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 topology for a photonic signal processor, which overcomes the basic recursive frequency response problem that limits the passband range, is presented. The structure is based on a new multiple-wavelength offset-cavity structure that is cascaded with a series of unbalanced delay line structures. This not only can synthesize a very narrow notch response with good shape factor but also permits a multifold extension of the free spectral range (FSR) and passband width. Results on the interference mitigation filter demonstrate a stopband of 1% of center frequency and a fourfold increase in the FSR and passband width, while also having a very small shape factor, in excellent agreement with predictions.

High-resolution photonics-based interference suppression filter with wide passband

A new photonic microwave phase shifting structure that can realize a continuous 0° to 360° phase shift with only little frequency dependent amplitude and phase variation over a wide frequency range is presented. It is based on controlling the amplitude and phase of the optical carrier and two antiphase RF modulation sidebands of two phase modulated optical signals by adjusting the wavelength of the optical carriers that fall on the rising and falling edges of an optical bandpass filter with a nonlinear phase response. The new photonic microwave phase shifter has a simple structure. It only requires one normal electro-optic phase modulator and one low-cost commercially available optical filter. It does not involve any electrical component, and has the advantages of small size, lightweight, and robust performance. Experimental results are presented which demonstrate the realization of a continuous 0° to 360° phase shift, with close to flat phase and amplitude response performance over a wideband microwave range.

All-Optical Photonic Microwave Phase Shifter Based on an Optical Filter With a Nonlinear Phase Response

A novel high-resolution microwave photonic signal processor is presented, which can realize single bandpass response, narrow passband characteristic, and widely tuned center frequency with shape-invariance. It realizes the single passband signal processing function within the optical link via shifting the dispersion induced RF fading of the modulated bipolar optical broadband source. The configuration can overcome the distortion in shifted dispersion induced RF fading caused by the non-uniformity in the group delay slope of dispersive delay lines. Therefore, a wider spectrum source can be used to improve the selectivity of the passband response. Experimental results verify the new proposed structure and demonstrate a shape-invariant tunable bandpass filter with a 3 dB bandwidth of 157 MHz over 0-20 GHz range.

High-Resolution Single Bandpass Microwave Photonic Filter With Shape-Invariant Tunability

An analysis of the optimum optical modulation index of laser transmitters in SCM systems is presented. Nonlinear distortion arising from overmodulation in a laser-limiter combination is studied. A generalised analysis, based on rectangular signal input power spectral density and broadband transmission, is given for the nonlinear noise spectral density. A computer algorithm is developed to generate the optimum modulation index which maximises the received CNR for SCM transmission.

Optimum optical modulation index of laser transmitters in SCM systems

A new microwave photonic filter structure that can achieve a high factor, high stopband rejection, and high skirt selectivity bandpass filter response simultaneously is presented. It is based on reflecting the signal back into a single amplified optical recirculating delay line and comprises coherent summation of the multiple signals that constitute each tap and incoherent summation of the successive taps. This introduces a new class of filter operation and effectively enables the realization of a higher order bandpass filter characteristic in a very simple structure. Experimental results are presented that demonstrate a multiple-tap high- bandpass filter response that also displays high stopband rejection level and high skirt selectivity.

Robert A. Minasian

Papers

High-resolution photonics-based interference suppression filter with wide passband

All-Optical Photonic Microwave Phase Shifter Based on an Optical Filter With a Nonlinear Phase Response

High-Resolution Single Bandpass Microwave Photonic Filter With Shape-Invariant Tunability

Optimum optical modulation index of laser transmitters in SCM systems

Reflective Amplified Recirculating Delay Line Bandpass Filter