  We have demonstrated displacement- and frequency-noise free laser
interferometry (DFI) by partially implementing a recently proposed optical
configuration using bi-directional Mach-Zehnder interferometers (MZI). This
partial implementation, the minimum necessary to be called DFI, has confirmed
the essential feature of DFI: the combination of two MZI signals can be carried
out in a way which cancels displacement noise of the mirrors while maintaining
gravitational wave signals. The attained maximum displacement noise suppression
allowed a simulated-SNR of 45dB.
