The composition of an ODN Network [GPON Technical Posts - 16]

Hi there, friends!

This post is regarding the composition of an ODN Network, as part of the section GPON Technical Posts. Please see below.

BACKGROUND INFORMATION

A PON network is a passive optical network that starts from an optical line terminal (OLT) in a central office (CO) equipment room and reaches optical network units (ONU) on the user side through an optical distribution network (ODN). The ODN is located between the CO equipment room and users and provides optical channels to distribute, protect, and connect optical fibers and protect connection points. 

The ODN can be divided by 2 points into 3 sections from the CO to the subscriber side. The 2 points refer to the optical distribution point and the optical access point. The 3 sections refer to feeder optical cables, distribution optical cables, and optical drop cables.

In a CO equipment room, a fiber patch cord from the OLT is connected to the optical distribution frame (ODF) panel. The service scope of an ODF is the coverage area of the CO equipment room. The number of optical fiber cores that can be managed ranges from 576 to 1440.

The output optical cables are distributed by the ODF and contained in pipes. The output optical cables are called feeder optical cables. Generally, outdoor optical cables are used. The number of optical cable cores ranges from 12 to 144 depending on site requirements.

If the ODF and a fiber distribution terminal (FDT) are far away from each other, a splitting and splicing closure (SSC) is usually installed between the ODF and FDT to connect the ODF and FDT.

The FDT is used to distribute optical cables for a second time. It is referred to as an optical distribution point on the ODN network. The service scope of an FDT can be a community or street block. The number of fiber cores that can be managed by an FDT ranges from 144 to 576. Select an FDT with proper specifications based on the number of users to be connected.

The section between the FDT and FAT is referred to as the distribution optical cable section. If the distance between the FDT and the FAT is large, an SSC is also installed for connection. A distribution optical cable can be an outdoor optical cable or indoor aluminum core optical cable depending on the FDT position. The number of optical cable cores ranges from 12 to 144 depending on site requirements.

A fiber access terminal (FAT) is a user access point used to connect distribution optical cables and drop cables. An FAT can manage 8–48 optical cable cores, and generally covers a building corridor or villas in a small area. 

The drop cable refers to the optical cable from an FAT to a user's home. Generally, a drop cable is an indoor or outdoor leather optical cable with 1 or 2 cores (occasionally 4 cores) depending on the location. 

A terminal box (TB) or access terminal box (ATB) is located at the far-end of the ODN and connected to ONUs. The difference between a TB and ATB is that a TB is installed outdoors and an ATB is installed indoors. A TB or ATB can manage an optical cable with 1, 2, or 4 cores. 

In an ODN, there is an important component called optical splitter which splits one optical input channel into multiple optical output channels, so that the traditional P2P optical transmission network becomes a P2MP optical network.

Splitters can be flexibly installed in the ODF, FDT, SSC, or FAT as required.

Now, do not hesitate to read through the post and give us your correct answers. If you have any difficulty understanding the content or want to learn more about the GPON technology, please leave a message and reply to the post. We are looking forward to your comments. 

ANSWERS FOR THE PREVIOUS SESSION  

If a rogue ONU exists, the rogue ONU occupies the communication timeslots of other ONUs for a long or short time. As a result, other ONUs connected to the same PON port cannot work normally. 

If a rogue ONU is in continuous mode, other ONUs connected to the same PON port cannot go online. 

If a rogue ONU sends a signal irregularly, other ONUs connected to the same PON port may go online and offline frequently.

QUESTIONS FOR THIS SESSION  

Under what conditions will the SSC be used?

[GPON Technical Posts 15] Rogue ONU Processing

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Mainstream OLT, MDU, and ONT products that support GPON features include:

• OLT: MA5800, EA5800, MA5680T, MA5600T;

• MDU: MA5633, MA5818, EA5821, MA5671;

• ONT: HG8240, HG8010H, HG8040, EG8080P, EG8040P.

Thanks.