R05410403 Optical Communications B.Tech Question Paper : djriet.edu.in
Name of the College : Dasari Jhansi Rani Institute Of Engineering And Technology
University : JNTUK
Department : Electronics & Communication Engineering
Subject Code/Name : R05410403 – Optical Communications
Year : 2008
Degree : B.Tech
Year/Sem : IV/I
Website : djriet.edu.in
Document Type : Model Question Paper
Optical Communications : https://www.pdfquestion.in/uploads/djriet.edu.in/3003-R05410403-OPTICAL-COMMUNICATIONS.pdf
DJRIET Optical Communications Question Paper
IV B.Tech I Semester Regular Examinations, November 2008 :
OPTICAL COMMUNICATIONS :
( Common to Electronics & Communication Engineering and Electronics & Telematics)
Time: 3 hours
Max Marks: 80
Related : Dasari Jhansi Rani Institute Of Engineering And Technology RR320403 Electronic Measurements And Instrumentation B.Tech Question Paper : www.pdfquestion.in/3023.html
Set – I
Answer any FIVE Questions :
All Questions carry equal marks :
1. (a) Give any three applications of optical fibers for instrumentation and explain them with the necessary figures.
(b) Calculate the number of modes at 1550 nm and 1300 nm in a graded index optical fiber having a parabolic index profile, a 20 µm core radius, n1 = 1.48 and n2 = 1.46. [8+8]
2. (a) Write short notes on Plastic Optical Fibers”.
(b) Find the radius of curvature R at which the number of modes decreases by 50 percent in a graded index fiber take a = 2, n2 = 1.5, = 0.01, a = 25 µm, ? = 1.3 µm. [8+8]
3. Define and distinguish between the different types of signal distortion in optical fibers. [16]
4. Explain the modulation capability of the laser diode and its temperature effects. How to compensate for variations in temperature? [16]
5. (a) Discuss the dependence of equilibrium numerical aperture on power coupling from a source into a fiber.
(b) Estimate the losses encountered while coupling power from a source to a fiber due to mismatch in their numerical apertures and surface areas. [6+10]
6. Describe the following briefly:
(a) Functioning and performance of an analog fiber optic receiver.
(b) Noise sources in a PIN photo detector. [8+8]
7. (a) Discuss the effect of mode mixing factor on modal dispersion for calculating the maximum allowable transmission data rate in a fiber optic link.
(b) The rise times for various components of intensity modulated fiber optic link are listed below. Determine if these specifications support a 5 Km repeater- less fiber optic link with 6 MHz optical bandwidth: [8+8]
Risetime of LED transmitter electronics = 10ns Inter modal dispersion induced = 8ns/Km Intra modal dispersion induced = 2ns/Km Risetime of Detector and receiver electronic = 3ns
8. (a) How can the maximum achievable transmission distance with a set of active and passive components in an optical link be calculated? Explain with the help of necessary transmission curves.
(b) Describe eye patterns analysis for assessing the performance of a digital fiber optic link. Is it possible to estimate BER also from eye patterns? [8+8]
Set – II
1. (a) Explain step index fiber structure in detail.
(b) The core of an optical fiber is made of glass of refractive index 1.55 and in clad with another glass of refractive index 1.0. Determine:
i. Numerical Aperture
ii. Acceptance angle
iii. Critical angle. [8+8]
2. (a) Explain about “chalgenide glass fibers”.
(b) Commonly available single mode fibers have beat lengths in the range 10cm<Lp<2m.
What range of refractive index differences does this correspond to for ?= 1300 nm? [8+8]
3. (a) Explain about double eccentric and multiple fiber connectors.
(b) A single mode fiber operating at the wavelength of 1.3 µm is found to have a total material dispersion of 2.81 ns and a total wave guide dispersion of 0.495 ns. Determine the received pulse width and approximate bit rate of the fiber if the transmitted pulse has a width of 0.5 ns. [8+8]
4. (a) Two multimode step index fibers have NAs of 0.2 and 0.4 respectively and both have the same core refractive index which is 1.48. Estimate the insertion loss at a joint in each fiber caused by a 50 angular misalignment of the fiber core axes. It may be assumed that the medium between the fibers in air.
(b) Explain the intrinsic coupling losses at fiber joint due to mismatch of core diameter, NA and refractive index profile difference. [8+8]
5. (a) Sketch the radiation patterns from a surface emitting LED in both axial and perpendicular planes with reference to active emitting region. Support the sketches with corresponding mathematical expressions.
(b) Derive an expression for power coupling from a large surface emitting LED into a smaller step-index fiber. [8+8]
6. (a) List out the materials used and the desired features of a photo diode for usability in fiber optic links.
(b) Derive an expression for total mean-square noise signal in a photo detector and hence the Signal-to-Noise Ratio at the output of a receiver. [8+8]
7. Write a short note on the following:
(a) System considerations in the design of a fiber optic link.
(b) System rise time calculation with the help of an example. [8+8]
8. (a) List the conditions under which cut-back method of measurement of fiber attenuation yields more accurate values.
(b) Suggest a non-destructive method for measurement of fiber attenuation. Mention the principle behind this method.
(c) Output of a PIN detector preamplifier of an optical receiver for 1.6Km fiber is 2.26 Volts at 820nm wavelength. The output of PIN preamplifier increases to 9.06 Volts when this fiber is cutback to 4m length at the same wavelength. Compute the total attenuation and attenuation per unit length (dB/Km) of the cut-off fiber. [5+5+6]