The services on a network fail to be deployed

The services on a network fail to be deployed because the connectors on the live network mismatch the connectors of new devices.

Product

OSN 6800, OSN 8800

Fault Symptom

According to engineering design files, the insertion loss and distance between sites A and B on an OTN network are 40 dB and 130 km respectively. On the live network, however, the line insertion loss in the east direction and that in the west direction are 45 dB and 46 dB respectively, and the actual line distance is 160 km. Services on the network cannot be deployed.

Network Topology

The following figure shows the network topology.

Cause Analysis

The connectors on the ODF are the FC/APC type, and the connector of the E2000 jumper for connecting the new RPC board is the FC/UPC type. After these two types of connectors are interconnected, the line insertion loss significantly increases, which introduces intensive reflection after lasers on the RPC boards are enabled. As a result, services on the OTN network cannot be deployed.

Procedure

1. Check the configurations of the link insertion loss and dispersion.
   The configurations comply with the design requirements.
2. Check the optical power of the line between the OBU205 board (the board at site A is used for the purpose of this example) to the receive end on the ODF.
   The insertion loss of link A–B is 45 dB and that of the link B–A is 46 dB. The lines are in a normal state.
3. Measure the insertion loss of the link between the RPC board and the OBU101 board.
   The link insertion loss is about 2 dB.
   Measure the insertion loss of the link from the ODF to the RPC board and then to the OBU101 board.
   The link insertion loss is 2 dB (the insertion loss of the RPC board is 1.5 dB). This indicates that the RPC board and the jumper are normal.
4. Measure the ODF and the RPC board using an optical power meter after they are connected.
   No light is measured. This result conflicts with the measured results of the links between the ODF and the RPC board. This indicates that the insertion loss was introduced by the connector of the ODF.
5. Replace the connector on the ODF and jumper.
   The fault persists. The insertion loss of the connector is larger than 5 dB.
   Further analyze the connector on the ODF and the connector of the jumper.
   The connector on the ODF is the FC/APC type, and the E2000 jumper on the RPC board is the FC/UPC type. After these two types of connectors are interconnected, the line insertion loss significantly increases, which introduces intensive reflection after lasers on the RPC board are enabled. As a result, services on the OTN network cannot be deployed.
6. Replace the jumper with a new one whose connectors at the two ends are the FC/UPC and FC/APC types.
   Services on the network are available.
   
   Figure 1 Parameters for different connectors

Conclusion and Suggestion

Familiarize yourself with different types of connectors and be aware that some types of connectors cannot be directly interconnected.

There is a slight difference between the FC/APC and FC/UPC connectors: An FC/UPC connector has a plane surface, and an FC/APC connector has an inclined surface with a slope of 8 degrees.

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