The Fiber Optic Association

  The Fiber Optic Association, Inc.
the non-profit professional society of fiber optics

Reference Guide To Fiber Optics

Topic: Premises Cabling Systems Standards - TIA-568-C Table of Contents: The FOA Reference Guide To Fiber Optics

Changes In TIA-568-C Standard For Premises Cabling Systems

Current as of January 2011 but subject to change in the standards committees.

The terminology in TIA-568-C.0, Generic Telecommunications Cabling For Customer Premises, has changed to a more generic (i.e. not traditional telecom) nomenclature. Current plans are to revise the other T568/T569/T570 documents to this nomenclature over the next 3-5 years.

Unfortunately, all this can be confusing, so we'll present the TIA wording and explain our interpretation in CAPS and give you a diagram of our explanation.

The traditional terms for the location of the ends of the cabling or interconnections have been changed to "connection points."

Distributor C: Initial or central connection point in a hierarchical star topology. EQUIPMENT ROOM OR MAIN CROSS CONNECT

Distributor B: Intermediate connection point between Distributor A and Distributor C in a hierarchical star topology.  AN OPTIONAL SECOND PATCH IN EQUIPMENT OR TELECOM ROOM OR MEDIA CONVERTER AND/OR REPEATER

Distributor A: Intermediate connection point between Distributor C and Equipment Outlet in a hierarchical star topology. HORIZONTAL CROSS CONNECT, e.g. TELECOM ROOM or ZONE MUTOA 

Equipment Outlet: Final connection point in a hierarchical star topology. WORK AREA OUTLET

In a typical commercial building, 
Distributor C  would be the main cross-connect, Distributor A would be the horizontal cross-connect, and Equipment Outlet would be the telecommunications outlet (TO. ) Distributor B is optional and not often used.

Connecting these points are "cabling subsystems" defined as:

Cabling Subsystem 2 or 3: Cabling between either 
Distributor A and Distributor C or Distributor B and Distributor C. BACKBONE

Cabling Subsystem 2: Cabling between 
Distributor A and Distributor B. CROSS CONNECT

Cabling Subsystem 1: Cabling between 
 Distributor A and Equipment Outlet. HORIZONTAL

In addition, some of the definintions have changed:

Centralized cabling, Fiber optics with a direct connection from the equipment to user is defined as: A cabling configuration from Distributor C to a centralized cross-connect using pull through cables, an interconnect, or splice at Distributor A.

Consolidation point: A connection facility within Cabling Subsystem 1 for interconnection of cables extending from building pathways to the equipment outlet.

These drawings illustrate some of the options within the standard architecture.

Below is the "traditional" view of TIA-568 architecture:

TIA 568 C Architecture

Distributor B is optional and can be used for a connection, e.g. fiber splices, or media converters:

TIA 568 C Architecture

In fact, no intermediate connections are required, e.g. centralized fiber:

TIA 568 C Architecture
Within Connection Point C, there are two methods of connection from active equipment to Cabling Subsystem 3, the interconnect and cross-connect configurations:

TIA-568 CP-C

Here is a diagram of old and new nomenclature in a typical structured cabling system using the illustration we have used previously:

TIA-568-C Nomenclature

Table of Contents: The FOA Reference Guide To Fiber Optics


(C)1999-2011, The Fiber Optic Association, Inc.