In this work, a dual functionality fiber optic sensing system for thermoset cure monitoring has been developed and successfully tested. Principle of operation relies on the use of a standard optical fiber in single ended configuration containing a single infiber Bragg grating. The change in refractive index directly related to material density at fiber end and the variation in the wavelength reflected by the fiber grating have been monitored simultaneously, throughout an In-Mould curing process of an epoxy resin. A compact and low cost in-fiber dual wavelength demodulation system has been developed and experimental results demonstrate the capability to on line identify the degree of cure, gel point, residual stresses and the glass transition temperature of the cured resin. (C) 2003 Elsevier B.V. All rights reserved.