Construction of Heterodyne Detection System Utilizing Fiber Bragg Grating

Abstract

In this study, a heterodyne detection system is designed and constructed to detect the wavelength shift between the reference and sensing signals that results from temperature changes. A laser diode 1550 nm optical source is employed as a reference arm. While the sensing arm is represented by Erbium Doped Amplifier Fiber (EDAF). Fiber Bragg Grating (FBG) is used as a tunable element to generate different wavelengths according to the change in temperature. The Optical Spectrum Analyzer (OSA) displays the intermediate signal (beat signal) which, represents the difference between reference and sensing signals. As the temperature rises, the wavelength shifts linearly to a longer wavelength, whereas the wavelength shifts toward shorter wavelengths with the decrease in temperature. In the temperature range of (30-80) degrees Celsius, from the linear relation of beat (intermediate) wavelength and beat frequency versus the temperature, wavelength Sensitivity (WS) and Frequency Sensitivity (FS) as well as the resolution for heterodyne detection system in the case of heating and cooling, are analyzed and calculated.