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TELE-audiovision International — The World‘s Leading Digital TV Industry Publication
— 03-04/2015
—
TELE-audiovision.comsignal containg all the tran-
sponders from the original
satellite Ku Band. What can
we do with that?
Those of our readers who
still remember our previous
test reports of GlobalInva-
com products may remem-
ber another of GlobalInva-
com’s products: a dedicated
device converting the whole-
band electrical signal to the
optical domain: the GI Fi-
breIRS ODU. Normally, you
would use the GI FibreIRS
ODU along with the above
mentioned LNBm. But if you
want to multiply your distri-
bution system you connect
the GI FibreIRS ODU to the
wholeband output of the GI
FibreIRS O2E. For this pur-
pose, you need a special
short and thick coax cable
because of the high band-
width. At the output of the
GI FibreIRS ODU we get the
optical signal again but much
stronger than at the input of
the GI FibreIRS O2E. We may
say that a combination of the
O2E and the ODU forms a
kind of an optical amplifier.
However, it is not an ordi-
nary amplifier. An ordinary
amplifier would amplify op-
tical signals but could not
maintain the signal quality as
good as in the input. In other
words, we would get a strong
enough signal to be split
again but its carrier-to-noise
or MER would be worse. Not
so here! The combination of
the GI FibreIRS O2E with the
GI FibreIRS ODU does not
just amplify the signal but
regenerates it. It means that
digital errors are corrected
during demodulation and
re-modulation of the signal.
Now, if we connect another
1:32 splitter after combining
the GI FibreIRS O2E with the
GI FibreIRS ODU we can ex-
pect a strong and error free
output signal as in the origi-
nal installation before that
combination.
So far about the theory.
But does it really work like
that in real life? That’s our
job to find out in the TELE-
audiovision test center! So
we collected all necessary
products: we took an opti-
cal LNB (GI FibreMDU), GI
FibreIRS Split32pro, GI Fi-
breIRS O2E, GI FibreIRS
ODU, GI FibreIRS Split16pro
and GI FibreIRS Quad GTU
converter. We connected all
these devices as shown in
the measurement setup cir-
cuit diagram (Fig. 1).
Figure 1 also presents our
optical signal measurement
results. As you can see, the
strong signal at the output
of the optical LNB is attenu-
ated by 16.65 dB when pass-
ing through the 1:32 splitter,
then it is boosted by 16.4
dB after passing the O2E
and ODU combination. So,
in fact, its original strength
is almost exactly recreated
at the output of the ODU.
We decided to split the sig-
nal again, this time by a 1:16
splitter and convert it to the
form acceptable for a regu-
lar satellite receiver in the
Quad GTU converter. Would
we have used another 1:32
splitter we would have got-
ten almost exactly the level
of -8.9 dBm which was pre-
sent at the input of the O2E
and ODU combination. So we
may say that combining the
GI FibreIRS O2E and the GI
FibreIRS ODU plus a GI Fi-
breIRS Split32pro will result
Fig. 1 Test setup circuit diagram.