The following terminology list contains three types of items:
This is an informal list gathered within the participants
of COST270, and is aimed to help for the work of COST270.
All three kinds of items are in the same list, organized in
alphabetic order, capital letters before small letters.
It is our aim that the definitions are as correct as possible
and similar to the international standards (IEC and ITU).
However, there are no guarantees for the correctness or any
review or approval process involved.
The users of this web site, COST270 participants, as well
as anyone are welcome to propose correction or an addition
of new terms, definitions and acronyms. The proposals shall
be sent by email, as text or in a separate attached Word-file,
to kirje.laatikko@ofcon.se.
|
Acronym or term
|
Definition, meaning, explanation
|
| |
|
|
AFM
|
Atomic force microscope
|
|
ANSI
|
American National Standards Institute
|
|
ASE
|
Amplified Spontaneous Emission
|
| |
|
|
CCITT
|
The former name for ITU, see ITU.
|
|
CDF
|
Cumulative Distribution Function
|
|
CECC
|
An European standardisation committee, before it changed
its name to CENELEC
|
|
CENELEC
|
Comité Européen de Normalisation Electrotechnique
|
|
COST
|
European co-operation in the field of scientific and
technical research
|
|
COST-TIST
|
One of the 17 COST research areas, titled "Telecommunications,
Information Science and Technology". TIST contains
9 under domains of which Optical Networking is one,
to which COST270 belongs.
|
|
COST218
|
A COST Action, titled "Optical Fibre, Component
and Cable Reliability ", active 1987- 1992, before
COST 246.
|
|
COST246
|
A COST-TIST action, titled "Materials and Reliability
of Passive Optical Components and Optical Fibre Amplifiers
in Telecommunications Networks", active within
5 Oct 1993 – 31 Dec 1998
|
|
COST270
|
A COST-TIST action, titled "Reliability of Optical
Components and Devices in Communications Systems and
Networks", running since Dec2000.
|
|
CSO
|
Committee of Senior Officials, highest hierarchy level
of COST
|
|
CW
|
Continuous wave
|
|
CWDM
|
Coarse wavelength division multiplexing
|
| |
|
| |
|
|
DIN
|
Deutsche industri standard
|
|
DMA
|
Dynamic Mechanical Analysis
|
| |
|
|
DSC
|
Differential Scanning Calorimetry
|
|
DWDM
|
Dense wavelength division multiplexer
|
|
EC
|
European Commission
|
|
ECL
|
External cavity laser
|
|
EUR
|
European currency. In Nov 2001 1 EUR= 0.93 USD. Earlier
name of this currency was ECU. 1 ECU = 1 EUR
|
|
EIA
|
Electronic Industry Association, USA
|
|
EDFA
|
Erbium doped fibre amplifier
|
|
EN
|
European Norm, CENELEC’s standard
|
|
ETS
|
European Telecommunications Standard
|
|
ETSI
|
European Telecommunications Standards Institute
|
|
Failure function, (= failure probability before time
t
|
) Failure function, also called as unreliability function
or cumulative distribution function (CDF)
where S(t) is the survival probability, n(0) is the
original population and n(t) is the surviving population.
This equation describes the probability of failing before
time t, i.e. the fraction of the population expected
to fail before time t.
|
|
Failure probability per unit time ( = Probability density
function (PDF))
|
Probability density function (PDF) f(t) describes the
probability of failure per unit time at time t for any
member of the original population n(0)
where F(t) is the failure function as defined above.
|
|
Failure rate
|
Failure rate l (t), also called
as hazard rate, failure intensity, force of mortality
and instantaneous failure rate, describes the probability
of failure per unit time at time t, for the members
of the original population which survived until time
t.
where S(t), f(t) and other parameters
are defined as given above. The units used for failure
rate are: %/time unit and FITs. The probability
of failure f(t)dt is the instantaneous failure probability
during a very short time period from t to t+dt, but
l (t)dt is the probability of failure during a
longer time after t, from t to 2t or more.
Failure rate can be calculated by using
equation
If now D n/n(0) = 10-2
= 1 % and D t = 104 h » 1 year,
then l = 10-6 /h, which is an inconvenient
dimension. Therefore if we calculate the same by using
the time unit of Gigahours, so failure rate in Fits
can be calculated
For the above given example failure
rate l = 1000 FITs, which corresponds to 1 % of
a population fails in about 1 year. If the reliability
requirement for a component type is defined so that
failure probability F £ 10-3 is required
for 30 years, the allowed maximum failure rate l
= 4.6 FITs.
The reliability requirements vary depending on country,
operating company and application. For example a reliability
requirement for optical fibres in optical cables including
splices of fibres, can be defined: the allowed failure
probability F £ 10-3 for 100 km fibres
for 40 years lifetime. This equals to the failure rate
requirement: less than 1 failure/100 000 km fibre is
allowed during 40 years lifetime. The maximum allowed
failure rate in FITs is 0.029 FITs/km.
Failure rate l (t) as a function of time (usually
looks like a bath tub curve) is a sum of the failure
rate functions of infant mortality rate (which decreases
as a function of usage time) and wear-out failure rates
of failure mechanisms (which increase as a function
of time). In addition, there might be failures due to
accidents and natural catastrophes and so called freak
failures, which are caused by temporary manufacturing
process mistakes or other odd reasons which are not
statistically enough frequent to be obtained at any
tests.
|
|
FBG
|
Fiber Bragg grating
|
|
FIT
|
Estimated number of failures in 109 hours
time period of service
|
|
FO
|
Fibre Optic Division of TIA
|
|
FOTP
|
Fibre Optic Test Procedure
|
|
FTIR
|
Fourier transform infrared reflectometer
|
|
FTTH
|
Fibre to the home
|
|
FWHM
|
Full width half maximum
|
|
GI
|
Graded index fibre
|
| |
|
| |
|
| |
|
|
IEC
|
International Electro-technical Commission, a standardisation
body
|
|
IL
|
Insertion loss
|
|
ITU
|
International Telecommunications Union, a standardisation
body
|
|
IWCS
|
International Wire and Cable Symposium
|
|
Life test
|
A test or test series which is done on a large population
of components, in order to define the lifetime or failure
rate parameters in service.
|
|
Lifetime
|
Lifetime of optical fiber, cable, active or passive
component etc. is the period of utilization (service)
time from the installation to the point the allowed
highest failure rate (or fracture probability) is reached.
This means that the lifetime is defined for a large
population of installed components in service, not for
a single component.
Usually a very low failure probability and long lifetime
is required for components in communications networks
and systems. Distribution of lifetimes within a population
of components may be wide. Thus the lifetime of an individual
component may on average be very much longer than the
specified lifetime.
It is good to know that for many materials, e.g. plastic
materials, the lifetime is defined as the time to the
mechanical strength is decreased by 50 %. This kind
of change in a plastic cover or jacket material does
not thus necessarily cause an immediate failure of the
component.
|
|
LED
|
Light emitting diode
|
|
MC
|
Management committee
|
|
MCM
|
Management committee meeting
|
|
MFD
|
Mode field diameter
|
|
MOPA
|
Master oscillator power amplifier
|
|
MoU
|
Memorandum of Understanding. The document and contract
that defines a COST Action, singed by the countries
that are interested to attend into an action. Technical
description of the action, including the scope and objectives
etc.
|
|
MRS
|
Material Research Society, USA
|
|
MTBF
|
Mean Time Between Failures (MTBF) is the average time
between failures. In order to calculate this, the distribution
of failure times must be known. If the failure rate
is a constant. The mean time between failures is the
inverse of the failure rate. MTBF parameter is used
for low failure rate components with a huge range of
failure times, such as fibres in cables.
|
|
MTTF
|
Median Time To Failure (MTTF) is the time from the
moment of installation to the point when 50 % of the
component population have failed. This time is longer
than the lifetime defined at a low failure probability.
It is used for components whose lifetime distribution
is relatively narrow, e.g. bulbs, lasers etc.
|
|
MTTR
|
Mean Time to Repair (MTTR) is estimated from the field
failure repair times including the measurement to localize
the failed component. It describes how long time the
service is cut due to the failure. At least some kind
of experience of the repair and maintenance processes
is needed. Usually, a complete device or a component
circuit board is exchanged at repair in order to minimize
the time out of service. For cable failures the time
to repair can be significantly longer.
|
|
NFOEC
|
National Fiber Optic Engineering Conference, USA
|
|
OADM
|
Optical Add Drop Multiplexers
|
|
OFA
|
Optical fibre amplifier
|
|
OFC
|
Optical Fiber Communication Conference
|
|
OFMC
|
Optical Fibre Measurement Conference
|
|
OFSTP
|
Optical Fibre System Test Procedures
|
|
OIT
|
Oxidation induction time
|
| |
|
|
OSA
|
Optical spectrum analyser, and Optical Society of America
|
|
OTDR
|
Optical time domain reflectometer
|
| |
|
|
PAN
|
Primary access network
|
|
PDF
|
Probability Density Function
|
|
PE
|
Polyethylene
|
|
PIT
|
Plastics in Telecommunications (conference)
|
|
PMD
|
Polarisation mode dispersion
|
|
PMMA
|
Polymethylmethacrylate
|
|
POF
|
Plastic optical fibre
|
|
PON
|
Passive Optical Network
|
|
Pop-in
|
sudden further-cracking of an indentation flaw in a
glass material from the subtreshold situation to the
posttreshold situation
|
|
Proof test
|
By a proof test (sometimes called screen tests) the
rate of infant mortality is minimized to the failure
rate during service, but at the same time the start
time is shifted forwards, and proportion of wear-out
failures may slightly increase. For optical fibers a
proof test is done by pulling the fiber for a very short
moment by a tensile stress causing fractures at the
weakest flaws with a weaker strength than the pulling
stress. By this way the surviving weak flaw distribution
is modified and the weakest flaws are getting broken.
For other types of components, e.g. lasers, or passive
optical couplers, a proof test is usually a damp heat
aging or a temperature cycling test at a dry or humid
environment in a high temperature for 1 - 14 days. The
purpose of these kinds of proof tests is to minimize
the infant mortality rate, by causing a complete failure/fracture
on the worst/weakest components or by identifying those
components whose behavior (transmission properties or
mechanical properties) is not stable or become outside
of the specified limits of performance.
|
|
PP or pp
|
polypropylene
|
|
PVC
|
Polyvinylcloride
|
| |
|
|
Qualification tests
|
Qualification tests or tests series is done for new
components before coming to the market in order to define
the performance and properties in long-term service.
No reliability or lifetime or failure rates are (can
be) defined from these tests. (See Life test).
|
