Spectral Analysis of Brillouin Dynamic Grating Based on Heterodyne Detection

Abstract

Spectral analysis based on heterodyne detection is used to investigate Brillouin dynamic grating (BDG) in a small-core polarization-maintaining optical fiber. Thanks to direct heterodyning of the readout and diffraction waves, essential BDG properties can be fully investigated. It is experimentally characterized that the BDG diffraction wave has an identical frequency downshift from the readout wave as the pump–probe frequency offset in the BDG generation, which straightforwardly verifies the theoretical estimation of the BDG's phase-matching condition for the first time to our best knowledge. The spectral analysis also confirms that the maximum power of the main peak changes in the same way with the stimulated Brillouin gain and has an exponential (linear) dependence on the pump (probe) power.

Generation of dynamic Brillouin grating in polarization maintaining fiber

“…This approach permits to set the frequency of the probe with a 1 kHz resolution. The beam reflected by the DFB is beats with the signal generated by the DFB, downshifted by 40MHz by the acousto-optic modulator (AOM), which is then the local oscillator of a heterodyne detection system [12]. The careful selection of the modulation frequencies enables to obtain a beat note at a relatively low frequency which is measured by the electrical spectrum analyzer (ESA).…”

Brillouin Dynamic Gratings—A Practical Form of Brillouin Enhanced Four Wave Mixing in Waveguides: The First Decade and Beyond

“…Coherent detection, while more complex and expensive to implement, has proven instrumental in boosting the performance of BDG-based reflectometry [ 23 ], that otherwise requires time-consuming trace-averaging, which hinders its measurement speed. The low reflectivity of BDGs can also be partially mitigated by heterodyne detection [ 97 , 98 ].…”

Brillouin Scattering in Optical Fibers and Its Application to Distributed Sensors

“…Most recently, a heterodyne detection was demonstrated to straightforwardly characterize the physical BDG property in a high-delta PMF [96]. Figure 15(a) summarizes a 3D distribution of the heterodyne-detected electronic spectra between the BDG reflection and the readout wave while scanning the pump-probe frequency offset (ν 1 or f 1 -f 1 ') around the BFS of 10.510 GHz.…”

“…(After Ref. [96]; © 2013 JJAP.) pump-probe-based SBS process is well known to be changed when f 1 -f 1 ' is swept [12], which is herein reflected by the measured power dependence [see Fig.…”