QUESTION 1
As an Engineer, you are entrusted with the design of an ITU-T G.987 XG- PON FTTB broadband network to provide high bandwidth Internet access to each lecture hall within a university. The university campus is located at 10 Km from the nearest telephone exchange where an optical line terminal (OLT) will be installed. An optical network terminal (ONT) will also be installed in each lecture hall. A single PON port on the OLT will be used to serve 128 lecture halls. A single level of optical split is recommended. All equipment as well as splitter are connectorized. The average distance of the centralised splitter to each ONT is 500m. There are two fusion splices in between the OLT and the splitter; two mechanical splices in between the splitter and each ONT. A Class C optical distribution network (ODN) optics is assumed for this design. Splicing and connector losses are as per TIA 758. The OLT, ONT as well as the optical components specifications are listed below: Optical fiber specifications Optical fiber standard: G652.D Optical fiber channel bandwidth: 20 THz Optical fiber signal to noise ratio at ONT: 15 dB Optical fiber attenuation at 1577 nm: 0.25 dB/Km Optical fiber dispersion coefficient (????) at 1577 nm: 20 ps (nm.Km) Optical fiber dispersion coefficient (????) at 1260 nm: 3.5 ps (nm.Km) ONT optical port specifications Centre RX wavelength: 1577 nm Centre TX wavelength: 1260 nm RX sensitivity: -28 dBm Spectral width (????) of transmitter: 2.0 nm OLT XG-PON optical port specifications Centre RX wavelength: 1260 nm Centre TX wavelength: 1577 nm RX sensitivity: -30 dBm Spectral width (????) of transmitter: 0.1 nm Based on optical distribution network requirements described, fiber and equipment specifications provided, answer the following questions mentioning any assumptions
1. Draw a network diagram of the optical distribution network using TIA 587 symbols
2. Which fiber mode is not used in XG-PON network and why?
3. Which splitter topology is being used in the ODN?
4. Calculate the splitter loss
5. Calculate the maximum carrying capacity of the G.652D fiber using Shannon's theorem
6. What is the maximum allowable optical power loss range in Class C ODN?
7. Determine the ODN optical power loss for the FTTB network
8. What safety margin would you apply for such a network?
9. Determine the minimum OLT transmit power required to allow the ONTs to be registered by the OLT while considering required safety margin
10. Explain why a Fabry Perot laser is generally used in the ONT whereas a DFB laser is used in the OLT
11. Calculate chromatic dispersion for the fiber span in the downstream direction assuming that there is no modal dispersion in the fiber
12. Calculate chromatic dispersion for the fiber span in the upstream direction assuming that there is no modal dispersion in the fiber
13. Calculate maximum achievable throughput due to chromatic dispersion in the downstream direction
14. Calculate maximum achievable throughput due to chromatic dispersion in the upstream direction
15. Why is upstream throughput lower than downstream throughput on same optical fiber
16. Which wavelength would you use to test the ODN without affecting live data transmission
17. Calculate the maximum downstream throughput that each lecture hall can receive assuming that the OLT downstream throughput is uniformly divided among the lecture halls
18. What is the difference between power and wavelength optical splitters?
19. How do the multiple ONTs access the OLT?
20. How is upstream bandwidth allocated to the ONTs
QUESTION 2
(1) Briefly explain the purpose of synchronization and timing network in a telecommunication network
(2) Describe the hierarchy of clocks used in TDM communication networks
(3) Briefly explain the difference between the following data streams-
a. Synchronous streams
b. Asynchronous streams
c. Isochronous streams
d. Plesiochronous streams
(4) The minimum and maximum jitter observed in a 32-channel PCM signal is 463 ns and 512 ns respectively. Express the jitter variation in terms of the signal Unit Interval (UI). Is jitter level as per ITU-T G 811 standard requirements?
QUESTION 3
(1) Describe the Asynchronous Transfer Mode (ATM) protocol
(2) Different ATM Adaptation Layers (AALs) are defined for supporting different types of traffic or broadband services. Name the various types of traffic and associated typical services which are related to the various adaptation layers
(3) Derive the base synchronous Transport module (STM-1) transport rate
(4) Outline the Synchronous Digital Hierarchy (SDH) frame structure, explaining the importance of the section overhead (SOH)
QUESTION 4
(1) Explain the limitations of copper-based broadband access technologies
(2) What is the difference between far end and near end crosstalk on copper pairs? Which DSL technology is most affected by crosstalk?
(3) Explain how vector DSL technology can support higher data transmission rate using copper pairs. Which type of noise cannot be eliminated by vector DSL?
(4) Briefly explain the framing structure of ADSL technology