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

Small erbium-doped amplets and semiconductor optical amplifiers will be used in current and future metro and enterprise networks in various configurations. Many new system architectures will be enabled as these low-cost technologies are used to compensate for transmission and impairment-compensating component losses. This paper discusses the definition, use, and technologies associated with these new classes of optical amplifiers which, though little, will impact next-generation networks a great deal.

Amplifiers for the masses: EDFA, EDWA, and SOA amplets for metro and access applications

Performance of high-concentration Er/sup 3+/-Yb/sup 3+/-codoped phosphate fiber amplifiers in a copumping configuration is presented. Gain, noise figure, and output signal saturation power of fiber amplifiers with different lengths are reported. From a 3.6-cm-long fiber, 18-dB internal gain, i.e., 5 dB/cm, for small signal input at 1535 nm, was achieved. To the best of our knowledge, this is the highest gain per unit length for erbium-doped fiber amplifiers ever reported.

Performance of high-concentration Er/sup 3+/-Yb/sup 3+/-codoped phosphate fiber amplifiers

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

Summary form only given. In our previous work we have shown the efficiency of our ion-exchange technology in producing waveguide amplifiers in erbium/ytterbium (Er/Yb) co-doped phosphate glass. In this paper we report the gain performances at both 1534 and 1548 nm wavelengths and we discuss the respective advantages of these new waveguide laser amplifiers.

Net gain of 27 dB with a 8.6-cm-long Er/Yb-doped glass-planar-amplifier

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

Integrated optics are used to achieve astronomical interferometry inside robust and compact materials, improving the instruments stability and sensitivity. In order to perform differential phase measurements at the Hα line (656.3nm) with the 600-800nm spectro-interferometer FIRST, a photonic integrated circuit (PIC) is being developed. This PIC performs the visible combination of the beams coming from the telescope pupil sub-apertures. In this work, TEEM Photonics waveguides fabricated by K+ : Na+ ion exchange in glass are characterized in terms of single-mode range and mode field diameter. The waveguide diffused index profile is modeled on Beamprop software. FIRST beam combiner building blocks are simulated, especially achromatic directional couplers and passive π/2 phase shifters for a potential ABCD interferometric combination.

C. Cassagnettes

Papers

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

Net gain of 27 dB with a 8.6-cm-long Er/Yb-doped glass-planar-amplifier

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

Photonic chip for visible interferometry: laboratory characterization and comparison with the theoretical model