Optical Fibers Technology.

optical fibers are made up of glass, plastics or silicaplastic fiber are least efficient, but tend to be cheaperand more reggudphysically a fiber-optic cable consists of three concentric layer inner core, a cladding around it and the outer protective coating. the inner core which has a diameter of 8 to 200 micrometers, consists of a bunch of optical fibers. the cladding around it is made of plastic or glass and has a refractive index less than that of the core. the characteristics of light propagation depend primarily on the fiber size. its construction the refractive index profile and the nature of the light source.

Communication Satellite Technology

The main problem with microwave communication is that the curvanture of the earth, mountain and other structure often block the line-of -sight. due to this reason, several repeater stations are normally required for long distance transmission between two points. this problem is overcome by using satellites.
these satellite are launched either by rockets or space shuttles and are precisely positioned it is stationary relative to earth and always stays over the same point on the ground. this allows the gruond station to aim its antenna at a fixed point in the sky. each satellite can receive and retransmit signals.to sightly less then half of the earths surface therefore at least three satellite are needed in geosynchronous orbit to provide world wide data transmission service. hundereds of satellite are now in orbit to handle international and domestic data voice and video communication needs. the JNSAT service of nepal satellites are positioned in outer space in a manner to be accessible from any place in nepal.
to enables a large number of users to benefit from satellite communication it was realized that the size and cost of the receive transmit earth station have to be considerably reduced so that one can easily install a private earth station. to meet this requirements, smaller dish antennas having lower power transmitters and receivers have been built for installation at user's sites.

Electronic mail technology

The electric mail service is known as email in short which allows the Internet users to send a mail message to another Internet users. In any part of the world in a near-real-time manner. the message takes anywhere from a few seconds to several minutes to reach its destination, because it must be pass from one network to another until it reaches its destination.
Email service has many similarities with the postal mail service, which all of us are familiar with all Internet user has a logical mail box just like each one of us has a mail box in our house. when sending a mail to another user, the sender specifies the email address of the receiver just as we write the postal address of the receiver in the postal mail system. the email service delivers on already sent mail in to the receiver mail box. the receiver extracts the mail from the mail box and reads it at his/her own convenient time just like in a postal mail system. after reading the message the receiver can save it, delete it, and pass it on to someone else, or respond by sending another message back.
message in email service the Internet has proved to be a rapid and productive communication for millions of users.