Troubleshooting

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If, in the course of testing, an OptoTest unit begins to experience issues, please consult the below table for basic troubleshooting help. If after consulting the table the unit is still having issues, please contact OptoTest for further assistance.

Problem Possible Cause Solution
Unstable
measurements
Dirt and damage on
endfaces
Inspect all endfaces including any SAVer cables and the front panel connector on the instrument. Clean or repolish any dirty or damaged connectors. For more info, please consult Application Note AN-137.
Dirt and damage on
detectors
Inspect both the detectors and any adapters being used with them for dirt and damage. Clean the detectors and adapters as needed. Replace adapters that appear damaged. In the event of a damaged detector, please contact OptoTest to schedule a repair or replacement.
Dwell times Increasing the IL and RL Dwell times in software or on the Settings screen of the unit (see page 27) can improve stability by allowing the detectors more time to settle.
Damaged bulkheads and detector adapters Broken ceramic sleeves inside of bulkheads and bulkheads that are damaged or misshapen can cause severe misalignment issues which can affect stability. If the bulkhead on the front panel is damaged, contact OptoTest for a replacement or guidance on the proper bulkhead to replace it with.
Hybrid bulkheads The problem generally arises because the ferrules do not properly align due to differences in ferrule alignment. These misalignments lead to decreased repeatability and stability. Additionally, differences in contact force between connector types can sometimes be difficult to rectify and can result in failing values from otherwise passing cables.
Return Loss on connectors takes some time to stabilize Certain push-in connectors are known for having a long settling time for RL This is typically a mechanical settling issue with the two ferrules taking time to properly align as the spring force relaxes. Push-in connectors with higher spring force, such as SC and E-2000, take some time for the spring and mating to reach equilibrium. This issue is typically pronounced on new connectors and becomes less prevalent as it gets connected more.
Dirt and damage Inspect all endfaces including any SAVer cables and the front panel connector on the instrument. Clean or repolish any dirty or damaged connectors.
Dwell times Increasing the IL and RL Dwell times in software or on the Settings screen of the unit (see page 27) can improve stability by allowing the detectors more time to settle.
Unit shows low output power Dirt and damage Inspect all endfaces including any SAVer cables and the front panel connector on the instrument. Clean or repolish any dirty or damaged connectors.
Misaligned adapters Sometimes FC connectors can screw into place without being properly keyed. This will result in low output power and unstable results. Disconnecting the FC connector and reconnecting it with the proper key alignment should yield a more stable connection. Further, hybrid bulkheads (especially SC-LC) often have issues with alignment. If the cores of the fibers do not align properly, the power will be considerably lower.
Mismatched fiber size When launching light into optical fiber, if the DUT or launch cable has a smaller core size than the source, there can be a considerable drop in power. Changing from 62.5/125µm fiber to 50/125µm can result in a drop of about 3-5dB of power, and launching multimode light into a single mode cable can result in a drop of 20dB of power.
Return Loss will not reference APC connector on DUT By default, OptoTest units require a large reflection to reference return loss. Using one of a few different options, the unit can reference return loss with APC connectors. Instructions for doing this on a standalone unit can be found in this manual – Example 2: Referencing Return Loss with APC Reference Cables on page 36.
Return Loss measures
80.1dB (SM) or 58.1dB (MM)
Large reflections in front of the connection under test If there is a reflection of magnitude 60dB or greater within 2-4 meters of the connection under test, the unit could potentially be unable to accurately determine the magnitude of the reflection. Clean the interfaces and if that doesn’t improve the result, try increasing the length of the reference cable by 3-5 meters. If the issue persists it might be a damaged front panel connector, in which case it will need to be repolished or replaced.
Dirt and damage Inspect all endfaces including any SAVer cables and the front panel connector on the instrument. Clean or repolish any dirty or damaged connectors. For more info, please consult Application Note AN-137.
Connector measures above the limitations of the unit In Scan mode, if a reflection is seen when the connector is open,but no reflection is seen once the DUT is connected, it is possible that the DUT has a high quality polish that exceeds the linearizedrange of the return loss meter. For example, many APC matings will measure better than 80dB for SM cables and 58dB for MM cables when properly mated.

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