The demonstration of an interferometric temperature sensor based on a no-core fiber (NCF) with a thin layer of copper oxide-polyvinyl alcohol (CuO-PVA) coating is presented in this paper. The sensing principle relies on the multimode interference (MMI) effect that occurs in a pure silica multimode fiber (MMF) sandwiched between two single-mode fibers (SMFs), where the MMF section is an NCF. To accomplish high sensitivity, the cladding of the NCF was chemically etched at a rate of ∼2.84 μm min⁻¹ until it reached a diameter of 18 μm. Then a thin film of CuO-PVA was coated onto the etched region to act as the sensitive cladding layer, whose refractive index (RI) varies with the environmental temperature variation. The effective interaction between the CuO-PVA and the strong evanescent field of the etched NCF results in temperature sensing with a maximum resonant wavelength shift of 21.5 nm. The maximum sensor sensitivity obtained was 0.101 nm/°C with a linear coefficient of 99.1 % in the range of 25 °C to 235 °C. To the best of our knowledge, this is the first demonstration of a temperature sensor based on an etched NCF coated with CuO-PVA thin film. This work presents an important step to enhance the performance of an all optical temperature sensor in terms of sensitivity and repeatability.

本文演示了一种基于无芯光纤（NCF）并具有一层薄薄的氧化铜-聚乙烯醇（CuO-PVA）涂层的干涉式温度传感器的演示。传感原理依赖于夹在两条单模光纤（SMF）之间的纯石英多模光纤（MMF）中发生的多模干扰（MMI）效应，其中MMF部分为NCF。为了实现高灵敏度，以约2.84μmmin ^-1的速率对NCF的覆层进行化学蚀刻。直到直径达到18μm。然后，将CuO-PVA薄膜涂覆到蚀刻区域上以用作敏感覆层，其折射率（RI）随环境温度变化而变化。CuO-PVA与蚀刻后的NCF的强消逝场之间的有效相互作用导致温度感测的最大共振波长偏移为21.5 nm。获得的最大传感器灵敏度为0.101 nm /°C，线性系数在25°C至235°C范围内为99.1％。就我们所知，这是首次基于涂覆有CuO-PVA薄膜的NFC蚀刻温度传感器的演示。这项工作为提高全光学温度传感器的灵敏度和可重复性提供了重要的步骤。