Dual photonic-delay line cross correlation method for phase noise measurement

We describe the application of a cross-correlation method with dual photonic delay-line for homodyne phase noise measurement of low-noise microwave oscillators. This method combines a delay-line discriminator and cross correlation with the use of a low-loss kilometer-long photonic delay. By using a 4.5 km optical fiber as a photonic delay, we demonstrated a measurement noise floor of -158 dBc/Hz at 10 kHz offset without a reference oscillator.