ONS (Optical Node Segmentation
aka “node splitting”)
Nbn had an objective to deliver 100/40 speeds over the HFC network, and to all properties (residential and commercial) that the networks past. This requirement was far greater than what the existing network operators had envisaged or required. To do this, it was a requirement to deliver additional CMTS capacity to the distribution network.
When TPS upgraded the 4,400 optical nodes, we had installed segment able nodes (OM4100’s). Telstra operated these in 1×4 mode which enabled them to deliver 1 CMTS service group to the optical node, however if nbn elected to upgrade them to 4×4 nodes, a total of 4 service groups could be delivered. The challenge wasn’t as simple as just changing some parts in the node, but rather it encompassed a series of complicated predecessor tasks to be performed. Apart from site surveys, logistics associated with node components and usual change management and OSP (outside plant) work activities it was necessary to first conduct some detailed ISP (Inside Plant) work activities.
Specifically, a new ONS high density transmission rack needed be constructed and connected to the existing RF combiner platform, then optical connectivity from the OSP fibre network to the new rack needed to be established. TPS worked in conjunction with Telstra and developed and prototyped a new ONS rack which could be deployed at Telstra exchanges. To date, TPS have manufactured, FAT (Factory Acceptance Tested), installed, commissioned and operated in excess of 300 ONS racks nationwide.
Once the ONS rack has been commissioned, it is necessary to have technical OSP staff in the field at the node location and technical staff at the ISP rack location. Together they work to upgrade the components at the optical node site and commission the new 4 transmission pathways.
To effect the change in the specified planned service interruption change window, staff need to rapidly splice in new fibre for each optical node and recertify the links. Often a complicated task, as the work take place in existing fibre OFDF’s (Optical Fibre distribution Frames) which have often been established since the early 1990’s. Special care needs to be taken.
When the optical links have been certified and commissioned, RF commissioning begins. As part of these works, the RF links to the coaxial distribution network are commissioned inside the optical node. RF connectivity to Telstra and nbn CMTS’s & uBR’s is tested and balanced by injection of RF pilot tones which are measured whilst receivers in the exchange are adjusted to attain the appropriate RF drive levels.
During early operation of the program, we identified problems where there was insufficient electrical voltage to operate a node in 4×4 mode. This is primarily due to the fact that the 4×4 nodes consumes significantly more electrical energy. As a result of this, TPS developed a power pre-auditing process which could be carried out prior to node segmentation to ensure that sufficient voltage was present. If their was insufficient voltage, we would either perform changes on the day to redirect power around the distribution network, or a more complicated change would be invoked, often resulting in the requirement to install an addition LPS (Line Power Supply) into the network.
Subsequent to the program of segmenting existing 1×4 nodes, nbn also have a requirement to deploy additional segmented nodes into the footprint and migrate distribution network from the existing node onto the new node. This was referred to as PNS (Physical Node Segmentation).
TPS designed and performed the very first PNS activity in Toorak, Victoria. The works were performed on existing node TKOC and despite some physical access issues, the activity completed successfully.