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 coherence-free single-wavelength microwave photonic notch filter, which is widely tuneable, and which is compatible to be inserted in a conventional fiber-optic link, is presented. It is based on self-wavelength cross gain modulation in a semiconductor optical amplifier placed at an off-centre location in a Sagnac loop. The structure can realize a high free spectral-range negative tap notch filter response, and does not have any coherent interference and phase-noise limitations. Moreover, it enables widely tunable notch filtering to be simply realized. Experimental results are presented which demonstrate a large continuous filter tuning range of an octave, robust operation with a narrow linewidth source, and wide passband notch filtering operations.

Coherence-Free Equivalent Negative Tap Microwave Photonic Notch Filter Based on Delayed Self-Wavelength Conversion

We present a novel technique based on matrix pencil assisted deconvolution to improve the measurement resolution in scanning receiver systems for microwave frequency measurements. By modeling the scanning receiver output as the cross-correlation of the input modulated signal with the filter’s spectral response and applying the matrix pencil algorithm to convolve the detected optical signal at the receiver output, our technique offers precise estimations of both the frequency and power information of microwave signals with an improved measurement resolution. A multi-tone microwave signal measurement based on an optical filter is experimentally demonstrated, showing a significant measurement resolution reduction from 1 GHz to 0.4 GHz for two radio frequency (RF) tones, which is only about 30.2% of the optical filter bandwidth.

https://bura.brunel.ac.uk/bitstream/2438/17935/1/FullText.pdf

Photonic-Assisted Scanning Receivers for Microwave Frequency Measurement

A new technique is presented to reconfigure the dispersion-induced RF fading in a spectrum-sliced microwave photonic filter to an arbitrary spectral shape, including the flat-top response with rectangular shape and operating frequencies beyond conventional baseband. The technique is based on the Fourier transform of the modified optical source power spectrum, which is realized by applying a designed optical amplitude and phase manipulation using a diffraction-based spectral pulse shaper to the ports of a dual-output Mach-Zehnder electro-optic modulator in combination with a broadband light source. This scheme is fundamentally different from earlier finite-impulse-response-based spectrum-sliced microwave-photonic filters that require specific slicing elements for optical taps, but offers the same flexibility in realizing various filter passband characteristics with the added benefit of widely shape-invariant tuning and a single passband response. Experimental results verify the technique and demonstrate a continuously tunable dispersion-induced RF fading up to 20 GHz, exhibiting shape invariance and a flat-top response.

Spectrum-Sliced Microwave-Photonic Filter Based on Fourier Transform of Modified Optical Spectrum

A novel, reflective, high performance microring sensing probe based on narrowband microwave photonic notch filtering is proposed and experimentally demonstrated. The system employs an integrated silicon-on-insulator microring resonator with a reflective loop as a sensing probe, which allows the sensed light to be reflected back and measured from a point source, thus enabling the capability to perform remote measurements at locations with limited accessibility. To enhance the beating cancellation of the optically filtered sideband, a programmable wideband optical equalization filter is used to create an amplitude equalization profile of the sidebands, thus achieving a desirable narrowband microwave photonic notch filter, which is a key feature for implementing sensor interrogation systems with high resolution. As an application example, a highly sensitive temperature sensor which monitors the temperature dependent notch locations of the narrowband microwave photonic notch filters has been experimentally verified. It achieves a high sensitivity of 11.57 GHz/$^{\mathrm{o}}$C, which provides the capability to detect and convert a small temperature change into a large variation in the radio frequency domain with clear notch frequency shifts in the order of several hundred MHz.

Reflective Microring Sensing Probe based on Narrowband Microwave Photonic Notch Filter

Dielectric rod antennas have advantages as elements of focal plane arrays for imaging applications at terahertz frequencies. As well as good directivity and moderate bandwidth they are readily integrated with diode detectors. To demonstrate these attributes we describe the fabrication of a prototype antenna by laser ablation. Theoretical and measured results are presented for a dielectric rod antenna operating at 600 GHz.

Robert A. Minasian

Papers

Coherence-Free Equivalent Negative Tap Microwave Photonic Notch Filter Based on Delayed Self-Wavelength Conversion

Photonic-Assisted Scanning Receivers for Microwave Frequency Measurement

Spectrum-Sliced Microwave-Photonic Filter Based on Fourier Transform of Modified Optical Spectrum

Reflective Microring Sensing Probe based on Narrowband Microwave Photonic Notch Filter

A 600 GHz dielectric rod antenna