In network engineering we use media to connect things together. There are basically 3 kinds of media, fiber, copper and wireless. Fiber media is made from glass or plastic. Back in the day, when I first started running fiber, there was one manufacturer, which was Corning. Now there are several more. Fiber optic cable uses a light signal and copper cable uses an electrical signal. The light signal has to be converted to an electrical signal by the switch or router with an sfp or gbic that accepts the fiber optic cable or a separate “converter” that connects to the switch or router with a fiber connector on one end and a copper connector on the other end.
| Single-mode fiber is called single mode because of the path of the light down the fiber. It is best described with a picture: As you can see there is a single light stream and it goes straight down the path without bouncing off of the cladding because of the very narrow core. This allows the light to travel farther because of less attenuation, allowing signals to travel up to 100km (60miles). |
Multimode fiber is called multimode because of multiple paths of light down the fiber. Picture below:
There is a wider path where the light beam bounces along the cladding. So the propagation of the light is shorter. It depends on the application, but maximum is about 10 miles or about 16km.
The advantages of fiber optic cable is that is can go a lot farther distance that copper cabling. Also, it is not affected by electromagnetic interference, or radio frequency interference, since it is light.
Copper cabling or unshielded twisted pair, for ethernet, has a distance of 100M. There are different categories of unshielded twisted pair cabling. POTs, or plain old telephone cabling used to be category 1, then the cabling companies upgraded the ethernet cabling to category 2 for token ring at 4Mbps. Category 3 was able to transmit an ethernet signal of 10Mbps for 100 meters. Category 4 was able to transmit a token ring signal of 16Mbps up to 100M. Cat 5 cable is able to transmit an ethernet signal of 100Mbps up to 100M. Now we have cat 5e, 6, 7, 7a, and 8 for speeds up t 25Gbps. The category of copper cabling is determined mainly by the amount of twists in the pairs. Ethernet cabling has 4 pairs of wires. The tighter the twists, the higher the category.
In conclusion, single mode fiber, multi mode fiber and copper cabling are all media types to connect networking devices together. There are advantages and disadvantages of each. One rule of thumb that we used to use was to run copper from the workstation to the switch, multimode fiber in between floors in a building, and single mode fiber between buildings. But, it just depends on the budget and what devices you’re connecting together. As always you need to specify your equipment to make sure it will accommodate the media you are running, or spec out the media to match the equipment you are installing. You will need to take all this into account to make sure you are fulfilling the business needs of your customer.
Ken Hagen CCIE #56460 