IDEAL INDUSTRIES LANTEK 6 Basic, Руководство пользователя

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Chapter 5
Fiber Optics Cable Field Calibration and Testing
VIEWING RESULT DETAILS
When an Autotest is saved, the data is stored with a unique name. Test results can be
viewed, printed, or deleted from the Stored Tests screen.
1. On the Ready screen, select Stored Tests to open the Job List screen.
2. Highlight the desired Job. Press ENTER to open the job.
3. Press the ARROW keys to highlight the desired test record.
4. Press ENTER to open the record.
5. Press ESCAPE at any time to return to the previous screen.
MEASURING RETURN LOSS
Simply stated, return loss is the ratio of power reflected by a connector or other event
compared to the power that arrived at the event. The scale of measure for return loss
is dB (decibel). Because the scale of return loss is by definition a negative value, a
larger (negative) number is better.
However, by convention, most people usually omit the negative sign and use it as a
positive value. For example, a return loss measurement of 0 dB means that 100% of
the power arriving at the connector was reflected back to the transmitter.
In reality a 0 dB measurement is impossible in fiber-optic systems; the worst
reflection possible is about –14 dB which would be created by a perfect glass-to-air
interface. In most cases a field polished connector will yield a return loss of
approximately -30 to -40 dB, meaning .1% to .01% of the power was reflected
upstream. Factory terminated Ultra Physical Contact (UPC) connectors usually perform
to –50 dB or better (.001% reflection).
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