Dual-Fiber Wavelength-Tuned Photonic-Delay Phase-Noise Measurement

The development of microwave photonics has revitalized the field of microwave measurements where, among other factors, the need to characterize phase noise is essential for the development of oscillators. Optical fiber, with its low losses and its ability to implement long time delays, attracted attention to the delay-line method for phase-noise measurements. However, for correct operation, an accurate adjustment of the phase and/or delay is required. We address this issue by utilizing the chromatic dispersion of the optical fiber to implement the wavelength-tuned time delay. A novel, dual-fiber, wavelength-tuned, photonic-delay solution for the measurement of phase noise is proposed, which extends the phase-tuning range and enables self-adjustment. The proposed approach is experimentally demonstrated and validated by measuring 10-GHz microwave oscillators. The noise floors achieved during the experiment were -117 dBc/Hz and -136 dBc/Hz at 1 kHz and 10 kHz, respectively.