Assignment 9.1:
Chapter 12
1. List five advantages of an optical communications link.
• Enormous Bandwidths
• Low transmission loss
• Immunity to cross talk
• Electrical Isolation
• Small size and weight
2. Define refractive index
• Ratio of the speed of light in free space to its speed in a given material.
3. What are the commonly used wavelengths in fiber optic systems?
• Dense Wavelength division Multiplexing.
4. What are the typical core/cladding sizes (in microns) for multimode fiber?
• The two types of fiber are multimode and single mode. Within these categories, fibers are identified by their core and cladding diameters expressed in microns (one millionth of a meter), e.g. 50/125 micron multimode fiber.
• Most fibers are 125 microns in outside diameter - a micron is one one-millionth of a meter and 125 microns is 0.005 inches- a bit larger than the typical human hair.
5. Define mode field diameter.
• The Diameter base protocol is intended to provide an Authentication, Authorization and Accounting (AAA) framework for applications such as network access or IP mobility.
6. What are the four factors that contribute to attenuation?
• Scattering
• Absorption
• Macrobending
• Microbending
7. What are the three types of dispersion?
• Modal dispersion
• Chromatic dispersion
• Polarization mode dispersion
8. What is a dispersion compensating fiber?
• A fiber that acts like an equalizer, negative dispersion canceling positive dispersion.
9. What is a narrower spectra advantageous in optical systems?
• The light output wavelength spread, or spectrum, of the DL is much narrower than that of LEDs. About 1nm compared with about 40nm for an LED.
10. What is the purpose of an optical attenuator?
• Variable attenuators are typically for temporary use in calibration, testing, and laboratory work but more recently are being used in optical networks, where changes are frequent and require programmability.
11. What is the advantage of fusion splicing over mechanical splicing?
• Mechanical splices can be permanent and a economical choice for certain fiber-splicing applications. Mechanical splices also join two fibers together, but they differ from fusion splices in that an air gap exists between the two fibers.
12. What is the purpose of a GBIC?
• GBIC modules are designed to plug into interfaces such as routers and switches.
13. What is the purpose of a logical fiber map?
• A logic map – or a logic model – is a visual representation of the relationship between the various components of your program of work.
14. What is FDDI?
• Fiber Distributed Data Interface
15. What are the two different types of environments for fiber links?
• Environments that contain a large amount of electrical interference.
• It has also made it the standard for connecting networks between buildings, due to its immunity to the effects of moisture and lighting.
16. What steps can be taken if the designed receive signal power does not meet the minimum RSL requirement?
• Attenuators
17. What is a receiver dynamic range?
• The dynamic range of a receiver is essentially the range of signal levels over which it can operate. The low end of the range is governed by its sensitivity whilst at the high end it is governed by its overload or strong signal handling performance.
18. Examine the OTDR trace provided in figure 12-27. Explain the trace behavior of points A, B, C, D, and E. • Point A is a dead zone or a point too close to OTDR for a measurement to be made. The measured value begins at about 25 dB and decreases in value as distance traveled increases.
• Point B is a disturbance in the light propagating down the fiber.
• The Same type of event occurs in both point C and D.
• Point E is most likely the jumpers and patch-panel connections at the fiber end.
Part 2
1. Define PBX?
• Private branch exchange - the user’s own telephone system
2. Define PSTN?
• Public switched telephone Network - the telephone company
3. What is the purpose of a gateway
• Is to combine hardware and software.
4. List four enhanced features of SS7.
• Toll-free services
• Worldwide telecommunications
• Enhanced call features
• Local number portability
5. What are the signaling techniques used in IP telephony?
• H.323
• SIP
• SSIP
• Virtual tie line
6. What are RTP and RTCP used for in VoIP?
• RTP - real-time protocol
• RTCP –Real-time Control protocol
7. What is the purpose of a VoIP gateway?
• Provides the proper signaling of digitized voice data for transport over the IP network
8. What is another term for a VoIP gateway?
• VoIP Relay
9. What are two advantages of replacing an existing PBX tie line with a VoIP/data network
• Much easier to install & configure than a proprietary phone system
• Significant cost savings using VOIP providers
10. List two advantages of upgrading the PBX to support VoIP
• Customers are more in control
• - IP-PBX systems provide PBX functionality such as call holding, conference calling, and auto attendant over IP-based networks instead of traditional circuit-switched networks. From a technology perspective, an IP PBX is a telephone switch that supports VoIP by converting IP phone calls into TDM connections for the PSTN. Many IP PBXs also support hybrid environments, allowing businesses to route analog and digital calls as well.
11. What are three QoS issues for a VoIP network?
• Jitter
• Network latency and packet loss
• Queuing