Abstract: In translucent (or managed reach) WDM optical
networks, regenerators are employed at specific nodes. Some of
the connections in such networks are routed transparently, while
others have to go through a sequence of 3R regenerators that serve
as “refueling stations” to restore their quality of transmission
(QoT). We extend an online multicost algorithm for transparent
networks presented in our previous study [1], to obtain an IA-RWA
algorithm that works in translucent networks and makes use,
when required, of the regenerators present at certain locations
of the network. To characterize a path, the algorithm uses a
multicost formulation with several cost parameters, including the
set of available wavelengths, the length of the path, the number of
regenerators used, and noise variance parameters that account for
the physical layer impairments. Given a new connection request
and the current utilization state of the network, the algorithm calculates
a set of non dominated candidate paths, meaning that any
path in this set is not inferior with respect to all cost parameters
than any other path. This set consists of all the cost-effective (in
terms of the domination relation) and feasible (in terms of QoT)
lightpaths for the given source-destination pair, including all the
possible combinations for the utilization of available regenerators
of the network. An optimization function or policy is then applied
to this set in order to select the optimal lightpath. Different optimization
policies correspond to different IA-RWA algorithms.
We propose and evaluate several optimization policies, such as the
most used wavelength, the best quality of transmission, the least
regeneration usage, or a combination of these rules. Our results
indicate that in a translucent network the employed IA-RWA
algorithm has to consider all problem parameters, namely, the
QoT of the lightpaths, the utilization of wavelengths and the
availability of regenerators, to efficiently serve the online traffic.
Abstract: Switching in core optical networks is currently being
performed using high-speed electronic or all-optical
circuit switches. Switching with high-speed electronics
requires optical-to-electronic (O/E) conversion of the
data stream, making the switch a potential bottleneck
of the network: any effort (including parallelization) for
electronics to approach the optical speeds seems to be
already reaching its practical limits. Furthermore, the
store-and-forward approach of packet-switching does
not seem suitable for all-optical implementation due to
the lack of practical optical random-access-memories
to buffer and resolve contentions. Circuit switching on
the other hand, involves a pre-transmission delay for
call setup and requires the aggregation of microlows
into circuits, sacriicing the granularity and the control
over individual lows, and is ineficient for bursty traf-
ic. Optical burst switching (OBS) has been proposed
by Qiao and Yoo (1999) to combine the advantages of
both packet and circuit switching and is considered a
promising technology for the next generation optical
internet.
Abstract: We present recent advances in multi-wavelength, power-equalized laser sources that incorporate a semiconductor optical amplifier (SOA) and simple optical filters, such as Lyot-type and Fabry-Perot, for combgeneration. Both linear and ring-cavity configurations are presented, and single-pass optical feedback technique is proposed to improve the performance in terms of the number of simultaneously oscillating lines and output channel power equalization. This technique resulted in a broadened oscillating spectrum of 52 lines spaced at 50 GHz, power-equalized within 0.3 dB. Finally, a simplified version that uses only an uncoated SOA for both gain and combgeneration is demonstrated.
Abstract: Recent activity in the field of Internet-of-Things experimentation has focused on the federation of discrete testbeds, thus placing less effort in the integration of other related technologies, such as smartphones; also, while it is gradually moving to more application-oriented paths, such as urban settings, it has not dealt in large with applications having social networking features. We argue here that current IoT infrastructure, testbeds and related software technologies should be used in such a context, capturing real-world human mobility and social networking interactions, for use in evaluating and fine-tuning realistic mobility models and designing human-centric applications. We discuss a system for producing traces for a new generation of human-centric applications, utilizing technologies such as Bluetooth and focusing on human interactions. We describe the architecture for this system and the respective implementation details presenting two distinct deployments; one in an office environment and another in an exhibition/conference event (FET'11, The European Future Technologies Conference and Exhibition) with 103 active participants combined, thus covering two popular scenarios for human centric applications. Our system provides online, almost real-time, feedback and statistics and its implementation allows for rapid and robust deployment, utilizing mainstream technologies and components.