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COURSE DEMO Page 2 of 12 backward button1forward button

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Planning a Fiber System

1
Link Calculations

7. What is the total expected loss for the link between A and C? 850nm _________ dB 1300nm __________ dB

Link Loss Calculation Steps
1. Figure length of fiber link
2. Convert to meters
3. Add up connectors, divide by two
4. Figure expected loss by adding length loss to connector loss

We add the expected connector loss (3.75 dB) to arrive at the total expected loss at 850 nm. 1.30 dB plus 3.75 dB equals 5.05 dB. By adding the length loss at 1300nm, .558dB, to the expected connector loss, 3.75dB, we find that the total expected loss at 1300nm is 4.308dB. Notice that there is less expected loss at 1300 nm than at 850 nm. Also note that the expected losses from the connector sets remains the same value, regardless of the wavelength being calculated. The “optical budget” of the proposed fiber connection using the two links has been determined. The installation company can now consider what optoelectronic device set will deliver the signals needed, and be able to operate within the expected loss values.
1 Remember that these are just calculations, not field tests. It is very important to field test the link(s) with an optical loss meter set to determine that the links are within industry standards. Excessive bending, poor installation, or poor connectors may cause the fiber link to be unusable without repair or modifications.
LESSON REVIEW

Key Points:

1. Added the expected length loss to the expected losses from connector pairs and splices provides an optical budget estimate for a fiber link.

2. Links should be tested with an optical loss meter set to verify link calculations.

3. If the loss meter test indicates higher than expected loss, there is either problems with the installation or the original calculation is incorrect.

Pop Quiz:
True or False

Multimode fiber links will have more loss at 1300nm than at 850nm.

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Slayton Solutions Ltd. Chicago IL USA (708) 212-5150, slaytonsolutions@sbcglobal.net. Copyright 2016.