Opt Quant Electron (2010) 42:15–28 DOI 10.1007/s11082-010-9418-7 LED based fiber optic surface plasmon resonance sensor Sarika Singh · R. K. Verma · B. D. Gupta Received: 22 December 2009 / Accepted: 21 September 2010 / Published online: 8 October 2010 © Springer Science+Business Media, LLC. 2010 Abstract Modeling of a miniaturized fiber optic sensor based on surface plasmon reso- nance utilizing a broad band diffuse source is presented. Attenuated total internal reflection with Kretschmann configuration is the basis of the theoretical model. For simulation both meridional and skew rays are considered. The performance of the sensor is evaluated in terms of sensitivity, detection accuracy and signal to noise ratio. Effects of the numerical aperture of the fiber, core diameter and length of the sensing region on the performance parameters of the sensor are studied. The results are obtained for gold and silver metallic layer on the core of the fiber. The theoretical results obtained are compared with SPR based fiber optic sensor utilizing focused beam on the end face of the fiber from a collimated source. The advantages of using broadband LED (diffuse source) source for launching light in the fiber are the miniaturization, compactness and low cost of the sensor. Keywords Surface plasmon · Optical fiber · Evanescent wave · Sensor · LED 1 Introduction From the last few years, surface plasmon resonance (SPR) technique has revolutionized the field of fiber optic sensor technology. Introduction of optical fiber has made the sensing technique very important because of its light weight, smaller size and capability of use in distributed and remote sensing (Liedberg et al. 1983; Jorgenson and Yee 1993; Ozdemir and Sayan 2003; Mitsushio et al. 2004; Diaz-Herrera et al. 2006; Rajan et al. 2006; Gentleman and Booksh 2006; Rajan et al. 2007). Surface plasmons are TM polarized electromagnetic excitations at the boundary between the metal and a dielectric with their field decaying exponentially both in the metal as well as in the dielectric medium. In SPR based sen- sors, Kretschmann’s configuration is widely used to excite surface plasmons using evanes- cent field of a p-polarized light. Since the light guidance in an optical fiber occurs due to S. Singh · R. K. Verma · B. D. Gupta (B ) Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India e-mail: bdgupta@physics.iitd.ernet.in 123