Field Trial of Optical Fibre Cable-TV System Optical Fibre System for ...

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If the customer does not have special
requirements as regards the presentation
of reliability data, Ericsson usually
provides a separate report with data
concerning:
- failure rate and MTBF for individual
function blocks (e.g. magazine or
shelf)
- failure rate, MTBF, trustworthiness
reliability, availability and down time
for a selected, worst case system or
link combination
- failure rate and MTBF for the whole
equipment quoted for
- maximum number of failures for
equipment in accordance with the
two previous items, which with a certain
probability will not be exceeded
during a given period of time
- the prediction method and its trustworthiness
These data are a best estimate, and in
the case of a guarantee a higher confidence
level is chosen. The amount of
equipment, operating conditions and
verification methods must also be carefully
specified.
There are different methods and models
for verifying that the equipment meets
the guaranteed reliability. In all cases,
however, the test plan must define:
- the equipment to be tested
- the beginning and end of the test
period
- operating conditions and failure concepts
- statistical evaluation method.
The text in the technical part of the guarantee
should be clear, unambiguous
and easy to understand, and only contain
data that can easily be checked. It
could be formulated as follows:
"An MTBF>6.7 years is guaranteed for
the specified equipment, i.e. a failure
rate z