Analysis of optical pulse coding in spontaneous Brillouin-based distributed temperature sensors

Abstract

Abstract:A theoretical and experimental analysis of optical pulse coding techniques applied to distributed optical fiber temperature sensors based on spontaneous Brillouin scattering using the Landau-Placzek ratio (LPR) scheme is presented, quantifying in particular the impact of Simplex coding on stimulated Brillouin and Raman power thresholds. The signal-to-noise ratio (SNR) enhancement and temperature resolution improvement provided by coding are also characterized. Experimental results confirm that, differently from Raman-based sensors, pulse coding affects the stimulated Brillouin threshold, resulting in lower optimal input power levels; these features allow one to achieve high sensing performance avoiding the use of high peak power pulses.

Distributed optical fibre sensors based on spontaneous Brillouin scattering employing multimode Fabry-Pérot lasers

“…We show that with such multimode lasers we can increase the maximum input power threshold value before the onset of fibre nonlinearities, enhancing the sensor performance. In addition, this technique can be efficiently combined with the use of optical pulse coding techniques for further performance enhancement [3].In SpBS-based sensors the SpBS intensity (DP B ) and BFS (Dv B ) are both linearly dependent on strain and temperature; this makes the simultaneous strain (D1) and temperature (DT ) sensing along a single optical fibre possible by using the following matrix relation: …”

“…We show that with such multimode lasers we can increase the maximum input power threshold value before the onset of fibre nonlinearities, enhancing the sensor performance. In addition, this technique can be efficiently combined with the use of optical pulse coding techniques for further performance enhancement [3].…”

“…The performance of SpBS-based sensors is essentially limited by the onset of nonlinear optical effects, most notably SBS, which imposes the maximum peak power allowed at fibre input. We have shown that optical pulse coding can be effectively used in SpBS-based sensors allowing for a sensing performance enhancement [3], although reducing the SBS threshold depending on the code length.…”

Simultaneous distributed strain and temperature sensing based on combined Raman–Brillouin scattering using Fabry–Perot lasers

“…Finally, it has been recently demonstrated that optical pulse coding techniques provide enhanced SNR in both SpBS-based [7] and SpRS-based [5] sensors, allowing for significantly improved sensing performance. However, the use of coding is limited in SpBS-based sensors by the SBS threshold, which constrains the maximum optical power at the fiber input [7].…”

“…Finally, it has been recently demonstrated that optical pulse coding techniques provide enhanced SNR in both SpBS-based [7] and SpRS-based [5] sensors, allowing for significantly improved sensing performance. However, the use of coding is limited in SpBS-based sensors by the SBS threshold, which constrains the maximum optical power at the fiber input [7]. In the proposed scheme employing FP lasers this limitation can be effectively overcome; the total laser power is in fact distributed among several longitudinal modes, each one being limited by the SBS threshold, thus allowing for higher total peak power levels.…”