Abstract
Microwave photonic approaches for the generation of microwave signals have attracted substantial attention in recent years, thanks to the significant advantages brought by photonics technology, such as high frequency, large bandwidth, and immunity to electromagnetic interference. An optoelectronic oscillator (OEO) is a paradigmatic microwave photonic oscillator that produces microwave signals with ultra-low phase noise, thanks to the high-quality-factor of the OEO cavity that is achieved with the help of optical energy storage elements, such as low-loss optical fiber or a high-quality-factor optical resonator. Different OEO architectures have been proposed to generate spectrally pure single-frequency microwave signals with ultra-low phase noise. Multiple oscillation mode control methods have been proposed in recent years to obtain different kinds of microwave signals. With the rapid development of photonic integration technologies, prototypes of integrated OEOs have been demonstrated with compact size and low power consumption. Moreover, OEOs have also been used for sensing, computing, and signal processing. This Tutorial aims to provide a comprehensive introduction to the developments of OEOs. We first discuss the basic principle and the key phase noise property of OEOs and then focus on its developments in spectrally pure low phase noise signal generation and mode control methods, its chip-scale integration, and its applications in various fields.
Highlights
An optoelectronic oscillator (OEO) is a hybrid microwave and photonic system capable of producing self-sustained microwave oscillations when modulated light waves from a modulator fall on a photodetector
III, we provide examples to generate spectrally pure low phase noise microwave signals using different OEO architectures, including dual-loop OEO, coupled OEOs (COEOs), OEO based on a high-Q ring resonator, and PT-symmetric OEO
We investigate methods such as frequency tuning using tunable filters, chirped signal generation using Fourier domain mode-locking, stable multimode oscillation based on a nonlinear parametric process, complex oscillation based on nonlinear dynamics, and random oscillation based on random scattering
Summary
An optoelectronic oscillator (OEO) is a hybrid microwave and photonic system capable of producing self-sustained microwave oscillations when modulated light waves from a modulator fall on a photodetector. Several mode control and selection methods have been proposed and demonstrated to generate ultra-low phase noise single-frequency microwave signals and other complex microwave waveforms. Single-frequency microwave signals with low phase noise can be generated in a single-loop OEO, where an electrical filter is used for mode selection. A narrowband filter is used for mode selection, and an optical fiber is adopted to ensure low phase noise An optical amplifier, such as an erbium-doped fiber amplifier (EDFA) or/and an electrical amplifier (EA), can be used to provide enough gain for the oscillating signal in the OEO loop. We use the Yao–Maleki model as an example to analyze the OEO operation In this model, the oscillation signal of the OEO is linearized if a loop filter with a narrow enough bandwidth is used to block all harmonic frequency components.
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