Long Variable Delay and Distributed Sensing Using Stationary and Localized Brillouin Dynamic Gratings

Abstract

Stationary and localized Brillouin dynamic gratings are generated using phase modulation of both pump waves by a pseudo-random bit sequence. The gratings are applied to long variable delay of pulses and to cm-level distributed sensing.

Brillouin Scattering in Optical Fibers and Its Application to Distributed Sensors

“…Up to date, the BDG in a PMF has been used for many applications in microwave photonics, all-optical signal processing, and Brillouin-based distributed sensors. For example, the BDG programmed in position or spectrum is very useful in microwave photonics of tunable optical delays [98,[104][105][106] or programmable microwave photonic filter [107]. Besides, it can also find significant applications in all-optical signal processing such as storing and compressing light [108], ultrawideband communications [109], and all-optical digital signal processing [110].…”

Brillouin distributed sensing using localized and stationary dynamic gratings

“…The correlation peaks, with the exception of the zeroth-order one, can be scanned across a fiber under test through changing the code length factor M or the symbol duration T. Since there is no frequency modulation of the pumps the spatial period of the acoustic grating does not oscillate, and the subsequent readout of the acoustic grating by a ŷ polarized interrogating wave becomes considerably simpler than in B-OCDA over PM fibers 25 . Figure 1 illustrates the experimental setup that was used for the generation and characterization of dynamic acoustic gratings, driven by random phase modulation of both pump waves [35][36][37][38] . A single distributed feed-back (DFB) laser diode of frequency 1 ω was used to generate both pump waves.…”

“…In this work, we apply a novel, recently proposed method for the generation of stationary and localized dynamic gratings [34][35][36][37][38] to 5 cm-scale distributed temperature sensing over polarization maintaining fibers. The method relies on the phase modulation of the two pump waves by a common pseudo-random bit sequence (PRBS), with a symbol duration T that is much shorter than τ.…”

“…The separation between neighboring correlation peaks, however, is governed by the length of the PRBS, and it is uncorrelated with the length of the localized gratings. We have previously employed this method in the long variable delay of probe read-out pulses [35][36]38 , and in the generation of tunable microwave-photonic filters [36][37] . Here we report the application of the technique to high-resolution distributed sensing over polarization maintaining fiber, in larger detail.…”

All-optical storage and processing in optical fibers

“…Since reflecting gratings are created at any position along the fiber, a signal pulse can be also reflected at different points, thus showing a delay due to the time-offlight for the back-reflected signals [3,10,11]. Since the acoustic grating can only be built up where the SBS interaction between the two pump pulses takes place, it can be flexibly created at any preset position over the entire length of the HiBi fiber, simply by retiming Pump 1 pulse.…”