High-efficiency DBA-BOTDA with optimized SNR by multiple bandwidths pump modulation

Huiliang Ma; Xinhong Jia; Kai Lin; Cong Xu

doi:10.3788/COL201917.010603

Journals >Chinese Optics Letters >Volume 17 >Issue 1 >Page 010603 > Article

Chinese Optics Letters
Vol. 17, Issue 1, 010603 (2019)

High-efficiency DBA-BOTDA with optimized SNR by multiple bandwidths pump modulation

Huiliang Ma, Xinhong Jia^*, Kai Lin, and Cong Xu

Author Affiliations

College of Physics and Electronic Engineering, Sichuan Normal University, Chengdu 610101, China

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DOI: 10.3788/COL201917.010603 Cite this Article Set citation alerts

Huiliang Ma, Xinhong Jia, Kai Lin, Cong Xu. High-efficiency DBA-BOTDA with optimized SNR by multiple bandwidths pump modulation[J]. Chinese Optics Letters, 2019, 17(1): 010603 Copy Citation Text

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Abstract

For Brillouin optical time-domain analysis (BOTDA) based on distributed Brillouin amplification (DBA), constant Brillouin response achieved by the exponentially variable bandwidth/intensity pump modulation suffers from the much lower pumping efficiency for long-range sensing, which counterbalances the merit of DBA. In this Letter, pump modulation by multiple constant bandwidths was proposed and demonstrated. The ～98.9 km sensing with ～5 m spatial resolution and no use of optical pulse coding (OPC) was achieved by ～8 dBm Brillouin pump, which is lower by ～9 dB in theory by comparison with exponentially increased bandwidth modulation. Compared with traditional DBA-BOTDA, signal-to-noise ratio (SNR) enhancement with >4.6 dB was obtained. The flattened standard deviation (STD) of Brillouin frequency shift (BFS) (less than ～2 MHz) along the whole fiber was demonstrated.

P_{p} (z) = P_{p} (0) \exp (- α z) \exp [\int_{0}^{z} g_{BP} (ξ) P_{B} (ξ) d ξ],

(1)

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P_{B} (z) = P_{B} (L) \exp [- α (L - z)],

(2)

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g_{BP} (z) = \frac{g_{0}}{1 + \frac{Δ ν (z)}{Δ ν_{B}}} \to \frac{g_{0}}{\frac{Δ ν (z)}{Δ ν_{B}}} (if Δ ν ≫ Δ ν_{B}),

(3)

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Δ ν (z) = Δ ν (0) \exp (α z),

(4a)

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P_{B} (L) = \frac{α Δ ν (0)}{g_{0} Δ ν_{B}} \exp (α L) .

(4b)

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P_{B} (L) = \frac{α L}{g_{0} Δ ν_{B} {\frac{L_{eff}^{AB} \exp [- α (L_{BC} + L_{CD})]}{Δ ν_{AB}} + \frac{L_{eff}^{BC} \exp [- α L_{CD}]}{Δ ν_{BC}} + \frac{L_{eff}^{CD}}{Δ ν_{CD}}}},

(5a)

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L_{eff}^{i} = \frac{1 - \exp (- α L_{i})}{α} (i = AB, BC, CD) .

(5b)

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V_{FM} (t) = V_{0} \cos [(2 π ν_{MSW 1} t) + φ (t)] = V_{0} {\cos (2 π ν_{MSW 1} t) \cos [φ (t)] - \sin (2 π ν_{MSW 1} t) \sin [φ (t)]},

(6a)

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φ (t) = φ_{0} + 2 π \int_{0}^{t} δ ν (τ) d τ,

(6b)

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Huiliang Ma, Xinhong Jia, Kai Lin, Cong Xu. High-efficiency DBA-BOTDA with optimized SNR by multiple bandwidths pump modulation[J]. Chinese Optics Letters, 2019, 17(1): 010603

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