Besides distinct features on RF/optical signal generation, optoelectronic oscillators (OEOs) have also been rapidly developed as emerging techniques towards sensing, measurement, and detection. In this paper, we start with the conceptual architecture and the analytical model of OEOs. Then, three operation principles behind sensing, measurement, and detection applications are categorized, including the variation on the time delay of loop, the passband reconfiguration of microwave photonic filter in loop, and the oscillation gain from injection locking, which clearly clarify the X-to-frequency mapping (X denotes target parameter or signal) for supporting practical solutions and approaches. Next, a comprehensive review to advances in OEO-based sensing, measurement, and detection applications is presented, including length change and distance measurement, refractive index estimation, load and strain sensing, temperature and acoustic sensing, optical clock recovery, and low-power RF signal detection. As a new application example, a novel approach for in-line position finding is proposed. When a long fiber Bragg grating inserted into OEO is locally heated to slightly broaden its reflection spectrum, the target position heated is mapped into the oscillating frequency shift, according to the first operation principle. A sensitivity of 254.66 kHz/cm is obtained for position finding in the experiment. Afterward, solutions for calibration and stabilization are briefly introduced, which enable us to improve the accuracy and reliability. Finally, features and future prospects on the sensing, measurement, and detection applications are discussed, such as compact and integrated OEOs.

Optoelectronic Oscillators (OEOs) to Sensing, Measurement, and Detection

Time-delayed optoelectronic oscillators are at the center of a large body of scientific literature. The complex behavior of these nonlinear oscillators has been thoroughly explored both theoretically and experimentally, leading to a better understanding of their dynamical properties. Beyond fundamental research, these systems have also inspired a wide and diverse set of applications, such as optical chaos communications, pseudorandom number generation, optoelectronic machine learning based on reservoir computing, ultrapure microwave generation, optical pulse-train synthesis, and sensing. The aim of this review is to provide a comprehensive survey of this field, to outline the latest achievements, and discuss the main challenges ahead.

Optoelectronic oscillators with time-delayed feedback

An optoelectronic oscillator (OEO) is a microwave photonic system that produces microwave signals with ultralow phase noise using a high-quality-factor optical energy storage element. This type of oscillator is desired in various practical applications, such as communication links, signal processing, radar, metrology, radio astronomy, and reference clock distribution. Recently, new mode control and selection methods based on Fourier domain mode-locking and parity-time symmetry have been proposed and experimentally demonstrated in OEOs, which overcomes the long-existing mode building time and mode selection problems in a traditional OEO. Due to these mode control and selection methods, continuously chirped microwave waveforms can be generated directly from the OEO cavity and single-mode operation can be achieved without the need of ultranarrowband filters, which are not possible in a traditional OEO. Integrated OEOs with a compact size and low power consumption have also been demonstrated, which are key steps toward a new generation of compact and versatile OEOs for demanding applications. We review recent progress in the field of OEOs, with particular attention to new mode control and selection methods, as well as chip-scale integration of OEOs.

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Recent advances in optoelectronic oscillators

Photonics-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.

Photonics-Based Microwave Frequency Mixing: Methodology and Applications

The optoelectronic oscillator (OEO) has attracted a great deal of attention in recent years as a high-performance microwave source. Thanks to the high quality-factor (Q-factor) provided by the optical delay line, the OEO can generate spectrally pure microwave signals with ultralow phase noise. Various approaches for realization of OEO architectures for the generation of single-frequency microwave signals have been demonstrated in the past two decades. Seeded by the microwave signal generated by OEO, the generation of complex microwave waveforms has been demonstrated, which can be used in applications such as radar and communication systems. OEO has also been demonstrated to perform other specific functionalities in different applications, including optical pulses and frequency comb generation, optical sensing, low-power microwave signal detection, and optical signal processing. This paper reviews the developments of OEO over the past two decades. An integrated OEO with monolithically integrated photonic parts and radio frequency subsections is reported as a promising example toward the monolithic integration of OEO. Key features of OEO and prospects for future development of the integration of OEO are also described.

Toward Monolithic Integration of OEOs: From Systems to Chips

We demonstrate a novel scheme to generate full-duty-cycle triangular microwave waveforms using an optoelectronic oscillator (OEO). The OEO produces high-quality local oscillator signal. Thus, an external microwave source, which is usually involved in orthodox approaches obviates the need. A polarization modulator is involved in both the OEO loop and a microwave photonic filter (MPF) structure. To generate a triangular waveform, the undesired electrical harmonics are suppressed by the MPF. The proposed method is theoretically analyzed and experimentally verified. Triangular waveforms at fundamental tone of 4.6 GHz and frequency doubling tone of 9.2 GHz are generated, which fit well with the stimulated ones. The root mean square errors between the generated and the simulated triangular waveforms are 6.6e-5 and 1.61e-3 for triangular pulses at 4.6 and 9.2 GHz, respectively.

Triangular Microwave Waveforms Generation Based on an Optoelectronic Oscillator

The invention discloses a broadband tunable single-passband microwave photon filter generating system. The system comprises a laser, an optical coupler, a polarization modulator, a dispersion displacement optical fiber, a photoelectric detector, a vector network analyzer, a strength modulator and an optical fiber; the laser is used for providing continuous light signals; the optical coupler is used for dividing the continuous light signals into the first path of light signals and the second path of light signals; the polarization modulator is used for modulating the polarization state of the first path of light signals; the dispersion displacement light fiber is used for performing stimulated Brillouin scattering on the detection light signals under the induction effect of pump light signals; the photoelectric detector is used for receiving the detection light signals which are processed in a stimulated Brillouin scattering mode and output by the dispersion displacement optical fiber and generating microwave signals; the vector network analyzer is used for receiving microwave signals output by the photoelectric detector, performing measurement frequency response on the microwave signals, and outputting the microwave signals to the a first polarization modulator at the same time; the strength modulator is used for modulating the polarization state of the first path of light signals and outputting the first path of light signals which are modulated; the optical fiber is used for filtering the first path of light signals which are modulated, and the first path of light signals serve as the pump light signals.

Broadband tunable single-passband microwave photon filter generating system

The invention discloses a microwave signal optical fiber stationary phase transmission system based on a microwave phase shifter. The system comprises a central station, a far end and a single-mode optical fiber. The central station is connected with the far end through the single-mode optical fiber. The central station is composed of a semiconductor laser device, a dual-drive Mach-Zehnder modulator, a microwave signal source, a first power divider, a first optical filter, an erbium-doped optical fiber amplifier, an optical coupler, a first array waveguide grating, a first photoelectric detector, a frequency eliminator, a second power divider, an optical source, a strength modulator, a second optical filter, an optical circulator, a second photoelectric detector, a first electric mixer, a band-pass filter, a second electric mixer, a low-pass filter and a linear voltage amplification circuit. The far end is composed of a second array waveguide grating, a third photoelectric detector and a Faraday polariscope. According to the invention, the advantage of low building and maintenance cost can be realized; and the phase jitter of microwave signals can be extracted and fed back on a real-time basis.

Microwave signal optical fiber stationary phase transmission system based on microwave phase shifter

A wideband photonic microwave phase shifter using polarization-dependent intensity modulation

The invention discloses a device for producing a random waveform microwave signal based on cross polarization modulation The device comprises a narrow linewidth laser device, a polarization beam splitter for splitting detection light into two beams of polarization-state detection light perpendicular to each other and respectively propagating the light in clockwise and anti-clockwise directions, a laser device for producing control light, an intensity modulator for utilizing a radio-frequency signal to perform intensity modulation on the control light, an optical coupler for coupling the detection light propagated in the clockwise direction with the control light, a high-nonlinearity optical fiber for producing the cross polarization modulation effect under the induction effect of the light subjected to the intensity modulation, performing the cross polarization modulation on the detection light propagated in the clockwise direction and producing modulation sidebands, a polarizer, a first optical filter, a photoelectric detector for producing the random waveform signal according to detection light carrier waves and the detection light output by the optical filter

Wang Wenting

Papers

Triangular Microwave Waveforms Generation Based on an Optoelectronic Oscillator

Broadband tunable single-passband microwave photon filter generating system

Microwave signal optical fiber stationary phase transmission system based on microwave phase shifter

A wideband photonic microwave phase shifter using polarization-dependent intensity modulation

Device for producing random waveform microwave signal based on cross polarization modulation