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

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

/pdf/the-observation-of-gravitational-waves-from-a-binary-black-58srpupgg9.pdf

The Observation of Gravitational Waves from a Binary Black Hole Merger

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

An overview of analog microwave photonics will be presented. The performance requirements for externally-modulated analog microwave photonic links will be reviewed with specific emphasis placed on modulator efficiency, laser noise, detected photocurrent, and link linearity.

http://ieeexplore.ieee.org/iel5/6387506/6403300/06403360.pdf

Microwave photonics

The simultaneous wireline (600 MHz) and wireless (5.5 GHz) transmission of data over cable service interface specification (DOCSIS) signals in a hybrid fiber-radio access network is presented. The DOCSIS signal wireless replica is generated by means of an optical harmonic up-conversion technique based on a dual-drive Mach-Zehnder modulator. The optical signal is fed to a base station (BS) where a packaged asymmetric Fabry-Pe/spl acute/rot modulator/detector acts simultaneously as a photodetector and an optical modulator. At the BS, the DOCSIS signals can be fed either to a wireline or a wireless access network, in a highly flexible approach. Full-duplex operation has been demonstrated for both access types, including indoor wireless transmission.

Full-duplex DOCSIS/WirelessDOCSIS fiber-radio network employing packaged AFPM-based base-stations

Microwave frequency synthesis can be realised by mixing the output of two or more DFB lasers injection locked to the same optical comb. The noise and stability problems of this approach are studied.

Microwave frequency synthesis using injection locked laser comb line selection

The use of optical signals to control microwave devices offers novel possibilities in microwave system design. This paper will review the optical control behaviour of a number of important devices, including MESFETs and IMPATT diodes. Relevant properties of optical sources will be discussed, and techniques for obtaining high optical modulation rates for optical signal injection in millimetre-wave systems examined.

Optical control of microwave devices.

We report the first demonstration of a uni-traveling carrier photodiode (UTC-PD) used as a 5 Gbps wireless receiver. In this experiment, a 35.1 GHz carrier was electrically modulated with 5 Gbps non-return with zero on-off keying (NRZ-OOK) data and transmitted wirelessly over a distance of 1.3 m. At the receiver, a UTC-PD was used as an optically pumped mixer (OPM) to down-convert the received radio frequency (RF) signal to an intermediate frequency (IF) of 11.7 GHz, before it was down-converted to the baseband using an electronic mixer. The recovered data show a clear eye diagram, and a bit error rate (BER) of less than 10-8 was measured. The conversion loss of the UTC-PD optoelectronic mixer has been measured at 22 dB. The frequency of the local oscillator (LO) used for the UTC-PD is defined by the frequency spacing between the two optical tones, which can be broadly tuneable offering the frequency agility of this photodiode-based receiver.

5 Gbps wireless transmission link with an optically pumped uni-traveling carrier photodiode mixer at the receiver.

Recent work on optical signal distribution and control techniques for phased-array radar is described. Experimental results for millimeter-wave reference signal generation by heterodyning the outputs of two semiconductor lasers are presented. Mixers in which the local oscillator input is an intensity-modulated optical signal are described. The use of these developments, together with other optically controlled devices, in phased-array element architectures is discussed. >

Alwyn J. Seeds

Papers

Full-duplex DOCSIS/WirelessDOCSIS fiber-radio network employing packaged AFPM-based base-stations

Microwave frequency synthesis using injection locked laser comb line selection

Optical control of microwave devices.

5 Gbps wireless transmission link with an optically pumped uni-traveling carrier photodiode mixer at the receiver.

New developments in optical control techniques for phased array radar