【作者】 莫秋菊；

【导师】 饶云江；

【作者基本信息】 重庆大学 ， 光学工程， 2006， 硕士

【摘要】 在导师饶云江教授及朱涛老师的指导下,延伸了本实验室已有的高频CO₂激光脉冲写入的周期为数百微米的长周期光纤光栅的研究成果,对高频CO₂激光脉冲在普通单模、熊猫偏振保持、弯曲不敏感光纤中写入的周期达数毫米数量级的超长周期光纤光栅进行了探索性研究。研究包括高频CO₂激光脉冲在普通单模光纤中写入的超长周期光纤光栅及其温度、外界折射率、应变、扭曲等特性,在熊猫保偏光纤中写入的超长周期光纤光栅及其偏振控制、温度、应变、扭曲等特性,及在弯曲不敏感光纤中写入的超长周期光纤光栅及其温度、应变、扭曲特性等。研究发现,高频CO₂激光脉冲在普通单模光纤中写入的超长周期光纤光栅不同谐振峰的温度、外界折射率灵敏度不同,利用此特性,提出了一种温度与折射率同时测量的髙灵敏度折射率计,此折射率计不仅折射率测量灵敏度髙,还可以实现一根光栅就可补偿折射率测量中温度带来的干扰。本文还利用单模光纤中写入的超长周期光纤光栅有的谐振峰波长的扭曲测量灵敏度是普通长周期光纤光栅谐振峰波长扭曲灵敏度的4倍,且其幅值随扭曲的变化改变很小的特性,设计了一种髙灵敏度的扭曲传感器,其扭曲测量灵敏度达到了0.4394dB/（rad/m）。研究还发现,高频CO₂激光脉冲在熊猫保偏光纤上写入的超长周期光纤光栅两个垂直偏振分量上的谐振峰幅值随着入射椭圆偏振光偏振角度的改变发生周期性变化,周期为π。在相同偏振角度下其幅值差呈近似于锯齿波的周期性变化,周期也为π,两个谐振峰的差值在最大值与最小值之间与偏振角度成线性关系。在入射椭圆偏振光偏振角度为90°时,随着温度、应变的改变,两个偏振分量上的谐振峰波长都往同一方向漂移,而两个偏振分量上的谐振峰幅值变化方向却相反。而随着扭曲率的不断增加,两个垂直偏振分量上的谐振峰谐振波长与幅值都几乎没有任何改变。对高频CO₂激光脉冲在弯曲不敏感光纤上写入的超长周期光纤光栅的研究发现,其各个谐振峰温度、应变、扭曲灵敏度各自不同。本文还对高频CO₂激光脉冲在普通单模光纤及保偏光纤中写入的超长周期光纤光栅及其基础特性进行了定性的理论分析。更多还原

【Abstract】 Ultra long period fiber gratings which have much longer periods than that of ordinary long period gratings and are induced by high frequency CO₂ laser pulses are studied by the author here under the supervision of Prof. Rao and teacher Zhu Tao, and these researches have much significance in extending the research which have been done for several years by Prof Yunjiang Rao and his students on long period fiber gratings with periods of several hundred micrometers and are also induced by high frequency CO₂ laser pulses.The studies mainly include:1. Researches on ultra long period fiber gratings written in ordinary single-mode fiber, and its temperature, refractive index, strain and twist characteristics.2. Researches on ultra long period fiber gratings written in panda polarization maintain fiber and its polarization, temperature, strain and twist characteristics.3. Researches on ultra long period fiber gratings written in bend-insensitive fiber and its temperature strain and twist characteristics.The researches show that different resonant peaks of ultra long period gratings written in ordinary single mode fiber have different temperature and refractive index sensitivities, and using this characteristic, a new high sensitivity refractive index sensor with temperature self-compensating is proposed in this thesis. This refractive index sensor can not only sensitively measure the refractive index of the outside environments, but can also compensate the measuring errors brought by the temperature changes of them. The researches also show that the torsion sensitivities of some resonant peaks of ultra long period gratings written in ordinary single mode fiber arrive 4 times of that of ordinary long period fiber gratings, and a highly sensitivity twist sensor is also proposed in this thesis based on this characteristic. The sensitivity of this twist sensor arrives 0.4394dB/（rad/m）.The researches on ultra long period gratings written in panda polarization maintain fiber show that the amplitudes of two resonant peaks on two vertical polarization directions of ultra long period gratings changed periodically with a period ofπwhen the polarization angle of incident elliptical polarization light varied from ? 2πto 2π. The phase difference of amplitude changes of them isπ, and the amplitude difference of them in the same incident polarization angle varied periodically as a zigzag wave also更多还原