Optical Vernier Effect in Fabry-Perot Interferometers Based on Ultra-Short Fiber Bragg Gratings

The optical Vernier effect (OVE) generated by optical fiber Fabry-Perot interferometers (FPIs) has gain emphasis for sensing applications due to the high sensitivities and resolutions these devices can achieve. Here, we experimentally demonstrate the production of cascaded intrinsic FPIs with amplified sensitivity by the OVE, using ultra-short fiber Bragg gratings (USFBGs) inscribed with a Nd:YAG laser system. This method is an alternative solution with great versatility and repeatability, which can improve the production and dissemination of devices with enhanced sensitivity. Three sensing devices are proposed, and their viability is demonstrated, where different magnification factors and operation bandwidths are presented. Strain and temperature tests were performed to the proposed sensors, demonstrating sensitivity magnifications of about 25 and 42 when compared with a single USFBG-based FPI. These sensors have great potential in terms of production and sensing applications, by allying the main advantages of the FBG technology with the OVE.