基于D形DBR光纤激光器的传感技术研究

Research On Sensing Technology Based On D-shaped DBR Fiber Laser

杨新锋

11749093

硕士

光学工程

邵理阳

2019-05-24

2019-07-19

哈尔滨工业大学

深圳

光纤是一种体积小、质量轻、抗电磁干扰、抗辐射性能好的光波导，工作频带宽，在通信领域得到广泛的应用。与此同时，人们也将光纤应用到传感技术中，光纤传感具有结构紧凑、可复用、耐腐蚀性强等优势，因此光纤传感技术被人们广泛的研究，近年来光纤传感被应用于各种学科领域，如基础科学，工程，航空航天，医学等。光纤传感之所以能够不断发展，主要归功于人们对基础原理、材料性质和光纤结构的不断探索。光纤传感技术通常利用光信号的强度、偏振、波长及相位作为传感参量，然而光谱分析仪的光谱分辨率限制了光纤传感器件的探测极限，使得分辨率难于进一步的提高。随着人们对光学基础原理的探索，人们发现借助于拍频手段将光信号的频率降到GHz量级，然后利用光电探测器将光信号转化为微波信号。将光纤传感中的探测信号由光谱信号转变为频谱信号，这样可以大大提高传感的分辨率，从而实现高精度的光纤传感。掺铒光纤的出现为光纤激光器的实现提供了可能性，一种简单紧凑的光纤激光器结构—分布式布拉格反射（DBR）成功被研制出来，该结构能够持续稳定的输出单纵模激光，且具有较高的信噪比，深受光纤通信和光纤传感领域的青睐。本文提出了一种基于D形DBR光纤激光器的光纤传感器，该传感器可以同时实现轴向拉力和折射率的测量。该DBR结构是在一段长度为45 mm的铒镱共掺光纤上刻写长度分别为16 mm和24 mm的两段光纤布拉格光栅，然后利用轮式侧抛系统对DBR的结构进行加工，这样可以为DBR光纤激光器引入一定的双折射，同时可以提高器件的传感性能。该装置的工作原理是DBR受到的轴向拉力和外界折射率的变化都会引起DBR结构双折射的改变，从而引起DBR光纤激光器输出的两个正交偏振模式光拍频信号频率的改变，因此，可将激光输出的两偏振模式光的拍频信号用于测量DBR受到的轴向拉力和外界环境的折射率。这种器件制造工艺简单、成本低，轴向拉力和折射率分辨率高，其轴向应力分辨率可达到5.6014×10-8N，折射率分辨率可达到1.9259×10-5 RIU。

The optical fiber is an optical waveguide with small volume, light weight, anti-electromagnetic interference and good radiation resistance, and the working frequency bandwidth is widely used in communication. At the same time, people also use optical fiber in sensing technology. Fiber sensing has many advantages, such as compact structure, reusability, and strong corrosion resistance. Therefore, optical fiber sensing technology has become very diverse. Enable them to be applied to a variety of disciplines such as basic science, engineering, aerospace, medicine, etc. The continuous development of optical fiber sensing is mainly due to the continuous exploration of material properties, fiber structure and basic principles.Optical fiber sensing technology usually uses the intensity, polarization, wavelength and phase of the optical signal as sensing parameters. However, the spectral resolution of the optical spectrum analyzer limits the detection limit of the fiber-optic sensor device, making the resolution difficult to further improve. With the exploration of the basic principles of optics, people have reduced the frequency of optical signals to the order of GHz by the principle of beat frequency. Then, the photodetector is used to convert the optical signal into the microwave signal, and the detection signal in the optical fiber sensing is converted from the spectral signal to the spectral signal, which can greatly improve the sensing resolution, thereby realizing high-precision optical fiber sensing. In recent years, a simple and compact fiber laser structure, Distributed Bragg Reflector (DBR), has appeared in our field of vision. The structure can continuously and stably output a single longitudinal mode laser, has a high signal to noise ratio, and is favored by the field of optical fiber communication and optical fiber sensing.In this paper, an optical sensor based on DBR fiber laser is proposed, which can simultaneously measure axial force and refractive index. The DBR structure is obtained by writing a fiber Bragg grating with a length of 16 mm and 24 mm respectively on a length of 45 mm long erbium-doped fiber, and then processing the structure of the DBR by using a wheel-side polishing system. Introducing a certain amount of birefringence for the DBR fiber laser, and improving the sensing performance of the device. The working principle of the device is that the axial tension of the DBR and the change of the external refractive index will cause the birefringence of the DBR structure to change, which causes the frequency of the two orthogonal polarization modes beat signals output by the DBR fiber laser to change. The two-polarization modes beat signal of the laser output is used to measure the axial tensile force received by the DBR and the refractive index of the external environment. The device is simple in manufacturing process, low in cost, high in axial force and refractive index resolution, and has resolution limits of 5.6014×10-8 N and 1.9259×10-5 RIU, respectively.

光纤传感 分布式布拉格反射 轴向拉力 折射率 轮式侧抛系统

Optical fiber sensing Distributed Bragg Reflector Axial force Refractive index Wheel side-polishing system

中文

联合培养

南方科技大学

杨新锋. 基于D形DBR光纤激光器的传感技术研究[D]. 深圳. 哈尔滨工业大学,2019.