Fig. 2. Sensor fabrication process: (i) two customized optical fibers with flat cleaved ends; (ii) the sensor is made by physically combining two single fibers together into one using sillicone glue; (iii) a thin layer of PDMS is then coated onto the combined end of bifurcated fiber; and (iv) the gas sensing beads with optical dyes are coated onto the thin PDMS layer; silicone glue, PDMS and micro-beads are shown below.