面向高温环境的特种传感光纤研究

Fiber-optic sensors have shown a great potential in a broad range of applications in the harsh environment of high temperature. The project aims to develop high-temperature resistant optical fiber sensors with strong mechanical strength, targeting for the applications in aircraft engines, gas turbines and other systems with an urgent need of high-temperature fiber sensors. This project proposes a novel type of fiber sensor doped with high concentration of alumina. Based on the fabrication method by introducing a sapphire rod into a quartz tube, we will solve the problems of fibers that can endure high temperature, achieve the structure of fiber with high concentration dopant, develop the model of doping diffusion during fiber drawing process, and strengthen mechanical properties of material. At the same time, in order to solve the problem of high pressure sensing in high temperature environment, a sensing fiber by introducing micro-structure into fiber cladding is proposed. Especially, the precise control of the micro-structure will be investigated. Based on the proposed fiber, we can achieve the modification of the refractive index by the localized crystallization effect in the alumina-doped region. This localized crystallization effect enables to improve the mechanical performance of the fiber that can endure high temperature. Moreover, we propose the method of tuning the microstructure in the fiber cladding, so that the electrical field of propagating mode can be controlled and the sensitivity to pressure can be improved. The outcomes of the project are expected to solve the problems faced by all the current silica optical fiber sensors whose mechanical performance is significantly degraded in high temperature environments. So the project is of great significance to promote the rapid development of China's aeroengine, gas turbine and other major national defense fields.

光纤传感器在高温恶劣环境下具有广阔应用前景，本项目面向航空发动机、燃气轮机等系统研发中对耐高温光纤传感器的迫切需求，以研制具有耐高温、高机械强度的传感功能光纤及光纤传感器为目标。提出研制具有高浓度氧化铝掺杂增强结构的传感光纤，基于蓝宝石棒与石英套管的管棒法，研究耐高温、高机械强度掺杂结构设计、光纤拉制扩散物理模型、增强材料机理等关键科学技术问题；同时，针对高温环境下高压传感难题，提出具有包层辅助微孔的传感光纤，研究高温拉丝微孔控制问题。利用上述传感光纤，针对传感器件耐高温难题，提出基于析晶效应的局部折射率改变方案，研究局域析晶材料机理及耐温性能提升问题；提出基于辅助孔局域微形变的光纤高压传感器方案，着重解决微形变调控光纤模场及压敏增强等科学问题。预期成果有望突破高温环境中石英传感光纤机械强度及传感器件结构恶化的瓶颈限制，对于促进我国航空发动机、燃气轮机等国防重大工程的快速发展具有重要意义。

以高熔点蓝宝石棒与石英套管相结合，采用管棒法拉制具有高浓度氧化铝掺杂光纤，在高温恶劣环境下具有广阔应用前景。本项目通过建立了氧化铝掺杂石英光纤拉丝扩散模型，拉制了光纤直径125μm、~32 mol.%的单芯氧化铝掺杂光纤和~16 mol.%多芯氧化铝掺杂光纤。在上述特种光纤研制基础上，提出了光纤析晶折射率调制新方法，通过热处理技术（电弧放电、CO2激光加工技术等）在高浓度氧化铝掺杂石英光纤芯内实现局部析晶，析晶效应实现~0.03的折射率改变量。利用局域析晶折射率调制方法，成功研制了析晶FPI、MZI、LPG等新型耐高温传感器件。所研制的析晶FPI，实现了1200℃的高温传感（最高可承受1600℃）和1000℃的高温应变传感，为航空航天领域开发耐高温光纤传感器提供了重要的支撑。本项目还开展了多芯氧化铝掺杂光纤传感特性的研究，所制备的析晶MZI传感器，实现了900℃的高灵敏度温度传感和大曲率范围的弯曲传感。针对高温环境下高压传感难题，研制了具有包层辅助微孔传感光纤，借助微孔结构实现了18MPa的抗压测试。并借助微孔结构的周期性，通过CO2激光结合压力辅助技术，提出制备了一种基于纤芯等效折射率调制的新型LPG，为包层微孔结构高温、高压传感提供了新型光纤功能器件。为了实现高温、高压场景下的准分布式光纤感测，研制了阶梯式双包层光纤，利用阶梯式双包层光纤和单模光纤间的折射率差异，交互焊接，在焊点处形成准分布式低反射界面，实现了1000℃的准分布式温度测量。本项目的研究成果对于为我国航空发动机、核电、燃气轮机等领域的高温监测技术提供重要支撑。.本项目在上述研究过程中，形成的研究成果包括：发表相关学术论文55篇，其中，SCI收录期刊49篇，EI收录论文6篇；申请中国发明专利13项、授权16项；培养博士研究生10名，硕士研究生8名，其中获学位毕业14名。