Simultaneous Interrogation of a Hybrid FBG/LPG Sensor Pair Using a Monolithically Integrated Echelle Diffractive Grating

A simultaneous interrogation technique of a hybrid fiber Bragg grating (FBG) and long-period grating (LPG) sensor pair is proposed and demonstrated using a monolithically integrated echelle diffractive grating (EDG). The operation principle that is based on the monotonic temperature dependence of the EDG transmission wavelengths is presented. Initial results show that a 1-pm resolution and 24-nm interrogation range are achieved by using the proposed interrogation technique, which can effectively be implemented to interrogate hybrid FBG/LPG-based sensor pairs for the discrimination of refractive index (RI)/temperature in RI measurement. The specially designed EDG-based interrogator has the added features of low cost and compact size.