Flow cell with hybrid LPG and FBG optical fiber sensor for refractometric measurements

The combination of a long period grating and a fiber Bragg grating written on the same fiber is described as method to reduce noticeably the interferences caused by strain and temperature in the measurement of refractive index. The hybrid LPG and FBG optical fiber sensor is manufactured and located in a small volume flow cell. The whole system with its flow cell and the gratings fabrication are extensively described as well as both the acquisition and data processing. The maximum sensor sensitivity and resolution are about 3120 nm/RIU and 2 x 10-5 RIU, respectively.