  Refractive-index (RI) sensing plays a pivotal role in various domains,
encompassing applications like glucose sensing, biosensing, and gas detection.
Despite the advantages of optical fiber sensors, such as their compact size,
flexibility, and immunity to electromagnetic interference, they are often
plagued by temperature-induced drift, which adversely impacts the accuracy of
RI measurements. This study introduces an innovative approach to alleviate
temperature-induced drift in RI-sensing optical frequency combs (OFCs) by
employing active-dummy compensation. The central idea revolves around the
utilization of a dual-comb setup, comprising an active-sensing OFC that
monitors both sample RI and environmental temperature, and a dummy-sensing OFC
that exclusively tracks environmental temperature. The disparity between these
sensor signals, denoted as delta_frep, effectively nullifies the effects of
temperature variations, yielding a temperature-independent sensor signal for
precise RI measurements. This investigation delves into the relationship
between active-dummy temperature compensation and delta_frep. It becomes
evident that diminishing delta_frep values enhance temperature compensation,
thereby diminishing fluctuations in delta_frep caused by environmental
temperature shifts. This compensation technique establishes a direct link
between delta_frep and sample RI, paving the way for absolute RI measurements
based on delta_frep. The findings of this research are a valuable contribution
to the advancement of accurate and temperature-compensated RI sensing
methodologies using dual-comb setup. The insights gained regarding delta_frep
dependency and the strategies proposed for enhancing measurement precision and
stability hold significant promise for applications in fields of product
quality control and biosensing.
