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13/02/2015

Useful Guidelines for EPON Solutions Design (Pt.1)

Certain considerations are very important when designing an EPON Solution: Calculations must be made, conditions must be analyzed, etc. Many factors affect these solutions in different ways, for example the number of subscribers, the distance, the user's and office's location, and much more. To avoid issues when implementing the solution it is paramount to have a good design beforehand.

These considerations include:

1. Bandwidth Requirements
2. Network Nodes
3. Splitting Architecture
4. Distance
5. Optical power budget
6. Services to provide
7. Updating the existing network
8. Cables

1. Bandwith Requirements:

These are:

- Number of subscribers
- Bandwidth for each subscriber
- Bandwidth Calculation
- PON card number calculation in accordance with the effective bandwidth of each PON port (about 900M) 
- Distribution of different bandwidth to different users according to the situation
- Reservation of bandwidth for updates if needed

2. Network Nodes:

Central Office:

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 25mm2
- Ground resistance should be less than 5 ohm

Local Convergence Point (LCP):

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

Network Access Point:

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

User Terminal:

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

3. Splitting Architecture:

a) The splitting architecture depends on user distribution, and service providing requirements

b) Decide between 1-stage splitting or 2-stage splitting

c) Consider if average splitting will be used. Generally in an EPON system PLC splitters are used for equal optical power division and FBT splitters for unequal optical power division.

Here we have a comparison between these two splitter types:

We have the following splitting architectures:

1. Distribution Splitting
2. Aggregation Splitting
3. Centralized Splitting

Distribution Splitting:

Cascading Splitting (1 x 8 / 1x 4 or 1x 4 / 1x 8)

Placement:
- POS Located in LCP and NAP

Features:
- Multi-point testing and maintenance
- High optical loss
- Low OLT PON port utilization rate
- Complicated network structure, hard to maintain

 

Aggregation Splitting:

Single Splitting (1 : 32)

Placement:
- LCP

Features:
- Integrated link testing and user management
- Low Optical loss
- High OLT PON port utilization rate
- Low cost for splitters
- Simple network topology, easy to maintain

Centralized Splitting:

Placement:
- CO

Features:
- Single point link testing and maintain
- Low Optical loss
- High OLT PON port utilization rate
- Low cost for splitters
- Dedicated cable for each house
- Flexible topology
- Huge infrastructure cost

The rest will be continued in Part 2.

22:18 Écrit par frequence2 | Tags : fiber optique, ftth, fttb, fttp | Lien permanent | Commentaires (0) | |  Facebook | | | | |  del.icio.us