De Ben

Tunable Frequency-Quadrupling Dual-Loop Optoelectronic Oscillator

A tunable frequency-quadrupling dual-loop optoelectronic oscillator (OEO) based on a polarization modulator is proposed and demonstrated. The introduce of frequency quadrupling in the proposed OEO not only increases the maximal achievable frequency by four times, extends the tuning range by four times, but also enables powerful optical signal processing functions. By incorporating an electrical-tunable yttrium-iron-garnet bandpass filter in the proposed OEO and employing a fiber Bragg grating as a wavelength-fixed optical notch filter, a high-quality microwave signal with a frequency tunable from 32 to 42.7 GHz is generated. The phase noise of the generated frequency-quadrupling signal is also studied.

Tunable Optoelectronic Oscillator Based on a Polarization Modulator and a Chirped FBG

A wideband-tunable optoelectronic oscillator (OEO) is proposed and experimentally demonstrated based on a tunable microwave photonic filter (MPF) consisting of a polarization modulator, a chirped fiber Bragg grating, and a polarization beam splitter (PBS). By simply adjusting the polarization state of the signal before the PBS, the center frequency of the MPF is tuned. The proposed OEO is experimentally demonstrated. A high-purity microwave signal with a tunable frequency within 5.8-11.8 GHz is generated. The single-sideband phase noise of the generated signal is -104.56 dBc/Hz at 10-kHz offset.

High-Performance Photonic Microwave Downconverter Based on a Frequency-Doubling Optoelectronic Oscillator

Photonic microwave downconversion based on an optoelectronic oscillator (OEO) is interesting because the local oscillator signal is directly extracted from the RF signal, but some of the frequency components in the RF signal would leak to the oscillation signal due to the limited rejection ratio of the electrical bandpass filter in the OEO, which degrades the downconverted signal. In this paper, a high-performance photonic microwave downconverter based on a frequency-doubling OEO (FD-OEO) is proposed and demonstrated to avoid the direct degradation from the RF signal. A 20-GHz RF signal with 1-Gb/s data modulation is successfully downconverted by the FD-OEO. The phase noise at 10-kHz frequency offset of the extracted RF carrier by the FD-OEO is 14 dB lower than that extracted by a conventional OEO, and the receiver sensitivity of the downconverted signal has a 1.173-dB improvement. The downconverter needs only low-frequency devices, which may find application in phased-array antenna arrays, electronic warfare receivers, avionics, and wireless communication systems.

Frequency-Quadrupling Optoelectronic Oscillator for Multichannel Upconversion

A frequency-quadrupling dual-loop optoelectronic oscillator (OEO) is proposed and demonstrated by two cascaded polarization modulators. The introduction of frequency quadrupling to the proposed OEO requires no optical filtering, which not only increases the maximal achievable frequency by four times, but also enables powerful optical signal processing functions. An experiment is carried out. A high-quality millimeter-wave signal at 39.75 GHz is generated using low-frequency devices. Photonic microwave upconversion at two wavelength channels is also demonstrated on the basis of the proposed frequency-quadrupling OEO.

Injection-locked fiber laser for tunable millimeter-wave generation

A dual-ring injection-locked fiber laser consisting of a ring of optoelectronic oscillator (OEO) and a ring of fiber laser is proposed and demonstrated for tunable millimeter-wave (mm-wave) generation. The approach combines the advantages of mm-wave generation based on OEOs and fiber lasers, which can generate a high-frequency, low-phase-noise, and a mode-hopping-free mm-wave signal with a large tuning range. A low-phase-noise mm-wave signal with a tunable frequency of 30-50 GHz and a tuning step of 10 GHz is obtained in a proof-of-concept experiment. The tuning range can be as large as 140 GHz if a high bandwidth photodetector is applied.

Distributed MIMO chaotic radar based on wavelength-division multiplexing technology

A distributed multiple-input multiple-output chaotic radar based on wavelength-division multiplexing technology (WDM) is proposed and demonstrated. The wideband quasi-orthogonal chaotic signals generated by different optoelectronic oscillators (OEOs) are emitted by separated antennas to gain spatial diversity against the fluctuation of a targets radar cross section and enhance the detection capability. The received signals collected by the receive antennas and the reference signals from the OEOs are delivered to the central station for joint processing by exploiting WDM technology. The centralized signal processing avoids precise time synchronization of the distributed system and greatly simplifies the remote units, which improves the localization accuracy of the entire system. A proof-of-concept experiment for two-dimensional localization of a metal target is demonstrated. The maximum position error is less than 6.5 cm.

Influence of large signal modulation on photonic UWB generation based on electro-optic modulator.

Various schemes based on electro-optic modulators have been reported to generate ultra-wideband (UWB) signals in the optical domain, but the availability of these methods always relies on small signal modulation. In this paper, the influence of large signal modulation on two typical schemes, representing two major categories of external-modulator-based photonic UWB generation schemes, is analytically and numerically studied. While the quasi single-sideband UWB (QSSB-UWB) pulse can maintain its shape, the Gaussian UWB (GUWB) generation scheme suffers serious modulation distortion when the phase modulation index is greater than π/6. The modulation distortion would have negative impact on the receiver sensitivity when the signal is sent to a correlation receiver.

Tunable up-converting optoelectronic oscillator based on Stimulated Brillouin Scattering

A widely tunable up-converting optoelectronic-oscillator (OEO) based on Stimulated Brillouin Scattering is proposed and demonstrated, which can convert a low-quality and low-frequency IF signal to a high-quality and high-frequency signal without introducing any high-Q electrical filter. Low-phase-noise microwave signals from 10.15 to 42.15 GHz are experimentally generated.

Tuning of Transmission Responses of an Optical Microring With Negligible Wavelength Shift

The tuning of transmission response of an optical microring resonator (MRR) always associates with significant shift of the resonant wavelength, which leads to serious problems for most of applications. In this letter, we demonstrate that the Mach–Zehnder-interferometer (MZI)-coupled microring resonators with asymmetric directional couplers in the MZIs could still have large magnitude and phase tuning range, while maintaining the resonant wavelength unchanged. An add-drop MZI-coupled microring resonator with asymmetric directional couplers is fabricated on a silicon-on-insulator chip, and the measurement agrees well with the theoretical prediction. Our study would be interesting to photonic integrated circuits, which require tunable MRRs.