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

The very broad bandwidth of low-loss optical transmission in a single-mode fiber and the recent improvements in single-frequency tunable lasers have stimulated significant advances in dense wavelength division multiplexed optical networks This technology, including wavelength-sensitive optical switching and routing elements and passive optical elements, has made it possible to consider the use of wavelength as another dimension, in addition to time and space, in network and switch design The independence of optical signals at different wavelengths makes this a natural choice for multiple-access networks, for applications which benefit from shared transmission media, and for networks in which very large throughputs are required Recent progress in multiwavelength networks are reviewed, some of the limitations which affect the performance of such networks are discussed, and examples of several network and switch proposals based on these ideas are presented Discussed also are critical technologies that are essential to progress in this field >

Dense wavelength division multiplexing networks: principles and applications

The change in refractive index Delta n produced by injection of free carriers in InP, GaAs, and InGaAsP is theoretically estimated. Bandfilling (Burstein-Moss effect), bandgap shrinkage, and free-carrier absorption (plasma effect) are included. Carrier concentrations of 10/sup 16//cm/sup 3/ to 10/sup 19//cm/sup 3/ and photon energies of 0.8 to 2.0 eV are considered. Predictions for Delta n are in reasonably good agreement with the limited experimental data available. Refractive index changes as large as 10/sup -2/ are predicted for carrier concentrations of 10/sup 8//cm/sup 3/ suggested that low-loss optical phase modulators and switches using carrier injection are feasible in these materials. >

Carrier-induced change in refractive index of InP, GaAs and InGaAsP

Wavelength multiplexers, demultiplexers and routers based on optical phased arrays play a key role in multiwavelength telecommunication links and networks. In this paper, a detailed description of phased-array operation and design is presented and an overview is given of the most important applications.

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PHASAR-based WDM-devices: Principles, design and applications

We present a review of the use of diode lasers in atomic physics with an extensive list of references. We discuss the relevant characteristics of diode lasers and explain how to purchase and use them. We also review the various techniques that have been used to control and narrow the spectral outputs of diode lasers. Finally we present a number of examples illustrating the use of diode lasers in atomic physics experiments.

Using diode lasers for atomic physics

A new mechanism for polarization rotation in rib waveguides is suggested and demonstrated in InP waveguides The polarization rotation is achieved by loading a rib waveguide in a periodic asymmetric way Complete TE↔TM conversion, with only 2–3 dB excess loss, is obtained in a 37‐mm‐long InP loaded waveguide Strong polarization rotation (80%), in shorter devices (03 mm long), is also demonstrated

Polarization rotation in asymmetric periodic loaded rib waveguides

We have integrated a broadly tunable grating‐assisted vertical coupler as an intracavity filter to demonstrate a novel monolithic multiple‐quantum‐well InGaAsP/InP laser. The narrow, bandpass intracavity filter results in an extended cavity laser with a measured electrical tuning range of 57 nm with single‐frequency operation over most of that range.

Broadly tunable InGaAsP/InP laser based on a vertical coupler filter with 57‐nm tuning range

We report the first observation of the quantum‐confined Stark effect in InGaAs/InP multiple quantum wells grown by organometallic vapor phase epitaxy. The effect is observed both in transmission and photoconductivity measurements. The observed spectral shift agrees with the theory.

Quantum‐confined Stark effect in InGaAs/InP quantum wells grown by organometallic vapor phase epitaxy

We describe a photonic integrated circuit composed of three 1.5 μm wavelength multiple quantum well tunable lasers with a passive optical power combiner and an optical output amplifier. Independent channel operation with 1–2 mW/channel output power is demonstrated.

Uziel Koren

Papers

Polarization rotation in asymmetric periodic loaded rib waveguides

Broadly tunable InGaAsP/InP laser based on a vertical coupler filter with 57‐nm tuning range

Quantum‐confined Stark effect in InGaAs/InP quantum wells grown by organometallic vapor phase epitaxy

Wavelength division multiplexing light source with integrated quantum well tunable lasers and optical amplifiers

Wavelength division multiplexing light source with integrated quantum well tunable lasers and optical amplifiers