IV B.Tech I Semester Supplementary Examinations, February 2007
OPTICAL COMMUNICATION (SET -I)
( Common to Electronics & Communication Engineering and Electronics &Telematics)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
1. (a) Compare the advantages and disadvantages of guided optical communication
lines with that of Microwave systems. [5+3]
(b) What are the various elements of an optical communication system? Explain
each element in brief. [2+6]
2. (a) Explain in detail elliptical and circular propagation of light. [8]
(b) Describe the quantum nature of light. Explain basic optical laws in detail
with relevant mathematical expressions. [3+5]
3. (a) Discuss briefly about radiative losses in the optical fiber [8]
(b) Explain the core and cladding losses in the optical fiber and also derive the
expression for those losses [4+4]
4. (a) With respect to LED what is internal quantum efficiency and derive the ex-
pression for the lifetime reduction caused by interfacial recombination. [3+5]
(b) If the radiative and non radiative recombination lifetimes of the minority car-
riers in the active region of an LED are 1ns and 100ns, respectively, find the
internal quantum efficiency and the bulk recombination lifetime in the absence
of self absorption and recombination at the heterojuntion. [4+4]
5. (a) Why power bandwidth is an important parameter in an optical communication
system?
(b) Explain in detail the various factors which affects the performance of optical
source. [6+10]
6. (a) What are the requirements of an optical receiver? Using a flow chart explain
the receiver design. [4+4]
(b) Derive an expression for receiver sensitivity. [8]
7. (a) Discuss about the Point to Point Fiber Optic Link and its characteristics with
an example? [5+3]
(b) Explain about the frequency chirping and its effects. [5+3]
8. (a) A single-mode fiber has a normalized frequency V=2.40, a core refractive index
n1=1.47, a cladding refractive index n2= 1.465, and a core diameter 2a=9µm.
Find the insertion losses of fiber joint having a lateral offset of 1µm.
(Assume if any data is missed)
(b) How to inter connect two fibers in a low loss manner? Explain. [8+8]
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IV B.Tech I Semester Supplementary Examinations, February 2007
OPTICAL COMMUNICATION (SET -II)
( Common to Electronics & Communication Engineering and Electronics &Telematics)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
1. (a) Briefly explain historical development of Optical fiber communication..
(b) What are the applications of optical fiber communication? [8+8]
2. (a) Explain numerical aperture with reference to ray theory transmission? [8]
(b) A silica optical fiber with a core diameter large enough to be considered by
ray theory analysis has a core refractive index of 1.5 and a cladding refractive
index of 1.47. Determine
i. Critical angle at the core cladding interface
ii. Acceptance angle in air for the fiber. [4+4]
3. (a) Explain in detail the signal attenuation or transmission loss in the optical fiber
with necessary equations and prove that this loss is a function of wavelength
using graphical analysis. [5+3]
(b) The average optical power launched into a 10-km length of fiber is 100µw and
the average output power is 25 µw. Calculate
i. The signal attenuation in dB through the fiber. It is assumed that there
are no connectors or splices.
ii. Signal attenuation per km of the fiber
iii. Overall signal attenuation for the 11km optical link using the same fiber
with 3 splices each having an attenuation of 0.8dB
iv. Numerical value of the ratio between input & output power. [4+4]
4. (a) Write notes on broadening of pulse in the fiber dispersion.
(b) For a fiber material dispersion parameter is 58.8 ps/nm/km.The relative spec-
tral widthδλ/λ of the source is 0.0012 at the wavelength of 850nm.Calculate
the R.M.S. pulse broadening per km. [8+8]
5. (a) Define the quantum efficiency and the responsivity of a photo detector. Derive
an expression for the responsivity of an intrinsic photo detector in terms of the
quantum efficiency of the device and the wavelength of the incident radiation.
[2+2+6]
(b) Determine the wavelength at which the quantum efficiency and the responsiv-
ity are equal. [6]
6. (a) What are the requirements of an optical receiver? Using a flow chart explain
the receiver design. [4+4]
(b) Derive an expression for receiver sensitivity. [8]
7. (a) Discuss about the Point to Point Fiber Optic Link and its characteristics with
an example? [5+3]
(b) Explain about the frequency chirping and its effects. [5+3]
8. (a) What are the principal requirements of a good connector design?
(b) Explain about tapered sleeve connectors?
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