Principles of terahertz (THz) interferometric synthetic aperture imaging with heterodyne and optical techniques are presented. A THz interferometric experiment based on optical up-conversion is set up. The received THz signal is modulated into an optical carrier and transmitted in a fiber. To simulate phase differences between two THz receivers, the output of receiver is divided and a phase shifter is placed before electro-optical modulation (EOM). Interferometric spectra of these modulated opti