At the beginning of each test cycle.
- Once the reference has been set, it is critical to verify the Test Reference Cords (TRCs) before testing and save the results of the verification.
- It is recommended to verify the TRCs at regular intervals* and document their performance. Doing so will also ensure the reference has not drifted.
- If you verify the TRCs and find your loss is negative, you should reset the reference as this is an indication that the source has drifted. Then verify the TRCs again.
- Likewise, if the TRCs verification fails - reset the reference and verify the TRCs again. A failing TRC verification could be due to damaged TRCs or the source drifting.
What if the unit(s) powers down?
Power the unit(s) back on within five minutes. Verify the TRCs. If the values look good, there is no need to set a new reference. Continue to verify the TRCs at regular intervals.
*Standards do not specify how often you should verify the TRCs. You are responsible for specifying how often this should be carried out. As a guide, you could set the TRC verification requirement to occur every 288 fiber tests. In less than ideal environments (where dust is an issue), shorter intervals may be required. Poor test reference cords often lead to false failures and retesting, so consider TRC verification as a critical part of your test procedure/specification.