Laser coupling to single-mode fibre using graded-index lenses and compact disc 1.3 ?m laser package

A 1.3 ?m laser in a compact disc package is coupled to single-mode fibre using two graded-index lenses in a nearly confocal scheme. An increase in the alignment tolerance at the lens-lens interface by a factor of six suggests the design for a potentially very low-cost connectorised laser package. The coupling efficiency of approx. 6% (?12 dB) is shown to be adequate for local loop applications.     

The Symbiotic Sustainability Model: Conceptualizing NGO–Corporate Alliance Communication

We introduce the Symbiotic Sustainability Model (SSM) as a macrolevel explanation of nongovernmental organization (NGO)–corporate alliances. The SSM presents NGO–corporate alliances as distinct interorganizational communication relationships, symbolized to stakeholders to influence the mobilization of capital. We contend that alliance partners communicatively co‐construct the alliance with stakeholders in order to mobilize economic, social, cultural, and political capital. By focusing on the communication of alliances' existence and character, new propositions emerge concerning the role of communication, capital mobilization resulting from NGO–corporate alliances, NGOs and corporations' choice(s) of alliance partner(s), the number of partners with whom organizations are likely to communicate, and potential risks and rewards. The model is illustrated using the Rainforest Alliance and Chiquita Better Banana program as an abbreviated case study.     

Spectroscopy and rectification of three donor-sigma-acceptor compounds, consisting of a one-electron donor (pyrene or ferrocene), a one-electron acceptor (perylenebisimide), and a C19 swallowtail

We report spectroscopic characterization and unimolecular rectification (asymmetric electrical conduction) measurements of three donor-sigma-acceptor (D-sigma-A) compounds N-(10-nonadecyl)-N-(1-pyrenylmethyl)perylene-3,4,9,10-bis(dicarboximide) (1), N-(10-nonadecyl)-N-(4-[1-pyrenyl]butyl)perylene-3,4,9,10-bis(dicarboximide) (2), and N-(10-nonadecyl)-N-(2-ferrocenylethyl)perylene-3,4,9,10-bis(dicarboximide) (3). These molecules were arranged as one-molecule thick Langmuir-Blodgett monolayers between Au electrodes. In such an "Au | D-sigma-A | Au" sandwich, molecule 1 is a unimolecular rectifier, with rather small rectification ratios (between 2 and 3 at +/-1 V) that decrease upon cycling. Molecule 2 does not rectify. Molecule 3 rectifies, with a rectification ratio of between 14 and 28 at +/-1 V; the through-film rectification and currents persist, even with scans of +/-2 V, for up to 40 cycles of measurement. Qualitative arguments, based on a two-level rectification mechanism, are consistent with the current asymmetries observed in the monolayers of 1 and 3.     

Powering the fiber loop optically-a cost analysis

Recent successes in transporting optical power near the 1-W level via optical fiber suggest that it may be possible to operate conventional telephone station sets using electricity derived photovoltaically from light in a fiber. The authors investigate the constraints on optical powering in fiber-in-the-loop (FITL) applications and assess its applicability in terms of end-to-end efficiency, loop length, and system cost. To make this assessment, they look at several different optical-powering system architectures and components vis-a-vis their cost-versus-delivered-power capability. Related issues such as safety and reliability are discussed.<>     

Temperature effects on dispersion and loss for high-bit-rate LED-based lightwave systems

Examination of the impact of wide temperature extremes on high-bit-rate LED-based systems indicates that the LED room-temperature wavelength should be selected below 1300 nm to avoid excess loss owing to the 1390 nm water peak in fibre.     

Transmission experiments at 560 Mbit/s and 140 Mbit/s using single-mode fibre and 1300 nm LEDs

Transmission at 560 Mbit/s has been demonstrated using single-mode fibre and LEDs at 1300 nm. Surface-emitting, edge-emitting and super-radiant LEDs were used to transmit over maximum distances of 4.5 km, 15 km and 25 km, respectively. At 140 Mbit/s, the corresponding distances achieved with the same set of LEDs are 7.5, 35 and 50 km. respectively.     

Coupling sensitivity of an edge-emitting LED to single-mode fiber

An edge-emitting LED coupled to a single-mode fiber shows increased coupling sensitivity to fiber displacement compared with multimode fiber. Sensitivity to lateral misalignment in the direction perpendicular to the junction plane of the LED increases by at least a factor of three, regardless of the coupling scheme used. A reciprocal relationship between peak coupling efficiency and sensitivity to misalignment is observed. We show that a previous theory for laser coupling can be extended to include edge-emitting LED's, and that it predicts this relationship. The results for different coupling schemes are discussed with respect to LED packaging.     

Fiber-to-the-Home: 1977–2007

Fiber has been envisioned for delivering broadband services to the residential customer for over 30 years, yet it has only recently entered the mainstream. Currently, fiber-to-the-home (FTTH) is being installed in many countries at remarkable rates (even though it still constitutes only a fraction of all broadband lines in most countries). Other lightwave transmission technologies have progressed far faster. What has held FTTH up for so long? What improvements along the way have occurred? What recent changes have made it successful? This article follows the progress in moving fiber toward the home and major architectural changes that have reduced costs while increasing capabilities to meet today's needs.