Formalin detection using singlemode-multimode-singlemode fiber structure

We demonstrate the singlemode-multimode-singlemode (SMS) fiber structure for formalin detection. Formalin is a formaldehyde compound in water with an average concentration of 37 % and 15 % of methanol and water. Formalin consists of two substances; formaldehyde and water. Formaldehyde contamination in foods causes a negative effect for body. International Agency for Research on Cancer (IARC) classifies formaldehyde into Group 1 (carcinogenic to humans). Detection contamination of formalin in foods is very important. In this work, SMS fiber structure was used for formalin detection due to easy fabrication, cheap and more accurate in readings. This experiment utilized a difference in refractive index that affects the power output from optical fiber.