Transmission Media

In network communication work can not be separated from transmission media, that all make communication and connected between all network equipment to arround the world. Actually in transmission media divided into two kind:
1. Conducted or guided media
Use a conductor such as a wire or a fiber optic cable to move the signal from sender to receiver.
2. Wireless or unguided media
use radio waves of different frequencies and do not need a wire or cable conductor to transmit signals.
The following is description about two kind transmission media above:
1. Guided Transmission Media:
Transmission capacity depends on the distance and on whether the medium is point-to-point or multipoint

Twisted Pair Wires
- Consists of two insulated copper wires arranged in a regular spiral pattern to minimize the electromagnetic interference between adjacent pairs
- Often used at customer facilities and also over distances to carry voice as well as data communications
- Low frequency transmission medium
Types of Twisted Pair
- STP (Shielded Twisted Pair)
The pair is wrapped with metallic foil or braid to insulate the pair from electromagnetic interference
- UTP (Unshielded Twisted Pair)
Each wire is insulated with plastic wrap, but the pair is encased in an outer covering
Ratings of Twisted Pair
Cat 3:
Data rates of up to 16 Mbps are achievable
Cat 5:
Data rates of up to 100mbps are achievable
More tightly twisted than Category 3 cables
More expensive, but better performance
Cat 6:
Cable standard for Gigabit Ethernet
PINOUT
RJ 11 Pinout

RJ 21 Pinout

RJ 45 Pinout
Cable Type:
Straight

Crossover

UTP Cable

Crimping tools
The equipment can help you to crimping cable in module Rj 45.

Tester
The function to do testing twisted pair about quality cable, potition pair after crimping, and segmentation point which problem.

PoE
Power over Ethernet (PoE) technology enables ordinary Ethernet network cables to function as power cords. In a PoE enabled network, direct electrical current (DC) flows over the network cable together with normal Ethernet data traffic.

Barel
Connector to connect UTP cable.

Roset
Connector to connect wired cable to connect Rj 11.

Coax Cable

Coax Advantages
- Higher bandwidth
400 to 600Mhz
up to 10,800 voice conversations
- Can be tapped easily (pros and cons)
- Much less susceptible to interference than twisted pair
Coax Disadvantages
- High attenuation rate makes it expensive over long distance
- Bulky

Fiber Optic Cable
- Relatively new transmission medium used by telephone companies in place of long-distance trunk lines
- Also used by private companies in implementing local data communications networks
- Require a light source with injection laser diode (ILD) or light-emitting diodes (LED)

Fiber Optic Types
- Multimode step-index fiber
The reflective walls of the fiber move the light pulses to the receiver
- Multimode graded-index fiber
Acts to refract the light toward the center of the fiber by variations in the density
- Single mode fiber
The light is guided down the center of an extremely narrow core
Fiber Optic Advantages
- Greater capacity (bandwidth of up to 100 Gbps)
- Smaller size and lighter weight
- Lower attenuation
- Immunity to environmental interference
- Highly secure due to tap difficulty and lack of signal radiation
Fiber Optic Disadvantages
- Expensive over short distance
- Requires highly skilled installers
- Adding additional nodes is difficult
Fiber Connectors

OTDR
An Optical Time Domain Reflectometer (OTDR)
An OTDR may be used for estimating the fiber’s length and overall attenuation, including splice and mated-connector losses. It may also be used to locate faults, such as breaks, and to measure optical return loss. To measure the attenuation of multiple fibers, it is advisable to test from each end and then average the results, however this considerable extra work is contrary to the common claim that testing can be performed from only one end of the fiber.

2. Wireless (Unguided Media) Transmission
- transmission and reception are achieved by means of an antenna
- directional
transmitting antenna puts out focused beam
transmitter and receiver must be aligned
- omnidirectional
signal spreads out in all directions
can be received by many antennas
Wireless Examples
- Terrestrial microwave
used for long-distance telephone service
uses radio frequency spectrum, from 2 to 40 Ghz
parabolic dish transmitter, mounted high
used by common carriers as well as private networks
requires unobstructed line of sight between source and receiver
curvature of the earth requires stations (repeaters) ~30 miles apart
Antena Radio

VSAT

Thats all my knowledge about that. I hope this article useful for readers.
Source:
Abud Susanto
Training at My Office by Luthfi