Broadband high-resolution microwave frequency measurement based on photonic undersampling via using three cavity-less optical pulse sources with coprime repetition rates.

A photonic-assisted broadband and high-resolution microwave frequency measurement scheme is proposed and demonstrated based on undersampling via using three cavity-less optical pulse sources with coprime repetition rates. After undersampling by three ultrashort pulse trains with repetition rates in the order of gigahertz, input microwave signal is down-converted to three intermediate-frequency (IF) signals located in the first Nyquist frequency range. Through measuring the frequencies of the IF signals via fast Fourier transform after digitization by the commercially available analog-to-digital convertors, the input microwave signal frequency can be retrieved based on the frequency identification algorithm.

Self-referenced frequency response measurement of high-speed photodetectors through segmental up-conversion based on low-speed photonic sampling.

A self-referenced electrical method is proposed for measuring the frequency responses of high-speed photodetectors (PDs) through segmental up-conversion based on low-speed photonic sampling. The proposed method provides a very narrow linewidth and ultra-wideband optical stimulus by the segmental electro-optic up-conversion, and eliminates the uneven responses of mode-locked laser diode (MLLD) and electro-optic modulator (MOD) based on the symmetric frequency photonic sampling, which is free of any extra calibration. Moreover, it achieves ultra-wide and scalable frequency response measurement of PDs with 2M-fold measuring frequency range, where the symmetric sweeping frequency up to Nfr/2 of MOD enables the measuring frequency range of M × N×fr.

Frequency response measurement of high-speed electro-optic phase modulators via a single scan based on low-speed photonic sampling and low-frequency detection.

An approach to measuring frequency response of high-speed electro-optic phase modulators via a single scan is proposed and experimentally demonstrated. This method employs low-speed photonic sampling to transfer the response information at any high frequency to a fixed low-frequency duplicate in the first Nyquist frequency range by setting the microwave frequency sweeping step equal to the repetition rate of the mode-locked laser. Through low-frequency detection and analysis in the electrical domain, the relative frequency response can be directly calculated from the relative intensity between the low-frequency duplicate and the direct current component without calibration of the photodetector response.

Cross-referenced deadband-free microwave frequency measurement with cascaded-four-wave-mixing-based photonic harmonic down-conversion.

A cross-referenced and deadband-free method with photonic harmonic down-conversion is proposed for microwave frequency measurement based on cascaded-four-wave-mixing (CFWM) in semiconductor optical amplifiers. The proposed method enables ultra-wide and accurate frequency measurement with low-frequency spectrum detection, and at the same time achieves deadband-free and multi-tone frequency measurement by cross-referenced frequency discrimination. For a proof of concept, microwave signal measurement is experimentally demonstrated up to the 40 GHz frequency range with an 0.

Broadband high-resolution microwave frequency measurement based on low-speed photonic analog-to-digital converters.

An approach to microwave frequency measurement with a high resolution and a broad bandwidth is proposed based on three parallel low-speed photonic analog-to-digital converters (ADCs) architecture. Through simultaneously bandpass sampling the input microwave signal with the three photonic ADCs, the input frequency can be calculated from the Fourier frequencies of the photonic ADCs using the proposed frequency recovery algorithm. Theoretical analysis and simulation results indicate that the proposed method is applicable for both single-tone and multi-tone microwave signals.

Broadband linearization in photonic time-stretch analog-to-digital converters employing an asymmetrical dual-parallel Mach-Zehnder modulator and a balanced detector.

A broadband linearization scheme for time-stretch analog-to-digital converters (TS-ADCs) is proposed based on an asymmetrical dual-parallel Mach-Zehnder modulator and a balanced detector. The theoretical and simulation results indicate that, compared with the differential and arcsine operation method generally employed in TS-ADCs, the proposed scheme has a superior performance on enhancing the spur-free dynamic range and suppressing the even-order distortions and the third-order spurs even under a large modulation depth. Additionally, the proposed scheme realizes online linearization.