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i. The table below shows the devices available to design a GPON network to provide subscribers with 17 FTTH service and 15 corporate VPN services respectively. In the design the first splitter is 18 Km from the OLT, second splitter 40 Km from the OLT and the third splitter 9 Km from the nearest splitter to the OLT. Node/device Quantity OLT 1 1:2 splitter 1 1:16 splitter 2 ODF 1 ODN 1 ONT 32 Type of optical fibre ?

a. Design the GPON. (2 marks)

b. Explain in detail the downstream and upstream transmission of information or data.

c. Predict your own transmit power, safety margin, the type of optical fiber and estimate the optical link power budget.

d. Clients connected to the third splitter cant have access to the services they subscribed. Explain in detail the investigation process using OTDR.

e. Based on your network, if there is a break between the first and third splitter list the affected customers. Explain how you will restore services to all the affected subscribers.

2. An optical fiber link consists of electrical and optical interfaces, sketch a simple fiber link indicating these interfaces and explain the operation from source to sink.

ii. A fiber fabricator uses Pure silica oxide and doped silica oxide with Germanium for the core and cladding respectively. Explain how the preform for this fiber will be made.

iii. Determine refractive indices of the core and cladding of the fiber, and estimate

a. The pulse duration after travelling through 2Km length of the manufactured fiber.

b. The fiber bit rate length product. Explain the implication of your answer.

3. In an optical fiber laboratory experiment the following measurement were observed, numerical aperture of 0.20 and a cladding refractive index of 1.59. Determine:

a. The acceptance angle for the fiber in water.

b. The critical angle at the corecladding interface. Comment on any assumptions made about the fiber.

ii. Define the normalized frequency for an optical fiber and explain its use in the determination of the number of guided modes propagating within a step index fiber.

iii. A step index fiber in air has a numerical aperture of 0.16, a core refractive index of 1.45 and a core diameter of 60 m. Determine:

a. The number of guided modes propagating in the fiber when light at a wavelength of 0.9 m is transmitted.

4. A Laser is used in a network to transmit light from a source, with the aid of suitable diagrams, discuss the principles of operation of the injection laser.

ii. If a pn photodiode is used at the receiver explain the detection process. Compare this device with the pin photodiode.

iii. Given the optical fiber preform explain the drawing process of the fiber.

What are the advantages and disadvantages of the drawing method used?