基于双波长激光的超短FBG中心波长解调方法

Central Wavelength Interrogation Method of Ultra-Short FBG by Dual-Wavelength Laser

为实现光纤光栅中心波长的解调,写制了栅区长度小于1mm、反射率大于60%、3dB带宽大于1.5nm、反射谱边缘有效线性区大于1.5nm的超短光纤布拉格光栅(US-FBG)。以US-FBG为传感单元,提出了一种基于双波长激光的中心波长解调方法。当中心波长位于光谱线性区的稳频激光入射到US-FBG,随着光栅光谱的漂移,反射光功率随之变化并具有良好的线性关系,其实验结构的线性度为0.998。为了充分利用其反射光谱左右两侧的线性区,采用双波长激光的互补解调方法,将波长解调范围扩展到3nm。将测量值与实际值进行比较,两者具有较好的一致性。该方法具有结构简单、功耗小、测量空间分辨率高等优势。

To realize the demodulation of the fiber grating center wavelength, we fabricate an ultra-short fiber Bragg grating （US-FBG）, with grating length of less than 1 mm, reflectivity of over 60%, 3 dB bandwidth of wore than 1.5 nm, and the edge linear region of the reflection spectrum of more than 1.5 nm. We use US-FBG as the sensing element, and propose a central wavelength interrogation method based on dual-wavelength laser. When the frequency stabilized laser with the central wavelength in the spectral linear region is incident on the US-FBG, the reflected optical power changes linearly with the drifts of the US-FBG spectrum, whose linearity is 0. 998. .In order to make full use of the linear region on the two sides of reflection spectrum, we use the complementary interrogation method with dual-wavelength lasers to extend the wavelength demodulation range to 3 nm. The measured values are in great agreement with the actual values. The method has the advantages of simple structure, low power consumption, and high spatial resolution.