Two compact Tunable Diode Laser Absorption Spectroscopy (TDLAS) sensor systems were developed based on different structural optical cores. The two optical cores combine two recent developments; gallium antimonide (GaSb)-based ICL and a compact multipass gas cell (MPC), with the aim of developing a compact TDLAS-based sensor for mid-IR gas detection with high detection sensitivity and low power consumption. The two-floor structure sensor was used for methane (CH4) measurements and the single-floor structure sensor was used for formaldehyde (CH2O) concentration measurements, with the two optical sensor cores consuming 3.7 W of power. Detection limits of ~5 nL/L and ~3 nL/L with measurement precisions of ~1.4 nL/L and ~1 nL/L were achieved for CH4 and CH2O concentration measurements, respectively. In addition, the two-structure system was used for CH4 and C2H6 detection under the same conditions over a period of 66 h campus. The results show that the sensors worked steadily and effectively. They can satisfy the system requirements of non-contact, online, real-time, high-precision, and rapid signal acquisition, as well as strong anti-jamming and high stability.