High spatial resolution OFDR based on broadened optical frequency sweeping by four-wave-mixing

We demonstrate a method for high spatial resolution optical frequency domain reflectometry (OFDR) by utilizing degenerated four-wave-mixing (FWM) for broadening the frequency sweeping. High order sideband is obtained from an optical comb and is consequently utilized as the pump for the FWM. An idler wavelength is produced after the FWM and 21-times broadened optical frequency sweeping is achieved compared with the radio frequency (RF) sweeping. 0.75-cm spatial resolution is obtained with RF frequency sweeping span of 638.4 MHz.