Agilent Technologies J-BERT N4903B, User Manual, Page: 247 / 572

operates with a BER better than let us say 10 -12 ; whether the true BER is 1.1 ×
10 -13 or 2.7 × 10 -15 is irrelevant.
To abort the measurement for a single point and proceed to the next, we need two
limits that tell us whether the BER is above or below the given threshold.
These limits have been calculated from the error probability density functions
applicable to BER measurements. The equations were solved for a level of
confidence of 95%. The calculations have led to the following table:
Table 25
95% confidence level lower limits, BER
> 10
-12
95% confidence level upper limits, BER
< 10
-12
Min number of
errors Max number of
compared bits (×
10
12
)
Max number of
errors Min number of
compared bits (×
10
12
)
1 0.05129 0 2.996
2 0.3554 1 4.744
3 0.8117 2 6.296
4 1.366 3 7.754
5 1.970 4 9.154
6 2.613 5 10.51
7 3.285 6 11.84
The BER threshold of 10 -12 and hence the setting of the multiplication factor to
10
12
is just an example-by changing the exponent, the table applies analog to other
thresholds.
The following figure shows a plot of this table.
Advanced Analysis
6
Agilent J-BERT N4903B High-Performance Serial BERT 247