363-206-305
Technical Specifications
Issue 3 June 2000
10-39
Plug-In Maintenance Sparing Guidelines
10
Table 10-20 provides a guideline for determining the number of DDM-2000
FiberReach plug-in spares needed for a given number of plug-ins in the field. The
sparing guide serves as an initial estimate and is calculated with the following
assumptions:
â–
The method for calculating spares follows the procedure described in
Telcordia Technologies SR-TSY-000385, Issue 1.
â–
The steady-state failure rate is assumed. Failure rates are based on the
reliability prediction procedure (RPP) method described in
TR-TSY-000332, Issue 4.
â–
The spare availability objective (SAO) is 99 percent. The SAO is the long-
term probability that a spare plug-in is available when it is needed.
â–
A no-trouble-found (NTF) factor of 1.67 is multiplied to the failure rate. This
accounts for replacements of plug-ins when actually no failure has
occurred. The NTF factor is expected to approach 1.25 as the product
matures. The likelihood of an NTF decreases as the product matures, and
sparing needs will therefore diminish over time.
â–
Turnaround time of a returned plug-in is two weeks.
Table 10-20. Sparing Guidelines
SAO = 99%
DDM-2000 OC-3 and OC-12, FiberReach NTF factor = 1.67
Turn around time (weeks) = 2
Turn around time (hours) = 336
Plug-In Code (FIT)
Number of Spares Revised Date
NS=1 NS=2 NS=3 NS=4 NS=5 NS=6
NRT
0.14 0.43 0.82 1.27 1.78 2.3
BBF1 (745) 335 1029 1962 3038 4258 5502
BBF1B (859) 290 892 1701 2635 3693 4772 09/02/1998
BBF2 (2739) 91 280 534 826 1158 1497
BBF2B (2311) 108 332 632 979 1373 1774
BBF2C (2345) 106 327 623 965 1353 1748 08/24/1999
BBF3 (1310) 190 585 1116 1728 2422 3129 09/02/1998
BBF3B (1235) 202 621 1183 1833 2569 3319 09/02/1998
BBF4 (2345) 106 327 623 965 1353 1748 08/24/1999
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