Design System of Optical Heterodyne Detection Based on Temperature Sensor

Abstract

Optical Heterodyne Detection (OHD) technique is based on two separate sources with optical interference between them. The optical signal from a specific light source is compared with a separate reference signal from another source. The Fiber Bragg grating (FBG) reflect a specific wavelength λB and transmit the other wavelengths within the laser source spectral. This is achieved by changing the refractive index generated by periodic variation of optical fiber core, which reflect a specific wavelength, so FBG can be used to withhold a certain wavelength and allow other wavelengths to transmit. In this paper, a new method of an OHD has been designed using Optisystem software. Optical fiber as a temperature sensor element with single source and two FBGs have used in this system. the first FBG used as a tunable source and the other has used as a sensing element. The two optical signals have been combined utilizing a photodetector. It has a linear response to the light energy, while having a quadratic response with the amplitude of the electromagnetic field. The results show that the beat frequency shift has a linear response to the temperature with sensitivity about 2.24 GHz/Co.