# Communication Engineering II

# Optical Fiber

* What is optical fiber? Show its typical construction

* Define the terms:

  * Critical Angle

  * Acceptance Angle

  * Numerical Aperture

  * Absorption Coefficient

  * Quantum Efficiency

  * Responsivity

* Define different dispersions in fiber optic waveguide.

* What are the effect of dispersion?

* Draw loss vs wavelength characteristics of silica fiber with indication of different loss component

* Write down the names of the light sources used in fiber optic communication

* What is hetero-structure?

* How does a concentrated beam of light obtained from hetero-structure light source?

* What is PD?

# Telephony and Telegraphy

* Define:

  * Telephony

  * Telegraphy

  * Trunk

  * SLIC

  * Simplex Telephone Circuit

  * Half-Duplex Telephone Circuit

  * Duplex Telephone Circuit

  * Line Hunter

  * Line Finder

* Draw the simplified diagram of a typical telephone exchange network

* Classify microphone with necessary diagrams.

* Describe the operation of a microphone.

* Why AC signal is necessary to generate ringing signal in a telephone handset?

* What is interoffice connection? Describe three of them.

* Explain briefly OSI reference model with their different functions.

* What is DTMF?

* What are the advantages of DTMF?

* Show the variation of network cost with the number of exchanges.

* Explain how electrical energy is converted to sound energy in a telephone receiver.

* What will happen if PM is not used in the receiver?

* What are the necessities of side tone in telephone?

* How can you reduce side tone?

* Draw the typical format of Dial tone, Busy tone and Number unobtainable tone

* Show the routing of local call in Stroger switching system when a subscriber dials the number 3582.

* Classify switching techniques.

* Why message switching technique can not be used for voice communication?

* What is switching?

* What is transducer?

* What is a gravity switch?

* Why DTMF is faster than pulse dialing?

* Describe ASTIC

* Describe magneto bell used in a receiver

* Draw internal diagram of a telephone hand set and then describe elaborately the operation of each component

* What are the main two mechanisms to transmit the identity of the called subscriber to the exchange?

* What are the functions of SLIC?

* Describe over voltage protection mechanisms in telephone transmission system

* What are the advantages of automatic switching?

* What are the difference between "circuit switch" and "packet switch"

* Explain the working principle of a telephone receiver

* What is the role of PM in a receiver? Describe with necessary illustrations and mathematic

* Why is signaling necessary for telephone system?

* What are the mechanisms available to transmit the identity of a called subscriber?

* What is "talk-off" and how it is overcome?

* Why telecommunication is practically implemented by loop signaling instead of single wire signaling?

* Classify switching system

* Describe the operation principle of crossbar switching system?

* What criteria should have a switching system?

* What are the advantages and disadvantages of local and central battery operations?

## Traffic Engineering

* Define:

  * GOS

  * BHCR

  * CCR

  * Erlangs

  * CCS

  * Traffic

* Using B-D process, derive the differential equation that governs the dynamics of a switching system. Show its steady state solutions when K>= 1 and K=0