Promax HD RANGER+ Manual page 171

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, so that it only measures selectively the power of
these signals for each wavelength.
There is also a switch that allows the user to select the wavelength to convert.
The selected wavelength goes through the selective optical converter.
The selective optical converter consists of a photo-diode which converts the
optical signal to radio-frequency. The input wavelength for optical input signals
are between 1260 — 1600 nm.
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 is not required
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 (-1 dB),
occurs twice 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.
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April 2013