Fiber Optic cable types

Unanswered Question
Oct 11th, 2009


What are the differences between the following cable types. What does µ and mm 50mm or 62 etc 125µ values determine? Where to use which?

Dorax 8 Core MM 50/125µ F/O

DR-5613-12 Dorax 12 Core MM 62.5/125µ F/O

DR-5613-24 Dorax 24 Core MM 62.5/125µ F/O

DR-5613-4 Dorax 4 Core MM 62.5/125µ F/O

DR-5613-8 Dorax 8 Core MM 62.5/125µ F/O

12 Core SM 9/125µ F/O

Dorax 24 Core SM 9/125µ F/O

DR-5913-4 Dorax 4 Core SM 9/125µ F/O

DR-5913-8 Dorax 8 Core SM 9/125µ F/O


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viyuan700 Mon, 10/12/2009 - 06:13

MM here means Multimode Fiber

SM here means Single mode

µ is for micrometer (micron)

An optical cable whether Multimode or Single mode have 2 diameters

One called Core where your signal travels

In multimode it is 50 or 62.5 Micron

In single mode it is 8/9 Micron

Second is cladding diameter which is same in both Multimode & Single mode and is alaways 125micron.

4/8/12 core here i think here mean that there are 4/8/12MM/SM fibers are in that cable.

As you know light travel in fiber due to Total Internal Reflection and this layer of silica has different refrative index so reflect the light again to the core instead of going out and lost. Few terms here are from ur college course so if you feel bored can ignore it.

Tom Randstrom Mon, 10/12/2009 - 07:14

For any MM 50/125µ F/O cable, you will want to know what specification it is: i.e. OM2, OM3 or OM4.

As speeds on your links increase from 1G to 10G and future 40G to 100G, you want to make sure your fiber spans will support the bandwidth upgrade.

The attached article may help understand.

husycisco Mon, 10/12/2009 - 13:47

Thankyou guys

"In multimode it is 50 or 62.5 Micron

In single mode it is 8/9 Micron "

What does differ between these microns? What is the effect of these values on determining to buy which gbic?

Tom Randstrom Mon, 10/12/2009 - 14:04

Transceiver and fiber selection is based on link bandwidth and distance between devices. If you look at the transceiver data sheets, you will see there are many type of transceivers to meet your networking requirements.

A multimode link (fiber and transceivers) is designed for shorter links (within building or campus) and is less expensive to purchase. The fiber has a larger core size and the transceivers use lower cost LED/Laser light sources. 50 micron multimode is typically being deployed to provide some level of future proofing.

A singlemode link (fiber and transceivers) is designed for longer links (between campuses, metros, etc) is more expensive to purchase.

Hopefully this helps!

viyuan700 Mon, 10/12/2009 - 17:11

What does differ between these microns?

As their name suggest Multimode Fiber has many modes and these modes reaches the other end at different times means signal disperse. So difficult to retrieve the signal sent. You can get very limited distance. As Tom pointed out better to take 50micron fiber than 62.5Micron. In 50micron you have few more choice depend on your budget, distance speed.

MM fiber diameter is big enough so transmitter can be LED or cheap laser. Cable is less costly, transmitter also but limited distance.

In Single mode they reduce the fiber diameter so much that only one mode can travel but you need a high quality laser to launch light in that small diameter. You get better distance but transmitter, cable all are costly.

Check your distance and speed and budget and see what is good for network.

husycisco Thu, 10/15/2009 - 12:48

Great information, thank you guys. How is fiber terminated? I mean fiber comes to fiber patch panel then what? Type of connectors? What is pigtail and how is it used? Can you explain step by step in order ,,thanks

Tom Randstrom Thu, 10/15/2009 - 13:08

Typically, the fiber ends are terminated into a patch panel, using SC or LC connectors. Then jumpers attached to the patch panel to the equipment.

A pigtail is just a fiber with one enter terminated with a connector and the other end a bare fiber. You can splice (fusion or mechanical) the pigtails to the fiber cable ends and install them in a patch panel.

It is difficult to install connectors on singlemode fibers so installers purchase factory made pigtails or they purchase preterminated patch panels to terminate (connectorize) the fiber.

Connectors can be attached to multimode fiber in the field using polishing equipment or special mechanical connectors (depending on the volume of connectors).

There are all sorts pre-terminated products (cables, connector modules, patch panels, etc) on the market that reduce the need for the user to field terminate the fiber ends.

I've attached a couple of links, one for product and one for fiber basics.


Panduit Fiber Products

Fiber Optic Association


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