Name of the College : SREE CHAITANYA COLLEGE OF ENGINEERING
University : JNTUH
Department : Electronics And Communication Engineering
Subject Code/Name : 07A70410/OPTICAL COMMUNICATIONS
Year/Sem : IV/I
Website : scce.ac.in
Document Type : Model Question Paper
Download Model/Sample Question Paper : https://www.pdfquestion.in/uploads/scce.ac.in/4931-07A70410-OPTICALCOMMUNICATIONS.pdf
SCCE Optical Communications Question Paper
Code No: 07A70410 R07 Set No. 2
IV B.Tech I Semester Examinations,December 2011
Related : Sree Chaitanya College Of Engineering 07A70501 Network Management Systems B.Tech Question Paper : www.pdfquestion.in/4930.html
Time: 3 hours
Max Marks: 80
Answer any FIVE Questions :
All Questions carry equal marks :
1. (a) Explain the function of each block with a help of neat block diagram of a digital optical ber communication system.
(b) Compare the ber structure and NA in step index and graded index bers. [8+8]
2. (a) Discuss the dependence of equilibrium numerical aperture on power coupling from a source into a ber.
(b) Estimate the losses encountered while coupling power from a source to a ber due to mismatch in their numerical apertures and surface areas. [6+10]
3. (a) A graded index ber with a parabolic refractive index profile core has a refractive index at the core axis of 1.5 and a relative index dierence of 1%. Estimate the maximum possible core diameter which allows single mode operation at a wavelength of 1.3 m.
(b) Discuss material absorption losses in silica glass bers. [8+8]
4. (a) A graded index ber has a parabolic refractive index profile (=2) and a core diameter of 50 mm. Estimate the insertion loss to a 3 m lateral misalignment at a ber joint when there is index matching and assuming.
i. There is uniform illumination of all guided modes only,
ii. There is uniform illumination of all guided and leaky modes,
(b) Describe possible losses due to lateral and angular misalignments between fibers. [8+8]
5. (a) List the estimates and conclusions possible from transmission distance versus bit rate plot for a given wavelength-LED-PIN diode combination.
(b) Discuss the dierence between a dispersion limited and an attenuation limited fiber optic link.
(c) Explore the possibility to include system margin in rise-time budget analysis also. [6+6+4]
6. (a) Explain the principle behind the operation of an Avalanche Photo Diode.
(b) Compare and contrast the properties of a PIN diode and an APD.
(c) Compute the responsivity of a silicon APD operating at 850 nm with a quantum eciency of 72% if only 20% of the internally generated photoelectrons are collected at the detector terminals. [5+6+5]
7. (a) Enumerate the necessity of line coding of signals before transmission over optical bers?
(b) Dierentiate between Source coding, channel coding and Line coding?
(c) Describe a method to measure chromatic dispersion in optical bers?[4+6+6]
8. (a) Write notes on \dispersion shifted ber and dispersion compensating ber”.
(b) Explain in detail about the refractive index profile dispersion and dispersion Vs bandwidth of an optical ber. [8+8]
Code No: 07A70410
R07 Set No. 4
1. (a) Discuss the system criteria for design of a point-to-point ber optic link.
(b) An optical ber system uses a ber cable with a loss of 6 dB/Km. Average distributed splice losses is estimated as 1.4 dB/Km. Determine the maximum possible repeater-less transmission distance if the total permitted ber loss is 36dB. Allocate system safety margin of 5dB. [8+8]
2. Describe the following briefly:
(a) Line coding in Optical Communication links.
(b) Inter modal dispersion measurement in optical bers. [8+8]
3. (a) A Ga As LED source emits light at 0.85 m having a spectrum width of 0.30 nm and the material dispersion parameter is 0.035. Find the value of bandwidth distance product.
(b) Explain the following with respect to LED.
i. Radiance
ii. Emission response time
iii. Quantum eciency
Explain how can one achieve high values for the above parameters. [8+8]
4. (a) Reason out if the two parameters, ‘quantum eciency’ and ‘responsivity’ signify the same properties of a detector diode.
(b) A PIN diode is characterized by a quantum eciency of 72% at a wavelength of 900 nm. Calculate:
i. Responsivity of the PIN diode at 900 nm.
ii. Received optical power if the mean photo current is 10 mA at 900 nm.
iii. Number of received photons for 1 mA mean photo generated current. [8+8]
5. (a) Write expression for power coupled into a step index ber from an LED source.
(b) An LED with circular emission region of diameter 100m and an axial radiance of 100 W / cm2- Sr at 100mA drive current is coupled into a step index ber of 50 m diameter and of 0.22 numerical aperture. Compute the power coupled into this step index ber. Compute the %dierence in coupled power if the radius of the ber is
i. Halved.
ii. Doubled. [4+12]