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B-40 GB1400 User Manual
confidence that the stressed error rate is less than 10
−5
. By extrapolation, we are 95% confident the
unstressed BER is less than 10
−9
.
10
12
10
10
10
9
10
8
10
7
10
6
10
5
BER
Attenuation (dB)
10
4
543210
(elec)
0
0.5 1
1.5
2 2.5 (opt)
Example 3
Example 4
Figure 7. This plot determines the attenuation necessary to turn a test for BER=10
-9
with no stress
into a test for BER=10
-5
with stress (the third example in text). Draw a straight line from BER=10
-9
at no attenuation parallel to the dashed lines until it rises to BER=10
-5
. The electrical attenuation at
this point is 3 dB. In the fourth example in the text, 1 dB of optical attenuation is needed to turn a
test for BER=10
-10
with no stress into a test for BER=2 x 10
-7
with stress.
In this case stressing has reduced the test time by a factor of 10,000. This is probably more reduction than
is needed. It would be better to stress the system less so the test conditions are not so greatly different
than the normal conditions. Less stress increases the test time, but that could be afforded here.
Example 4
A 51.84-Mbit/s optical system is to have a BER no more than 10
−10
. This corresponds to an error rate of
r = 51840000 × 10
−10
= 0.005184 errors per second. If it tests error-free for T = 3 / r = 579 seconds, we
are 95% that the BER is less than 10
−10
. We will shorten the test time by using stressing.