Rapid development of a new type of air-core guiding fibers, the so-called Antiresonant Hollow-Core Fibers (ARHCFs), have brought a wide range of new application areas of the optical fiber technology. One of them is the laser spectroscopy of gases, where the interaction path length between the gas molecules and the laser beam is one of the most important factors defining the detection capability of the sensors. Due to the ability of efficient light guiding in an empty core, ARHCFs can be filled with the target gas and form long and low-volume absorption cells in the sensor, delivering the interaction distance required by the user and application. However, successful application of the gas-filled ARHCFs necessitates combining several factors, i.e. low-loss guidance and optimized structure of the ARHCF, proper sensor setup, and an efficient gas sensing technique. In this work, we report for the first time the development of a Chirped Laser Dispersion Spectroscopy (CLaDS) sensor of ethane (C2H6) aided with a 30 m long ARHCF-based absorption cell. Thanks to this unique configuration with an extended laser-gas molecules interaction path, the sensor reached a superb detection capability of ∼15 parts-per-trillion by volume (pptv) for a 25-s integration time with a noise equivalent absorption (NEA) coefficient of 3.5 × 10−10 cm−1. The sensitivity of the sensor beats the performance of the reported up to date detectors utilizing mid-IR hollow-core fibers (HCFs).