## [MCQ’s] Optical Communication

#### Module 01

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
Explanation: The grating period is denoted by Λ. It is given by-
Λ = λB/ 2n
Where λB = 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
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
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
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
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
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
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
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%
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
Explanation: The number of stages M within the ladder design is given by 2M=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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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 _____________
b) Node transfer
c) Signal control
d) Amplification
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
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

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
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
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
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
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
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
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
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
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
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
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
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.

#### Module 03

1. SONET stands for
a) synchronous optical network
b) synchronous operational network
c) stream optical network
d) shell operational network

2. In SONET, STS-1 level of electrical signalling has the data rate of
a) 51.84 Mbps
b) 155.52 Mbps
c) 466.56 Mbps
d) none of the mentioned

3. The path layer of SONET is responsible for the movement of a signal
a) from its optical source to its optical destination
b) across a physical line
c) across a physical section
d) none of the mentioned

4. The photonic layer of the SONET is similar to the _____ of OSI model.
a) network layer
c) physical layer
d) none of the mentioned

5. In SONET, each synchronous transfer signal STS-n is composed of
a) 2000 frames
b) 4000 frames
c) 8000 frames
d) 16000 frames

6. Which one of the following is not true about SONET?
a) frames of lower rate can be synchronously time-division multiplexed into a higher-rate frame
b) multiplexing is synchronous TDM
c) all clocks in the network are locked to a master clock
d) none of the mentioned

7. A linear SONET network can be
a) point-to-point
b) multi-point
c) both (a) and (b)
d) none of the mentioned

8. Automatic protection switching in linear network is defined at the
a) line layer
b) section layer
c) photonic layer
d) path layer

9. A unidirectional path switching ring is a network with
a) one ring
b) two rings
c) three rings
d) four rings

10. What is SDH?
a) SDH is similar standard to SONET developed by ITU-T
b) synchronous digital hierarchy
c) both (a) and (b)
d) none of the mentioned

11) A local telephone network is an example of a _______ network
a) Packet switched
b) Circuit switched
c) both of the mentioned
d) none of the mentioned

12) Most packet switches use this principle
a) Stop and wait
b) Store and forward
c) Both of the mentioned
d) None of the mentioned

13) If there are N routers from source to destination, total end to end delay in sending packet P(L->number of bits in the packet R-> transmission rate)
a) N
b) (N*L)/R
c) (2N*L)/R
d) L/R

14) Method(s) to move data through a network of links and switches
a) Packet switching
b) Circuit switching
c) Line switching
d) Both a and b

15) The resources needed for communication between end systems are reserved for the duration of session between end systems in ________
a) Packet switching
b) Circuit switching
c) Line switching
d) Frequency switching

16) As the resouces are reserved between two communicating end systems in circuit switching, this is achieved
a) authentication
b) guaranteed constant rate
c) reliability
d) store and forward

17) In _________ resources are allocated on demand.
a) packet switching
b) circuit switching
c) line switching
d) frequency switching

18) Identify the incorrect statement
a) FTP stands for File Transfer Protocol
b) FTP uses two parallel TCP connections
c) FTP sends its control information in-band
d) FTP sends exactly one file over the data connection

19) If 5 files are transfered from server A to client B in the same session. The number of TCP connection between A and B is
a) 5
b) 10
c) 2
d) 6

20. A remote procedure is uniquely identified by
a) program number
b) version number
c) procedure number
d) all of the mentioned

21. The network layer concerns with
a) bits
b) frames
c) packets
d) none of the mentioned

22. Which one of the following is not a function of network layer?
a) routing
b) inter-networking
c) congestion control
d) none of the mentioned

23. The 4 byte IP address consists of
c) both (a) and (b)
d) none of the mentioned

24. In virtual circuit network each packet contains
a) full source and destination address
b) a short VC number
c) both (a) and (b)
d) none of the mentioned

25. Which one of the following routing algorithm can be used for network layer design?
a) shortest path algorithm
b) distance vector routing
d) all of the mentioned

26. Multidestination routing
a) is same as broadcast routing
b) contains the list of all destinations
c) data is not sent by packets
d) none of the mentioned

27. A subset of a network that includes all the routers but contains no loops is called
a) spanning tree
b) spider structure
c) spider tree
d) none of the mentioned

28. Which one of the following algorithm is not used for congestion control?
a) traffic aware routing
d) none of the mentioned

29. The network layer protocol of internet is
a) ethernet
b) internet protocol
c) hypertext transfer protocol
d) none of the mentioned

30. ICMP is primarily used for
a) error and diagnostic functions
c) forwarding
d) none of the mentioned

31. SONET stands for ___________
a) synchronous optical network
b) synchronous operational network
c) stream optical network
d) shell operational network
Explanation: SONET stands for synchronous optical network. Frame relay uses SONET to physically transmit data frames over a Frame Relay network as SONET is cheaper and provides better network reliability than other carriers.

32. In SONET, STS-1 level of electrical signalling has the data rate of _________
a) 51.84 Mbps
b) 155.52 Mbps
c) 2488.320 Mbps
d) 622.080 Mbps
Explanation: STS-1 level provides the data rate of 51.84 Mbps, STS-3 provides a data rate of 155.52 Mbps, STS-12 provides a data rate of 622.080 Mbps and STS-48 provides a data rate of 2488.320 Mbps.

33. The path layer of SONET is responsible for the movement of a signal _________
a) from its optical source to its optical destination
b) across a physical line
c) across a physical section
d) back to its optical source
Explanation: The path layer in SONET is responsible for finding the path of the signal across the physical line to reach the optical destination. It is ideally expected to find the shortest and the most reliable path to the destination.

34. The photonic layer of the SONET is similar to the __________ of OSI model.
a) network layer
c) physical layer
d) transport layer
Explanation: The photonic layer in SONET is like the physical layer of the OSI model. It is the lowest layer among the four layers of SONET namely the photonic, the section, the line, and the path layers.

35. In SONET, each synchronous transfer signal STS-n is composed of __________
a) 2000 frames
b) 4000 frames
c) 8000 frames
d) 16000 frames
Explanation: SONET defines the electrical signal as STS-N (Synchronous Transport Signal Level-N) and the optical signal as OC-N (Optical Carrier Level-N). The building block of SONET is the STS-1/OC-1 signal, which is based on an 8-kHz frame rate and operates at 51.84 Mbps.

36. Which one of the following is not true about SONET?
a) frames of lower rate can be synchronously time-division multiplexed into a higher-rate frame
b) multiplexing is synchronous TDM
c) all clocks in the network are locked to a master clock
d) STS-1 provides the data rate of 622.080Mbps
Explanation: In SONET, STS-N stands for Synchronous Transport Signal Level-N. STS-1 level provides the data rate of 51.84 Mbps, and STS-12 provides a data rate of 622.080 Mbps.

37. A linear SONET network can be ________
a) point-to-point
b) multi-point
c) both point-to-point and multi-point
d) single point
Explanation: Synchronous Optical Network (SONET) is basically an optical fiber point-to-point or ring network backbone that provides a way to accommodate additional capacity as the needs of the organization increase to multipoint networks.

38. Automatic protection switching in linear network is defined at the _______
a) line layer
b) section layer
c) photonic layer
d) path layer
Explanation: The Line layer in SONET operates like the data link layer in the OSI model and it is responsible for the movement of signal across a physical line. The Synchronous Transport Signal Mux/Demux and Add/Drop Mux provide the Line layer functions.

39. A unidirectional path switching ring is a network with __________
a) one ring
b) two rings
c) three rings
d) four rings
Explanation: One ring is used as the working ring and other as the protection ring in which each node is connected to its respective adjacent nodes by two fibers, one to transmit, and one to receive.

40. What is SDH?
a) sdh is similar standard to SONET developed by ITU-T
b) synchronous digital hierarchy
c) sdh stands for synchronous digital hierarchy and is a similar standard to SONET developed by ITU-T
d) none of the mentioned
Explanation: SDH is a standard that allows low bit rates to be combined into high-rate data streams and as it is synchronous, each individual bit stream can be embedded into and extracted from high-rate data streams easily.

41.SONET defines a hierarchy of electrical signaling levels called
a.Synchronous Transport System
b.Synchronous Transport Station
c.Synchronous Transport Signals
d.Synchronous Transport Solution

42.In Sonet network, a switch in a network mesh is called a
a.Cross-Connect
b.Cross-Switch
c.Cross-Communication
d.Cross-Cells

43.System Transport Signal (STS) multiplexer multiplexes signals from multiple sources and creates
a.Optical Network
b.Optical Signal
c.Optical device
d.None of the Above

44.Another alternative switching ring in a SONET ring network is
a.UPSR
b.BLSR
d.MPSR

45.In Sonet Network, a point-to-point network is normally made of an
a.STS multiplexer
b.STS demultiplexer
c.Regenerators

46.Multiplexing is synchronous
a.FDM
b.WDM
c.TDM
d.CDMA

47.One problem with ring networks is the lack of
a.Availability
b.Compatibility
c.Scalability
d.Visibility

48.The SONET standard includes four functional
a.Systems
b.Stations
c.Layers
d.Orbits

49.SONET defines Automatic Protection Switching (APS), to create protection against failure in
a.Multipoint Network
b.Ring Network
c.Mesh Networks
d.Linear Networks

50.In STS Multiplexing, concatenated signals carrying
a.44 ATM Data
b.44 ATM Signals
c.44 ATM Cells
d.44 ATM Frames

#### Module 04

1. Which of the following is used to provide wavelength signal service among the nodes?
a) Regularization
b) Optical enhancing
c) Hopping
d) Pulse breakdown
Explanation: The optical layer is dependent on wavelength. The entire physical interconnected network provides wavelength signal service among the nodes using hopping technique.

2. How many types of hopping are present?
a) Two
b) One
c) Three
d) Four
Explanation: There are two types of hopping. They are single hop and multihop. These techniques provide wavelength dependent service for interconnected physical network among the nodes.

3. How many switching layers are possessed by MG-OXC?
a) Two
b) Three
c) One
d) Six
Explanation: An MG-OXC has three switching layers. They are wavelength cross-connect (WXC), waveband cross-connects (BXC), and fiber cross-connects (FXC). These layers help to terminate the wavebands and individual wavelength channels.

4. _____________ supports a great number of wavelength channels and reduces the number of switches within the optical network.
a) Waveband switching
b) Optical remuneration
c) Optical genesis
d) Wavelength multiplexing
Explanation: Waveband switching reduces the number of ports within the optical network. It reduces the complexity of numerous wavelength-driven channels and makes it efficient.

5. Individual wavelength channels and wavebands are terminated through ________________ layers.
a) WXC and PXC
b) WXC and FXC

Explanation: The individual wavelength channels are terminated and the terminated waveband is then de-multiplexed. The de-multiplexing is in the form of individual channels which are sent to WXC layer as inputs.

6. The routing and wavelength assignment problem addresses the core issue of _____________
a) Traffic patterns in a network
c) Wavelength continuity constraint
d) Design problem
Explanation: The routing and wavelength assignment problem includes selecting a suitable path and allocating an available wavelength. These problems fall into two categories of sequential or combinational selections.

7. How many techniques of implementation are there for routing wavelength assignment (RWA)?
a) Two
b) Six
c) Three
d) Four
Explanation: The implementation of RWA can be static and dynamic. This depends on the traffic patterns in the network. Static RWA techniques are semi-permanent and dynamic RWA techniques are random in nature.

8. ____________ deals with establishing the light path in frequently varying traffic patterns.
a) Wavelength routing
b) Wavelength multiplexing
c) Static RWA
d) Dynamic RWA
Explanation: In dynamic RWA, the traffic patterns are not known. Thus, the connection requests are initiated in random fashion. Its random nature depends on the network state at the time of request.

9. Static RWA problem is also known as _____________
a) Routing problem
b) Virtual topology problem
c) Static wavelength problem
d) Light path problem
Explanation: Static RWA problem refers to the connection problems which remain connected for a smaller duration of time. Thus, network resources are assigned to each connection. It is also called as virtual topology design problem.

10. The ___________ provides information about the physical path and wavelength assignment for all active light paths.
a) Network state
b) RWA
c) LAN topology
d) Secluded communication protocol
Explanation: The physical path i.e. route is associated with the routing problem. Each connection is provided with network resources to reduce complexity in functioning. The network state is basically required to provide information related to routing and assignment problems.

11. ________________ plays an important role in determining the blocking probability of a network.
a) CGA algorithm
b) Semi-pristine environment
c) RWA algorithm
d) Pass key protocol
Explanation: RWA algorithm’s efficiency is calculated on the basis of no blocking or lowest blocking probability. It also provides the information about the availability of the path between the source and destination.

12. Wavelength assignment in RWA is independent on the network topology.
a) True
b) False