Design of low frequency fiber optic Fabry–Perot seismometer based on transfer function analysis

Huicong Li; Wentao Zhang; Wenzhu Huang; Yanliang Du

doi:10.3788/COL202119.051201

Journals >Chinese Optics Letters >Volume 19 >Issue 5 >Page 051201 > Article

Chinese Optics Letters
Vol. 19, Issue 5, 051201 (2021)

Design of low frequency fiber optic Fabry–Perot seismometer based on transfer function analysis

Huicong Li^1、2, Wentao Zhang^1、2、*, Wenzhu Huang^1、2, and Yanliang Du^3、**

Author Affiliations

¹Optoelectronic System Laboratory, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China

²College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China

³College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China

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DOI: 10.3788/COL202119.051201 Cite this Article Set citation alerts

Huicong Li, Wentao Zhang, Wenzhu Huang, Yanliang Du. Design of low frequency fiber optic Fabry–Perot seismometer based on transfer function analysis[J]. Chinese Optics Letters, 2021, 19(5): 051201 Copy Citation Text

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Abstract

We develop a low frequency fiber Fabry–Perot (F-P) seismometer based on transfer function analysis. The seismometer structure and demodulation system accuracy are limitations of low frequency seismic monitoring. The transfer function of the F-P seismometer is analyzed, and the mass displacement spectrum (MDS) is introduced. MDS provides guidance for mechanical structure design and optical interferometer analysis to achieve low noise. The F-P seismometer prototype is built. The experiment shows that the prototype has an average noise of

6.74 ng / \sqrt Hz

below 50 Hz, and its noise is less than that of the global new high noise model within 0.16–50 Hz, whose potential is considerable.

Keywords

fiber optics frequency seismometers

\ddot{x} + 2 ξ ω_{0} + ω_{0}^{2} x = - \ddot{y},

(1)

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K = \frac{32 E b h^{3}}{l^{3} + 16 r^{3} - 12 r^{2} l},

(2)

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Δ φ = \frac{4 π n_{0} Δ L}{λ},

(3)

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H (ω) = S_{0} \frac{1}{\sqrt{{[1 - {(f / f_{0})}^{2}]}^{2} + {(2 ξ f / f_{0})}^{2}}},

(4)

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S_{0} = \frac{π m (l^{3} + 16 r^{3} - 12 r^{2} l)}{8 λ E b h^{3}} .

(5)

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x_{NLNM} = \frac{a_{NLNM}}{\sqrt{{(ω_{0}^{2} - ω^{2})}^{2} + {(2 ξ ω_{0} ω)}^{2}}},

(6)

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x_{demodulation} = φ_{demodulation} \frac{λ}{4 π} .

(7)

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I_{R} = \frac{R_{1} + η R_{2} - 2 \sqrt{η R_{1} R_{2}} \cos (\frac{4 π L}{λ})}{1 + η R_{1} R_{2} - 2 \sqrt{η R_{1} R_{2}} \cos (\frac{4 π L}{λ})} I_{0},

(8)

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V = \frac{2 \sqrt{η R_{1} R_{2}} (1 + η R_{1} R_{2} - R_{1} - η R_{2})}{R_{1} + η R_{2} + η R_{1}^{2} R_{2} + R_{1} {(η R_{2})}^{2} - 4 η R_{1} R_{2}},

(9)

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η_{1} = \frac{4 (ε^{2} + 1)}{{(ε^{2} + 2)}^{2}},

(10)

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η_{2} = \exp [- {(\frac{n_{G} \sqrt{A} π x_{0} s_{0}}{λ})}^{2}],

(11)

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η_{3} = \exp [- {(\frac{θ}{n_{G} \sqrt{A} s_{0}})}^{2}],

(12)

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η_{4} = \frac{16 K^{2}}{{(1 + K)}^{4}},

(13)

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η = η_{1} \times η_{2} \times η_{3} \times η_{4}^{2} .

(14)

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Huicong Li, Wentao Zhang, Wenzhu Huang, Yanliang Du. Design of low frequency fiber optic Fabry–Perot seismometer based on transfer function analysis[J]. Chinese Optics Letters, 2021, 19(5): 051201

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