Optical Fiber Cable

 Optical Fiber:

Optical fiber is made of glass or plastic and transmits signals in the form of light.The speed of light depends upon the density of the medium through which it is traveling.Higher the density, Slower the speed.


If a ray of light traveling through one medium enters into another medium then its speed changes, making the ray to change its direction.This change is called refraction.When a beam of light moves from a denser medium to a low dense medium, as the angle of incidence increases angle of refraction also increases

Critical Angle

It is the angle of incidence where the refracted angle is 90 degree.

Total internal Reflection: Fiber optic cable works on this principle.

When a light ray passes from one medium to another the ray is refracted at the boundary of the medium. For angle of incidence above the critical angle the light is refracted back (reflection) to the same medium. None of it escapes to another medium.Thus a light ray incident at or above the critical angle is trapped inside the fiber and can propagate for many kilometers with virtually no loss.

Fiber Distributed Data Interface (FDDI )

Fiber Distributed Data Interface (FDDI )

Fiber Distributed Data Interface  is a high performance fiber optic token ring LAN running at 100Mbps and over a distance up to 200km and can have 1000 stations connected to it.It is generally used as backbone to connect due to its high bandwidth.

Unicast vs Multicast vs Broadcast

Broadcast Networks

Broadcast networks have a single communication channel that is shared by all the machine on the network.Broadcast systems allow the possibility of addressing a packet to all destinations by using a special code in the address field.

  • Unicast
  • Multicast
  • Broadcast
Unicast: One to One  
Sending a packet form one host to another in the same network or on a different network.

Multicast: One to Many  
Multicast addressing is a network technology for the delivery of information to a group of destinations simultaneously.It uses each link only once for message delivery.It use the class D addressing system.It uses IGMP (Internet Group Management Protocol).

Broadcast: One to All
Sending a packet form one host to all another hosts in the network as specified in the destination IP address
Example: Destination address means sending a packet to all hosts of the network specified by the network id 192.168.20

Advantages Layered Structure (ISO-OSI or TCP/IP)

Advantages  Layered Structure (ISO-OSI or TCP/IP)

Minimize Design Complexity: The whole structure is divided into different layers or modules.Each module is designed by experts specialized in that specific area.

Getting the best expertise: Experts can concentrate specifically on each module

Separate  Function: Functions of Each module is clearly defined that makes the analysis and understanding of the architecture easy.

Implementation Independence: Changes can be implemented in one layer with out affecting other layers.

Work distribution: The work is distributed among the layers as a series of  functions.

Flexibility: Can  choose the best  from avilable protocols in each layer , depending on the implementation requirements.

Ethernet- IEEE 802.3

IEEE 802.3 - Ethernet

It defines two categories.

1.    Base band: Base band uses the digital Manchester encoding technique.
2.    Broad Band

<Data Rate in Mbps><Signaling Method><Maximum Segment Length in 100 meters>

Example: 10BASE5

10 implies    - Data Rate 10Mbps

BASE implies - Signaling Method BASEBAND

5 implies -Maximum segment length =5*100 = 500meters

 Name                Cable                         Maximum segment Length
 10Base5       Thick Coaxial Cable  500m
 10Base2       Thin Coaxial Cable  200m
 10BaseT       Twisted Pair   100m
 10BaseF        Fiber Optic  2000m






Ethernet Properties

Ethernet LAN consists of coaxial cable called ether to which multiple computers connect.Ethernet is a bus network in which multiple computers share a single transmission media. While one computer transmits a frame to another, all other computers must wait.

Ethernet uses bus topology.

Ethernet offers connectionless communication.

Ethernet uses CSMA (Career sense multiple access) Access Method.
Advantages of Ethernet:

1.Low cost
2.Maintenance and administration simple
3.Ethernet cables are robust to noise, thus external disturbances are very less.

Disadvantages of Ethernet

1.As the load on Ethernet increases number of collision increases, therefore efficiency decreases.
2.Ethernet offers non-deterministic service, so it is not suitable for real time application.
3.No priority mechanism in Ethernet.
4.There is a restriction of minimum size of packet.