2-laser injection-locking configuration for Brillouin fibre sensors

We propose in this paper a novel method for generating the pump and probe signals for a Brillouin fibre sensor. It is based on the injection locking of two distinct semiconductor lasers, that makes possible the generation of high purity beat signals in the microwave frequency range. Such a technique can be used either in the pulsed pump-probe technique or the new correlation-based technique. Furthermore novel devices, such as laser modules presenting integrated electro-absorption modulators, can be exploited for achieving efficient and cost effective injection locking schemes.

Principle

When coherent light from one laser is coupled into the cavity of another laser, the latter may leave its own emission frequency and shift into the frequency of the injected light. The first laser is called the MASTER laser and the light source into which light is coupled is named the SLAVE laser. As the frequency locking of the slave laser is achieved by the injection of an external signal, the technique is referred to as laser injection locking. A suitable light isolation has to be introduced between the two lasers, in order to avoid that the light emitted by the slave laser perturbs the master laser emission.