The use of composite materials has increased considerably in the past 30 years. However, many of the molecular level processes occurring in the interfacial region have yet to be investigated. In this regard, an in situ Fourier transform near infrared technique has been demonstrated herein. This technique utilizes a seven-fiber bundle to examine monolayer and sub-monolayer level surfactant adsorption at the silica optical fiber/solution interface. It is felt that this technique will greatly increase the knowledge of the processes involved in the improvement of mechanical properties of silane treated composites.