Fiber Optic Design Guide - Maite y Mario

Power Meter Output (Volts)
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5
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1
0
1 2 3 4 5 6 7 8 9 10
Optical Input (mW)
Figure 1.4 - Optical Input (mW) vs. Power Meter Output (Volts)
Figures 1.3 and 1.4 show the response of the built-in optical power meter circuit in both dBm and mW. The dotted line
shows the typical, expected response of the circuit. Because the accuracy of the reading is affected by the variable mating
loss of the input optical connector, there is an error band of ±0.5 dB represented by the solid lines. For instance if the optical
input power was +6 dBm, the circuit would ideally output +5.0 Volts. Considering the possible errors introduced by the
optical connector, the reading could be as low as +4.5 Volts or as high as +5.4 Volts. Note that the circuit outputs a voltage
of +1.0 Volts with no light input.
The 7412-PA incorporates an optical attenuator that allows the user to adjust the incoming optical signal to the optimum
input of 2 mW (+3 dBm). This attenuator should be used as follows: Align the red dot on the top of the attenuator with the
red line painted on the outer fixation ring. Next take a reference reading from pin J2-4 to determine the optical power
reaching the receiver. With the red dot and line aligned, slowly rotate the inner control ring of the attenuator until the voltage
on pin J2-4 reads 3 Volts which is equal to the optimum input voltage of 2 mW (+3 dBm). (An attenuator adjustment
tool is included.) After the desired attenuation is reached, use the adjustment tool to turn the outer fixation ring 45° in
either direction to lock the control ring in place. NOTE: Do not try to rotate the control ring unless the red dot and the red
line are aligned. Do not turn either ring to their end points, or the attenuator may break.
PART NUMBERS AND CONFIGURATIONS
Transmitter Part Numbers
Part Number Tx Optical Output Recommended Max. CATV Channel Loading Optical Connector Type*
Link Loss
7403-6 +6 dBm 7 dB 80 FC/APC
7403-7 +7 dBm 8 dB 80 FC/APC
7403-8 +8 dBm 9 dB 80 FC/APC
7404-9 +9 dBm 10 dB 110 FC/APC
7404-10 +10 dBm 11 dB 110 FC/APC
7404-11 +11 dBm 12 dB 110 FC/APC
7404-12 +12 dBm 13 dB 110 FC/APC
Part Number Rx Optical Field
Receiver Part Numbers
CATV Channel Loading Optical Connector Type*
7412-P Integral Optical Power Meter 80/110 FC/APC
7412-PA Integral Optical Power Meter with Field
Optical Attenuator
80/110 FC/APC
7434 80/110 FC/APC
* NOTE: The FC/APC interface on the units use the “wide-key” standard. This means that the units are optimized for use
with FC/APC connectors that have a 2.14 mm wide alignment key. This allows “narrow-key” FC/APC connectors to
be used with the units. “Narrow-key” FC/APC connectors (2.02 mm) often referred to as JDS compatible, may be
used but will produce inferior results. Standard FC/APC connectors have a 2.36 mm wide key and cannot be
plugged into either unit.
Section 2
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