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Preform Rare-Earth Profiler (PREP)

预成型稀土剖面仪 (PREP)

基本信息

批准号：
EP/M020770/1
负责人：
Michalis Zervas
金额：
$ 39.72万
依托单位：
University of Southampton
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2015
资助国家：
英国
起止时间：
2015 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FM020770%2F1
关键词：
Preform Rare Earth Profiler PREP

项目摘要

Over the last decade, high power fibre amplifiers and lasers have been rapidly developed and successfully commercialized for a number of industrial applications such as cutting, welding, and marking. The industrial fibre laser business is currently worth over $800M/year, with compound annual growth rate of about 13% - the highest among the different laser technologies. One of the main contributors to this success has been the significantly improved rare-earth doped fibre fabrication technologies. High performance fibres rely on controlled incorporation of refractive index modifying dopants, as well as, gain providing rare-earth ions. High efficiency, high average and/or peak power industrial fibre lasers and amplifiers invariably use large-mode area fibres with complex refractive indices and rare-earth distributions. In most cases, a number of different dopants are used simultaneously in order to control the refractive index and gain distribution, and through it the fibre modality and modal differential gain. Additional dopants are also used to reduce nonlinear effects, such as Stimulated Brillouin and Raman Scattering, and other parasitic effects, such as photodarkening. The various dopants have different sizes, mobility, and diffusion rates and, as a consequence, the resulting refractive index profiles can in general be much different to rare earth distributions within the core, and one cannot be inferred from the other. In addition, depending on the fabrication technique, the distribution of dopants is not uniform along the fibre preform, rendering the drawn fibre performance variable and "patchy". In particular, Modified Chemical Vapour Deposition (MCVD) fabrication technique, among the most versatile and widely used fabrication techniques, is known to suffer from poor repeatability and large variability along the preform length. This compromises significantly the fibre yield and increases the fibre cost. In addition, and even more importantly, currently there is no reliable information regarding the "fitness-for-purpose" of fibre in advance. Its suitability can only be tested and quantified after a full fibre laser has been built and thoroughly tested, adding considerably to the fibre laser module turn-around time, yield and cost. So there is a need for unsuitable preforms or parts of preform to be identified early in the fibre drawing process and be discarded. Another requirement has lately appeared in the fibre telecom area. Over the last few years there has been a strong resurgence in multimode telecom systems research, with spatial-division multiplexing (SDM) promising to solve the predicted forthcoming telecom capacity crunch. Successful development of SDM systems relies exclusively on the development of high performance multimode fibre amplifiers with carefully optimized rare-earth (Erbium or Thulium) profiles for modal gain equalization. Again, detailed and accurate knowledge of the active dopant distribution over the fibre cross-section along the entire preform length is critical for successful demonstrations of this game-changing approach to single-fibre transmission capacity increase. The main aim of this proposal is to develop widely applicable, non-destructive characterization techniques for the accurate and detailed determination of active-dopant distribution in fibre preforms and provide the required reliable information well before the preforms are drawn into fibres. Such preform characterization techniques are expected to have a big impact on the performance and cost of advanced high-power fibre laser systems, as well as, currently researched SDM telecom systems, and increase the competiveness of the UK manufacturing basis as well as enhance the UK cutting-edge research activities in these areas.

在过去的十年中，高功率光纤放大器和激光器已经迅速发展，并成功地商业化了许多工业应用，如切割，焊接和标记。工业光纤激光器业务目前价值超过8亿美元/年，复合年增长率约为13%，是不同激光技术中最高的。这一成功的主要贡献者之一是显著改进的稀土掺杂纤维制造技术。高性能光纤依赖于折射率改变掺杂剂的可控掺入，以及提供稀土离子的增益。高效率、高平均和/或峰值功率的工业光纤激光器和放大器总是使用具有复折射率和稀土分布的大模面积光纤。在大多数情况下，同时使用许多不同的掺杂剂来控制折射率和增益分布，并通过它来控制光纤模态和模态差分增益。额外的掺杂剂也用于减少非线性效应，如受激布里渊散射和拉曼散射，以及其他寄生效应，如光变暗。各种掺杂剂具有不同的尺寸、迁移率和扩散速率，因此，所得到的折射率分布通常与核心内的稀土分布有很大不同，并且不能从另一个推断出来。此外，根据制造技术的不同，掺杂剂沿着纤维预制体的分布并不均匀，导致拉伸的纤维性能变化和“不均匀”。特别是，改性化学气相沉积（MCVD）制造技术是最通用和最广泛使用的制造技术之一，众所周知，它的重复性差，并且沿预制体长度变化很大。这大大降低了纤维产量并增加了纤维成本。此外，更重要的是，目前还没有关于纤维“适用性”的可靠信息。只有在全光纤激光器建成并经过彻底测试后，才能对其适用性进行测试和量化，这大大增加了光纤激光器模块的周转时间、产量和成本。因此，有必要在纤维拉伸过程中及早发现不合适的预成型件或预成型件，并予以丢弃。最近在光纤通信领域出现了另一个要求。在过去的几年里，多模电信系统的研究有了强劲的复苏，空分多路复用（SDM）有望解决预计即将到来的电信容量危机。SDM系统的成功开发完全依赖于高性能多模光纤放大器的开发，该放大器具有精心优化的稀土（铒或铥）配置文件，用于模态增益均衡。同样，详细和准确地了解沿整个预制棒长度的光纤横截面上的有源掺杂分布对于成功演示这种改变单光纤传输容量的方法至关重要。本提案的主要目的是发展广泛适用的非破坏性表征技术，以准确和详细地确定纤维预成型中的有源掺杂分布，并在预成型被吸入纤维之前提供所需的可靠信息。这种预制体表征技术预计将对先进的高功率光纤激光系统以及目前正在研究的SDM电信系统的性能和成本产生重大影响，并增加英国制造业基础的竞争力，并增强英国在这些领域的前沿研究活动。