Since the energy crisis and environmental protection are gaining increasing concerns in recent years, new research topics to devise technological solutions for energy conservation are being investigated in many scientific disciplines. Specifically, due to the rapid growth of energy consumption in ICT (Information and Communication Technologies), lot of attention is being devoted towards "green" ICT solutions. In this paper, we provide a comprehensive survey of the most relevant research activities for minimizing energy consumption in telecom networks, with a specific emphasis on those employing optical technologies. We investigate the energy-minimization opportunities enabled by optical technologies and classify the existing approaches over different network domains, namely core, metro, and access networks. A section is also devoted to describe energy-efficient solutions for some of today's important applications using optical network technology, e.g., grid computing and data centers. We provide an overview of the ongoing standardization efforts in this area. This work presents a comprehensive and timely survey on a growing field of research, as it covers most aspects of energy consumption in optical telecom networks. We aim at providing a comprehensive reference for the growing base of researchers who will work on energy efficiency of telecom networks in the upcoming years.

Energy Efficiency in Telecom Optical Networks

Erbium-doped fiber devices have been extraordinarily successful due to their broad optical gain around 1.5–1.6 μm. Er-doped fiber amplifiers enable efficient, stable amplification of high-speed, wavelength-division-multiplexed signals, thus continue to dominate as part of the backbone of longhaul telecommunications networks. At the same time, Er-doped fiber lasers see many applications in telecommunications as well as in biomedical and sensing environments. Over the last 20 years significant efforts have been made to bring these advantages to the chip level. Device integration decreases the overall size and cost and potentially allows for the combination of many functions on a single tiny chip. Besides technological issues connected to the shorter device lengths and correspondingly higher Er concentrations required for high gain, the choice of appropriate host material as well as many design issues come into play in such devices. In this contribution the important developments in the field of Er-doped integrated waveguide amplifiers and lasers are reviewed and current and future potential applications are explored. The vision of integrating such Er-doped gain devices with other, passive materials platforms, such as silicon photonics, is discussed.

Erbium-doped integrated waveguide amplifiers and lasers

We review the history and current status of ion exchanged glass waveguide technology. The background of ion exchange in glass and key developments in the first years of research are briefly described. An overview of fabrication, characterization and modeling of waveguides is given and the most important waveguide devices and their applica- tions are discussed. Ion exchanged waveguide technology has served as an available platform for studies of general waveguide properties, in- tegrated optics structures and devices, as well as applications. It is also a commercial fabrication technology for both passive and active wave- guide components. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

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Ion-exchanged glass waveguide technology: a review

For the first time, a novel flat-gain optical amplifier is proposed using a hybrid configuration with an Er-Yb co-doped waveguide amplifier (EYDWA) and a semiconductor optical amplifier (SOA) for 100 × 10-Gb/s dense wavelength division multiplexed system at 0.2 nm interval. With an EYDWA-SOA hybrid amplifier, a flat gain of is obtained across the effective bandwidth with a gain variation of the order of 0.75 dB without using any gain clamping techniques. It is observed that when the proposed hybrid amplifier is used as a booster for hybrid distributed Raman amplifier and erbium doped fiber amplifier, the gain variation is reduced from 2.01 to ~ 1.15 dB efficiently with acceptable bit error rate.

Novel Optical Flat-Gain Hybrid Amplifier for Dense Wavelength Division Multiplexed System

Arrays of buried channel waveguide lasers and amplifiers were fabricated by silver–sodium ion exchange in erbium–ytterbium doped phosphate glass substrates. The fabrication process, consisting of a thermal diffusion from fused salt followed by a field-assisted burial step, is optimized to get single-mode channel arrays fully compatible with standard single-mode fibres and fibre ribbon cables. The active channels were successfully tested realizing both lasers and amplifiers in the C-band suitable for optical communications. Erbium waveguide lasers exhibit a maximum output power of ∼1.7 mW and erbium-doped waveguide amplifiers provide a maximum internal gain of ∼11.3 dB at 1534 nm.

Active waveguide devices by Ag–Na ion exchange on erbium–ytterbium doped phosphate glasses

We demonstrate an 8/spl times/2.5 Gb/s wavelength-division-multiplexing metropolitan ring network in which each network-sourced wavelength constitutes a distinct multiuser virtual ring. The ring's four nodes feature erbium-doped waveguide amplifiers, which promise future integrability.

An eight-wavelength 160-km transparent metro WDM ring network featuring cascaded erbium-doped waveguide amplifiers

We demonstrate a 4/spl times/2.5 Gb/s WDM ring with network-sourced virtual rings comprising optically shared wavelengths. The ring's four nodes feature erbium-doped waveguide amplifiers (EDWAs), shown here for the first time in cascade, which promise future integrability.

A 160-km transparent metro WDM ring network featuring cascaded erbium-doped waveguide amplifiers

Er3+-doped planar waveguides is a promising technology for integration of active and passive functional components (such as e.g. loss-compensated splitters and amplifiers integrated with multiplexers) on a single chip [1].

Self-referenced Q-switched pump-probe transmission experiment for the determination of the degree of clustering in Er-doped planar waveguides

We report on the first Er/sup 3+/-Yb/sup 3+/ doped planar waveguide amplifier with +14 dBm output power which we use as a post-amplifier for the DWDM transmission of eight wavelengths, each carrying 35 6-MHz 64-QAM channels, over an unrepeated span of 175 km.

D. Barbier

Papers

An eight-wavelength 160-km transparent metro WDM ring network featuring cascaded erbium-doped waveguide amplifiers

A 160-km transparent metro WDM ring network featuring cascaded erbium-doped waveguide amplifiers

Self-referenced Q-switched pump-probe transmission experiment for the determination of the degree of clustering in Er-doped planar waveguides

High output power erbium doped waveguide amplifier for QAM distribution