So as to covalently graft a chemical on a substrate, the GraftFastTM process can be used; the only requirement is that the chemical has at least one aromatic primary amine. In this work, this simple and fast process is presently used to graft dyes that are pH sensitive on an optical fiber, thus creating a pH sensor called optode. The major asset of this grafting process is that the dye is covalently grafted on the fiber, resolving stability issues encountered with other techniques – like physical entrapment or electrostatic interactions. Two different dyes have been successfully grafted on gold lamellas (which are the reference substrates for the GraftFastTM process), and an innovative experimental method to increase the thickness of the dye layer has been developed.