communication mediums

Hello, i seem to have touched a nerve with some members with my first post. Yes, i am studying a part-time HND course but i was under the impression that this web site was an important source of information for students and engineers alike. I am in college one day a week, there is a very limited source of information concerning PLC's within the library (which is rarely open). I have tried other websites but most seem to want to sell me a course or product. Is there anywhere else i could get more information.
I am currently trying to explain the difference's between the varios communication mediums such as twisted pair, coaxial and fibre optic with regard to speed, bandwidth and maximum distance between terminals.
Any help or just a push in the right direction would be appreciated.

This is very simple AND available on the Web.

You go to any manufacturer.
You check which communication device they include in there systems.
You check-out these devices and protocols.

As to give you a short list of them, in order, with details.

Do the work yourself.

There are three categories of transmission media currently in use in industrial networks. They are twisted pair (TP) wires, coaxial cable and fiber-optic cable. The most commonly used media is twisted-pair. This is due to its ease of installation, low cost and low maintenance. Twisted-pair may be purchased with a shield or without.

EIA or the Electronics Industry Association defined a set of standards for twisted-pair cables in the EIA-586 Standard. STP or Shielded Twisted -Pair cables provide better immunity from electromagnetic induction or electrical noise than the UTP or Unshielded Twisted-Pair. STP provides a mesh wire jacket that is connected to earth ground. UTP does not provide this shield. In TP cables, each pair provides a communication channel. Generally, in a PLC local area network, shielded twisted-pair is used due to the high levels of electrical noise in the manufacturing environment. Twisted-pair cables are specified by their transmission speeds. The 16 megabits per second (16Mbs) cables typically have 3 to 4 twists per foot, and is used to transmit data at lower speeds over short distances. The 100 megabits per second cables normally have 3 to 4 twists per inch and carry data at higher speeds over longer distances.

Coaxial cable consists of a solid central conductor surrounded by an insulator. A shield of woven wire then surrounds the insulator. Coaxial cable is used to transmit high frequency signals. This type of cable is more expensive but provides a high degree of noise immunity. They are divided into 3 categories based on the type of signals they transmit. The categories are baseband, broadband and carrier band.

Baseband is a special 50-ohm cable used to carry digital signals only. It is normally referred to as Ethernet cable due to its original use in Ethernet networks.
Broadband and Carrier Band coaxial cables are typically 75-Ohm cables that are used to carry analog signals. This requires the used of a modem to convert the digital signal to an analog signal for transmission across the medium. A modem on the receiving end will then convert the signal back to a digital signal. Broadband coaxial cable is capable of carrying multiple analog signals. The cable television industry employs this type of cable to provide service to their customers. Carrier band cable, also sometimes called single channel broadband is capable of carrying only one analog frequency signal. Carrier band cable is less expensive than broad band coaxial cable and the modems used by carrier band are less expensive than those required by broad band cable.

Fiber-optic cables are thin glass or plastic fibers that use light to transmit the data. This type of transmission media is capable of carrying data at a rate of two gigabytes per second (2Gbs) over distances of tens of miles. Fiber optics offers by far the best noise immunity of all of the transmission media. They are also capable of carrying several signals simultaneously. This type of transmission media is much more expensive than those previously discussed.

Due to the low cost, twisted-pair cables are more often used for PLC local area networks. Most commonly, Belden #9842 is the cable of choice.