Distributed Fiber Sensors Based On Stimulated Brillouin Scattering With Centimeter Spatial Resolution

We propose a different pulse pair Brillouin optical time domain analysis (DPP-BOTDR) for centimeter or sub-centimeter spatial resolution using meter equivalent pulses. It is based on a pair of different pulses with small pulse width difference (much smaller than each of the pulse width). The process is analogous to the high pass filter which amplifies short stress section and provides high spatial resolution for the distributed Brillouin sensor using the large pulses (tens of nanoseconds) and extinction ratio of more than 30dB. This new approach achieves the centimeter spatial resolution over fiber length of kilometers with low pump and probe power. Using a pair of 50ns and 48ns pulses we achieve the spatial resolution of 2ns equivalent spatial resolution for two stress section of 50cm and separated by 1m fiber over 1km sensing length. The strain resolution is equivalent to 2.6MHz Brillouin frequency shift. The spatial resolution is determined by the convolution of the bandwidth of the detection system and pulse width difference. The signal to noise ratio of the sensor difference is also related to the pulse width difference.