Atec gigaBERT1400, User Manual

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BERT Technical Articles
GB1400 User Manual B-43
( µ
− σ
) / T < r ' < ( µ +
σ
) / T
or
r r T r r r T
− < < +
/ ' /
.
These two "bounds" are shown by the two curves in Figure S-2. The measured error rate r ' is seen to lie
between them most of the time. As T increases, the bounds get closer to r = 5 / hr, but there will always
be some deviation of r ' from r . Therefore the "actual" error rate r can never be known in practice; it
would take an infinite time to measure r .
The standard deviation of the error measurement n is
σ µ = =
rT
. But since µ and r can't be known
exactly in practice, we must use the estimates µ
≈
n and r
≈
r ' to get the estimate
σ ≈ =
n r T '
.
10
16
10
14
10
12
10
10
10
9
10
8
10
7
10
6
10
5
BER
Attenuation (dB)
10
2
10
3
10
4
11 10 9 8 7 6 5 4 3 2 1 0
0
0.5 1 1.5 2 2.5 3 3.5
4
4.5
5 5.5
(elec)
(opt)
Figure S-2.
Specially distorted scale so plots of
BER
versus signal
Attenuation
(electrical or
optical) are straight lines (parallel to the dashed lines) when the noise is Gaussian.
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