This paper demonstrates how the translucency of glass fiber-reinforced polymer (GFRP) laminates allows the derivation of their mechanical properties through optical measurements. Spectrophotometric, goniophotometric and tensile experiments were performed on unidirectional and cross-ply hand lay-up GFRP laminates with fiber volume fractions ranging from 0.15 to 0.45. An analytical model to predict the directional fiber volume fractionsand thus the mechanical properties of GFRP laminateshas been developed based on the total and diffuse transmittance and directional light scattering of the laminates. It is demonstrated that structurally optimized GFRP laminates can meet the requirements for GFRP skylights and the encapsulation of photovoltaic cells into translucent GFRP laminates.