Promax HD RANGER 2 User Manual page 208

5 5
A5.3
DESCRIPTION OF INTERNAL OPERATION
The selective meter consists, in first place, of a selective triple filter for 1310,
1490 and 1550 nm signals. The filter separates each wavelength and each one
leads to an independent circuit with a photosensor, which obtains the RF signal
that it carries. Next, a circuit measures the optical signal power received by the
photosensor. The RF signal obtained for each wavelength goes to a band switch.
The band switch receives a signal and converts it to a frequency within the RF
band (65 — 2150 MHz). In the case of a terrestrial/cable signal the signal is not
converted since that signal is within the RF range.
After the conversion, the RF signal output is connected to the analyser input
connector and the measurement is performed in the usual way to an RF signal.
In the conversion, bear in mind that for every unit of optical attenuation
(one dB), occurs two dBs of power loss in RF. As an example, every 3 dB of
optical attenuation for each splitter are equivalent to 6 dB of power loss for RF.
The following diagram explains graphically how works the module:
Figure A5.1.
57
June 2014