High-resolution DPP-BOTDA over 50 km LEAF using return-to-zero coded pulses

Coded optical probe pulses in return-to-zero/non-return-to-zero (RZ/NRZ) formats are used for long-range distance sensing based on a differential pulse-width pair Brillouin optical time-domain analysis (DPPBOTDA) in order to enhance the spatial resolution and measurement accuracy. It is found that using the RZ format maintains the Brillouin spectral shape, enhances the sensing range and leads to a higher signal-tonoise ratio compared to a single-pulse Brillouin optical time-domain analysis. With 512 bit RZ-coded pulse pairs of 60/55 ns for the DPP-BOTDA, a spatial resolution of similar to 0.5 m and a strain resolution of 12 mu epsilon (which is equivalent to a 0.7 MHz Brillouin frequency shift) have been achieved over a 50 km large effective area fiber. (C) 2010 Optical Society of America