Setting the Manual OTDR Mode - DTX Compact OTDR Module

Manual OTDR mode lets you optimize the OTDR trace for viewing specific events. To select Manual OTDR mode, turn the rotary switch to AUTOTEST, press F3 Change Test; then select Manual.

You can access these settings on the Fiber OTDR tabs in Setup.

Tip: To see the settings used for an OTDR test, press F2 View Events on the OTDR Results screen, press F3 View Details; then press F1 OTDR Settings. The settings used may be slightly different from the nominal values selected on the OTDR tab.

Listed below are the settings you can change in manual OTDR mode and how the settings affect the trace.

Description and Selection Guidelines for Manual OTDR Settings: 

  • Range: The range setting determines the maximum distance shown on the trace.
  • Auto
    : The tester selects the range that is nearest to, but not less than the end of the fiber. These ranges are not limited to the fixed ranges provided.

    Manual range selections: You select the range. Typically, you should select the range that is nearest to, but not less than, the distance to the event you want to study. If the tester does not correctly identify the end event, run the OTDR test again using the next higher range.
  • Averaging Time: The averaging time sets the number of measurements averaged together to create the final trace. Longer times reduce noise on the trace which increases dynamic range and accuracy and reveals more details, such as smaller non-reflective events. Shorter times decrease test time, but produce a noisier trace with less dynamic range and decreased visibility of events.
  • Auto: Adjusts the test parameters for a typical test time of 15 seconds per wavelength. This setting is used for Auto OTDR mode and is the default for Manual OTDR mode.
  • Auto Test Time: Adjusts the test parameters for a typical test time of 5 seconds per wavelength. This setting speeds up testing but provides less accuracy and increased deadzones.
  • Auto Deadzone: Adjusts the test parameters to minimize deadzones, which reveals more detail in and around reflective events. This usually takes longer than testing with Auto or Auto Test Time selected.

    Testing with Auto, Auto Test Time, or Auto Deadzone selected can take up to 3 minutes per wavelength, depending on the fiber's characteristics.

    Manual time selections: Lets you set the test time to 15 seconds, 30 seconds, 1 minute, or 3 minutes per wavelength. The tester adjusts the test parameters to meet the selected time.

Loss Threshold (Auto or User Defined):

  • User Defined: Lets you set the threshold (in decibels) for reporting loss events. Events at or above the threshold are included in the event table. The range for this setting is 0.01 dB to 1.50 dB inclusive.

    For smaller threshold values (0.01 dB to 0.3 dB), the tester reduces noise on the trace by taking more measurements for averaging or by using wider pulse widths. Therefore, smaller values may increase test times or deadzones on the trace.
  • Auto: Sets the threshold to the default value of 0.15 dB.

    Setting a loss threshold does not guarantee that all events at or above the threshold will be found. The fiber's characteristics or using a manual Averaging Time or Pulse Width may also limit which events are found.

    If the loss threshold is set to less than 0.15 dB, the tester may find many false events due to inherent imperfections in the fiber.

    Typically, you should use Auto OTDR mode when certifying cabling with the OTDR.

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