N G van Kampen 1981 Amsterdam: North-Holland xiv + 419 pp price Dfl 180 This is a book which, at a lower price, could be expected to become an essential part of the library of every physical scientist concerned with problems involving fluctuations and stochastic processes, as well as those who just enjoy a beautifully written book. It provides an extensive graduate-level introduction which is clear, cautious, interesting and readable.

https://iopscience.iop.org/article/10.1088/0031-9112/34/4/040/pdf

Stochastic Processes in Physics and Chemistry

A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Supercontinuum generation in photonic crystal fiber

We describe a method to estimate the capacity limit of fiber-optic communication systems (or ?fiber channels?) based on information theory. This paper is divided into two parts. Part 1 reviews fundamental concepts of digital communications and information theory. We treat digitization and modulation followed by information theory for channels both without and with memory. We provide explicit relationships between the commonly used signal-to-noise ratio and the optical signal-to-noise ratio. We further evaluate the performance of modulation constellations such as quadrature-amplitude modulation, combinations of amplitude-shift keying and phase-shift keying, exotic constellations, and concentric rings for an additive white Gaussian noise channel using coherent detection. Part 2 is devoted specifically to the "fiber channel.'' We review the physical phenomena present in transmission over optical fiber networks, including sources of noise, the need for optical filtering in optically-routed networks, and, most critically, the presence of fiber Kerr nonlinearity. We describe various transmission scenarios and impairment mitigation techniques, and define a fiber channel deemed to be the most relevant for communication over optically-routed networks. We proceed to evaluate a capacity limit estimate for this fiber channel using ring constellations. Several scenarios are considered, including uniform and optimized ring constellations, different fiber dispersion maps, and varying transmission distances. We further present evidences that point to the physical origin of the fiber capacity limitations and provide a comparison of recent record experiments with our capacity limit estimation.

Capacity Limits of Optical Fiber Networks

Real and Complex Analysis

Squeezed states of the electromagnetic field have been generated by nondegenerate four-wave mixing due to Na atoms in an optical cavity. The optical noise in the cavity, comprised of primarily vacuum fluctuations and a small component of spontaneous emission from the pumped Na atoms, is amplified in one quadrature of the optical field and deamplified in the other quadrature. These quadrature components are measured with a balanced homodyne detector. The total noise level in the deamplified quadrature drops below the vacuum noise level.

Observation of squeezed states generated by four-wave mixing in an optical cavity

We show that spatial filtering of Kerr spatial solitons produces sub-Poissonian (amplitude-squeezed) light. Filtering can be performed in either the near field or the far field of the spatial soliton at the output of the Kerr medium. Up to 6.5 dB of squeezing is predicted by placing a square aperture of 82% transmittance in the far field.

Sub-Poissonian light by spatial soliton filtering

We present a new receiver scheme that recovers complex-valued QAM modulated data while using two separate branches of direct detection. It seamlessly integrates dispersion compensation in the data recovery algorithm, and its power efficiency is far better than in other receiver schemes of comparable characteristics.

The Enhanced Kramers Kronig Receiver

We study the information capacity and the spectral efficiency of communication systems with optical amplifiers, in the direct detection intensity modulation case. We show that with typical values of OSNR of the order of 20 dB, multilevel signaling can increase the spectral efficiency by no more than a factor of 3.5 relative to binary modulated systems. The highest spectral efficiency is obtained with a symmetric optical spectrum, and it cannot be improved by removing one sideband as in the single sideband modulation case.

Limits on the spectral efficiency of intensity modulated direct detection systems with optical amplifiers

We measure the pump power dependence of efficiency and signal-to-background ratio in wavelength conversion using four-wave mixing in semiconductor optical amplifiers, for different lengths of the device We show that the efficiency for a 1-mm-long amplifier is about 40 dB larger and the signal-to-noise ratio is about 23 dB larger than for a 025 mm amplifier We also show that, unlike the efficiency, for constant ratio between pump- and signal-power, the signal-to-background ratio monotonically increases with the pump power We show theoretically that this behavior holds for any range of pump-power values

Noise in wavelength conversion using four-wave mixing in semiconductor optical amplifiers

We show that the spectral efficiency of a direct detection transmission system is at most 1 b/s/Hz less than the spectral efficiency of a system employing coherent detection with the same modulation format. Correspondingly, the capacity per complex degree of freedom in systems using direct detection is lower by at most 1 bit.

Antonio Mecozzi

Papers

Sub-Poissonian light by spatial soliton filtering

The Enhanced Kramers Kronig Receiver

Limits on the spectral efficiency of intensity modulated direct detection systems with optical amplifiers

Noise in wavelength conversion using four-wave mixing in semiconductor optical amplifiers

Information Capacity of Direct Detection Optical Transmission Systems