A. Optical Fiber 1. For a step -index multimode fiber , n, = 1.5 and An = 0.015, calculate n2, NA, and the maxim um acceptance angle ! Based on the previous problem, consider the same step-in dex fiber immersed in water of refractive in dex 1.33. Calculate the maxim um acceptance angle! The power of a 2-mW laser beam decreases to 15 wW after the beam traverses through 25 km of a single-mode optical fiber. Calculate the atten vation of the fiber! 4. A 5-mW laser beam passes through a 26-km fiber of loss 0.2 dB/km. Calculate the power at the output end ! 5. Consider an SIF with n, = 1.5, a = 40 um, and An= 0.015, operating at 850 nm with a spectral width of 50 nm. a) Is this a single-mode fiber or a multimode fiber? b) Calculate the material dispersion , intermodal dispersion , and total pulse dispersion 6. Based on the previous problem, consider a parabolic-in dex fiber with n, = 15 , a = 40 um, and An= 0.015, operating at 850 mm with a spectral width of 50 nm. a) Is this a singlemode fiber or a multimode fiber? b) Calculate the material dispersion, intermodal dispersion, and total pulse dispersion ! Optical Fiber Communication 1. A fiber of 1-km length has Pin = 1 mW and Pout =0.125 mW . Find the loss in dB / km .! 2. A communication system uses 8 km of fiber that has a 0.8-dB/km loss characteristic. Find the output power if the in put power is 20 mW ! 3. A 5-km fiber optic system has an input power of 1 mW and a loss characteristic of 1.5 dB/km . Determine the output power! 4. What is the maximum core diameter for a fiber to operate in single mode at a wavelength of 1310 nm if the N.A. is 0.12? 5 . A 1-km-length multimode fiber has a modal dispersion of 0 50 ns/km and a chromatic dispersion of 50 ps/km * nm. If it is used with an LED with a linewidth of 30 nm, (a) what is the total dispersion? (b) Calculate the bandwidth (BW ) of the fiber! 6. A digital M UX operates with 16 sources. The rate of data in each source is 8000 bytes/second (assume 8 bits per byte). Data are transmitted byte by byte. (a) What is the data rate of the MUX output? (b) What is the channel switching rate? 7. A receiver has a sensitivity Ps of- 40 dBm for a BER of 10- 9. What is the minimum power (in watts) that must be in cident on the detector? 8. A system has the following characteristics: . LED power (P ) = 1 mW (0 dBm ) . LED to fiber loss (L.) = 3 dB . Fiber loss per km (F) = 0.2 dB/km . Fiber length (L) = 100 km . Connector loss (Leann ) = 3 de (3 connectors spaced 25 km apart with 1 dB of loss each ) . Fiber to detector loss (L,) = 1 dB . Receiver sensitivity (P,) = - 40 dBm Find the loss margin and sketch the power budget curve! 9 . A 5-km fiber with a BW * length product of 1200 M Hz x km (optical bandwidth ) is used in a communication system. The rise times of the other components are t = 5 ns, t = Ins, t = 1.5 ns, and to = 5 ns. Calculate the electrical BW for the system! 10. A 4 * 4 star coupler is used in a fiber optic system to connect the signal from one computer to four terminals. If the power at an input fiber to the star coupler is 1 mW, find (a) the power at each output fiber and (b) the power division in decibels