Highly accessible low-loss fiber tapering by the ceramic housed electric furnace (CHEF) and frequency-domain real-time monitoring

Tapered optical fibers are versatile tools with a wide spectrum of applications, ranging from sensing to atomic physics. In this work, we developed a highly accessible and controllable fiber tapering system to fabricate tapered optical fibers with a routine optical transmission of 95% and above. With an optimal design, optical transmissions higher than 99% have been experimentally demonstrated. We achieved such results by developing two unique components in a traditional heat-and-pull system: a custom-made miniature heater named as the ceramic housed electric furnace (CHEF) and a real-time, frequency-domain monitoring method. The CHEF enables a well-controlled, uniform, and stable heating zone for an adiabatic tapering process, while the frequency-domain monitoring empowers one to reliably terminate the tapering right after the single-mode trigger. We designed and fabricated the CHEF using low-cost and readily accessible materials and equipment, in order to benefit a broader audience. We carried out a parametric study to systematically characterize the CHEF performance and provided guidelines for the CHEF design, fabrication, and operation. The frequency-domain monitoring method was developed based on our understanding of the dynamic evolution of optical modes in the tapered fiber. Such a method allows real-time visualization of the number of optical models and characterization of the taper adiabaticity during the tapering process, both of which are not available with the commonly used time-domain monitoring. The developed CHEF-based fiber tapering system will meet the urgent need of high-quality tapered optical fibers as well as opening doors to new applications of tapered optical fibers.