提出了一种耐高温光纤布拉格光栅阵列（FBGA）的制备方法。通过在拉丝塔上以聚酰亚胺作为涂层材料，利用相位掩模版技术和单脉冲在线刻写光栅，经过多次涂敷、烘干以及最后酰亚胺化，成功得到涂层直径为145~150 μm，中心波长范围为（1551.35±0.1）nm，反射率为0.06%，传输损耗为1.601 dB/km@1550 nm的聚酰亚胺涂层光纤布拉格光栅阵列（PI-FBGA）。然后对PI-FBGA的热稳定性和可靠性进行研究，结果表明，在线制备的PI-FBGA具有良好的热稳定性及可靠性，能够在300 ℃以下长期使用，300~400 ℃可短期使用。该传感光纤的成功制备扩大了常规在线弱光栅阵列的应用范围，在石油化工、环境监测、航空航天等领域具有广阔的应用前景。

Fiber Bragg grating (FBG) array, consisting of a number of sensing units in a single optical fiber, can be practically applied in quasi-distributed sensing networks. Serious signal crosstalk occurring between large-serial of identical FBGs, however, has limited the further increase in the number of sensing units, thus restricting applications only for short-distance sensing networks. To reduce the signal crosstalk, we design two novel types of 10-kilometer-long FBG arrays with 10 000 equally spaced gratings, written on-line using a customized grating inscription system, which is affiliated to a drawing tower. Main factors causing signal crosstalk, such as spectral shadowing and multiple reflections, are firstly investigated in theory. Consistent with the theoretical findings, experimental results are proving that ultra-weak (the reflectivity of ~–40 dB) and multi-wavelength gratings of a number more than 10 000 can be readily identified, with satisfied low crosstalk. The maximum attenuation of grating signal and minimum signal-to-noise ratio (SNR) in a single-wavelength array are 10.69 dB and 5.62 dB, respectively. As a comparison, by increasing the number of central wavelengths to three, the attenuation can be effectively reduced to 5.54 dB and the minimum SNR has been improved to 8.14 dB. The current study significantly enhances the multiplexing capacity of FBG arrays and demonstrates promising potentials for establishing large-capacity quasi-distributed sensing networks.

Sampled fiber grating is a special superstructure fiber Bragg grating with a wide range of applications in many fields. In this work, based on drawing tower in-line fabrication system, a new preparation method of the sampled fiber grating is proposed and experimentally demonstrated. Experimental result shows that the obtained sampled fiber gratings possess dense reflection spectra, with a minimum reflection peak interval of only 0.09 nm. This method exhibits promising application prospect in the fabrication of the high-quality sampled fiber grating. On the other hand, the spectral characteristics of the sampled fiber grating are analyzed when the sub-grating is affected by the external physical quantities such as, in this paper, strain. Wavelength shift and intensity change in the reflection peak of the spectra indicate that the grating is affected differently by micro strains, due to the different spatial positions along the axis of the sampled fiber grating. This work is aimed at exploring the potential applications of the sampled fiber grating in quasi-distributed micro-area sensing with the millimeter level.

A distributed fiber optic interferometric geophone array based on draw tower grating (DTG) array is proposed. The DTG geophone array is made by the DTG array fabricated based on a near-contact exposure through a phase mask during the fiber drawing process. A distributed sensing system with 96 identical DTGs in an equal separation of 20 m and an unbalanced Michelson interferometer for vibration measurement has been experimentally validated compared with a moving-coil geophone. The experimental results indicate that the sensing system can linearly demodulate the phase shift. Compared with the moving coil geophone, the fiber optic sensing system based on DTG has higher signal-to-noise ratio at low frequency.

设计并验证了一种采用全光栅光纤（AGF）作为随机反馈介质的窄线宽随机光纤激光器（RFL）。基于相位掩模法在利用拉丝塔在线制作的单模光纤纤芯上连续刻写长度为0.3 mm的布拉格光栅（FBG）约4.3×10⁵支，制作了长度为130 m的AGF。利用光学环形器将AGF接入由掺铒光纤放大器、光纤隔离器和窄带光滤波器组成的环形激光腔中，构成环形RFL。结果表明，通过窄带光滤波器选模，基于AGF的RFL输出连续单模激光的最大功率为1.26 mW，阈值电流为75 mA，斜率效率为56%。抽运电流恒定为100 mA时，基于AGF的RFL线宽为1.25 kHz，光信噪比为75 dB。当频率为1 kHz以上时，激光器输出的相对强度噪声达到-90 dB。相较于传统基于分立FBG的RFL反馈腔，基于AGF的RFL反馈腔具有更多的随机反馈点和更均匀的随机性，有利于RFL获得更窄的线宽。

This paper reviews the work on huge capacity fiber-optic sensing network based on ultra-weak draw tower gratings developed at the National Engineering Laboratory for Fiber Optic Sensing Technology (NEL-FOST), Wuhan University of Technology, China. A versatile drawing tower grating sensor network based on ultra-weak fiber Bragg gratings (FBGs) is firstly proposed and demonstrated. The sensing network is interrogated with time- and wavelength-division multiplexing method, which is very promising for the large-scale sensing network.

全同弱光栅通过时分/波分混合复用时，光栅阵列中的阴影效应、多重反射等对反射信号会产生影响。对全同弱光纤光栅阵列所作的时域反射信号仿真计算和分析表明，阴影效应和多重反射不会引起光栅中心波长漂移，但会导致光栅中心波长处的反射强度降低。若阵列中的单个光栅的反射率较高，受阴影效应的影响，光栅阵列远端的光栅将可能检测不到，不能达到增加光栅复用数量的目的；但若单个光栅的反射率太低，则又会使阵列上的光栅的被测反射信号强度降低，从而增加了信号检测难度。