Behavioral model of a self-mixing laser diode sensor

The spectral properties of a laser diode are modified when the optical beam is back-scattered into the active cavity of the laser. Based on the use of this optical feedback, the self-mixing effect has been demonstrated to be suitable for sensing applications. This is an emerging technique enabling notably displacement, distance and/or velocity measurements to be performed. However, the self-mixing signal shape is strongly modified by the strength of the back-scattering and by nonlinear phenomena governing the global behavior of the laser diode. This makes signal processing rather challenging. In this paper, a new high-level model is proposed to represent the self-mixing phenomenon and to simplify the solution of nonlinear equations involved in this problem. This model is represented by schematic block diagrams commonly used for the description of complex systems in the domains of nonlinear mechanics, telecommunications, sensors, actuators, etc. This approach will allow the use of powerful and standard simulation tools such as Spice, VHDL-AMS or MATLAB/Simulink to develop new methods for signal processing of optical feedback interferometers, notably in the case of displacements measurements.