propose a true distributed birefringence measurement of polarization-maintaining fiber based on transient Brillouin grating. A birefringence variation of 2.5 �? 10-6 along 8 m Bow-tie fiber is measured with 20 cm spatial resolution.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate a time-domain distributed temperature sensing based on birefringence effect on transient Brillouin grating (TBG) in a polarization-maintaining photonic crystal fiber (PM-PCF), which uses two short pump pulses (2 ns) to excite a TBG and a long probe pulse (6 ns) to map the transient Brillouin grating spectrum (TBGS) associated with the birefringence. The 2 ns pump pulses defines a spatial resolution of 20 cm and a temperature measurement range of a few hundred degrees Celsius, and the long probe pulse provides a narrow TBGS with a temperature resolution of 0.07 degrees C.
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