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摘要: 近年来,光纤布拉格光栅传感器与全分布式光纤传感器的融合技术受到了广泛关注,然而光纤布拉格光栅与布里渊信号之间的耦合特性鲜有报道。本文研究了光栅类型、波长、反射率及光纤的光致折射率对受激布里渊信号的影响规律,并探讨了空间分辨率对光纤布拉格光栅定位功能的影响。实验结果表明,在布里渊光时域分析系统中,光纤布拉格光栅处有尖锐的反射峰,而啁啾光栅、长周期光栅及光致折射率变化的光纤处均未出现尖锐的反射峰;光纤布拉格光栅反射率与受激布里渊散射功率谱无关;当光纤布拉格光栅的波长接近1 550 nm时,对受激布里渊频移测量的影响最大;在8 m的长度范围内,光纤布拉格光栅的定位误差约为4 cm,并且与空间分辨率无关。Abstract: Recently, the integration technique of fiber Bragg grating (FBG) sensors and distributed optical fiber sensors has attracted extensive attention. However, it is unknown about coupling properties between FBG and Brillouin signal. In this paper, we investigate the effects of optical grating types, wavelength and reflectivity and exposure-induced refractive index of optical fiber on stimulated Brillouin signal. Meanwhile, the influence of spatial resolution on positioning of FBG is discussed. Experimental results show that the sharp reflected peak from FBG occurs in the hybrid system of FBG sensor and Brillouin optical time-domain analysis (BOTDA), while no reflected peak occurs for chirped grating and long period grating, as well as exposure-induced refractive index of optical fibers. FBG reflectivity has no connection with power spectrum of simulated Brillouin scattering. It is also shown that when the wavelength of FBG is close to 1 550 nm, the influence on stimulated Brillouin signal is the largest. A positioning error of approximate 4 cm is obtained among a sensing range of 8 m, which is independent on the spatial resolution.
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图 8 反射率不同的光纤布拉格光栅的受激布里渊散射功率谱。(a)三个光纤样品的受激布里渊功率谱;(b)FBG1的受激布里渊功率谱;(c)FBG2的受激布里渊功率谱图;(d)FBG3的受激布里渊功率谱图
Figure 8. Power spectra of stimulated Brillouin scattering of FBG with different reflectivities. (a) Power spectra of stimulated Brillouin scattering of three fiber specimens; (b) Power spectra of stimulated Brillouin scattering for FBG1; (c) Power spectra of stimulated Brillouin scattering for FBG2; (d) Power spectra of stimulated Brillouin scattering for FBG3
表 1 不同类型光栅的性能参数
Table 1. Characteristic parameters of different kinds of gratings
Grating Parameter Location of
the gate/mFiber length/m Wavelength/nm Refractive index/% Bandwidth/nm Long period grating 1 538.49 99 4.39 2.5 3.1 Chirped grating 1 545.12 99 1.24 2.4 4.07 FBG 1 545.13 90 0.24 1.72 4.1 表 2 光纤布拉格光栅特性参数对受激布里渊信号影响的实验中光纤布拉格光栅的性能参数
Table 2. Characteristic parameters of FBG in the experiment shown in Figure 5
Parameter Group 1 Group 2 Group 3 FBG 1 FBG 2 FBG 3 FBG 1 FBG 2 FBG 3 Wavelength/nm 1 510
1 530
1 5451 510
1 530
1 5451 510
1 530
1 5451 530
1 530
1 5301 530
1 530
1 5301 530
1 530
1 5301 549.8 Refractive index/% 34.08
34.68
33.1660.37
61.98
62.6790.73
89.88
90.5333.16
34.53
34.6861.452
58.98
61.54189.16
91.15
91.1596.34 Bandwidth/nm 0.17
0.18
0.170.23
0.23
0.240.18
0.17
0.180.15
0.15
0.160.20
0.20
0.180.27
0.27
0.260.21 表 3 空间分辨率对光纤布拉格光栅定位影响试验中光纤布拉格光栅的性能参数
Table 3. Characteristic parameters of FBG in the experiment of spatial resolution influence on FBG positioning
No. Parameter Wavelength/
nmRefractive
index /%Bandwidth/
nmSpacing/m FBG 1 1 545.18 90.39 0.24 FBG 2 1 555.15 90.81 0.25 7.98 FBG 3 1 560.19 89.86 0.27 8.02 表 4 不同空间分辨率下光纤布拉格光栅的空间位置及定位误差
Table 4. Spatial location and positioning error of FBG at different spatial resolutions
Spatial resolution/cm Spatial location/m Positioning error/cm FBG1 FBG2 FBG3 FBG1-FBG2 FBG2-FBG3 10 8.059 16.068 24.127 3.8 3.9 20 8.059 16.068 24.127 3.8 3.9 50 8.008 16.016 24.076 2.8 4 100 7.751 15.811 23.870 8 3.9 -
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