An optical reader system is described herein which has a single mode (SM) optical fiber launch/receive system that uses one or more SM optical fibers to interrogate a biosensor and does not use multimode (MM) optical fibers to interrogate the biosensor. The use of the SM optical fiber launch/receive system effectively reduces angular sensitivity, reduces unwanted system reflections, improves overall angular tolerance, and improves resonant peak reflectivity and resonant peak width. Two specific embodiments of the SM optical fiber launch/receive system are described herein which include: (1) a dual fiber collimator launch/receive system; and (2) a single fiber launch/receive system that interrogates the biosensor at a normal incidence.