摘要
利用耦合模理论和弹光效应原理研究了边孔光纤双折射与压力的依赖关系.仿真结果表明,双折射变化受到压力大小和作用方向共同影响.保持压力大小不变,双折射数值随作用方向呈余弦变化,且在π/2的偶数倍和奇数倍方向上分别取得最大值和最小值.保持作用方向不变,双折射数值与压力大小呈线性关系.当作用方向θ∈(kπ-π/4,kπ+π/4)(k∈Z),双折射数值随压力呈线性增加,而θ∈(kπ+π/4,kπ+3π/4),双折射数值随压力呈线性减小,在θ=kπ+π/4时,双折射数值基本不变.最后,基于偏振光干涉的实验装置测量了不同压力大小和作用方向下的双折射,实验结果与仿真结果相关系数r为0.992 2,在误差许可范围内,二者吻合较好.
Abstract
Amid the rapid advancements in optical fiber communications and sensing technologies,polarization-maintaining fibers have increasingly been utilized in fiber sensing systems.As a novel type of polarization-maintaining fiber,Side-Hole Fiber(SHF),with its unique microstructure and superior performance,holds broad application prospects in fields such as communication,sensing,and medical technology.The sensors made from SHF are highly sensitive,capable of monitoring multiple parameters simultaneously,and are easily integrated into the materials being measured.They play an extremely important role in the field of structural health monitoring,thereby attracting widespread attention.In recent years,many researchers have studied and analyzed the structure and birefringence properties of SHF.However,systematic analysis and research on the impact of pressure on the birefringence performance of SHF have not been reported.In this paper,the impact of radial pressure on the birefringence characteristics of SHF was analyzed systematically based on coupled mode theory and the photoelastic effect.To facilitate the experimental component of the study,a mechanical loading apparatus was engineered to apply varying levels of radial pressure on the SHF using different weights.Furthermore,we established an experimental system grounded in the principle of polarization interference,designed specifically to measure the birefringence of SHF under different pressure conditions.The experimental setup comprised a broadband light source,a polarizer,the SHF under test,and a spectrometer.Light from the broadband source,after passing through the polarizer,was transmitted through the SHF.The interference spectrum was subsequently captured by the spectrometer.Birefringence was quantified by analyzing the mean wavelength of troughs and the average interval between adjacent peaks within the interference spectrum.Experimental results indicated that while keeping the pressure magnitude constant,the birefringence values varied according to a cosine function with respect to the direction of application,achieving maximum and minimum values at even and odd multiples of π/2,respectively.When the direction of application was held constant,the birefringence values exhibited a linear relationship with the magnitude of pressure.Specifically,for angles 6 within the range(kπ-π/4,kπ+tt/4)(where kis an integer),birefringence values increased linearly with pressure.Conversely,for θ in the range(kπ+tt/4,kπ+3π/4),birefringence values decreased linearly with pressure.At θ=kπ+π/4 the birefringence values remained essentially unchanged.The correlation coefficient r between the experimental and simulation results was 0.992 2,indicating a high degree of consistency within the permissible error range.
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