FABRI–PEROT PARALLEL INTERFEROMETERS WITH INTEGRATED ADDRESSABLE FIBER BRAGG GRID FOR MEASURING TEMPERATURE AND PRESSURE

Abstract

The report presents a new two-parameter sensor based on parallel Fabry-Perot interferometers, each of which is formed on the basis of two ultra-short fiber Bragg gratings with different measuring bases, to create a reference and measuring channels for pressure control. Each interferometer has an additional built-in addressable fiber Bragg structure for temperature control and compensation. The uniqueness of the sensor lies in the fact that the use of addressable fiber Bragg structures is dual, its function in both channels is to form probing radiation with two and three components for interrogating interferometers, and to impart an addressable feature to measurements. The proposed sensor is characterized by low cost and ease of manufacture of interferometers, has structural integrity, since the Bragg gratings and structures are recorded in-fiber, allows operation in the range of high pressure measurement up to 5 MPa and high temperature up to 500 °C, since the fiber is used without an external polymer coating. High sensitivity of measurements is ensured by the spectral characteristic of the sensor, formed by the Vernier effect during the interaction of two parallel interferometers, as well as the use of microwave photonic interrogation of the Vernier envelope at the beat frequencies of the address structures’ components.