Optical FM-CW signal generation for millimeter-wave imaging and OFDR applications

For high-precision imaging by radio, a millimeter wave (MMW) is a promising candidate owing to its short wavelength and broad range of available bandwidths. However, high atmospheric attenuation in the MMW band strictly limits the transmission distance, and a lossy conventional coaxial cable cannot configure a network for the distribution of a signal. Radio-over-fiber (RoF) technology based on optical fiber communication aids in realizing easy signal distribution with a low-loss optical fiber [1]. Moreover, a recent optical modulation technique can form an MMW signal precisely at a frequency greater than 100 GHz, with broadband optical modulators and photodetectors [2]. In this study, we demonstrate optical-MMW signal generation for highly accurate frequency-modulated continuous-wave (FM-CW) radar as well as optical frequency domain refiectometry (OFDR).