DIY FTTx projects design: network nodes

FTTx PON Network Nodes Design

Fiber Network Nodes Engineering

Fiber network nodes structure

Fiber network nodes structure

Central Office:
  Central office originally referred to switching equipment and its operators, it is also used generally for the building that houses switching and related inside plant equipment. In the fiber optic network, a central office means an FTTH PON data exchange building, and is also location where PON OLT deploys.
a) Deployment and design requirements:

  • Capacity to easily handle large equipment
  • Enough space for device installation and storage
  • Good working environment (Temperature & Humidity)
  • Central Office construction standard
  • CO with fire safety equipment
  • The CO should be far away from high intensity vibration sources, noise sources, electromagnetic interference, and flammable and explosive materials

b) Power supply requirements:

  • Provide 48V power supply
  • Highest power load requirement that the area can have
  • Individual power line access, dedicated power distribution box
  • UPS power supply

c) Grounding requirements:

  • AC/DC Power supply grounding
  • Section size of grounding wire should greater than 25mm^2
  • Ground resistance should be less than 5 ohm

Local Convergence Point (LCP):

FTTX projects nodes structure

FTTX projects nodes structure

  The distribution of broadband access then continues at the local convergence point which serves as a point of flexibility and where splitters would be located in PON systems.

  • User aggregation point
  • Located in place that is easy to manage and maintain
  • Building distributor, weak current vertical shaft, outdoor optical crossconnection cabinet, man hole, pole etc
  • Active connection, easy to inspect and maintain

Network Access Point (NAP):

FTTx PON design

FTTx PON design

  A Network Access Point (NAP) was a public network exchange facility where Internet service providers (ISPs) connected with one another in peering arrangements. Usually it marked as “multimedia access cabinet” in residential or home subscribers area.

  • Close to the subscribers
  • The terminal device should not too big
  • Floor vertical shaft, staircase, electrical pole
  • Distribution cable spliced with drop cable

CPE (Customer Premises Equipment) Terminal:

  • For FTTH application, needs a dedicated box for ONU installation, embedded on the wall
  • Requires local power supply

FTTH PON Redundancy Case

FTTH PON Redundancy

OLT Duplex Feed
  The OLT duplex feed method relies on two separate FTTH PON feeds from the OLT. Each of these feeds can take a diverse route to the customer splitter distribution location (Distribution Point). The traditional 1×32 Splitter is replaced by a 2×32 splitter and each input is fed with a separate OLT feed. This provides fallback should one OLT feed become damaged, enabling a software switch on the OLT to a separate line card enabling uninterrupted data transmission. The major benefit with this method is that the ONT and customer drop can remain as standard items and ensure that costs are not too high.

Full Duplex Redundancy
  Full duplex redundancy requires two separate distribution nodes, coupled with two separate customer drops. This method provides a very effective redundancy method, however, the element with the highest cost of FTTH PON deployment needs to be duplicated (The last Mile). A second disadvantage is the requirement for a Dual input ONT, a costly product for the customers.

PON Full duplex redundancy

PON Full duplex redundancy

Full Duplex Redundancy, with dual Chassis OLT
  It is possible to add a second OLT at the head end. This method of resilience will provide the ultimate redundancy but essentially the operator will be duplicating the FTTH PON feed. So the customer will receive two separate FTTH PON circuits which can be fed into a Dual input ONT.

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