<p>This study presents a biological sensor based on terahertz beat frequency using a single short period uniform fiber Bragg grating (SP-uFBG) that has been specifically designed to exhibit remarkable sensitivity in the sub-terahertz range. The sensor demonstrates exceptional performance in the realm of biochemical, biomedical, and chemical sensing and other applications. The FBG is partitioned into two distinct regions, specifically the reference sub-region and the fully de-cladded sub-region, in order to optimize its performance for terahertz sensing applications. The proposed methodology employs the thoroughly removed portion to alter the reflected frequency of the de-cladded sub-region in relation to the reference sub-region. The sensitivity of modified FBG has been assessed using urea, glucose, and sodium chloride, demonstrating a noteworthy degree of sensitivity for the proposed sensor, which it reached to <b>~</b> -1.34 THz/RIU. The findings of this study illustrate the efficacy of a SP-uFBG in the detection of biological substances within the terahertz frequency range. These results highlight the remarkable sensitivity of the SP-uFBG across a wide range of analytes. The utilization of a single SP-uFBG Dual-wavelength in terahertz biological sensing shows a dependable sensing methodology that is compact, not complicated, high-repetition and economically viable, all the while upholding a commendable degree of sensitivity.</p>