There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Microwave photonics, which brings together the worlds of radiofrequency engineering and optoelectronics, has attracted great interest from both the research community and the commercial sector over the past 30 years and is set to have a bright future. The technology makes it possible to have functions in microwave systems that are complex or even not directly possible in the radiofrequency domain and also creates new opportunities for telecommunication networks. Here we introduce the technology to the photonics community and summarize recent research and important applications.

Microwave photonics combines two worlds

Course Description This is an advanced course in which we explore the field of Statistical Optics. Topics covered include such subjects as the statistical properties of natural (thermal) and laser light, spatial and temporal coherence, effects of partial coherence on optical imaging instruments, effects on imaging due to randomly inhomogeneous media, and a statistical treatment of the detection of light. Development of this more comprehensive model of the behavior of light draws upon the use of tools traditionally available to the electrical engineer, such as linear system theory and the theory of stochastic processes.

http://ieeexplore.ieee.org/iel5/3/23094/01073023.pdf

Statistical optics

Broadband and low loss capability of photonics has led to an ever-increasing interest in its use for the generation, processing, control and distribution of microwave and millimeter-wave signals for applications such as broadband wireless access networks, sensor networks, radar, satellite communitarians, instrumentation and warfare systems. In this tutorial, techniques developed in the last few years in microwave photonics are reviewed with an emphasis on the systems architectures for photonic generation and processing of microwave signals, photonic true-time delay beamforming, radio-over-fiber systems, and photonic analog-to-digital conversion. Challenges in system implementation for practical applications and new areas of research in microwave photonics are also discussed.

Microwave Photonics

A new microwave photonic notch filter structure that realises coherence-free, narrow notch width, and wide passband operation, is presented. It is based on a WDM technique with a double-pass modulation approach incorporating sequentially spaced reflectors that provide the appropriate time delays for the remodulations. Experimental results are presented which demonstrate a coherence-free microwave photonic filter that exhibits a narrow-notch, a wide passband, and no phase noise limitations, simultaneously.

Coherence-free microwave photonic notch filter with a wide passband and a narrow notch

We propose a machine learning (ML) assisted athermal microwave photonic (MWP) sensing scheme with high resolution based on a single microring resonance. The immunity of temperature interference of the high-resolution sensing is achieved by employing MWP sideband processing based interrogation, and supervised machine learning based on support vector regression (SVR) and neural tangent kernel (NTK) that are effective on small datasets. The MWP sideband processing transforms the variation of the target measurand into the shift of an ultra-deep notch in the radio frequency (RF) spectrum relieving the fabrication requirements on the microresonators, while ML accurately predicts the measurand by using the modulator bias voltage or RF passband transmission together with the RF notch position. The proposed sensor is demonstrated for relative humidity (RH) measurements using a silicon-on-insulator microring coated with polymethyl methacrylate. About 50 dB high RF rejection ratio is achieved over the sensing process, indicating a high sensing resolution. Despite the small experimental datasets, the established SVR and NTK models consistently exhibit lower mean absolute errors (MAEs) than the linear regression model in the RH prediction in the presence of temperature drifts. The NTK models achieve the lowest MAEs of 1.01% RH and 1.03% RH when the RF passband transmission and modulator bias are selected as the model input, respectively. The equivalent performances of the RF passband transmission and modulator bias voltage further demonstrate the feasibility of athermal sensing based solely on the MWP interrogation results of a single microring resonance, which simplifies the design and reduces the complexity.

Athermal Microwave Photonic Sensor Based on Single Microring Resonance Assisted by Machine Learning

Recent new methods in optical filtering for wideband microwave photonic signal processing are presented in this paper including optical waveguide filters for sideband suppression, optical-to-electrical filtering techniques, and cascaded microwave photonic signal processors.

Optical Filtering Techniques for Microwave Photonics

Photonic signal processing offers a new, powerful paradigm for processing high bandwidth signals. This overview presents recent new methods in wideband signal processing using optical delay lines, including state-of-the-art results, and capabilities for high-resolution processing.

Microwave Photonic Signal Processing

In this paper, a new microwave photonic (MWP) sensing scheme, which is based on interrogating microresonator sensors with fast speed and improved resolution by adopting a broadband linear frequency-modulated pulse (LFMP) in the MWP sideband processing, is presented. The LFMP modulates the interrogation light, creating the optical sideband that sweeps through the resonance rapidly. By using the optimized DC bias point, the resonance spectral dip with arbitrary characteristics can be transformed into the zero point in the temporal envelope of the transmitted LFMP, hence providing improved interrogation resolution of the resonance shifts caused by environmental changes. The proposed scheme was implemented with a microdisk resonance for temperature sensing, where up to 20-fold interrogation resolution improvement was demonstrated by tuning the DC bias voltage to the optimum. The interrogation speed is 500 kHz, which can be further improved by using a shorter repetition period and pulse width.

Robert A. Minasian

Papers

Coherence-free microwave photonic notch filter with a wide passband and a narrow notch

Athermal Microwave Photonic Sensor Based on Single Microring Resonance Assisted by Machine Learning

Optical Filtering Techniques for Microwave Photonics

Microwave Photonic Signal Processing

Microwave Photonic Sensor Based on Optical Sideband Processing with Linear Frequency-modulated Pulse