363-206-295
Technical Specifications
10-38 Issue 1 December 1997
DDM-2000 OC-12 Reliability 10
Summary 10
This section describes the Bellcore reliability requirements that apply to the
DDM-2000 OC-12 Multiplexer and the calculations used to predict how the
DDM-2000 OC-12 Multiplexer meets those standards.
The DDM-2000 OC-12 Multiplexer meets all the applicable Bellcore reliability
requirements that cover transmission availability, OS availability, silent failures,
optical module maintenance, and infant mortality. Table 10-21 summarizes the
reliability predictions and requirements. The applicable Bellcore requirements and
objective were clarified through interactions with Bellcore during their audit of the
DDM-2000 OC-12 Multiplexer. The basis for these requirements comes from
TA-TSY-000418, "Generic Reliability Assurance Requirements for Fiber Optic
Transport Systems." The method and assumptions used to calculate the
DDM-2000 OC-12 Multiplexer reliability predictions are described in the following
sections. Each section is devoted to one of the reliability parameters which must
meet a Bellcore requirement or objective.
Transmission Availability 10
Bellcore
requirements
state that the probability of a hardware-caused outage on a
two-way channel within a SONET multiplexer should be less than 1.75 minutes
per year in a CO environment
*
and 5.25 minutes per year in a RT environment.
†
Bellcore
objectives
for outages are 0.25 minutes per year for the CO
‡
and 0.75
minutes per year for RT environments.
§
The outage requirements and objectives apply to any part of the product needed
to process an incoming high-speed or low-speed signal (DS3 to OC-12 or OC-12
to DS3). An outage is defined, for this and all other outage requirements, as any
1-second interval with a bit error rate of 10
-3
or worse.
¶
The predicted hardware
outages for various configurations of the DDM-2000 OC-12 system are given in
Table 10-21.
A Markov model was used to calculate the predicted system outage. The model
assumes a mean time to repair of 2 hours for the CO environment and 4 hours for
the RT environment. Individual circuit pack failure rates used in the model were
calculated using the method described in TR-TSY-000332, Issue 4, "
Reliability
Prediction Procedure for Electronic Equipment (RPP)
." A summary of the circuit
* TA-NWT-000418, Issue 3, November 1991, p. 17.
† TA-NWT-000418, Issue 3, November 1991, p. 28.
‡ TA-NWT-000418, Issue 3, November 1991, p. 18.
§ TA-NWT-000418, Issue 3, November 1991, p. 28.
¶ TR-TSY-000009, Issue 1, May 1986, p. 4-11.
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