2. A GaAs optical source having a refractive index of 3.2 is coupled to a silica fiber having a refractive index of 1.42. Determine Fresnel reflection at interface in terms of percentage.
Correct : D. 14.8%
3. A particular GaAs fiber has a Fresnel reflection magnitude of 17.6% i.e. 0.176. Find the power loss between the source and the fiber?
Correct : C. 0.84 db
4. Two joined step index fibers are perfectly aligned. What is the coupling loss of numerical aperture are NAR= 0.26 for emitting fiber?
Correct : B. -0.010 db
5. Two joined graded index fibers that are perfectly aligned have refractive indices αR=1.93for receiving fiber αE= 2.15 for emitting fiber. Calculate the coupling loss
Correct : A. 0.23 db
6. How many types of misalignments occur when joining compatible fiber?
Correct : D. three
7. Losses caused by factors such as core-cladding diameter, numerical aperture, relative refractive index differences, different refractive index profiles, fiber faults are known as
Correct : A. intrinsic joint losses
8. A step index fiber has a coupling efficiency of 0.906 with uniform illumination of all propagation modes. Find the insertion loss due to lateral misalignment?
Correct : C. 0.42 db
9. A graded index fiber has a parabolic refractive index profile (α=2) and core diameter of 42μm. Estimate an insertion loss due to a 2 μm lateral misalignment when there is index matching and assuming there is uniform illumination of all guided modes only.
Correct : D. 0.080
10. Determine coupling efficiency if the misalignment loss in a graded index fiber is 0.102
Correct : B. 0.898
11. In a single mode fiber, the losses due to lateral offset and angular misalignment are given by 0.20 dB and 0.46 dB respectively. Find the total insertion loss
Correct : A. 0.66 db
12. The intrinsic loss through a multimode fiber joint is independent of direction of propagation. State whether the given statement is true or false
Correct : B. false
13. The expanded beam connectors use ____________ for beam expansion and reduction.
Correct : C. spherical micro-lens
14. Lens-coupled expanded beam connectors exhibit average losses of _________ in case of single mode and graded index fibers.
Correct : B. 0.7 db
15. Sapphire ball lens expanded beam design is successful than spherical lens coupled design. State whether the given statement is true or false.
Correct : A. true
16. The fiber is positioned at the ________ of the lens in order to obtain a collimated beam and to minimize lens-to-lens longitudinal misalignment effects.
Correct : B. focal length
17. ___________ exhibits a parabolic refractive index profile with a maximum at the axis similar to graded index fiber.
Correct : D. grin-rod lens
18. The GRIN-rod lens can produce a collimated output beam with a divergent angle αof between _____________ from a light source situated on, or near to, the opposite lens face.
Correct : A. 1 to 5 degrees
19. In the given equation, if r is the radial distance, n is the refractive index; what does z stands for?
Correct : B. distance along the optical axis
20. The majority of the GRIN-rod lenses have diameters in the range of ____________
Correct : D. 0.5 to 2 mm
21. Which of the following factors does not cause divergence of the collimated beam from a GRIN-rod lens?
Correct : C. refractive index profile
22. GRIN-rod lens connectors have loss characteristics which are independent of the modal power distribution in the fiber. State whether the given statement is true or false.
Correct : A. true
23. A permanent joint formed between two different optical fibers in the field is known as a
Correct : A. fiber splice
24. How many types of fiber splices are available?
Correct : B. two
25. The insertion losses of the fiber splices are much less than the Fresnel reflection loss at a butted fiber joint. State whether the given statement is true or false.
Correct : A. true
26. What is the main requirement with the fibers that are intended for splicing?
Correct : B. smooth and square end faces
27. In score and break process, which of the following is not used as a cutting tool?
Correct : D. copper
28. The heating of the two prepared fiber ends to their fusing point with the application of required axial pressure between the two optical fibers is called as
Correct : B. fusion splicing
29. Which of the following is not used as a flame heating source in fusion splicing?
Correct : D. gas burner
30. Average insertion losses as low as _________ have been obtained with multimode graded index and single-mode fibers using ceramic capillaries.
Correct : A. 0.1 db
31. _____________ are formed by sandwiching the butted fiber ends between a V-groove glass substrate and a flat glass retainer plate.
Correct : B. v-groove splices
32. Mean splice insertion losses of 0.05 dB are obtained using multimode graded index fibers with the Springroove splice. State whether the given statement is true or false.
Correct : A. true
33. Alignment accuracy of the order ___________ is obtained using the three glass rod alignment sleeve.
Correct : C. 0.05 μm
34. In case of multiple fusion, splice losses using an electric arc fusion device with multimode graded index fiber range from
Correct : D. 0.04 to 0.12 db
35. The heating of the two prepared fiber ends to their fusing point with the application of required axial pressure between the two optical fibers is called as
Correct : B. fusion splicing
36. The rounding of the fiber ends with a low energy discharge before pressing the fibers together and fusing with a stronger arc is called as
Correct : A. pre-fusion
37. _____________ is caused by surface tension effects between the two fiber ends during fusing.
Correct : C. self-alignment
38. Mean splice insertion losses of 0.05 dB are obtained using multimode graded index fibers with the Springroove splice. State whether the given statement is true or false.
Correct : A. true
39. When considering source-to-fiber coupling efficiencies, the ________ is an important parameter than total output power.
Correct : B. radiance of an optical source
40. It is a device that distributes light from a main fiber into one or more branch fibers.
Correct : A. optical fiber coupler
41. Optical fiber couplers are also called as ________________
Correct : C. directional couplers
42. How many types of multiport optical fiber couplers are available at present?
Correct : D. three
43. The optical power coupled from one fiber to another is limited by
Correct : D. number of modes propagating in each fiber
44. ________ couplers combine the different wavelength optical signal onto the fiber or separate the different wavelength optical signal output from the fiber.
Correct : C. wdm
45. How many fabrication techniques are used for 3 port fiber couplers?
Correct : B. two
46. The most common method for manufacturing couplers is ____________
Correct : D. fused bi-conical taper (fbt) technique
47. Couplers insertion loss is same as that of excess loss. State whether the given statement is true or false.
Correct : B. false
48. A four-port multimode fiber FBT coupler has 50 μWoptical power launched into port 1. The measured output power at ports 2,3 and 4 are 0.003, 23.0 and 24.5 μW respectively. Determine the excess loss.
Correct : A. 0.22 db
49. A four-port FBT coupler has 60μW optical power launched into port one. The output powers at ports 2, 3, 4 are 0.0025, 18, and 22 μW respectively. Find the split ratio?
Correct : D. 45%
50. How many manufacturing methods are used for producing multimode fiber star couplers?
Correct : A. two
51. Calculate the splitting loss if a 30×30 port multimode fiber star coupler has 1 mW of optical power launched into an input port.
Correct : C. 14.77 db
52. A _____________ coupler comprises a number of cascaded stages, each incorporating three or four-port FBT couplers to obtain a multiport output.
Correct : A. star
53. A number of three-port single-mode fiber couplers are used in the fabrication of a ladder coupler with 16 output ports. The three-port couplers each have an excess loss of 0.2 dB along with a splice loss of 0.1 dB at the interconnection of each stage. Determine the excess loss.
Correct : D. 1.1 db
54. An FBG is developed within a fiber core having a refractive index of 1.30. Find the grating period for it to reflect an optical signal with a wavelength of 1.33μm.
Correct : A. 0.51 μm
55. It is a passive device which allows the flow of optical signal power in only one direction and preventing reflections in the backward direction.
Correct : C. optical isolator
56. Which feature of an optical isolator makes it attractive to use with optical amplifier?
Correct : B. wavelength blocking
57. Magneto-optic devices can be used to function as isolators. State whether the given statement is true or false.
Correct : A. true
58. How many implementation methods are available for optical isolators?
Correct : D. three
59. A device which is made of isolators and follows a closed loop path is called as a ____________
Correct : A. circulator
60. The commercially available circulators exhibit insertion losses around ________________
Correct : D. 1 db
61. A combination of a FBG and optical isolators can be used to produce non-blocking optical wavelength division add/draw multiplexers. State whether the given statement is true or false.
Correct : B. false
62. A device which converts electrical energy in the form of a current into optical energy is called as
Correct : A. optical source
63. How many types of sources of optical light are available?
Correct : C. three
64. The frequency of the absorbed or emitted radiation is related to difference in energy E between the higher energy state E2 and the lower energy state E1. State what h stands for in the given equation?
Correct : B. planck’s constant
65. The radiation emission process (emission of a proton at frequency) can occur in __________ ways.
Correct : A. two
66. Which process gives the laser its special properties as an optical source?
Correct : D. stimulated emission
67. An incandescent lamp is operating at a temperature of 1000K at an operating frequency of 5.2×1014 Hz. Calculate the ratio of stimulated emission rate to spontaneous emission rate.
Correct : B. 1.47×10-11
68. The lower energy level contains more atoms than upper level under the conditions of ________________
Correct : C. thermal equilibrium
69. __________________ in the laser occurs when photon colliding with an excited atom causes the stimulated emission of a second photon.
Correct : A. light amplification
70. A ruby laser has a crystal of length 3 cm with a refractive index of 1.60, wavelength 0.43 μm. Determine the number of longitudinal modes.
Correct : D. 2.2×105
71. A semiconductor laser crystal of length 5 cm, refractive index 1.8 is used as an optical source. Determine the frequency separation of the modes.
Correct : C. 1.6 ghz
72. Doppler broadening is a homogeneous broadening mechanism. State whether the given statement is true or false.
Correct : B. false
73. An injection laser has active cavity losses of 25 cm-1and the reflectivity of each laser facet is 30%. Determine the laser gain coefficient for the cavity it has a length of 500μm.
Correct : D. 49.07 cm-1
74. Longitudinal modes contribute only a single spot of light to the laser output. State whether the given statement is true or false.
Correct : A. true
75. Considering the values given below, calculate the mode separation in terms of free space wavelength for a laser.
Correct : B. 1.6×10-12
76. ____________________ lasers are presently the major laser source for optical fiber communications
Correct : C. injection
77. In Nd: YAG lasers, the maximum doping levels of neodymium is ____________
Correct : B. 1.5 %
78. Which of the following is not a property of Nd: YAG laser that enables its use as an optical fiber communication source?
Correct : D. semiconductors and integrated circuits
79. The Nd: YAG laser has a narrow line-width which is ________________
Correct : A. < 0.01 nm
80. The strongest pumping bands is a four level system of Nd: YAG laser at wavelength of range_________________
Correct : B. 0.75 and 0.81 nm
81. The Nd: YAG laser is costlier than earth-doped glass fiber laser. State whether the following statement is true or false
Correct : A. true
82. It is a resonant cavity formed by two parallel reflecting mirrors separated by a mirror separated by a medium such as air or gas
Correct : D. fabry-perot resonator
83. In a three level system, the threshold power decreases inversely with the length of the fiber gain medium. State whether the given statement is true or false.
Correct : B. false
84. Which of the following co-dopant is not employed by neodymium and erbium doped silica fiber lasers?
Correct : C. nitrogen
85. Dopants levels in glass fiber lasers are generally ___________
Correct : A. low
86. . _______________ fibers include addition of lead fluoride to the core glass in order to raise the relative refractive index.
Correct : D. zblanp
87. The lasing output of the basic Fabry-perot cavity fiber is restricted to between ____________
Correct : B. 5 and 10 nm
88. In Fabry-perot laser, the lower threshold is obtained by
Correct : C. reducing the slope efficiency
89. When did the non-semiconductor laser developed?
Correct : C. 1985
90. Y3Al5 O12 Is a molecular formula for _____________
Correct : D. yttrium-aluminum garnet
91. A perfect semiconductor crystal containing no impurities or lattice defects is called as
Correct : A. intrinsic semiconductor
92. The energy-level occupation for a semiconductor in thermal equilibrium is described by the
Correct : C. fermi-dirac distribution function
93. What is done to create an extrinsic semiconductor?
Correct : B. doping the material with impurities
94. The majority of the carriers in a p-type semiconductor are__________.
Correct : A. holes
95. _________________ is used when the optical emission results from the application of electric field.
Correct : C. electro-luminescence
96. In the given equation, what does p stands for?
Correct : D. crystal momentum
97. Calculate the radioactive minority carrier lifetime in gallium arsenide when the minority carriers are electrons injected into a p-type semiconductor region which has a hole concentration of 1018cm-3. The recombination coefficient for gallium arsenide is
Correct : B. 1.39ns
98. Which impurity is added to gallium phosphide to make it an efficient light emitter?
Correct : C. nitrogen
99. Population inversion is obtained at a p-n junction by
Correct : D. heavy doping of both p-type and n-type material
100. A GaAs injection laser has a threshold current density of 2.5*103Acm-2and length and width of the cavity is 240μmand 110μm respectively. Find the threshold current for the device.