Support-Free Thermally Insensitive Hollow Core Fiber Coil
Support-Free Thermally Insensitive Hollow Core Fiber Coil
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DOI：
10.1109/jlt.2023.3241255
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发表时间：
2023-05
影响因子：
4.7
通讯作者：
Xuhao Wei;A. Taranta;Bo Shi;Meng Ding;Zitong Feng;D. Richardson;F. Poletti;R. Slavík
中科院分区：
文献类型：
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作者：
Xuhao Wei;A. Taranta;Bo Shi;Meng Ding;Zitong Feng;D. Richardson;F. Poletti;R. Slavík
穿过光纤的光经受由温度驱动的各种局部相位扰动。这种热相位灵敏度在光纤干涉仪及其需要在传播后接收固定、稳定相位的应用中是不希望的。事实证明，与实芯光纤相比，使用空芯光纤（HCF）可以降低这种热相位灵敏度，在这里我们提出并演示了如何将HCF盘绕到规定的几何形状可以进一步显着降低这种灵敏度。我们的概念验证实验表明，相对于未盘绕的HCF，减少了1090倍，并且相对于未盘绕的实芯光纤，减少了超过三个数量级。我们的策略利用纤维线圈的弹性特性的细微差别，由此复合材料（纤维+涂层）的受约束的热膨胀可以导致具有压缩的内层和膨胀的外层的线圈。热膨胀是导致HCF中的热相位灵敏度的主要效应，并且在该方案中，压缩的内部线圈层补偿外部层的热膨胀。在本研究中，我们利用有限元模拟来设计线圈的参数，研究线圈性能与其关键参数之间的关系。该原理验证线圈直径为160 mm，包含548 m长的HCF，其中230 m的部分显示出几乎为零（略负）的热相位灵敏度。虽然线圈显示出低的热相灵敏度超过几十个小时，在研究中的HCF中使用的涂层材料的长时间恒定的粘弹性性能被证明限制了这些好处。为了使该策略对于具有快速温度动态的系统实用，可以使用具有更稳定的机械性能的涂层。对于其中长的热时间常数已经是标准的精确定时系统，该方案代表低成本并且提供了立即可行的热灵敏度的显著降低。
Light traversing an optical fiber is subject to various local phase perturbations driven by temperature. This thermal phase sensitivity is undesirable in fiber interferometers and their applications which require that a fixed, stable phase be received after propagation. The use of hollow core fiber (HCF) has been shown to reduce this thermal phase sensitivity over solid core fibers and here we propose and demonstrate how coiling HCF to a prescribed geometry can further significantly reduce this sensitivity. Our proof-of-concept experiment shows reduction by a factor of ∼90 with respect to the uncoiled HCF, and over three orders of magnitude with respect to uncoiled solid core optical fiber. Our strategy exploits a nuance of the elastic properties of fiber coils whereby the constrained thermal expansion of the composite material (fiber + coating) can result in a coil having compressed inner layers and expanded outer layers. Thermal expansion is the dominant effect responsible for thermal phase sensitivity in HCFs, and in this scheme the compressed inner coil layers compensate the thermal expansion of the outer layers. In this study we design the coil parameters using finite element simulations, studying the relationship between coil performance and its key parameters. The proof-of-principle coil has 160 mm diameter and incorporates a 548 m length of HCF out of which a 230 m section shows almost zero (slightly negative) thermal phase sensitivity. Though the coil shows low thermal phase sensitivity over tens of hours, the long-time constant viscoelastic properties of the coating materials used in the HCF under study are shown to limit these benefits. To make this strategy practical for systems with fast temperature dynamics, a coating having more stable mechanical properties could be used. For precision timing systems in which long thermal time constants are already the norm, this scheme represents a low-cost and provides a significant reduction to thermal sensitivity which is immediately practicable.