Gas weak absorption in near-infrared is considered as inherent limit hinder the achievement of the miniaturized gas sensor. Thus, cavity enhanced absorption spectroscopy (CEAS) techniques are used to enhance the sensitivity by improving light-matter interaction length. In this work, a novel cavity enhanced technique is proposed based on the detection of the optical signal beating on RF analyzer to enhance the signal to noise performance by eliminating the flicker noise. Besides, enhancing the effective interaction length. The source consists of a fiber drum, a directional coupler, a tunable filter with FWHM of 1 nm and a semiconductor optical amplifier pumped above the laser threshold. The ring length is 1004 m leading to an FSR of 199 kHz. The gas cell is inserted into another ring, which consists of two directional couplers. The ring length is 6 m leading to an FSR of 33 MHz. The large ratio between the lengths of the two rings eliminates the need for a mode-locking technique. The acetylene gas cell is measured around 1535 nm. The novel technique capable of enhancing measurement sensitivity, providing experimental sensitivity and flicker noise immunity.