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TELE-audiovision International — The World‘s Leading Digital TV Industry Publication

— 05-06/2015

strong the optical signal will

be. Strength of the signal de-

pends on the split ratio and

attenuation of the optic fiber


After examining all the

products, it was time to build

a test network. We connect-

ed Quad LNBs to the inputs

of TPF 41-2 Optical Trans-

mitter. At the output of the

transmitter we inserted the

TFS 1/32 FC Splitter and

then routed the optical sig-

nal to the input of the TFM

41/10 C Optical Multiswitch.

We knew very well that there

is little point in adding long

fiber cables between the de-

vices because they add very

little attenuation. The main

sources of attenuation in the

optic networks are the split-

ters and junctions if not kept

clean enough.

To evaluate the whole

system rather than its par-

ticular components, we de-

cided to measure and com-

pare the input signal, i.e.

the one coming from LNBs,

to the output signals avail-

able at the trunk and the

subscriber outputs (S1 and

S10) of the TFM 41/10 C Op-

tical Multiswitch. You can see

the results in two graphs:

one showing signal strength

and the other signal quality.

The first graphs answers the

question whether the sys-

tem has enough gain and the

other – to what extent signal

quality suffers when we split

it and deliver it to 320 sub-


The output signal strength

was almost the same as in

the input. For some frequen-

cies/subscriber outputs, it

was slightly lower and for

some others slightly higher

than the input. Please re-

member that the signal has

been split 32 times by the

optical switch and then 10

times by the TFM 41/10 C

Fig. 1 Test setup circuit diagram.

tiswitch itself as well as its

power supply leaves noth-

ing to be desired. They are

clearly labeled and it is re-

ally easy to figure out what

should be connected where.

Everything is obvious at the

first look. The TFM 41/10C

has independent gain ad-

justment of every satellite

and terrestrial output (20

dB range). The adjustment

is really needed because it

is not known a priori how