| 题名 | 基于光纤光栅的综合应用研究 |
| 作者 | 张承涛 |
| 学位类别 | 博士 |
| 答辩日期 | 2013 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 林尊琪 |
| 关键词 | 光纤光栅传感器 啁啾光纤光栅 啁啾脉冲放大 幅度调制效应 |
| 其他题名 | Application Research based on fiber Bragg grating technology |
| 中文摘要 | 光纤光栅作为新型的光纤器件，在光通信和传感等众多领域具有十分广阔的应用前景，国内外对它的相关技术进入了深入的研究。本文在调研分析了国内外相关文献和技术原理的基础上，开展了基于光纤光栅的综合应用研究。对FBG传感系统应用于船舶结构安全健康监测进行了实验研究；提出了基于CFBG的脉冲多程展宽器并进行了相关实验以满足ICF系统高功率激光器前端对脉冲展宽的需要；对CFBG补偿高功率激光器系统中的传输光纤色散引发的经过位相调制脉冲幅度调制效应的作用进行了验证性实验。主要的研究内容及研究结果如下： （1）光纤光栅在国内外大型工程结构监测的已有广泛的应用，但国内将其应用于现代船舶的结构健康监测方面尚为空白，我们在国内首次将FBG传感系统应用于船舶结构的监测，对振动频率为46 Hz〜335 Hz结构的23个应变测点和3个温度测点实现了陆上静态及海上航行时的准分布同时在线测试，实测应变范围达-3000～+3000με，最大受力达40MPa。系统的应变分辨率为1με，温度精度±0.3℃。测试时燃机的转速由5300 r/min到7000 r/min，叶片角度从20°改变到 33.5°，燃机的功率因子N/Ne由0.35增长到0.95。对各测点在不同燃机功率因子的情况下平均受力和瞬时最大受力情况进行测试分析，结果与设计方给出的理论范围一致。结合陆上测试的数据分析提供了海试时缺失数据的预报方法和结果，相关结论得到了委托方的肯定。设计FBG三向应变花的结构解决了平面剪切应力测量的同步性问题。设计了能克服船上恶劣条件并进行长期监测的FBG应变传感器，对原有的传感系统结构进行了改进设计以提高其测量的时间同步性和系统可靠性。 （2）在分析现有基于CFBG的脉冲展宽器的特点和不足的基础上，首次提出将CFBG与全光纤再生放大器的环形结构相结合，以实现同一CFBG对脉冲的多次展宽作用，并利用自主设计的CFBG开展了相关实验研究。该装置利用单程展宽量为345 ps的带宽7.1nm的短CFBG，将锁模激光器输出的16 ps宽度脉冲经腔内的7次循环展宽到1.855 ns，首次用单根短光栅实现了ICF高功率系统要求的皮秒脉冲到纳秒脉冲的展宽，同时设计了能够将展宽脉冲重新压窄的压缩器方案。这一实验较前人方案在结构稳定性和成本上具有较大优势，为ICF高功率激光系统的中的啁啾脉冲放大技术提供了新的具有前景的解决方案和研究方向。 （3）分析了引起ICF系统高功率激光驱动器中的幅度调制效应原因和抑制方法。利用CFBG对神光II前端输出并加入位相调制的脉冲开展了相关验证性实验研究，实验的结果表明：1. 一定长度的传输长纤会对加入位相调制的宽带光带来明显的幅度调制效应，对于位相调制频率为3 GHz，带宽为0.3 nm时，1.94 km的光纤色散引入的幅度调制率约为13%；2. 啁啾光纤光栅可以通过补偿传输光纤的色散来抑制幅度调制效应，采用4.5cm长的带宽为7nm的CFBG时，约能补偿7%的幅度调制率，相当于1.6km光纤色散引入的量。该实验为进一步降低系统的幅频效应奠定了相应的技术基础，相关结论为今后进一步研究提供了有益的指导和借鉴。 |
| 英文摘要 | As a new kind of fiber device, fiber Bragg grating (FBG) has a broad application prospects in optical communication, sensing and many other fields. It attracted the attention of many researchers at home and abroad. In this thesis, based on a study of the relevant literature and technical principles of the application of FBG, we apply the FBG sensing system on Structural Health Monitoring (SHM) to a modern ship. And an all-fiber optical pulse multi-pass stretcher based on chirped fiber Bragg grating (CFBG) is demonstrated. We also carry out validation experiments to compensate the FM-to-AM conversion caused by the dispersion of the transmission fiber in high power laser systems. Concretely, the most work can be presented as: 1. FBG has a wide range of applications in structural monitoring of large-scale projects at home and abroad, but application research on SHM of the ship is still blank in our country. We apply the FBG sensing system on SHM to a modern ship for the first time at home, and the static tests onshore and dynamic tests at sea are carried out to monitoring the strain distribution of supporting structures of the large thruster. The natural frequency of this measured structure is 46 Hz～335 Hz, the max blade frequency of thruster is around 110 Hz. In every test, the thruster runs at the rotation speed from 5300 r/min to 7000r/min, and the blades pitch angle from 20°to 33.5°, which means the Gas Turbine Power Factor (GTPF) N/Ne is from 0.35 to 0.95. We analyze the average and max stress in every N/Ne conditions. The testing strain range is -3000～+3000με and the max stress of the structure is more than 40 MPa. We analyze the fragmentary data from test at sea and make predictions for complete dynamic results based on the static results. Experimental results are accordant with mechanical theories, and the final reports have obtained clients’ approval. The rosette including 3 FBGs is designed to solve the synchronization problem of measurements of plane shear stress. To meet the future long-term safety monitoring requirements for ships with high-speed, we design new type of FBG strain sensors to overcome harsh work environment, and also improve the sensing system structure to satisfy the requirements of time synchronization and system reliability. 2. We research the advantage of using Chirped Fiber Bragg Grating (CFBG) as a pulse stretcher compared with conventional grating pairs, and the inadequacies of existing solutions are analyzed. An all-fiber optical pulse multi-pass stretcher using CFBG is demonstrated for the first time as our known. We combined the CFBG with the regenerative fiber amplification structure, and have the pulse stretched from 16 ps to 1.855 ns after it transmits 7 loops in the stretcher. The CFBG has a bandwidth of 7.1 nm and provides 345 ps time delay in every reflection. We also design a compressor to recompress the stretched pulse. This research will provide new promising solutions and research directions for the high power laser system of ICF. 3. The factors which cause the FM-to-AM conversion and the way to suppress it are analyzed. Validation experiments to compensate the FM-to-AM conversion caused by the dispersion of the transmission fiber in the front end of Shenguang II are carried out. The experimental results show that: Firstly, the transmission fiber with enough length will cause FM-to-AM conversion to the pulse when the phase modulation is applied. If the modulation frequency is 3 GHz, the bandwidth is 0.3 nm, the fiber with length of 1.94km can cause the rate of FM-to-AM conversion as 28%. Secondly, the CFBG can suppress the FM-to-AM conversion by means of compensating the dispersion of the transmission fiber in high power laser systems. When a 4.5 cm CFBG with the bandwidth of 7nm，it can suppress the rate of FM-to-AM conversion as 24%, the amount of which is equal to that caused by a section of 1.6-km fiber. The conclusions can provide useful guidance and reference to further researches. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15762]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 张承涛. 基于光纤光栅的综合应用研究[D]. 中国科学院上海光学精密机械研究所. 2013. |
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