Low in-band spurious arbitrary waveform generator based on a 1-bit time-wavelength interleaved photonic digital-to-analog conversion.

We proposed an arbitrary waveform generator based on a 1-bit photonic digital-to-analog conversion (PDAC). The system is based on the principle of photonic pulse sampling and time interleaving. High-speed optical pulses are generated and modulated by digital signals and then synthesized in one path. The analog signals are obtained by an optical-to-electrical conversion of the time-interleaved pulses. Due to the 1-bit structure, there are no spurious components in principle. In the experiment, a 1-bit PDAC of 50 GSa/s is realized, and the X-band linear frequency-modulated (LFM) waveform with a bandwidth of 4 GHz is generated, the signal-to-spur-rejection ratio is as high as 50 dB, and the millimeter-wave 64QAM signal is generated, with an EVM of 4.27%.

Result-oriented lumped error correction for photonic-assisted broadband phased array processors.

Imperfect optoelectronic devices deteriorate the performance of microwave photonic (MWP) systems and then hinder further practical application. This paper proposes a result-oriented lumped error correction to address the problem in the photonic-assisted broadband phased array. Herein, we focus on the evolution of the ultimate output resulting from various errors due to the nonideality of components. By establishing the static calibration base set (CBS) with tangent line approximation, the correction procedure is simplified, and the output degradation is greatly improved. Experimental results show the effective number of bits (ENOB) at the final output has been enhanced from 2.5 to 6.1. Further, double objectives optimization and imaging correction are demonstrated experimentally. The range resolution has been boosted from 3.9 cm to 2.4 cm, and the quality of the inverse synthetic aperture radar (ISAR) images is improved using the proposed method.

Ultrafast and temperature-insensitive strain interrogation using a PM-PCF based Sagnac loop interferometer and wavelength-to-time mapping.

A novel approach for ultrafast and temperature-insensitive strain interrogation using a polarization-maintaining photonic crystal fiber (PM-PCF) based Sagnac loop interferometer (SLI) and linear wavelength-to-time (WTT) mapping is proposed and experimentally demonstrated. The PM-PCF incorporated in the SLI is used as the sensing element to achieve stable strain sensing with ultra-low temperature-dependence due to its intrinsic thermal insensitivity, which can be used to eliminate the cross-sensitivity effect and increase the measurement accuracy. A dispersive element is employed to realize the WTT mapping and real-time strain interrogation is obtained by converting the strain-encoded wavelength shift to time shift in the temporal domain, which can be directly monitored by a real-time oscilloscope. The proposed system offers an ultrafast interrogation speed of 100 MHz and a strain sensitivity of -0.17 ps/µÎµ.

Stable, precisely controlled, and switchable thulium-doped fiber laser based on cascaded mode interference filters.

This research experimentally demonstrates a switchable, single-wavelength, thulium-doped fiber laser based on the cascading of a multimode-single-mode-multimode (MSM) fiber filter and a two-mode fiber (TMF) filter. When the MSM fiber filter suffers from bending, the blue-shift of the output spectrum can be obtained. A switchable lasing wavelength output is realized by bending the MSM fiber filter to cover different channels of the TMF filter. The output wavelength can be switched from 1982.54 to 1938.81 nm with an optical signal-to-noise ratio of higher than 40 dB. The wavelength interval of the switchable output is an integral multiple of the wavelength interval of the TMF filter. The stability of the output wavelength was tested within 60 min, and the wavelength shift and output power fluctuation were found to be less than 0.01 nm and 0.31 dB, respectively, which demonstrates a stable output performance.

Tera-sample-per-second single-shot device analyzer.

With the ever-increasing need for bandwidth in data centers and 5G mobile communications, technologies for rapid characterization of wide-band devices are in high demand. We report an instrument for extremely fast characterization of the electronic and optoelectronic devices with 27 ns frequency-response acquisition time at the effective sampling rate of 2.5 Tera-sample/s and an ultra-low effective timing jitter of 5.4 fs. This instrument features automated digital signal processing algorithms including time-series segmentation and frame alignment, impulse localization and Tikhonov regularized deconvolution for single-shot impulse and frequency response measurements. The system is based on the photonic time-stretch and features phase diversity to eliminate frequency fading and extend the bandwidth of the instrument.