Conventional measurement systems for monitoring blade vibration generally use strain gauges attached to the surface of blades. Alternative noncontact measurement techniques are investigated in order to minimise the adverse effects of this method. In this paper, a new method based on groups of regularly spaced optical sensors and on apposite treatments is presented. An analytical model of the proposed monitoring system is introduced and some properties are studied. A general upper bound of the dynamic range is proposed. Some examples are presented and discussed. They assess the efficiency of this technique. Some specific situations are commented.The main advantage of the new system is its ability to analyse multicomponent blade vibrational signals on a large dynamic range with a reduced number of probes. Another interesting feature is that it enables the monitoring of all blades in a row.