Hamid Reza Solaimany Nazar - Faculty of Electrical and Computer Engineering, Tarbiat Modares University, Tehran, Iran
Vahid Ahmadi - Faculty of Electrical and Computer Engineering, Tarbiat Modares University, Tehran, Iran
Ali Reza Solaimany Nazar - Chemical Engineering Dept., Faculty of Engineering, University of Isfahan, Isfahan, Iran

Creatinine (CR) is a byproduct of muscles that acts as a biomarker to evaluate human kidney function. In this paper, an effort has been made to present a fiber optic sensor based on the Vernier effect for measuring (CR) concentration in aqueous solutions. The sensor is fabricated by cascading two in-line Mach-Zehnder interferometers (MZI). MZIs exploit multimode–single-mode–multimode (MSM) configuration. The transmitted signal spectrum of the sensor with Vernier effect is recorded as the sensor is subjected to different concentrations of CR solutions. The wavelength shifts in the extracted envelope of the transmitted light are proportional to the concentration of CR solutions. The sensor exhibits a sensitivity of ۷۵۴۰pm/(mg/dL) in the physiological range of CR solutions (۰.۵ to ۳ mg/dL). The suggested sensor is easy to fabricate, ultra sensitive, and responds fast and linearly in low concentrations of CR solutions besides other benefits that fiber optic sensors offer such as being low cost and available.

Fiber optic sensor, Mach-Zehnder interferometer, Creatinine, Vernier effect