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18 TELE-audiovision International — The World‘s Leading Digital TV Industry Publication — 05-06/2015 —
Optical Multiswitch before
it reached a subscriber out-
put. All the gain settings in
the TPF 41-2 and TFM 41/10
C where set to maximum. It
proves that the overall sys-
tem gain is very precisely
calculated and is exactly
as needed for a 1:32 split.
if you built a system for a
lower number of receivers
you would need fewer split-
ting (say, 1:8) and then you
would have to reduce the
gain of the Tekniksat devices
to avoid over driving sub-
scriber receivers.
The second very important
characteristics of the distri-
bution system is its “quiet-
ness” or, in other words, the
measure how much it spoils
the signal-to-noise param-
eter. Taking into account
that we deal hear with two
signal conversions: electri-
cal to optical and optical to
electrical and additionally
the signal is split firstly in the
optical splitter and secondly
in the final multiswitch, one
could expect a significant
decrease in Modulation Error
Ratio (MER). But, no! Look at
the second graph. Although
there is a small degradation
of signal quality especially in
the lower sub band, the dif-
ference between input and
output is surprisingly low.
You can be pretty sure that if
you have a good signal from
the LNBs, almost equally
good signal will reach each of
the maximal possible num-
ber of 320 receivers.
And that is what we call the
“Power of light”. It is so easy
to achieve such good results
with fiber optic cables when
compared with traditional
electrical splitting.
After so good results with
satellite signals we wanted
to check the terrestrial path.
Our measurements revealed
that the output signal was
stronger by about 15-20 dB
with respect to the input sig-
nal and that signal-to-noise
ratio was again decreased