Passivation of the facets of 980 nm GaAs pump lasers by a pulsed UV laser-assisted technique

It is reported on the passivation of the mirror facets, opened in the air, of ridge waveguide InGaAs/GaAs/AlGaAs single quantum well (λ=980 nm) laser diodes. The passivation concept consists of two steps, namely, oxide removal by irradiation of the mirror facets with a pulsed KrF laser, immediately followed by the deposition of a thin silicon layer. The experimental arrangement (the process operation and the aging behavior-resistance to catastrophic optical damage) of the lasers thus treated are described. The structural modification of the laser facets, as probed by micro-Raman spectroscopy and Rutherford backscattering spectroscopy, and the calibration technique used to assess the rate of oxide removal are also presented.     

A novel implementation of the histogram-based technique for measurement of INL of LUT-based correction of ADC

The histogram-based technique is commonly used for testing of Analog-to-Digital Converters (ADC). One of the parameters measured thanks to this technique is the Integral Non Linearity (INL). INL is also used as an initial data related to the ADC performances for the computation of a correction table in case of a LUT-based correction technique. In this context of embedded INL measurement and embedded computation of the table for LUT-based correction of ADC, we propose a new implementation establishing what we consider the best trade-off between silicon area overhead and computing time. We compare our solution with the state of the art: (a) with VHDL-level simulation we compare time performance, and (b) with FPGA placer we estimate the final surface head-out.     

Synthesis of planar inductors in low temperature co-fired ceramic technology

A simple bisection algorithm for the synthesis of planar inductors using a fast electromagnetic analysis algorithm is presented in this work. Both bisection and electromagnetic analysis algorithms are based on a set of heuristic and physical rules obtained from the study of the electromagnetic behavior of these planar devices. With this procedure, the benefits are two fold: (i) the number of iterations is kept moderately low in the synthesis loop, and (ii) the analysis at each iteration step is speed up without compromising accuracy. The algorithm is applied to the development of an inductor library for a low temperature co-fired ceramic process technology.     

A Simplified Internet Routing Architecture

This paper studies the effect of disaggregation on the size of the routing table in the Internet’s Default Free Zone (DFZ). Current practises for traffic balancing and protection against prefix hijacking in the Internet are based in disaggregating prefixes that cause an increase in size of the Internet’s core routing table. I propose an algorithm to assess their effect on the table size of these techniques. This algorithm is applied on routing tables collected by the RIPE’s Routing Repository between January 2001 and February 2011. The results show that before 2010, the IPv4 addressing space was gradually getting more fragmented. This trend is slowing down since the beginning of 2010, possibly as the result of the economic downturn. In the second part of this paper, I propose an alternative architecture that allows local Traffic Engineering configurations but keeps their effects from spreading over the Internet and outline an implementation for this architecture on a Linux platform.     

Heteroatom Effect on Star‐Shaped Hole‐Transporting Materials for Perovskite Solar Cells

Three new star‐shaped hole‐transporting materials (HTMs) incorporating benzotripyrrole, benzotrifuran, and benzotriselenophene central cores endowed with three‐armed triphenylamine moieties ( BTP‐1 , BTF‐1 , and BTSe‐1 , respectively) are designed, synthesized, and implemented in perovskite solar cells (PSCs). The impact that the heteroatom‐containing central scaffold has on the electrochemical and photophysical properties, as well as on the photovoltaic performance, is systematically investigated and compared with their sulfur‐rich analogue ( BTT‐3 ). The new HTMs exhibit suitable highest‐occupied molecular orbitals (HOMO) levels regarding the valence band of the perovskite, which ensure efficient hole extraction at the perovskite/HTM interface. The molecular structures of BTF‐1 , BTT‐3 , and BTSe‐1 are fully elucidated by single‐crystal X‐ray crystallography as toluene solvates. The optimized (FAPbI₃)_0.85(MAPbBr₃)_0.15‐based perovskite solar cells employing the tailor‐made, chalcogenide‐based HTMs exhibit remarkable power conversion efficiencies up to 18.5%, which are comparable to the devices based on the benchmark spiro‐OMeTAD. PSCs with BTP‐1 exhibit a more limited power conversion efficiency of 15.5%, with noticeable hysteresis. This systematic study indicates that chalcogenide‐based derivatives are promising HTM candidates to compete efficiently with spiro‐OMeTAD.     

Designing and experimentally demonstrating automatic OPS/OCS/OpenFlow network control driven by ChoiceNet provider

Interconnection between our existing optical packet and circuit integrated network (OPCInet) and an ecosystem for network service provisioning named ChoiceNet enables network service providers to provide diverse services and realize control driven by the providers. In this paper, we design and implement control interfaces for the interconnection, which enables each ChoiceNet provider to explicitly control both OPCInet- and OpenFlow-based networks by use of a single common interface with proprietary/easily modifiable message formats for all control functions. We construct an experimental setup between the USA and Japan, and demonstrate that the OPCInet and an OpenFlow-based network placed in Japan are successfully controlled by request from the ChoiceNet provider installed in the USA. We also show that the time required to complete Telnet access to the OPCInet C-plane for each control is no more than 150 ms over the long distance from the USA to Japan.     

Power consumption reduction through elastic data rate adaptation in survivable multi-layer optical networks

Network survivability requires the provisioning of backup resources in order to protect active traffic against any failure scenario. Backup resources, however, can remain unused most of the time while the network is not in failure condition, inducing high power consumption wastage, if fully powered on. In this paper, we highlight the power consumption wastage of the additional resources for survivability in IP/multi-protocol label switching (MPLS) over dense wavelength division multiplexing multi-layer optical networks. We assume MPLS protection switching as the failure recovery mechanism in the network, a solution interesting for current network operators to ensure fast recovery as well as fine-grained recovery treatment per label switched path. Next, we quantitatively show how elastic optical technologies can effectively reduce such a power consumption by dynamically adjusting the data rate of the transponders to the carried amount of traffic.     

On the Complexity of Distributed Self-Configuration in Wireless Networks

We consider three distributed configuration tasks that arise in the setup and operation of multi-hop wireless networks: partition into coordinating cliques, Hamiltonian cycle formation and conflict-free channel allocation. We show that the probabilities of accomplishing these tasks undergo zero-one phase transitions with respect to the transmission range of individual nodes. We model these tasks as distributed constraint satisfaction problems (DCSPs) and show that, even though they are NP-hard in general, these problems can be solved efficiently on average when the network is operated sufficiently far from the transition region. Phase transition analysis is shown to be a useful mechanism for quantifying the critical range of energy and bandwidth resources needed for the scalable performance of self-configuring wireless networks.