Skip to main content 跳到主目录
Fluke Networks
  1. Home
  2. Support
  3. Knowledge Base
  4. Bi-Directional Testing - DTX Compact OTDR Module

Bi-Directional Testing - DTX Compact OTDR Module

DTX Compact OTDR 2014-02-28

If your launch lead has a different backscatter coefficient than the cable you are testing, you may well end up with a suspiciously low loss value for your launch event (first connector). You may even observe a negative loss. An example of this from the DTX Compact OTDR is shown below:

Bi-directional Testing with DTX Compact OTDR

You could make a launch lead using the same fiber as you are testing. Alternatively, you could make the measurement in the opposite direction and take the average. This is defined in IEC 14763-3 and is referred to as bi-directional testing. Bi-directional testing

  • Set the launch + receive fiber compensation - click here for details.

  • Rotate the dial on the DTX CableAnalyzer to SETUP.

  • Highlight Fiber OTDR and press ENTER.

  • Move to Tab 2 and make sure Testing From says End 1.

  • Rotate the dial to AUTOTEST.

  • Go ahead and test the link. Bidirectional OTDR Testing

  • Save it as 001 (or your own Cable ID scheme).

  • Continue to test the rest of your links whilst saving them to the DTX CableAnalyzer.

  • Rotate the dial on the DTX CableAnalyzer to SETUP.

  • Highlight Fiber OTDR and press ENTER.

  • Move to Tab 2 and make sure Testing From says End 2.

  • Rotate the dial to AUTOTEST.

  • Swap ends with the DTX CableAnalyzer (leave the launch/recieve fibers in place).

  • Go ahead and test the first link again. Bi-Directional Testing - DTX OTDR

  • Save it as 001 (or whatever you chose previously)

  • Continue to test the rest of your links whilst saving them to the DTX Cableanalyzer.

  • The bi-directional calculation is done within the LinkWare Software. Go ahead and download your OTDR results into LinkWare.

  • The two measurements made in different directions are recorded as one result.

  • Click on Utilities > Generate Bidirectional OTDR Results; the following window will open: Generating Bidirectional OTDR Testing Results

  • Select the Cable IDs you wish to implement bi-directional averaging on and click OK.

  • You will now see your test result calculated using bi-directional averaging: LinkWare Software - Fluke Networks

  • Looking at the result, we see:  OTDR Testing

  • The loss at each connector is 0.20 dB using bi-directional averaging in accordance with IEC 14763-3. Note the 0.02 dB reported when the measurement was made in one direction only.

Learn About:

-Bi-Direction Testing with an OTDR

Back to Knowledge Base