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

Optical amplifiers have played a leading
role in the evolution of telecommunications
over the course of the past
decade. What would the world of
telecommunications look like if optical
amplifier technology had not been developed?
For a start, wavelength-division
multiplexing (WDM) would be
impractical: At every repeating station
the signal would have to be demultiplexed,
electronically regenerated, and
retransmitted. In this scenario, multiple
fibers—rather than multiple wavelengths—
would probably be the most
economical way to increase transmission
system capacity.Cost per bit would
be much higher than is the case for
WDM systems. This added expense
would most certainly have limited the
growth of the Internet, since its market
penetration is primarily due to transmission
bandwidth availability and low
connection costs.

The Roles of Semiconductor Optical Amplifiers in Optical Networks

A simple and accurate method to measure the linewidth enhancement factor a in DFB semiconductor lasers is proposed. This method, based on the principle of external optical injection locking, does not require the knowledge of the absolute value of optical injection level.

Novel measurement technique of α factor in DFB semiconductor lasers by injection locking

Very high four-wave mixing (FWM) efficiency and signal-to-background ratio (SBR) are obtained in a 1.5-mm-long bulk semiconductor optical amplifier. The FWM efficiency is measured to be 5 dB at 1-THz pump-signal detuning, which is the highest value reported to date. With a pump power of -1.4 dBm, the SBR is in excess of 20 dB in a bandwidth of 12.5 GHz, for a pump-signal detuning range as large as 2 THz and the efficiency is under the same conditions larger than -1 dB for a pump-signal detuning range as large as 1 THz. These results make FWM an attractive method for practical wavelength conversion. Some low-detuning measurements show a maximum efficiency around 8 GHz.

Low-noise and very high-efficiency four-wave mixing in 1.5-mm-long semiconductor optical amplifiers

We study the frequency autocorrelation of the differential group delay (DGD) in fibers with polarization mode dispersion (PMD). We show that the correlation bandwidth of the DGD is comparable with that of the orientation of the PMD vector. Furthermore, we show that all the most general statistical properties of polarization mode dispersion in long fibers are uniquely determined by the mean DGD. An estimate of the accuracy of measurements in which the mean DGD is extracted by frequency averaging in a single fiber is obtained as a function of the measured bandwidth.

Study of the frequency autocorrelation of the differential group delay in fibers with polarization mode dispersion.

Repeaterless long-distance transmission schemes are investigated in the presence of the Kerr nonlinearity and of the spontaneous-emission noise of the in-line amplifiers. Second- and higher-order dispersion coefficients are assumed to be zero. Criteria for optimizing the system performance are given.

Antonio Mecozzi

Papers

The Roles of Semiconductor Optical Amplifiers in Optical Networks

Novel measurement technique of α factor in DFB semiconductor lasers by injection locking

Low-noise and very high-efficiency four-wave mixing in 1.5-mm-long semiconductor optical amplifiers

Study of the frequency autocorrelation of the differential group delay in fibers with polarization mode dispersion.

Long-distance transmission at zero dispersion: combined effect of the Kerr nonlinearity and the noise of the in-line amplifiers