Phase-coded Brillouin optical correlation domain analysis with 2-mm resolution based on phase-shift keying.

We report a phase-coded Brillouin optical correlation-domain analysis (BOCDA) based on phase-shift keying (PSK), in which the pseudo-random binary sequence (PRBS) phase coding is realized using a Mach-Zehnder modulator (MZM). Unlike the conventional phase-coded BOCDA using a phase modulator, which suffers from the non-rectangular transition in the encoded phase, the PSK can realize perfect phase switches between 0 and π with zero-width edges. It is not sensitive to the bandwidth of the modulator and the power of the radio-frequency modulation signal.

[Characteristics of the preferential flow and its response to irrigation amount in oasis cropland].

Preferential flow is a physical process describing how water and solutes move aiong cer- tain pathways through soil profile. Studying the cropland preferential flow patterns and its influential factors could quantify the deep percolation, improve water and fertilizer use efficiency and reduce the risk of agrochemicals contaminating shallow groundwater in oasis cropland. The dye tracer exper- ments were carried out in field oasis cropland, using a brilliant blue FCF solution.