Optoelectronic Microwave Research Articles

Noise Figure: Estimation of Noise Characteristics of a Radio- Photonic Path Based on the Results of Noise Figure Measurements

In radiophotonic microwave transmission systems, as in any radioelectronic systems, noise characteristics determine the potential of accuracy and range. As a measure of the difference between the noise characteristics of optoelectronic microwave signal converters from ideal ones, the use of the noise figures of the elements included in their composition is proposed. The effect of such a criterion is demonstrated by the example of the optoelectronic microwave oscillator (OEO). Based on the results of the study of the optoelectronic microwave oscillator noise parameters quantitative characteristics of the conversion of the OEO elements noise sources into phase and amplitude fluctuations of the output microwave oscillation are obtained. The analysis of the interaction of the OEO elements noise with the microwave harmonic oscillation is performed. The technique for measuring the noise conversion characteristics using the noise figure has been developed. The results of measuring characteristics of the interaction of harmonic oscillation with the optoelectronic components additive and multiplicative noise of optoelectronic components are presented. Based on the values of the noise figure, the possibilities of reducing the noise levels of microwave signal converters are evaluated and recommendations are made to reduce the influence of the noise.

ИЗМЕРЕНИЕ ФАЗОВЫХ И АМПЛИТУДНЫХ ШУМОВ ПОЛУПРОВОДНИКОВЫХ ЛАЗЕРОВ. МЕТОДИКА ИЗМЕРЕНИЙ. КАЛИБРОВКА. РЕЗУЛЬТАТЫ

The application of the frequency detector method for measuring the phase noise spectrum of semiconductor lasers has been experimentally demonstrated. The frequency detector is based on an unbalanced Mach-Zehnder interferometer and a photodetector. Analytical relations are obtained that allow one to choose the parameters of the Mach-Zehnder interferometer and perform experimental calibration of the measuring system. A technique is proposed for measuring the spectral components of the phase noise of lasers in the presence of a slow drift of the delay in fiber-optic lines and the frequency of the laser under study. The results of measuring the phase noise of a low-noise DX-1 laser module and high-noise laser diodes LSDLD155 (DFB) and LSFLD155 (FP) are presented. A strong correlation between the amplitude and phase noise levels of these lasers is found. The decisive influence of the noise of LSDLD155 and LSFLD155 lasers on the level of phase noise of optoelectronic (OE) microwave generators built using them is shown. It has been suggested that the low-noise laser module DX-1, which has a phase noise level 20–60 dB lower (in different parts of the spectrum), is not decisive in the level of phase and amplitude noise of an optoelectronic microwave generator. The investigated OE generator was built during the research in this work. The generator has low phase noise: −120 dBc/Hz at a frequency detuning of 10 kHz. Oscillation frequency 6.8 GHz; fiber optic delay line length 200 m.

On the Universality of Microwave Envelope Equations for Narrowband Optoelectronic Oscillators

Narrowband optoelectronic oscillators are time-delayed system that can generate ultrapure microwave signals. In order to study these oscillators, one approach is to derive a time-delayed envelope equation. In this article, we show that this approach is universal and applies to a wide variety of OEO families. By studying different oscillators, it is possible to show that their dynamics is governed by an envelope equation that can be rewritten under a generalized universal form. In this article, this universal microwave envelope equation is proposed and investigated analytically for optoelectronic microwave oscillators, and the bifurcation analysis of the deterministic envelope equation is performed. The universal model is further generalized and written in a stochastic form in order to predict the phase noise performance of the oscillators.

Optoelectronic reference X-band oscillator for radar systems

We present the design and results of studying the characteristics of an optoelectronic microwave oscillator in the free-running regime are presented, propose a method for synchronising it with a signal of a highly stable crystal oscillator using a phase-locked loop, and analyse the results of an experimental study on the frequency instability of an optoelectronic microwave reference oscillator. The optoelectronic microwave reference oscillator with optical gain and a 10 GHz oscillation frequency simultaneously provides ultra-low phase noise (less than – 142 dB Hz−1) at a 10 kHz frequency offset from the microwave carrier and a low level of spurs in the oscillation spectrum (no more than – 94 dBc). In this case, the temperature coefficient of the oscillation frequency is determined by the temperature instability of a highly stable crystal oscillator.

Noise conversion in delay-line optoelectronic microwave oscillators

We report the results of theoretical and experimental studies of noise in a delay-line optoelectronic microwave oscillator with optical gain. The effect of various noise sources on the parameters of an optoelectronic microwave oscillator is considered, and, in addition to the noise of its individual components, several linear and nonlinear mechanisms for converting optical carrier noise into microwave signal noise are taken into account. It is shown that, due to the nonlinearity of the energy characteristics of high-power microwave photodiodes in an optoelectronic generator, the low-frequency components of the laser relative intensity noise are converted into microwave signal noise, as a result of which sources of correlated amplitude and phase noise appear in the oscillator loop.

A theoretical and experimental study of the frequency pulling phenomenon in a single-loop optoelectronic microwave oscillator due to RF signal injection

An approximate strong injection perturbation mathematical model to analyze the frequency pulling and non-linear dynamics in radio frequency (RF) signal driven optoelectronic microwave oscillator (OEO) is presented here. The formulas regarding the lock-range, the beat frequency and the average frequency are derived, which help to estimate the amount of phase perturbation in pulled (unlocked-driven) OEO more accurately considering both weak and strong RF signal injection. The analytical expressions for the spectral components of the pulled OEO are also given to predict the frequency pulling phenomenon of the pulled OEO. It is presented that our proposed analytical model has the capability to accurately determine the phase-locking and assessing the frequency pulling of RF driven single-loop OEO when injected by weak and strong RF signal. The verification of the accuracy of the proposed model is also done by the experiments.

Photonics‐Based Microwave Frequency Mixing: Methodology and Applications

AbstractPhotonics‐based microwave frequency mixing provides distinct features in terms of wide frequency coverage, broad instantaneous bandwidth, small frequency‐dependent loss, and immunity to electromagnetic interference as compared with its electronic counterpart, which can be a key technical enabler for future broadband and multifunctional RF systems. Herein, all‐optical and optoelectronic microwave frequency mixing techniques are reviewed, with an emphasis on the latest advances in photonics‐based microwave frequency mixers with improved performance in terms of conversion efficiency, dynamic range, mixing‐spur suppression, mixing functionality, and polarization independence. Innovative applications enabled by photonics‐based microwave frequency mixers, such as radio‐over‐fiber communication systems, radar systems, satellite payloads and electronic warfare systems, are also reviewed. In addition, efforts in implementing integrated photonics‐based microwave mixers that lead to a dramatic reduction in size, weight, and power consumption are also reviewed.

Regenerative Talbot Laser for Generating Tunable Pulse Train With a Low Phase Noise

We propose and demonstrate an improved Talbot laser including a regenerative RF feedback loop. This architecture greatly enhances both amplitude and noise performances of the pulsed laser, while preserving the broadband tunability of its repetition rate. The phase noise power spectral density of the associated RF signal is found to be independent of the repetition rate. For a 4.9 GHz repetition rate, the timing jitter is as low as 54 fs (integrated between 10 kHz and 100 MHz offset frequency). This architecture paves the way towards tunable high performances coupled opto-electronic microwave oscillators.

Study of phase-locking of optoelectronic microwave oscillators considering amplitude perturbation

This paper presents a detailed study of the phase-locking phenomenon in single-loop optoelectronic microwave oscillators considering strong radio frequency (RF) signal injection. The analyses are made in terms of the lock-range, beat frequency and the spectral components of the unlocked-driven oscillator in presence of amplitude perturbation. An approximate expression for the amplitude perturbation of the oscillator is derived and the influence of amplitude perturbation on the phase-locking dynamics is analysed. The influence of external RF signal on the frequency pulling of the unlocked-driven optoelectronic oscillator (OEO) is also studied. It is shown that the unlocked-driven OEO output signal has a very non-symmetrical sideband distribution about the carrier. Also, analytical technique for studying the response characteristics of a phase-locked OEO to pure continuous wave amplitude modulated signal is presented. The simulation findings are also given in partial support of the conclusions of the analysis.

Mechanism for Forming Quantum-Size AlGaN/GaN/InGaN/GaN Heterostructure Layers

The use of silicon in optoelectronic elements and microwave devices is limited by its electrical properties. In this range of application, silicon is replaced by wider-gap materials, e.g., GaN, AlN, InN, and solid solutions based on them. This allows highly efficient devices, including light-emitting diodes and photodetectors operating in a wide radiation spectral range, to be fabricated. In addition, GaN-based materials have been successfully used in designing high-power microwave devices, in particular, transistors with highly mobile electrons operating at high temperatures. We discuss specific features of the technology for fabricating active layers in the AlGaN/GaN/InGaN/GaN heterostructures with the use of metalorganic compounds. The initial substances used are ultra-pure ammonia NH3 and gallium, aluminum, and indium metalorganic compounds in the trimethyl form. The temperature dependence of the epitaxial GaN layer growth rate is investigated. This dependence is shown to be weak in a wide temperature range. The importance of adsorption processes occurring on the growth surfaces is confirmed. Thermodynamical analysis of the regularities of the investigated process is carried out to simulate the process and establish the conditions for forming GaN-based solid solutions. It is shown that during the formation of Ga1 – xInxN solid solutions in the high-temperature region the attainable InN content is not higher than 0.4 mole fractions. As the growth temperature decreases to 600°С, the conditions for incorporating In in the solid solution are noticeably improved and the InN concentration increases to 0.9 mole fractions. It is demonstrated that growing the GaAlN solid solutions in a wide temperature range makes it possible to obtain the AlN content ranging from 0.1 to 0.9 mole fractions. The experimental investigations are confirmed by the calculations. Therefore, when growing the Ga1 – xInxN quantum well layers in the active heterostructural area for commercial blue light-emitting diode chips with an indium content of х = 0.1–0.15, the growth temperature should be reduced. At low temperatures, however, it is difficult to grow epitaxial layers with a high crystal quality.

Phase-locking dynamics in optoelectronic oscillator

This paper analyzes the phase-locking phenomenon in single-loop optoelectronic microwave oscillators considering weak and strong radio frequency (RF) signal injection. The analyses are made in terms of the lock-range, beat frequency and the spectral components of the unlocked-driven oscillator. The influence of RF injection signal on the frequency pulling of the unlocked-driven optoelectronic oscillator (OEO) is also studied. An approximate expression for the amplitude perturbation of the oscillator is derived and the influence of amplitude perturbation on the phase-locking dynamics is studied. It is shown that the analysis clearly reveals the phase-locking phenomenon and the associated frequency pulling mechanism starting from the fast-beat state through the quasi-locked state to the locked state of the pulled OEO. It is found that the unlocked-driven OEO output signal has a very non-symmetrical sideband distribution about the carrier. The simulation results are also given in partial support to the conclusions of the analysis.

基于光电微波振荡器的三角波和正弦信号发生器

基于光电微波振荡器的三角波和正弦信号发生器

A resonance system of an optoelectronic oscillator based on a transmission-type planar optical disk microcavity

It is noted that the best technical characteristics of optoelectronic microwave self-oscillators (OESO) are reached in schemes employing high-Q optical microresonators (OMR) working in the traveling wave modes (TWM). A possibility of using disk OMRs excited by fundamental whispering gallery modes (WGM) has been considered. Multielement coupling devices (CD) for such resonators have been investigated. They are constructed on the basis of planar optical waveguides (POWG) located over the disk resonator surface in a region bounded by the outer and inner caustics of the WGM. Models of this device have been proposed. The corresponding calculations have been provided.

Analysis of Phase-Locking in Optoelectronic Microwave Oscillators Due to Small RF Signal Injection

In this paper, we analyze the phase-locking phenomenon in a single-loop optoelectronic microwave oscillator, when subjected to the influence of small radio-frequency (RF) signal. We derive the differential equations for the amplitude and phase variations in the oscillator. Using quasi-linear approximation, analytical expressions for the lock range and phase-shift after phase-locking are presented. In addition, beat frequency of the unlocked-driven optoelectronic oscillator (OEO) is obtained and the phase-locking dynamics of the driven oscillator is discussed. Also, the spectrum components of the pulled OEO is derived as a function of the frequency detuning, lock range, beat-frequency, and frequency-shift induced by the phase perturbation of the injection signal. It is shown that all the analytical closed-form expressions clearly demonstrate the phase-locking mechanism starting from the fast-beat state through the quasi-locked state to the locked state of the pulled OEO. Finally, the simulation results are given to validate the analytical results.

Photonic microwave signals with zeptosecond-level absolute timing noise

Photonic synthesis of radiofrequency revived the quest for unrivalled microwave purity by its seducing ability to convey the benefits of the optics to the microwave world. In this work, we perform a high-fidelity transfer of frequency stability between an optical reference and a microwave signal via a low-noise fiber-based frequency comb and cutting-edge photo-detection techniques. We demonstrate the generation of the purest microwave signal with a fractional frequency stability below 6.5 x 10^-16 at 1 s and a timing noise floor below 41 zs.Hz^-1/2 (phase noise below -173 dBc.Hz^-1 for a 12 GHz carrier). This outclasses existing sources and promises a new era for state-of-the-art microwave generation. The characterization is achieved by building two auxiliary low noise optoelectronic microwave reference and using a heterodyne cross-correlation scheme with lowermost detection noise. This unprecedented level of purity can impact domains such as radar systems, telecommunications and time-frequency metrology. Furthermore, the measurement methods developed here can benefit the characterization of a broad range of signals, beyond comb-based systems.

Исследование моделей подавления паразитных мод оптоэлектронного СВЧ-автогенератора на основе инжекционной и многоконтурной схем

Исследование моделей подавления паразитных мод оптоэлектронного СВЧ-автогенератора на основе инжекционной и многоконтурной схем

Theoretical and experimental investigation on the narrow-linewidth photonic microwave generation based on parallel polarized optically injected 1550 nm vertical-cavity surface-emitting laser

Photonic microwave generation has attracted much attention in recent years due to its potential applications in various fields such as radio-over-fiber communication, signal processing and radar systems. So far, different photonic microwave generation schemes have been proposed and investigated, such as the optical heterodyne method based on the beat of two independent lasers with a certain wavelength difference, the external modulation method based on electro-optical modulator, the dual-mode beat method based on the monolithic dual-mode semiconductor lasers, and the optoelectronic microwave oscillator method based on optoelectronic feedback loops. These schemes have their own advantages and deficiencies. Unlike the above schemes, in this paper we propose an all optical scheme for generating high-quality microwave based on a 1550 nm vertical-cavity surface-emitting laser (1550 nm-VCSEL). For such a scheme, high frequency microwave can be obtained based on a 1550 nm-VCSEL subjected to external optical injection, where the polarization of the injected light is the same as that of the dominant mode of the free-running 1550 nm-VCSEL (named parallel-polarized optical injection) and its wavelength is adjusted to being close to the wavelength of the suppressed polarization mode of the free-running 1550 nm-VCSEL. With the aid of double optical feedback, the linewidth of the obtained microwave can be narrowed. In this work, firstly, the feasibility of microwave generation based on parallel-polarized optically injected 1550 nm-VCSEL is analyzed theoretically by using the spin-flip model. Next, a corresponding experimental system is constructed, and the performance of microwave generation is preliminarily investigated experimentally. The experimental results show that 30 GHz microwave signals could be obtained based on a parallel-polarized, optically injected 1550 nm-VCSEL under suitable injection parameters, but the linewidth of microwave signal is relatively wide (hundreds of MHz). Finally, after introducing double optical feedback, the linewidth of microwave signal can be reduced by more than two orders of magnitude and narrowed to less than 1 MHz, meanwhile the signal-noise ratio is larger than 40 dB. This work is helpful to develop relevant techniques to acquire high-performance narrow linewidth photonic microwave.

Microwave filter based on Lamb modes for optoelectronic generator

Experimental results for narrowband filter based on yttrium iron garnet film epitaxially grown on gadolinium gallium garnet substrate have been shown. The principle of operation of the filter is based on excitation of Lamb modes in the substrate. We demonstrated also that the use of single crystal diamond as a substrate will significantly reduce the phase noise of the designed optoelectronic microwave generator.

Theory of a tunable spin-wave optoelectronic microwave oscillator

A theory that describes the threshold regime of the formation of auto-oscillation spectrum is proposed for a tunable ring optoelectronic microwave oscillator (OEO). The main elements of the OEO are series-connected optical fiber, spin-wave narrow-band microwave film filter, and broadband semiconductor microwave amplifier. It is demonstrated that a relatively low level of the OEO phase noise is provided by both the optical fiber and spin-wave filter.

Electronically tunable spin-wave optoelectronic microwave oscillator

The characteristics of a spin-wave optoelectronic microwave oscillator are experimentally studied for the first time. The oscillator represents a ring structure the microwave circuit of which contains a spinwave delay line based on the yttrium–iron-garnet film. The optical part of the oscillator contains a fiberoptic delay line with a length of 100 m. It is demonstrated that the spin-wave delay line makes it possible to tune the output frequency in wide ranges at a relatively low level of the phase noise. In the gigahertz frequency range, the level of the phase noise is no greater than–110 dBc/Hz at a detuning of 10 kHz from the carrier frequency.