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

We describe fast recovery at a wavelength of 1550 nm in a multiple-quantum-well (MQW) saturable absorber with InGaAsP quaternary wells and barriers using electric-field-induced carrier sweepout. The MQW SA is integrated with a distributed Bragg reflector in a p-type–intrinsic–n-type structure. Pump–probe measurements show that the recovery time can be reduced from >900 to 28 ps by application of a 151 kV/cm sweepout field. We measure the dependence of the recovery time on the energy of the saturating pulse and explain our results in terms of carrier dynamics in the sweepout field.

28 ps recovery time in an InGaAsP/InGaAsP multiple-quantum-well saturable absorber employing carrier sweepout

A computer model for the performance of a semiconductor laser amplifier under static and dynamic input conditions is presented. In particular, the model is used to study the behaviour of the amplifier with sinusoidally intensity-modulated input signals. The distortion arising from gain modulation at low modulation frequencies is investigated. It is shown that at microwave modulation frequencies the gain takes an average value and the response becomes linear. Semiconductor laser amplifiers are therefore suitable for applications in microwave optoelectronics, such as reference signal distribution in optically controlled phased-array antennas.

Computer model for semiconductor laser amplifiers with RF intensity-modulated inputs

We report generation and transmission of single side-band millimeter-wave modulated optical signals using a reference-modulated optical injection phase-lock loop. A 36-GHz 68-Mbit/s differential phase shift keyed signal is transmitted over a 65-km unamplified standard single-mode fiber using no dispersion compensation with a BER < 10/sup -9/.

A 65-km span unamplified transmission of 36-GHz radio-over-fiber signals using an optical injection phase-lock loop

This paper outlines an approach to optical feedforward linearisation technique to reduce nonlinear distortion generated by a directly modulated semiconductor laser diode for Wireless Local Area Network (WLAN) operating in the Industrial Scientific -Medical (ISM) band 2.4 GHz (IEEE802.11b) for Radio over Fibre (RoF). Various linearization techniques are reviewed. Results with feedforward linearis ation have shown over 10 dB reduction in Intermodulation Distortion IMD in frequency range of 2.2 GHz – 2.7 GHz.

/pdf/nonlinear-distortion-reduction-in-directly-modulated-5aoih9eogx.pdf

Nonlinear distortion reduction in directly modulated semiconductor laser using feed-forward linearization

The low-loss, wide bandwidth capability of optical fibre transmission systems makes them attractive for the distribution and processing of microwave signals. This paper will review the techniques used for generating, transmitting and detecting microwave modulated optical signals and will describe typical systems applications.

Alwyn J. Seeds

Papers

28 ps recovery time in an InGaAsP/InGaAsP multiple-quantum-well saturable absorber employing carrier sweepout

Computer model for semiconductor laser amplifiers with RF intensity-modulated inputs

A 65-km span unamplified transmission of 36-GHz radio-over-fiber signals using an optical injection phase-lock loop

Nonlinear distortion reduction in directly modulated semiconductor laser using feed-forward linearization

Microwave opto-electronics