AI Article Synopsis
- This study uses dual-output Mach-Zehnder modulators to compare a femtosecond pulse train with a microwave signal, effectively reducing amplitude-to-phase modulation conversion noise by over 40 dB.
- A high-sensitivity phase noise measurement technique is developed, achieving impressive results with phase noise levels of -186 dBc/Hz at frequencies above 10 kHz, corresponding to thermal noise from a +9 dBm carrier signal.
- The method effectively compares a 1-GHz femtosecond laser to a 1-GHz microwave signal from a mode-locked laser, with observed noise limitations primarily due to the characteristics of the used lasers and photodetector.
Article Abstract
We demonstrate the use of two dual-output Mach-Zehnder modulators (DO-MZMs) in a direct comparison between a femtosecond (fs) pulse train and a microwave signal. Through balanced detection, the amplitude-to-phase modulation (AM-PM) conversion effect is suppressed by more than 40 dB. A cross-spectrum technique enables us to achieve a high-sensitivity phase noise measurement (-186 dBc/Hz above 10-kHz offset), which corresponds to the thermal noise of a +9 dBm carrier. This method is applied to compare a 1-GHz fs monolithic laser to a 1-GHz microwave signal generated from photodetection of a free-running 500 MHz mode-locked laser. The measured phase noise is -160 dBc/Hz at 4-kHz, -167 dBc/Hz at 10-kHz, and -180 dBc/Hz at offset frequencies above 100-kHz. The measurement is limited by the free-running 500-MHz laser's noise, the flicker noise of the modified uni-traveling carrier photodiode and the thermal noise floor, not by the method itself. This method also has the potential to achieve a similar noise floor even at higher carrier frequencies.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5847530 | PMC |
| http://dx.doi.org/10.1038/s41598-018-22621-1 | DOI Listing |
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View Article and Find Full Text PDFHigh-sensitivity optical to microwave comparison with dual-output Mach-Zehnder modulators.
Sci Rep
March 2018
Department of Physics, The University of Colorado, Boulder, Colorado, 80309-0390, USA.
Article Synopsis
- This study uses dual-output Mach-Zehnder modulators to compare a femtosecond pulse train with a microwave signal, effectively reducing amplitude-to-phase modulation conversion noise by over 40 dB.
- A high-sensitivity phase noise measurement technique is developed, achieving impressive results with phase noise levels of -186 dBc/Hz at frequencies above 10 kHz, corresponding to thermal noise from a +9 dBm carrier signal.
- The method effectively compares a 1-GHz femtosecond laser to a 1-GHz microwave signal from a mode-locked laser, with observed noise limitations primarily due to the characteristics of the used lasers and photodetector.
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View Article and Find Full Text PDFTo generate linearly chirped microwave signals with a large frequency tunable range, a photonic approach is proposed. Firstly, A dual-output dual-parallel Mach-Zehnder modulator (DPMZM) followed by the polarization beam combiner and an optical filter is utilized to generate orthogonally polarized ± second-order optical sidebands. Then a polarization modulator is employed to achieve the phase modulation of the two wavelengths.
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