Deutsche Telekom

About: Deutsche Telekom is a company organization based out in Welwyn Garden City, United Kingdom. It is known for research contribution in the topics: Telecommunications network & Terminal (electronics). The organization has 3473 authors who have published 5208 publications receiving 65429 citations. The organization is also known as: DTAG & German Telecom.

40 Gb/s and 4/spl times/40 Gb/s TDM/WDM standard fiber transmission

Abstract: We investigate the possibilities of 40 and 4/spl times/40 Gb/s time division multiplexing wavelength division multiplexing (TDM/WDM) return-to-zero (RZ) transmission over embedded standard single-mode fibers (SMF) at a transmission wavelength of 1.55 /spl mu/m both experimentally and theoretically. Dispersion of the SMF is compensated by a dispersion compensating fiber (DCF). Transmission over a span of 150 km of SMF in the single-channel case and of 100 km SMF in the multichannel case are reported. Numerical calculations are employed to investigate the possibility of cascading the spans both for single-channel and multichannel transmission. For single-channel transmission, it is shown that optimum performance is achieved with postcompensation of the DCF. The input power at the SMF and DCF input have to be chosen carefully. For four channel transmission, the performance is mainly limited by residual dispersion in the outermost wavelength channels. It is shown numerically that improvement is achieved by employing the newest type DCF which also compensates the dispersion slope of the SMF. For a WDM channel separation of 2 nm no significant additional degradation due to cross-phase modulation (XPM) or four-wave mixing is observed.

Shape-changing mobiles: tapering in one-dimensional deformational displays in mobile phones

Abstract: In this paper, we present a new shape-based display technique for mobile phones: A rotatory deformation of the phone's chassis, resulting in a tapering between the phone's front and back panel. It draws on proprioceptive skills of the human hand, which we hypothesize to be sensitive to paralellism and tapering of two opposing panels.We present a number of applications for such an actuation system: Interactive Feedback, User Notification, and Ambient Display. The proposed system is evaluated in a user study, which results point to certain advantages, as well as drawbacks, in comparison to other mobile actuation systems.We conclude by discussing areas in which tapering-based deformational displays may be used advantageously, and how the proposed system may be improved in the future.

Multilayer traffic engineering for GMPLS-enabled networks

Abstract: In recent years, significant work has been completed on traffic engineering enhancements to the generalized multiprotocol label switching protocol suite (E. Mannie Oct 2004) (D. Katz et al., Sept. 2003) (K. Kompella et al., Oct 2003). As a next step, reproducing the current trend of switching layers' integration happening in the data plane, network control is foreseen to go beyond the traditional per layer approach and tend toward an integrated model (K. Shimoto et al., Oct 2004) (E. Dotaro et al., Dec. 2004). In these multilayer environments, a single GMPLS control plane drives various distinct switching layers at the same time and as a coherent whole, taking benefit from the "common" property of GMPLS. Beyond this application of supporting network control across different technologies, in this article we catalog the unified traffic engineering paradigms, discuss their applicability, and present their enforcement techniques. Furthermore, we show that the common GMPLS concept has the advantage of low operational complexity, and enables unified TE capabilities such as efficient network resource usage and rapid service provisioning.

Tailored DFB laser properties by individually chirped gratings using bent waveguides

Abstract: DFB lasers with continuously and arbitrarily chirped gratings of ultrahigh spatial precision are implemented by a method we proposed recently, using bent waveguides on homogeneous grating fields. Choosing individual bending functions we generate special chirping functions and obtain additional degrees of freedom to tailor and improve specific device performances. We present two applications for lasers showing several improved device properties and the effectiveness of our method. First, we implement continuously distributed phase-shifted lasers, revealing a considerably reduced photon pile-up, higher single-longitudinal mode stability, higher output power, lower linewidth, and higher yield than conventional abruptly phase-shifted lasers. Second, a novel tuning principle is applied in chirped multiple-section DFB lasers, showing 5.5-nm wavelength tuning, without any gaps, maintaining high side-mode suppression. >

Performance of optimized routing in LEO intersatellite link networks

Abstract: An ATM based routing concept for LEO intersatellite link networks is proposed. The challenges arising from the complex time-variant ISL network topology are tackled by a discrete-time network model and routing procedure. The approach is based on the combination of a modified standard routing scheme and the ATM VPC concept. The routing scheme works completely off-line, i.e. prior to system operation. In a first step, a virtual topology is set up for all successive time intervals, providing instantaneous sets of alternative VPCs (paths) between all source-destination satellite pairs. In the second step, path sequences over a series of time intervals are chosen from that according to a certain optimization procedure. Two different optimization procedures are discussed in detail, and a numerical performance evaluation is presented for telephony service in an example ISL network (Iridium). The overall routing performance is evaluated in terms of remaining delay jitter due to inevitable path handover. The results show that optimized routing strategies are specifically capable of minimizing severe delay jitter, and thus in turn reduce the complexity of ATM based operation in a connection-oriented service environment.