1. 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.
a) 0.51 μm
b) 0.58 μm
c) 0.61 μm
d) 0.49 μm
Answer: a
Explanation: The grating period is denoted by Λ. It is given by-
Λ = λ_B/ 2n
Where λ_B = wavelength
n = refractive index.

2. It is a passive device which allows the flow of optical signal power in only one direction and preventing reflections in the backward direction.
a) Fiber slice
b) Optical fiber connector
c) Optical isolator
d) Optical coupler
Answer: c
Explanation: Ideally, an optical isolator transmits the signal power in the desired forward direction. Material imperfections in the isolator medium generate backward reflections. Optical isolators can be implemented by using FBG.

3. Which feature of an optical isolator makes it attractive to use with optical amplifier?
a) Low loss
b) Wavelength blocking
c) Low refractive index
d) Attenuation
Answer: b
Explanation: Optical isolators are made using FBGs. Since FBGs are wavelength dependent, the optical isolators can be designed to allow or block the optical signal at particular wavelength. The wavelength blocking feature makes the optical isolator a very attractive device for use with optical amplifier in order to protect them from backward reflections.

4. Magneto-optic devices can be used to function as isolators.
a) True
b) False
Answer: a
Explanation: Magneto-optic devices use the principle of Faraday rotation. It relates the TM mode characteristics and polarization state of an optical signal with its direction of propagation. The rotation of polarization plane is proportional to the intensity of component of magnetic field in the direction of optical signal. Therefore, it is possible to block and divert an optical signal using magnetic properties which is a function of an isolator.

5. How many implementation methods are available for optical isolators?
a) One
b) Four
c) Two
d) Three
Answer: d
Explanation: Optical isolators can be implemented using three techniques. These are as follows:
-By using FBGs
-By using magnetic oxide materials
-By using semiconductor optical amplifiers (SOAs).

6. A device which is made of isolators and follows a closed loop path is called as a ____________
a) Circulator
b) Gyrator
c) Attenuator
d) Connector
Answer: a
Explanation: Isolator can be connected together to form multiport devices. A circulator is formed from isolators connected together to form a closed circular path. In circulator, the signal continues to travel in closed loop and does not get discarded unlike isolator.

7. The commercially available circulators exhibit insertion losses around ________________
a) 2 dB
b) 0.7 dB
c) 0.2 dB
d) 1 dB
Answer: d
Explanation: A number of isolators can be used to implement a circulator. However, as the number of ports increases, the device complexity increases. Hence, three-or four-port circulators are used for optical interconnection with insertion losses around 1 dB and high isolation in the range of 40-50dB.

8. A combination of a FBG and optical isolators can be used to produce non-blocking optical wavelength division add/draw multiplexers.
a) True
b) False
Answer: b
Explanation: Optical wavelength divisions add/draw multiplexers can be produced by a combination of a FBG and a circulator. Non-blocking NXM optical wavelengths divisions add/draw multiplexer is produced where N and M denotes the number of wavelength channels and add/drop channels.

9. 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?
a) 42%
b) 46%
c) 52%
d) 45%
Answer: d
Explanation: Split ratio indicates the percentage division of optical power between the outputs ports. It is given by
Split ratio = [P₃/(P₃+P₄)]*100%
Where P₃ and P₄ are output powers at ports 3 and 4 respectively.

10. How many manufacturing methods are used for producing multimode fiber star couplers?
a) Two
b) One
c) Three
d) Five
Answer: a
Explanation: The manufacturing methods of star couplers are mixer-rod technique and FBT technique. In the mixer-rod method, a thin platelet of glass is employed, which mixes light from one fiber, dividing it among the outgoing fibers. FBT method involves twisting, heating and pulling of fiber

11. When considering source-to-fiber coupling efficiencies, the ________ is an important parameter than total output power.
a) Numerical aperture
b) Radiance of an optical source
c) Coupling efficiency
d) Angular power distribution
Answer: b
Explanation: Radiance is the optical power radiated into a unit solid angle per unit emitting surface area. Since this optical power is dependent on radiance, radiance is much important factor than optical power.

12. It is a device that distributes light from a main fiber into one or more branch fibers.
a) Optical fiber coupler
b) Optical fiber splice
c) Optical fiber connector
d) Optical isolator
Answer: a
Explanation: Nowadays, requirements to divide combined optical signals for applications are increasing. Optical fiber coupler is one such device that is used for dividing and combining optical signals. It is generally used in LANs, computer networks etc.

13. Optical fiber couplers are also called as ________________
a) Isolators
b) Circulators
c) Directional couplers
d) Attenuators
Answer: c
Explanation: Optical fiber couplers are passive devices. The power transfer in couplers takes place either through the fiber core cross-section by butt jointing the fibers or by using some form of imaging optics between the fibers. It distributes light from one fiber to many fibers and hence it is also called as a directional coupler.

14. How many types of multiport optical fiber couplers are available at present?
a) Two
b) One
c) Four
d) Three
Answer: d
Explanation: Multiport optical fiber couplers are subdivided into three types. These are three and four port couplers, star couplers and wavelength division multiplexing (WDM) couplers. These couplers distribute light among the branch fibers with no scattering loss.

15. The optical power coupled from one fiber to another is limited by ____________
a) Numerical apertures of fibers
b) Varying refractive index of fibers
c) Angular power distribution at source
d) Number of modes propagating in each fiber
Answer: d
Explanation: When two fibers are coupled to each other, the optical power is limited by number of modes propagating in each fiber. For example, when a fiber propagating with 500 modes is connected to a fiber that propagates only 400 modes, then at maximum, only 80% of power is coupled into the other fiber.

16. ________ couplers combine the different wavelength optical signal onto the fiber or separate the different wavelength optical signal output from the fiber.
a) 3-port
b) 2*2-star
c) WDM
d) Directional
Answer: c
Explanation: WDM coupler is abbreviated as wavelength division multiplexing coupler. It is a category of multiport optical fiber couplers. It is designed to permit a number of different peak wavelength optical signals to be transmitted in parallel on a single fiber.

17. How many fabrication techniques are used for 3 port fiber couplers?
a) One
b) Two
c) Three
d) Four
Answer: b
Explanation: There are two fabrication techniques available for three port couplers. First is a lateral offset method which relies on the overlapping of the fiber end faces and the other is the semi-transparent mirror method. Using these techniques, three port couplers with both multimode and single-mode fibers can be fabricated.

18. Which is the most common method for manufacturing couplers?
a) Wavelength division multiplexing
b) Lateral offset method
c) Semitransparent mirror method
d) Fused bi-conical taper (FBT) technique
Answer: d
Explanation: The FBT technique is basic and simple. In this technique, the fibers are generally twisted together and then spot fused under tension such that the fused section is elongated to form a bi-conical taper structure. A three port coupler can be obtained by removing one of the input fibers.

19. Couplers insertion loss is same as that of excess loss.
a) True
b) False
Answer: b
Explanation: Excess loss is defined as the ratio of input power to output power. The insertion loss is defined as the loss obtained for a particular port-to-port optical path. Thus, the insertion loss and excess loss are different in nature.

10. A four-port multimode fiber FBT coupler has 50 μW optical 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.
a) 0.22 dB
b) 0.33 dB
c) 0.45 dB
d) 0.12 dB
Answer: a
Explanation: Excess loss is a ratio of power input to power output of the fiber and it is given by Excess loss = 10log₁₀ P₁/(P₃+P₄)
WhereP₁, P₃, P₄ = output power at ports 1,3 and 4 resp.

21. Demountable fiber connectors are more difficult to achieve than optical fiber splices.
a) True
b) False
Answer: a
Explanation: Fiber connectors must maintain tolerance requirements similar to splices in order to couple light efficiently between the fibers. Also, fiber connectors must accomplish this in a removable fashion. The connector design must allow repeated connection and disconnection without any problems of fiber alignment.

22. What is the use of an index-matching material in the connector between the two jointed fibers?
a) To decrease the light transmission through the connection
b) To increase the light transmission through the connection
c) To induce losses in the fiber
d) To make a fiber dispersive
Answer: b
Explanation: The index-matching material used might be epoxy resin. It increases the light transmission through the connection while keeping dust and dirt from between the fibers. It also provides optimum optical coupling.

23. How many categories of fiber connectors exist?
a) One
b) Three
c) Two
d) Four
Answer: c
Explanation: Fiber connectors are separated into two broad categories. They are butt-jointed connectors and expanded beam connectors. Butt-jointed connectors rely upon alignment of the two fiber ends butted to each other whereas expanded beam connectors uses interposed optics at the joint.

24. The basic ferrule connector is also called as _____________
a) Groove connector
b) Beam connector
c) Multimode connector
d) Concentric sleeve connector
Answer: d
Explanation: The basic ferrule connector is the simplest connector. The ferrules are placed in an alignment sleeve within the connector. The alignment sleeve is concentric which allows the fiber ends to be butt-jointed.

25. What is the use of watch jewel in cylindrical ferrule connector?
a) To obtain the diameter and tolerance requirements of the ferrule
b) For polishing purposes
c) Cleaving the fiber
d) To disperse a fiber
Answer: a
Explanation: Ferrule connectors have a watch jewel in the ferrule end face. It is used instead of drilling of the metallic ferrule end face which takes time. It is used to obtain close diameter and tolerance requirements of the ferrule end face whole easily.

26. The concentricity errors between the fiber core and the outside diameter of the jeweled ferrule are in the range of ___________ with multimode step-index fibers.
a) 1 to 3μm
b) 2 to 6μm
c) 7 to 10μm
d) 12 to 20μm
Answer: b
Explanation: The fiber alignment accuracy of the basic ferrule connector is dependent on the ferrule hole into which the fiber is inserted. The concentricity errors in the range of 2 to 6μm gives insertion losses in the range 1 to 2dB with multimode step index fibers.

27. The typical average losses for multimode graded index fiber and single mode fiber with the precision ceramic ferrule connector are _____________ respectively.
a) 0.3 and 0.5 dB
b) 0.2 and 0.3 dB
c) 0.1 and 0.2 dB
d) 0.4 and 0.7 dB
Answer: b
Explanation: Unlike metal and plastic components, the ceramic ferrule material is harder than the optical fiber. Thus, it is unaffected by grinding and polishing process. This factor enables to provide the low-loss connectors which have low losses as low as 0.2 and 0.3 dB in case of optical fibers.

28. Bi-conical ferrule connectors are less advantageous than cylindrical ferrule connectors.
a) FalseStat
b) True
Answer: a
Explanation: Cylindrical and bi-conical ferrule connectors are assembled in housings to form a multi-fiber configuration. The force needed to insert multiple cylindrical ferrules can be large when multiple ferrules are involved. The multiple bi-conical ferrule connectors are more advantageous as they require less insertion force.

29. In connectors, the fiber ends are separated by some gap. This gap ranges from ____________
a) 0.040 to 0.045 mm
b) 0.025 to 0.10 mm
c) 0.12 to 0.16 mm
d) 0.030 to 0.2mm
Answer: b
Explanation: In connectors, gaps are introduced to prevent them from rubbing against each other and becoming damaged during connector fixing/engagement. The gap ranges from 0.025 to 0.10 mm so as to reduce the losses below 8dB for a particular diameter fiber say 50μm.

30. 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.
a) 1.9 dB
b) 1.4 dB
c) 0.9 dB
d) 1.1 dB
Answer: d
Explanation: The number of stages M within the ladder design is given by 2^M=16. Hence M=4.
Thus, excess loss is given by-
Excess loss = (M×loss in each 3-port coupler) + (Number of splices×Loss in each stage)
Where number of splices = 3 (as the value of M is equal to 4).

31. A permanent joint formed between two different optical fibers in the field is known as a ____________
a) Fiber splice
b) Fiber connector
c) Fiber attenuator
d) Fiber dispersion
Answer: a
Explanation: The jointing of two individual fibers is called as fiber splicing. It is used to establish long-haul optical fiber links by joining two small length fibers.

32. How many types of fiber splices are available?
a) One
b) Two
c) Three
d) Four
Answer: b
Explanation: Splices are divided into two types depending upon the splicing technique used. These are fusion splicing (welding) and mechanical splicing.

33. The insertion losses of the fiber splices are much less than the Fresnel reflection loss at a butted fiber joint.
a) True
b) False
Answer: a
Explanation: The Fresnel reflection loss is usually more because there is no large step change in refractive index with the fusion splice as it forms a continuous fiber connection. Also, some method of index matching tends to be utilized with mechanical splices.

34. What is the main requirement with the fibers that are intended for splicing?
a) Smooth and oval end faces
b) Smooth and square end faces
c) Rough edge faces
d) Large core diameter
Answer: b
Explanation: A curved mandrel is used which cleaves the fiber to achieve end preparation. The edges must be smooth and have square face at the end for splicing purpose.

35. In score and break process, which of the following is not used as a cutting tool?
a) Diamond
b) Sapphire
c) Tungsten carbide
d) Copper
Answer: d
Explanation: The score and break process is also called as scribe and break. It involves the scribing of the fiber surface under tension with a cutting tool. Copper is not used as a cutting tool.

36. 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 ____________
a) Mechanical splicing
b) Fusion splicing
c) Melting
d) Diffusion
Answer: b
Explanation: Fusion splicing is also called as welding. It refers to the welding of two fiber ends. It is essential for fusion splicing that the fiber ends are adequately positioned and aligned in order to achieve good continuity of the transmission medium at the junction point.

37. Which of the following is not used as a flame heating source in fusion splicing?
a) Microprocessor torches
b) Ox hydric burners
c) Electric arc
d) Gas burner
Answer: d
Explanation: Micro-plasma torches uses argon and hydrogen and alcohol vapor. The most widely used heating source is an electric arc. Thus, gas burner is not used in fusion splicing.

38. 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 ____________
a) Pre-fusion
b) Diffusion
c) Crystallization
d) Alignment
Answer: a
Explanation: Pre-fusion involves rounding of fiber ends. It removes the requirement for fiber end preparation which has a distinct advantage in the field environment. It is utilized with multimode fibers giving average splice losses of 0.09dB.

39. _____________ is caused by surface tension effects between the two fiber ends during fusing.
a) Pre-fusion
b) Diffusion
c) Self-alignment
d) Splicing
Answer: c
Explanation: The two fiber ends are close but not aligned before fusion. During fusion, the surface tension affects the fiber ends to get aligned. After fusion, they are aligned in such a way that a transmission medium can get a good continuity.

40. Average insertion losses as low as _________ have been obtained with multimode graded index and single-mode fibers using ceramic capillaries.
a) 0.1 dB
b) 0.5 dB
c) 0.02 dB
d) 0.3 dB
Answer: a
Explanation: Mechanical techniques for splicing involve the use of an accurately produced rigid tube in which fiber ends are permanently bonded. It utilizes a ceramic capillary in which an epoxy resin is injected through a transverse bore to provide mechanical sealing and index matching. This technique which uses ceramic capillaries provides insertion losses as low as 0.1dB.

41. Each stage of information transfer is required to follow the fundamentals of ____________
a) Optical interconnection
b) Optical hibernation
c) Optical networking
d) Optical regeneration
Answer: c
Explanation: Optical networking uses optical fiber as a transmission medium. It provides a connection between users to enable them to communicate with each other by transporting information from a source to a destination.

42. ____________ is a multi-functional element of optical network.
a) Hop
b) Optical node
c) Wavelength
d) Optical attenuation
Answer: b
Explanation: An optical node is a multi-functional element which acts as a transceiver unit capable of receiving, transmitting and processing the optical signal. The optical nodes are interconnected with optical fiber links.

43. A signal carried on a dedicated wavelength from source to destination node is known as a ___________
a) Light path
b) Light wave
c) Light node
d) Light source
Answer: a
Explanation: A light path is a dedicated path from a source to a destination. The data can be sent over the light paths as soon as connections are set up. A controlling mechanism is present to control the data flow.

44. The fundamentals of optical networking are divided into _______ areas.
a) Two
b) One
c) Four
d) Three
Answer: d
Explanation: The fundamentals divided into three areas contain mainly optical network terminology. The other two areas include functions and types of optical network node and switching elements and the wavelength division multiplexed optical networks.

45. The optical networking fundamentals are _____________ of the transmission techniques.
a) Dependent
b) Independent
c) Similar
d) Dissimilar
Answer: b
Explanation: The optical networking fundamentals include transfer of data. Irrespective of the difference in the transmission techniques, the fiber networking fundamentals remain the same.

46. The network structure formed due to the interconnectivity patterns is known as a ____________
a) Network
b) Struck
c) Topology
d) D-pattern
Answer: c
Explanation: A topology is a combination of patterns interconnected to each other. It provides connection patterns to users at different places. It embarks on the principle of multi-usability.

47. In the __________ topology, the data generally circulates bi-directionally.
a) Mesh
b) Bus
c) Star
d) Ring
Answer: b
Explanation: In a bus topology, data is input via four port couplers. The couplers couples and stations the data bi-directionally and are removed from the same ports.

48. The ring and star topologies are combined in a ________ configuration.
a) Mesh
b) Fringe
c) Data
d) Singular
Answer: a
Explanation: The mesh configuration is a combination of ring and star topologies. It is referred to as full-mesh when each network node is interconnected with all nodes in the network.

49. The full-mesh configuration is complex.
a) False
b) True
Answer: b
Explanation: The full-mesh topology is a combination of two or more topologies. It is often preferred for the provision of either a logical or virtual topology due to its high flexibility and interconnectivity features.

50. How many networking modes are available to establish a transmission path?
a) Three
b) One
c) Two
d) Four
Answer: c
Explanation: There are two networking modes often referred to the networking. These are connection-oriented and connectionless networking modes. These include an end-to-end and bidirectional communication environment between source and destination.

51. Electrical devices in optical network are basically used for _____________
a) Signal degradation
b) Node transfer
c) Signal control
d) Amplification
Answer: c
Explanation: The optical infrastructure in networks constitutes a transparent network in which electronic devices are present. They are basically used for signal control. The other use includes providing interconnection to other networks.

52. Signals are defined as ________________ if their significant instants occur at nominally the same rate, any variation being constrained within specific limits.
a) Plesiochronous
b) Opt-electric
c) Physiometric
d) Opt-immune
Answer: a
Explanation: With any multiplexing strategies, come some setbacks. This includes the differentiation in the frequencies occurring throughout a network. This is called as plesiochronous transmission.

53. The bit stuffing in the plesiochronous digital hierarchy is complex and uneconomic.
a) False
b) True
View Answer

Answer: b
Explanation: The bit stuffing is a complex process as it does not provide individual channel extraction. For individual channel extraction, the whole de-multiplexing procedure is to be performed again. This is both uneconomic and complex.

54. A ____________ digital hierarchy was required to enable the international communications network to evolve in the optical fiber era.
a) Asynchronous
b) Dedicated
c) Seismic
d) Synchronous
Answer: d
Explanation: The plesiochronous digital hierarchy was uneconomic and complex in execution. To reduce the complexity and efficient bit stuffing purpose, a synchronous digital hierarchy was required. It transformed the international communications into an optical fiber era.

55. The standardization towards a synchronous optical network termed SONET commenced in US in _______
a) 1985
b) 1887
c) 2001
d) 1986
Answer: a
Explanation: Synchronous optical network mechanism was efficient and its standardization process mainly started in 1985. Some modifications in the plesiochronous hierarchy were retained and some new features were added in the optical era to achieve efficient bit stuffing.

56. ______________ is a packetized multiplexing and switching technique which combines the benefits of circuit and packet switching.
a) Synchronous mode
b) Asynchronous transfer mode
c) Circuit packet
d) Homogeneous mode
Answer: b
Explanation: ATM transfers the information in fixed size units called cells. Each cell contains the information identifying the source of the transmission. It generally contains less data than packets.

57. The ___________ sits at the top of hierarchy of the OSI layer model.
a) Session layer
b) Transport layer
c) Application layer
d) Data link layer
Answer: c
Explanation: Application layer is the seventh layer and sits at the top of the hierarchy. It provides a means for a user to access information on or utilize the network by receiving a service.

58. The ____________ controls the dialogs between intelligent devices.
a) Physical layer
b) Transport layer
c) Application layer
d) Session layer
Answer: d
Explanation: The session layer is fifth in the OSI layer model. It controls the sessions between the devices and manages the connections between the remote and local application.

59. The network layer looks after the flow and error control mechanism.
a) True
b) False
Answer: b
Explanation: The network layer is the third level in the OSI layer model. It provides procedural and functional method for transferring data sequences from source to destination.

60. The physical layer is located at the bottom of the OSI model.
a) True
b) False
Answer: a
Explanation: The physical layer defines all the electrical, optical and media specifications for devices. Hence, it is located at the bottom of the OSI model. It establishes and terminates the connection between the media devices.

61. In order to access for end-to-end networking of optical channels to transparently convey information, the _____________ is employed in the OTN structure.
a) Presentation layer
b) Session layer
c) OPU
d) OCh layer
Answer: d
Explanation: The OCh stands for optical channel. It provides end-to-end access in networking of optical channels. It includes the multiplexing section to support multi-user networking.

62. An advanced type of reconfigurable OTN is referred to as an _______________
a) Automatic OTN
b) Auto-generated photon
c) Automatically switched optical network
d) Optical reimbursement
Answer: c
Explanation: Automatically switched optical network (ASON) is capable of switching the optical channels automatically when requested. It is specified in the ITU-T Recommendation G.8080 and it is basically a transport layer.

63. The __________ is a network layer that contains both addressing and control information to enable packets to be routed within a network.
a) TCP
b) Internet protocol (IP)
c) UDP
d) SONET/SDH protocol
Answer: b
Explanation: Internet protocol forms a part of the network layer. It controls the logical architecture within the network and addresses the issues accordingly. It routes the packets within a network.

64. The mapping of IP frames in SDH/SONET is accomplished in ___________ stages.
a) Four
b) Two
c) Three
d) One
Answer: c
Explanation: Mapping requires three stages. In the first stage, point-to-point protocol is used. The second and the third stage includes synchronous mapping of data onto the SDH/SONET frame.