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SIDDHARTH GROUP OF INSTITUTIONS :: PUTTURSiddharth Nagar, Narayanavanam Road – 517583

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Subject with Code : Optical Fiber Communication [16EC430] Course & Branch: B.Tech - ECE

Year & Sem: IV-B.Tech & I-Sem Regulation: R16

UNIT –I

Introduction to Optical Fibers

1. _________ among the following is provided by an optical receiver for the regeneration of data signal with minimum error?2. Light is confined within the core of a simple optical fiber by __________3. __________ makes optical fibers immune to EMI?4. _________ type of light source opt for single-mode fiber5. Speeds of laboratory fiber optic Local Area Networks are now in the range of _________6. Metals can ________ the light beams.7. Metals are _______.8. Metals can transmit these ______9. Reflectivity of metals _________10. Refractive index of materials is approximately equal to square root of ____________11. Snell’s law relates ____________.12. Bouguer’s law relates ____________.13. Sky looks blue because the sun light is subjected to __________.14. Luminescence is because of _________15. Fluorescence occurs within _______.16. Electro-luminescence occurs in _________.17. Pyrometer works based on ________18. Solar cell works based on ______19. Optical fiber operates on the principle of _________20. The first semiconductor used in optical fiber is __________21. WDM stands for _______22. The boundary between truly guided modes and leaky modes are defined as _______23. The modes are cutoff when β = __________24. Each LP0m mode is derived from an __________25. The modes propagate with different phase velocities, and the difference between their effective refractive indices is called the fiber ___________26. The number of degenerative modes for LP02 is ___________27. The number of degenerative modes for LP11 is ___________28. In the structure of fiber optic cable, the refractive index of core is always _______the refractive index of cladding29. In the structure of a fiber, ______ component provides additional strength and prevents the fiber from any damage?30. ______ method allows large number of independent, selectable channels to exist on a single fiber?31. _______ type of optical fiber would best be used in the Multiple Channel Architecture (MCA)?32. ________ type of light source opt for multi-mode fiber

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33. Visible light’s wavelength range ______________.34. Planck’s constant value is ____________35. _________ Sum of these is unity36. The operating wavelength of optical cable in the 2nd generation is ____________37. The pulses that can preserve their shape by counteracting the negative effects of dispersion is _______38. The maximum angle in which the light incidents on fiber to propagate down the fiber is __________39. The _____ of a mode is equal to the number of field zeros across the guide.40. In _________ generation optical amplifiers are used as replacement for repeaters

UNIT –II

Signal Degradation in Optical Fibers

1. Different indices of refraction, composition and attenuation coefficients is known as _________2. The speed at _____ energy in a particular mode travels along the fiber3. A measure of the information capacity of an optical waveguide is specified by the ________4. Material Dispersion is also known as ___________ dispersion5. The variation of the refractive index of the core material as a function of wavelength is _______6. A single mode fiber confines only about 80% of the optical power to the core is ___________7. Material Dispersion and Waveguide Dispersion are the main causes of ____________8. Each mode having a different value of group velocity at a single frequency is known as ________9. The resulting difference in propagation times Δτ between the two orthogonal polarization modes will result in pulse spreading is called __________10. For wavelengths below about 1 μm is _________11. For wavelengths longer than 1 μm is ________12. If the bend radius is made a bit smaller once this threshold point has been reached, the loss suddenly becomes ________13. For LEDs the rms spectral width is approximately ____ of a central wavelength14. Empirical relationship is given as _________15. αuv=CeE/E0 is known as ____________16. Large curvature radiation losses are also known as _________17. The radius that are large compared with the fiber diameter is called ________18. The fiber axis that can arise _____ the fibers are incorporated into cables 19. The bends caused either by non uniformities in the manufacturing of the fiber or by non uniform lateral pressures created during the cabling of the fiber is ________20. By extruding a compressible jacket over the fiber can minimize _______21. Signal attenuation is also known as __________22. _______ determines the maximum transmission distance between a transmitter and a receiver or an in- line amplifier23. The basic mechanisms in a fiber are ________24. As light travels along a fiber, its power ______ exponentially with distance25. Optical powers are commonly expressed in units of __________26, Attenuation coefficient is commonly expressed in units of _________27. Absorption is caused by _________28. ____ damage effects depend on the energy of the ionizing particles or rays, the radiation flux and the fluence is29. The higher the radiation level, the attenuation will be ________30. Impurity absorption losses occurs because of _____________31. ______ occurs when a photon interacts with an electron in the valence band and excites it to higher

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energy level32. ɗ Tmod = _______________

33. A fiber with a given index profile α will exhibit different pulse spreading according to the source wavelength used is generally called ___________34. Pulse distortion will increase less rapidly after a certain initial length of fiber because of ________35. ______ method to reduce fiber dispersion by spreading the dispersion minimum out over a wide range36. The cladding portion next to the core has s lower index than the outer cladding region is known as ____37. The cutoff wavelength of the first higher order mode is _________38. Scattering is associated with ____________39. 1 rad(Si) = ______40. When the material is in a perfect state with no density variations, impurities, material inhomogeneities is called __________

UNIT –III

Fiber Optical Sources and Coupling

1. In a pure crystal at low temperature, the conduction band is completely _______ of electrons2. In a pure crystal at low temperature, the valence band is completely _______ of electrons3. The simplest recombination process of electrons and holes, having the same momentum value is called __4. The conduction band minimum and the valence band maximum energy levels occurs at different values of momentum is called __________5. The spacing between the atoms or groups of atoms is called the _________6. The _____ method creates regions of high resistivity, thus restricting the current to a narrow path between

these regions7. The average time that the photon resides in the lasing cavity before being lost by absorption is called ___8. The _____ is a function of the semiconductor band structure and the carrier concentration9. When any losses that are speckle pattern dependent are present in a link is _________10. Intensity fluctuations in the longitudinal modes of a laser diode is caused by _______11. The coupled efficiency of a fiber is defined as ________12. A device with a short length of optical fiber, attached in an optimum power coupling configuration is __13. The reflection coefficient is the ratio of ________14. R = (n1-n / n1+n)2 , Where R is the ___________15. If the source emitting area is larger than the fiber core area then the optical power coupled into fiber is _16. A permanent bond connection of fiber is generally referred to as a ________17. A demountable joint connection of fiber is known as _________18. Edge emitting diode have an emission pattern , in the plane perpendicular to active region, has a FWHM of _______19. Edge emitting diode have an emission pattern , in the plane parallel to the junction, has a FWHM of __20. The fiber to fiber coupling loss LF is given in terms of Ηf _____21. When the two axes form an angle so that the fiber end faces are no longer parallel is called _____22. The principal light sources used for fiber optic communications applications are ____23. Heterojunction structured semiconductors are ________24. A ________ consists of two adjoining semiconductor materials with different band-gap energies25. The optical output from an LED is _____26. The optical output from an LASER is _________27. LEDs have been employed in high speed local area applications in which one wants to transmits several

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wavelengths on the same fiber, this technique is called ________28. The isotropic pattern from a surface emitter is called a ________29. The peak output power occurs at 810nm, The width of the spectral pattern at its half power point is known as __________30. FWHM stands for _______31. The fraction of the electron –hole pair that recombine radiatively is known as _______32. The ratio of the photons emitted from the LED to the number of internally generated photons _______33. Stimulated emission will exceed absorption only if the population of the excited states is greater than that of the ground state. This condition is called ________34. The extrapolation of the lasing region of the power versus current curve is defined as _________35. The central region has a higher refractive index than the outer regions _______ index36. The central region of the active layer has a lower refractive index than the outer regions ____ index37. In fiber transmission applications an LED must have a __________38, Surface emitters and edge emitters are the two basic configurations of __________39. The Plane of the active light emitting region is oriented perpendicular to the axis of the fiber __ emitters40. The sources of the incoherent light, and two guiding layers is _________

UNIT –IV

Fiber Optical Receiver1. The important characteristics of photo detector are its ________2. Responsivity R =_______________________3. In most photodiodes the power level falling on the detector at a given photon energy is independent of__4. Avalanche photodiode ______ receiver sensitivity5. The carrier multiplication mechanisms is called___________________6. A commonly used structure for achieving carrier multiplication with very little excess noise is the___7. To generate a large signal power, the photo detector must have a _____ Quantum efficiency8. The photo detector and amplifier should be kept as ________ as possible.9. The sensitivity of a photo detector in optical fiber communication system is describable in terms of___10. The statistical nature of the production and the collection of photo electrons generates the_____11. For PIN photodiode, M (multiplication) and F(M) noise figure are________12. _____ photo detectors involve the conversion of photons to heat13. A photocathode and the electron multiplier packaged in a vacuum tube are capable of very high gain and very low noise is____14. The current flow in an external circuit, with one electron flowing for every carrier pair generated is called______________15. The time taken by an electron or hole to recombine is known as_______________16. The cutoff wavelength for Si in PIN photodector is about______________17. The cutoff wavelength for Ge in PIN photodector is about__________________18. The discrete nature of current flow in the device causes______________19. The unwanted noise from atmosphere and equipment-generated is called_____________20. ISI stands for___________________21. BER =________________22. The minimum received optical power required for a specified BER performance in a digital system is called_________________23. The Rise time of Ge for avalanche photodiodes is___________________24. The bandwidth of InGaAs for PIN photodiodes________________

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25. The mean square value ‹i2DS› = σ2

DS = 2qILB is______________26. The detector load resistor and the active elements of the amplifier circuitry dominates noises in___27. The thermal noise is less important and the photo detector noises usually dominate in__________28. To achieve a high quantum efficiency, the depletion layer width W must be much larger than____29. The responsivity of silicon for PIN photodiodes is___________30. The criterion for measuring the performance of a digital communication system is the ___Probability.31. Electrons or holes which are thermally generated in the pn junction of the photo diode gives raise to___32. The current which is dependent on surface defects, cleanliness, bias voltage, and surface area is______33. In normal usage, the _______ is operated in fully depleted mode34. The configuration, where boron and silicon are used as a dopants for silicon is______35. The average number of electron-hole pairs created by a carrier per unit distance traveled is called the___36. Electron ionization rate is denoted with _______________37. Hole ionization rate is denoted with____________38. The ratio k =______________39. The noise caused by spontaneous fluctuations of current or voltage in electric circuits is__________40. The random motion of electrons in a conductor generates______________

UNIT –V

Design of Analog &Digital Systems& WDM Concepts1. Parity check codes is used to _____________________2. Digital receiver performance is evaluated by__________________3. A simple fidelity criteria for analog receiver is the evaluation of ________4. ______ is required in analyzing an optical fiber link5. _________ coding , when 1 and 0 are to b transmitted, signal occupies logic high level and logic low level respectively 6. Bit error rate of optical receiver normally varies between___________ 7. _________ analysis determines the power margin between optical transmitter output and receiver sensitivity 8. BER is defined as _____________ 9. What are the error correction schemes______________ 10. CRC is a type of________ 11. _______analysis determines the dispersion limitations of the optical fiber link12. For RZ format, maximum bit rate is given by_______13. Reduction in SNR is known as _____________ 14. ___________noise occurs when speckle pattern dependent losses are present in fiber link 15. Delivering information from source to destination with minimum error is called as__________ 16. _______ occurs due to intensity fluctuations in longitudinal modes of multimode fibers 17. In _____coding, 1 is encoded by high to low pulse and 0 is encoded by low to high pulse 18. For NRZ format, maximum bit rate is given by ______ 19. Error control is done by means of________ 20. Parity check code is a common way to detect _________ 21. WDM means __________ 22. _____can be increased by means of multiplexing technique23. _______technique operates in optical domain24. ______components does not require any external control on their operation25. _______means transmission of multiple signals at a given time26. _______ components require external control on their operation

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27. ______ is the passive component 28. ______ is used to separate the optical signal into appropriate detection channels for signal processing29. In WDM ________is used to combine and separate individual wavelengths30. Degree of interaction between the guides depends on__________ 31. _______ allows very narrow wavelength band to be transmitted and all others are reflected 32. _________is a active component 33. Numbers of couplers required to from N X N star coupler ___________ 34. Excess loss is defined as _____________ 35. _________device that allows light to pass along a fiber in only one direction 36. _______ multiplexing technique is used to transmits analog signals 37. Dielectric Thin Film filters act as _____an optical fiber link 38. Diffraction grating is classified into________ 39. _________ are removable joints which allows easy, fast manual coupling and uncoupling of fibers 40. __________ is a device in which light entering at any particular port travels around the circulator and exit at the next port

Prepared by: Dr.P.G.Kuppusamy & Y.Murali

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