Scientific Missions of COST 270
General information
A scientific mission in a COST Action is a task of the action,
which is done as a collaboration between two institutes who
are participating the action. One expert or a younger researcher
visits the other laboratory for one to four weeks to perform
a special study or experiment for COST270 action program.
The results are reported to the respective working group and
MC of the action, and if ever possible also published.
The external costs (travelling and accommodation costs etc.)
are paid by COST270 grant, up to 2000 EUR. See also Rules and Forms
Applications
The money for each scientific mission must be applied from
the Management Committee of the action, by using the forms
given above. The written and signed application shall be
sent
to the secretary/grantholder as a letter and a copy
to the Dr. Hans G. Limberger.
Electronic copies, information of a becoming application,
etc.
shall be sent to both the chairman abd the secretary.
It is strongly recommended to send the applications of scientific
missions to the MC before a MC meeting to get a thorough
discussion
and approval. The management committee can also make a decision
upon voting
if necessary.
Each application will be evaluated by a group of evaluators
or by the entire MC of the action, and finally approved/disapproved
by the entire MC. The decision is delivered
by the chairman of the action to the respective host.
--- A scientific paper or a report is expected as a result.
Scientific Missions of COST270
A total of seven short-term scientific missions (STSM)
were organised. They are listed below together
with their abstracts.
STSM-1 “Availability modelling of optical networks” from
25th to 30th June 2002.
Marcel Held, EMPA (Switzerland) visited Prof. Lena Wosinska,
Laboratory of Communication Networks, Royal Institute of
Technology - KTH (Sweden).
Abstract : The main focus in this scientific mission
was put on objective 1 of work group 1, i.e. exchanging
scientific know-how between KTH, EMPA, and other WG1
partners mainly about availability/survivability modelling
approaches for networks. The goal was to establish a
procedure for the system definition and top-down decomposition
of an optical network into a mathematically treatable
structure, e.g. reliability block diagrams or state transition
diagrams as well as the comparison and suitability check
of software tools for RAM-modelling at KTH and EMPA.
The use of approximate analytical expressions for large
series-parallel reliability block diagram (RBD) structures
has shown to be not flexible enough to study a large
number of different and complex RBDs which is necessary
to investigate alternative designs. Another approach
for the estimation of availability for complex RBDs is
the use of Monte Carlo simulation.
The suitability of Monte Carlo simulation is checked
by investigating availability of complex reliability
block diagrams of optical cross connects containing
redundancy. A commercial software tool RELEX is used.
In RELEX RBDs
are graphically designed and probability distribution
functions for failure and repair times with the according
parameters are assigned to each block. In the investigated
examples it is assumed that failure free operating
times and repair times are exponentially distributed
with constant
failure rates ? and repair rates µ as parameters.
Monte Carlo simulation showed results that are very close
to analytical solutions. A relatively low number of iterations
in the investigated examples, 10.000 - 100.000, and therefore
short computation time is sufficient to obtain results
with accuracy required for engineering considerations.
It is therefore concluded that simulation tools are useful
to investigate complex structures of optical networks.
However, such calculation is of course very dependent
on input data, i.e. failure and repair rates of components
and devices. Failure rates of optical components can
be obtained from field data analysis and specific reliability
tests of manufacturers. Up to now there is no established
and accepted model for failure rate prediction for the
large variety of optical components. Thus, emphasis in
network availability analysis should not be put on the
absolute accuracy of calculated results but on the sensitivity
to input parameters.
STSM-2 “Reliability related effects originating
from the manipulation and use of fibre components” from
26th February to 2nd March 2003.
Frédérique de Fornel, CNRS Université de
Bourgogne (France) visited Dr.-Ing. Wolfgang Habel
and Prof. Dr.-Ing. Werner Daum, Federal Institute
for Materials
Research and Testing - BAM (Germany).
Abstract : A round table has been organized by F.de
Fornel and W. Habel to define open questions concerning
reliability-related effects due to the manipulation
and use of optical fibre components. Particular influences
which were considered involve the local modification
of optical fibres. A “modified” fibre can
be defined as :
• a fibre with chemically or mechanically stripped areas
;
• a fibre with fused and recoated areas ;
• a fibre with polished or etched areas ;
• a fibre with connectorized ends.
Experts from suppliers and user companies as well as
consulting offices were invited to present their activities
in this field and focus their open questions that have
been considered in the round table discussion. From
the Berlin meeting participant’s point of view, the
most important reliability-related issue is the effect
of the stripping process (decoating) of the fibre
and fibre components (e.g. for the inscription of fibre
Bragg gratings). One participant had the vision that one day
a single universal procedure to remove the coating
of a fibre should be available. Another point discussed
at the last COST 270 meeting concerned the evolution
of the fibres inside the connectors. With the exception
of one participant, nobody is working on such elements.
The meeting participants agreed that reliability
aspects of POF are interesting and should be considered too.
SG 2 recommends also to discuss the extension of
reliability issues to POF for future COST 270 activities.
STSM-3 “Influence of temperature on Polarization
Mode Dispersion (PMD) in single mode fibres with tight
buffers” from 19th to 23th May 2003.
Krzysztof Borzycki, NIT (Poland) visited Marcel Held,
EMPA (Switzerland).
Abstract : This project focuses on the experimental
investigation of PMD in tight buffered single mode fibres
and cables exposed to extreme operating temperatures,
accelerated aging and possibly other forms of degradation
likely to be experienced in real operating environments.
The purpose is to test and compare products manufactured
by different suppliers using different materials and
technologies. Of particular interest is the behaviour
of OPtical Ground Wires (OPGW) with tight buffered optical
units. Over 7000 km of such cables is installed in Poland.
They are also commonly used for LAN indoor cables with
fibres in 0.9 mm extruded thermoplastic buffers.
The samples were shipped from Poland and subjected
to variable temperatures changing between -20°C and
+70°C in a single cycle in 5°C steps, while
the PMD was measured. We tested one duplex LAN cable
with
LSOH sheath and aramide strength members, one 4-fiber
blown fibre unit (1 mm diameter) and two tight buffered
fibres for indoor cables with 0.9 mm extruded buffers.
All samples contained standard G.652 fibres. The results
can be summarized as follows:
• the complete cable exhibited very weak positive temperature
dependence of PMD ;
• the blown fibre unit had large, random changes of PMD
with temperature (2.5:1) ;
•
both tight buffered fibres showed a large PMD increase
at low temperatures, as expected. One of them also exhibited
a PMD increase at elevated temperatures above + 45°C.
• One fibre sample and the blown fibre unit suffered an
irreversible physical deterioration as a result of
the test : the fibre experienced a 20% volume shrinkage of
the buffer, the blown fibre unit saw a coating shrinkage
and a large attenuation increase at 1550 nm for 2 out
of the 4 fibres inside.
Those observations only partially confirm our previous
expectations, that the main effect will be a steady,
reversible increase of PMD with decreasing temperature
due to shrinking and an increased pressure of the
plastic coating on the glass fibre.
STSM-4 “Availability prediction for Free Space
Optic communication systems from local climate visibility
data” from 23rd June to 27th June 2003.
Maher Al Naboulsi, France Télécom
(France) visited Erich Leitgeb, INW-TU Graz (Austria).
Abstract : During this STSM we tried to combine the
physical aspects of light propagation in the atmosphere
related to Free Space Optical (FSO) communication with
the technical aspect describing the technology and
components of FSO systems. Laser beam propagation through
the atmosphere
under different weather conditions (especially fog
phenomenon) was reviewed from an empirical and theoretical
point
of view. Atmospheric attenuation caused by absorption
and scattering process was described to provide understanding
of the different simplified models allowing to predict
the attenuation. These models valid for the visible
and infrared spectral region until 2.4 µm are based
on visibility data and on the particles size distribution.
Following the results of the exact computation of the
scattering process, a more accurate model for simplified
calculation was derived leading to significant different
results than the previous low visibility (dense fog)
models. In fact, dense fog is the most important case
to consider if high availability for FSO transmission
systems should be achieved. In addition, characteristics
of the optical components of FSO systems were described
and a calculation of the link budget is explained in
theory and applied to a practical system installed
in the city of Graz. In conjunction with local climate
visibility
data, these models allow the prediction of the availability
for FSO systems. The relation between attenuation and
visibility at a given wavelength was applied to experimental
data. This data was obtained with the 2.7 km Free Space
Optic link in Graz during 1 year and the visibility
data was collected at the meteorological institute.
STSM-5 “Reliability of polymer waveguide-based
optical grating components manufactured using femtosecond
lasers” from 15th July to 7th August
2003.
Kyriacos Kalli, Higher Technical Institute (Cyprus)
visited David Webb, Aston University (United
Kingdom).
Abstract : We have demonstrated and reported on the
inscription of surface and sub-surface damage
lines and spots in PMMA slabs using a femto-second laser
system
operating in the near infra-red. We have seen
that the samples have a low threshold for optical damage
(we have
produced voids under modest laser powers) and
that structures having dimensions of a few microns can
be realized. This
lays the potential for single mode waveguides
and indeed we could use the microstructures that have been
formed
as channels to incorporate other organic materials.
Our measurements indicate that purely refractive index
changes
may be difficult to realize with PMMA alone
and we will most likely require sample doping in future
experiments.
Our goals have been to establish the correct
manufacturing techniques, which includes appropriate sample
preparation
and to determine the required inscription stability
for producing repeatable waveguide structures. Furthermore,
we have examined the stability of the structures
in PMMA
that have been inscribed to temperature excursions
below the glass transition temperature.
STSM-6 “A service oriented framework for intelligent
networks” from
12th June to 19th June 2004.
Barbara Martini, CNIT (Italy) visited
Lena Wosinska, KTH (Sweden).
Abstract : In the last few yeras there has been a boom in
requests\for broadband connections in the access segment
of telecommunication networks. Indeed, customers are willing
to use this broadband connection to support concurrent and
heterogeneous services. Telecommunication operators would
like to use the same transport infrastructure to deliver
these emerging services in an integrated way. We propose
an enhancement to the existing ASTN architecture in order
to deliver end-user customized services over legacy transport
infrastructure. The Intelligent Network Conceptual Model
(INCM) is used, where-in a service-independent transport
network is interfaced to the customer through an intermediate
layer, named Service Plane. The Service Plane permit to mask
the transport-related implementation details from the abstract
request of a service by an end-user. In addition, the Service
Plane introduction leads to the separation of the telecommunication
operator role in two distinct activities: the Network Provider
and the Service Provider. A testbed named SOON (Service Oriented
Optical Network) running the newly design service-oriented
software modules as an example of direct interaction between
customer and optical network for a dynamic service request.
The validation of the architecture is done by demonstrating
a VPN service provisioning.
STSM-7 “Title” from 23rd June to 30th June
2004.
Michael Gebhart, INW-Graz (Austria) visited Frédérique de
Fornel, Univ. de Bourgogne (France, La Turbie France Telecom
Test Facility)
Abstract
: Measurements were performed at the test facility of France
Telecom R&D at La Turbie, at the south coast of France.
In the period from June 23rd to 30th several events of dense
maritime fog with visibilities as low as 30 meters, corresponding
to specific attenuations close to 500 dB/km could be observed.
Attenuation measurement at 950 nm, 850 nm and 650 nm optical
wavelength were performed with systems developed by group
OptiKom at TU Graz in comparison with visibility data from
a transmissiometer instrument operating in the visible range
around 550 nm. The most commonly used light attenuation models
of Kruse and Kim were compared with measurement data for
dense fog conditions. The measurements indicate a preference
for wavelength independent attenuation as predicted by the
Kim model at low visibilities for specular light in the 500 – 1600
nm spectral range, which is used for typical FSO applications.
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