VDV Works Virtual Hands-On Training
Fiber Optics Testing: Using OTDRs
 
Part of the VDV Academy Fiber Optic Training Programs

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Viewing the trace

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 Understanding OTDRs

"Virtual Hands-On" Termination

"Virtual Hands-On" Testing


Fiber Testing Using OTDRsUsing and OTDR

OTDRs are valuable tools for testing fiber optics. They can verify splice loss, measure length and find faults. OTDRs are also commonly used to create a "picture" of fiber optic cable when it is newly installed. Later, comparisons can be made between the original trace and a second trace taken if problems arise. Analyzing the OTDR trace is made easier by having documentation from the original trace that was created when the cable was installed.

OTDRs work like "optical RADAR," sending out a test pulse and looking for return signals. This means OTDRs need access to only one of the fiber for most testing. Unlike meters and sources however, they do not measure loss like the actual transmission system, so they are not used for testing end-to-end loss.

There are a few different types of OTDRs that you may consider using to test the fiber optic cable plant.

Labratory OTDRs are typically used in test labs. They have an extrmely long range with many options and they are most commonly used for testing cables within manufacturing plants or for experimentation purposes in scientific laboratories. The cost for a labratory model OTDR may start at $40,000.

Mini OTDRs (right) are portable and designed for field testing. They have built in screens and provide data storage as traces are collected in the field. The price rises the number of options are added onto the machine (printers, storage capacity, etc.) Mini OTDRs sell for $12-25,000.

PC-based OTDRs connect with a personal computer and operate with windows based software. The resolution of the display is as good as the quality of the computer's monitor. The machines are versatile as they allow the user to save traces on a disk and then transfer data between computers. Using a PC with the OTDR also reduces the cost of the machine. PC based OTDRs range in price from $7,000 - $15,000 depending on the modules (SM/MM) that are purchased with it.
 

 Before you continue, you should read  Understanding OTDRs

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