Development of fiber optical delay line based 10 GHZ phase noise measurement system
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Microwave photonics is an emerging field of study exploiting broadband, low loss photonics technology for high spectral purity microwave generation, processing and distribution. Fiber optical delay lines are such systems employed successfully for generation and phase noise analysis of microwave signals with high spectral purity. Low loss and wide bandwidth of the fiber optical delay line permits much larger delays to be realized at a reasonable loss at microwave frequencies. In this study, fiber optical delay line based frequency discriminator phase noise measurement system is designed and implemented to resolve ultra low phase noise spectra of optoelectronic oscillators. System design is described in detail including fiber optical and microwave component characterizations, selection criteria, system stabilization against environmental uctuations and system calibration. Phase noise measurements for various RF synthesizers available in the laboratory are conducted with the developed system and compared to spectrum analyzer phase noise measurements to validate system calibration. Finally, phase noise spectra of optoelectronic oscillators (OEO) with 1 km and 2 km delay elements are demonstrated with the developed system. With 2 km OEO, system can resolve phase noise spectra as low as -140 dBc=Hz at 10 kHz offset from 10 GHz carrier frequency.