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MAY/JUNE 2014 | www.broadbandcommunities.com | BROADBAND COMMUNITIES | 69 troubleshooting process is illustrated in Fig. 1. TEST PROCEDURE FOR TROUBLESHOOTING A LIVE PON 1 Use an active ONT identifer to determine whether the ONT at the subscriber premises is responding to downstream signals from the OLT. Te active ONT identifer clamps onto 900 µm bufered fber or 2 mm or 3 mm jacketed fber and senses and reports the presence or absence of the 1310 nm upstream response from an active ONT. 2 If an active ONT is detected, the fault is either an equipment problem or a connection problem inside the customer premises (most likely) or the ONT itself (less likely). Optical tests at the ONT are unlikely to resolve the problem. 3 If an active ONT is not detected, the fault may be a failed ONT or a fault in the splitter, distribution or drop fber connecting the feeder fber to the subscriber. 4 In this case, disconnect the drop fber from the ONT and inspect and clean the optical connectors on the drop fber and the ONT. If a damaged optical connector is found on the drop fber, replace, clean and inspect the new connector before proceeding. If a damaged optical connector is found on the ONT, the ONT likely will have to be swapped out. 5 If connectors are clean and undamaged, use a PON power meter to check the downstream power level at the ONT. Some OTDRs, such as AFL's FLX380 FlexTester, include a PON power meter integrated into the OTDR port, enabling immediate detection and measurement of downstream power levels at both 1490 and 1550 nm. 6 If the measured downstream power levels are acceptable, the problem is likely a failed ONT. Swap out the ONT, clean and reconnect the drop fber and verify that the ONT is synchronized to the upstream OLT. 7 If the measured downstream power levels are not acceptable, the problem is likely a fault in the distribution or drop fber or a fault introduced at the splitter in the fber distribution hub. In this case, connect a live PON OTDR to the drop fber and initiate an upstream OTDR test using the out-of-band 1625 nm or 1650 nm wavelength. To prevent disrupting service on the live PON, select an OTDR that prevents the user from initiating 1310 nm, 1490 nm or 1550 nm OTDR tests when live trafc is present but allows a test at 1625 nm or 1650 nm. Te live PON OTDR must also include a flter to prevent downstream trafc at 1490 nm or 1550 nm from interfering with OTDR operation. 8 Some OTDRs also allow the operator to test only the customer fber (distribution and drop) or to test through the splitter. Unless multiple customers are afected, the problem is most likely in the distribution and drop fber, so Fig. 1: Troubleshooting a Live PON BBC_May14.indd 69 5/29/14 9:19 AM