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EIA/TIA 568 For Fiber Optics

The EIA/TIA 568 standard for premises cabling is used by most manufacturers and users of premises cabling systems in the US. Internationally, IEC/ISO 11801 is very similar, although there are differences in various countries. TIA-568 has been under continual revision since its inception. The current version is "568 C". It includes some major changes from earlier versions for fiber optics.

Work is already starting on TIA 568.D in late 2012. Several new issues are being addressed including passive optical LANs based on FTTH PONs and the high component losses allowed, especially connector loss at 0.75dB, but the biggest problem with TIA 568.C, organization, is also promised to be addressed. Since the work on various issues addressed in the C revision were completed at different times, the document was released in parts as they were completed. As a result, the C version has many issues with changes in one document affecting others, requiring amendments and cross references that are very confusing. There is widespread knowledge of this problem and it has been said that it will be addressed, hopefully by waiting to release all documents together.

Since its beginnings in early 1990s, additions and changes To TIA 568 included:

1. Add 50/125 micron fiber (OM2, OM3, OM4) as an alternative fiber type and specifies performance.
2. Allows alternate connectors to the SC, esp. small form factor connectors.
3. Adds performance standards for all connectors.
4. Includes bend radius specifications for cables.
5. Specifies requirements for connecting hardware.

 

Fiber Optic Cable Performance Standards

568 B3 added 50/125 fiber as an acceptable type and specifies the performance of cabled fiber as follows:

Fiber Type

Wavelength (nm)

Max Attenuation Coefficient (dB/km)

Bandwidth (MHz-km with overfilled launch)

50/125 (OM2, OM3, OM4)

850

3.5

500 (OM2), 2000 (OM3),
3500 (OM4)

1300

1.5

500

62.5/125 (OM1)

850

3.5

160

1300

1.5

500
Singlemode (OS1, OS2)
(Premises)

1310

1.0

NA

1550

1.0

NA
Singlemode (OS1, OS2)
(Outside Plant)

1310

0.5

NA

1550

0.5

NA

Note that these specs are quite conservative, compared to what is routinely available in the marketplace. The spec notes also that the cable manufacturer can use the fiber manufacturer's data on bandwidth, so they do not have to test it.

Hybrid Cables

The standard notes that hybrid cables are permitted, with markings per ANSI/EIA/TIA-598-A. ( Hybrid cables contain both multimode and singlemode fibers.)

Premises Cables

Horizontal cables with 2-4 fibers require a 25 mm bend radius after installation or 50 mm while being pulled with a tension of 50 pounds (222 N).

Other premises cables require a bend radius of 10 times the cable outside diameter unloaded and 15 times the OD when under the maximum rated pulling tension for that cable.

Outside Plant Cables

The standard calls for water-blocked cables with a minimum pulling tension of 600 pounds (2670 N).

Minimum bend radius is 20 times the cable diameter under max rated pulling tension and 10 times unloaded.

Drop Cables

The standard adds a definition for "drop cables," low fiber count cables used to connect high fiber count cables to smaller fiber count cables or patchcords in a single location. These cables must withstand 300 pounds pulling tension (1335 N).

Connectors and Connecting Hardware

Any connector design is permitted as long as it has a FOCIS document (Fiber Optic Connector Intermateability Standard). All small form factor connectors with FOCIS documents are acceptable.

Color Codes: Multimode connectors are beige for 62.5/125 fiber, black for 50/125 fiber, singlemode are blue, angle-polished singlemode are green, and outlets are also color coded accordingly. Cable color codes are the same as TIA-598.

Duplex connectors are keyed and are always crossover - that is Position A of one connector connects to Position B on the other end! Patchcords have this feature too, to permit correct connection of transmitters and receivers! Polarity for multipin connectors (MTP/MPO) are specified in several different versions and are very confusing.

Outlet boxes must have provision for termination of at least 2 fibers.

Patch panels and outlets must provide unique identification for the connecting cabling.

Connector Mating Loss:

Fiber Type

Wavelength (nm)

Loss (dB)

Optical Return Loss

(dB)

Multimode

850

0.75

20

1300

0.75

20

Singlemode

1310

0.75

26 (CATV:55)

1550

0.75

26 (CATV:55)

Remember these connector losses are maximum values. The loss is high to allow prepolished/splice connectors which have higher loss than adhesive/polish connectors. Users may specify lower loss for installations if agreed upon by all parties involved. As of 2012, options to lower connector losses, perhaps in a statistical manner, are being considered.

Notes:

Loss is tested per FOTP-171, single cable reference.

Maximum loss spec holds over temperature (0-60C), humidity (95% @ 40C), impact, pull strength of coupling (7.4 lb./33N), durability (500 matings), cable retention (11 lbs./50 N straight, 4 lbs./19N at 90)flex and twist.

Splices

Fusion or mechanical splices shall not have a loss of more than 0.3 dB. Multimode splices must have a return loss of better than 20 dB. Singlemode splices must be better than 26 dB ORL for general applications, 55 dB ORL for CATV broadband analog video.

 


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