PON Loss of Signal

Description

Signaled on an OLT when the OLT cannot communicate with any provisioned ONT on a PON at the optical layer. Since the PON-LOS alarm only occurs when all ONTs are affected, this indicates that the problem is likely at the OLT, or between the OLT and the first split point.

Pre-Conditions(s)

• No ACPWR-LOS/LWBATVG on all ONTs: If any ACPWR-LOS alarms (refer to ONT AC Power Failure) are standing on all ONTs, the likely cause is loss of commercial AC in the area. This is typically accompanied with a LOWBATVG alarm (refer to ONT Battery Low) in this situation once the batteries become discharged.
• Dying Gasp: If all of the ONTs on the PON show dying gasp (refer to ONT Dying Gasp), it may be that all of the ONTs are AC only ONTs and the commercial AC power has failed.

Laser Safety

Warning! Personnel handling fiber optic cables must be trained for laser safety.

Warning! Optical Fibers emit invisible laser radiation. Avoid direct exposure to the beam. Never look into the end of a Fiber or into a Fiber connector on a cable or a device. Permanent eye damage or blindness can occur quickly from laser radiation.

Fiber Optic Cable

Ensure that the fiber connectors are properly cleaned per local standards. Dirty connectors may result in inaccurate measurements.

Caution: Fiber optic cable installation and maintenance should only be performed by trained service personnel.

Caution:  Do not bend the fiber optic cable to a diameter smaller than 7.5cm/3 inches. Doing so may damage the fiber or prevent the signal from passing through properly.

Trouble Clearing

The probable causes of this alarm are: 

• Bad OLT Port: Since all ONTs are failed on the PON, the OLT optical transmitter/receiver may be failed. Measure the output power at the OLT Laser using a short pigtail and ensure the optical power is within specifications.

  Note: When testing the OLT laser output, ensure that the light meter is set for the 1490 nm optical wavelength used by the OLT. If the optical receive level is not within range when measured at the faceplate of the OLT, and the connectors are properly cleaned and seated, then it is likely the card in the OLT has failed and should be replaced.

• Splitter OLT Fiber Connection Problem: Since all ONTs are failed, the problem is likely in the connection from the OLT to the first splitter.
• All ONTs Removed: If all ONTs have been retired from the PON, it is possible to get this alarm. If the ONTs have been removed from the PON, set the serial number to zero (00000000) on the ONT to clear the alarms.

  Note: Prior to FP25.5, each ONT must be converted to a new type to clear the alarms.

• Air Gap: The connector may not be clean or fully/correctly seated at the splitter or at the OLT PON port. Ensure that all connectors are clean and seated correctly at the OLT and splitter. There should be two audible clicks when plugging in the fiber.
• Bad Fiber: The fiber connecting the OLT to the splitter may be bad. Check the received power at the fiber to the first split point to ensure that the optical signal is being received at the proper power level. If the power is low or not present, test the power at the output of the OLT. If the power at the OLT is good, then the trouble is in the fiber.