A Novel Phase-Noise Cancelled Optical ...

We propose a novel OFDR method which improves spatial resolution by cancelling laser phase noise. Laser light is intensity-modulated with linearly swept frequency. Both the backscattered light and the reference light are divided into upper- and lower-sideband by optical filter. These two signals are detected and multiplied each other. The laser phase noise is cancelled by this multiplication. The proposed method is confirmed experimentally. The laser phase noise having 1.5MHz linewidth is cancelled by this method. This result confirms that this method is feasible to improve spatial resolution for OFDR.