M.Tech. 1st Semester (ECE) [Batch 2021]
Optical Communication systems
Time Allowed: 3 Hours
Subject Code: PEC1MECE105
Maximum Marks: 100
Minimum Marks: 50
Note: Attempt one question from each Unit. All questions carry equal marks
Unit 1
1 × (20 𝑀𝑎𝑟𝑘)
Q1
a)
What are the various challenges associated with IOT?
b)
A step index fiber has normalized frequency (V-number) of 26.6 at bthe wavelength of 1300nm. If
the core radius is 25 microns, what is the numerical aperture?
OR
1 × (20 𝑀𝑎𝑟𝑘)
Q2
a)
What are the different layers of IOT protocol stack?
b)
Plot the following modes;
(i) LP23 (ii) LP04 (iii) LP32 (iv) LP01
Unit 2
Q3
a)
b)
1 × (20 𝑀𝑎𝑟𝑘)
Discuss different noises in the photodetectors and give the complete expression of SNR for
photo detector.
What do you mean by NEP. For In GaAs PD at 1550nm; ℜ= 0.90 A/W. what is NEP in the
thermal-noise limited case if the load is 1000 ohms and temperature is 300 kelvin.
OR
1 × (20 𝑀𝑎𝑟𝑘)
Q4
a)
What are various routing protocols for IOT? Discuss any two of them.
b)
Give the brief account iof optical Isolators and circulators.
Unit 3
1 × (20 𝑀𝑎𝑟𝑘)
Q5
a)
What is the need for IOT system management?
b)
Consider 100km long fiber for which polarization mode dispersion is 0.5ps/√𝑘𝑚. What is
maximum possible data rate for an NRZ encoded m signal, if the pulse spread can be no
more than 10% of pulse width.
OR
Q6
a)
b)
1 × (20 𝑀𝑎𝑟𝑘)
A SMF link at 1310nm intended for 1Gbps has parameters as- laser diode power of 0dBm,
PIN sensivity of -22dBm at 1Gbps, attenuation factor of 0.4db/km, 1dB connector at each
end and a required power margin of 8dB. Show that the max link length is 30km.
Explain link power budget for a point to point link.
Unit 4
Q7
1 × (20 𝑀𝑎𝑟𝑘)
M.Tech. 1st Semester (ECE) [Batch 2021]
Optical Communication systems
Time Allowed: 3 Hours
Subject Code: PEC1MECE105
Maximum Marks: 100
Minimum Marks: 50
a)
Suppose a 50-km SMF has a dispersion of 4.5ps/nm-km. Show that the required
length of a dispersion compensating fiber of -125 ps/nm-km should be 1.8km.
b)
Give the brief account of different network topologies.
OR
Q8
a)
b)
1 × (20 𝑀𝑎𝑟𝑘)
Discuss format of STS-1 sonet frame. How it is related to STM-1 SDH frame.
Discuss basic passive optical network architecture. Give the brief account of function and
composition of OLT, ONT and ONU.
Unit 5
1 × (20 𝑀𝑎𝑟𝑘)
Q9
a)
Explain Eye diagram in detail.
b)
A given 10 Gbps link is designed to operate with a 10-12 BER. What is gating time window for
accumulating 100bit errors.
OR
1 × (20 𝑀𝑎𝑟𝑘)
Q 10
a)
b)
Explain OTDR trace with help of diagram.
An OTDR is used to measure the attenuation of long length of fiber. If the optical power level
measured by the OTDR at the 8-km point is 0.5 of the measured value at 3km point, what is
the fiber attenuation