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GISplit16Pro Insertion Loss
Output #
dB
GISplit32pro Insertion Loss
Output #
dB
■
■
■
■
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TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine
— 03-04/2013
—
outputs each carrying 6.25%
of the input light. That’s be-
cause 100% / 16 = 6.25%.
Should we convert it to deci-
bels, it would be -12 dB. Of
course, real performance
must be somewhat worse
due to unavoidable coupling
losses. And indeed, GlobalIn-
vacom specify their GISplit-
16pro as having a typical in-
sertion loss of 13.3 dB.
Similarly, the GISplit32pro
should ideally split the input
to 3.125% and have -15 dB of
insertion loss but GlobalInva-
com specify the loss as 16.8
dB typically. The manufactur-
er’s specifications are explic-
itly provided on the labels at-
tached to the splitters as you
can see on the photographs.
And that was the first per-
formance parameter we
wanted to measure in our
test. For that, we used a
GlobalInvacom Optical LNB
and their FibreIRS ODU32
optical transmitter as signal
source. Additionally, we fed
the ODU32 with a terrestrial
signal to create the most re-
alistic test conditions. We
connected the output of the
ODU32 with the input of the
splitters. Then we measured
the optical power at the in-
put and at every output of
the splitter at 1490 nm wave-
length.
The first to go was GISplit-
16pro. As you can see in the
graph 1., the maximum in-
sertion loss was 13.8 dB and
minimum only 13.15 dB. The
average loss (green line) was
13.4 – so very close to the
typical value specified by the
manufacturer.
The next splitter – GISPlit-
32pro was even better. You
can see its results in the
graph 2. The average loss
(blue line) was only 16.2 dB
and all outputs had a lower
insertion loss than the speci-
fied typical value 16.8 dB!
Output number 23 was the
best – only 15.99 dB. Impres-
sive!
The insertion loss for both
optical splitters was really
very small – very close to the
theoretical limit. But to be
fully convinced that the opti-
cal systems built with GISPlit-
16pro and GISplit32pro are
really that perfect, we decid-
ed to compare the results we
got with the results we could
achieve in a classical way - in
purely RF systems.
For the satellite test, we
used the same dish but this
time with a classical high per-
formance LNB. Table 1 pre-
sents the outcome.
Channel Power
[dB]
MER
[dB]
Signal from a classical RF system
76.3
14.3
GISplit16pro->GTU Quad output
63.5
12.6
GISplit32pro->GTU Quad output
63.4
13.9
Table 1. Optical systems incorporating the GI splitters under
test in comparison with top class RF satellite system without
any splitters.
Channel Power
[dB]
MER
[dB]
Signal from a terrestrial antenna
49.3
25.4
GISplit16pro->GTU Quad output
61.2
28.0
GISplit32pro->GTU Quad output
62.7
29.2
Table 2. Optical systems incorporating the GI splitters under
test in comparison with a signal from a terrestrial antenna.
We used transponder 10720
V from HOTBIRD on 13° East
as our test signal. Please
note that we measured the
RF signal directly at the LNB
output without any RF split-
ters or multiswitches. Despite
the fact that the optical signal
was split to 16 or 32 outputs,
the results were only slightly
inferior to the top class single
LNB system with a very short
cable!
We did a similar test with a
terrestrial antenna and this
time we were even more sur-
prised. See our results in Ta-
ble 2.
The output signal in both
cases of optical setup was
better than a classical instal-
lation! Not only was the sig-
nal stronger but its MER was
also better! And remember
that we used only 3.125% of
the light power entering the
Graph 2.
Graph 1.
