1. Explain the fiber structure and give some commonly used type of optical fiber.

2. Use Maxwell’s equations to express the field components , , and  inside the fiber core in terms of and . Neglect the nonlinear part of the polarization for simplicity.

3. There exist several impairments in the fiber channel, including linear and nonlinear impairment . Please illustrate at least five types briefly.

4. Explain the origin of polarization modes dispersion (PMD) in the fiber. Why does PMD lead to pulse broadening?

5. Classifythe nonlinear effect of the fiber and explain them briefly. 

6. How can fiber birefringence be used to remove the low-intensity pedestal associated with an optical pulse?

7. What is meant by Raman scattering? Explain its origin. What is the difference betweenspontaneous and stimulated Raman scattering?

8. What ismeant by Brillouin scattering? Why does SBS occur only in the backward directionin single-mode fibers?

9. What are the main differences between SBS and SRS? What is the origin of these differences and how do they manifest in practice?

10. How can you use FWM for wavelength conversion in WDM systems? Derive an expression for the conversion efficiency.

11Calculate the carrier frequency for optical communication systems operating at 0.88,1.3, and 1.55 m. What is the photon energy (in eV) in each case?

12Calculate the transmission distance over which the optical power will attenuate by a factor of 10 for three fibers with losses of 0.2, 20, and 2000 dB/km.Assuming that the optical power decreases as , calculate (in ) for the three fibers.

13 Assume that a digital communication system can be operated at a bit rate of up to 1%of the carrier frequency. How many audio channels at 64 kb/s can be transmitted over a microwave carrier at 5 GHz and an optical carrier at 1.55?

14. Asingle-mode fiber has an index step . Calculate the coreradius if the fiber has a cut off wavelength of 1.

15. A 1.55- unchirped Gaussian pulse of 100-ps width (FWHM) is launched into a single-mode fiber.Calculate its FWHM after 50 km if the fiber has a dispersion of 16 ps/(km-nm).Neglect the source spectral width.

16. Anoptical amplifier can amplify a 1W signal to the 1-mW level. What is the output power when a 1-mW signal is incident on the same amplifier? Assume that the saturation power is 10 mW.

17. A semiconductor optical amplifier is used to amplify two channels separated by 1GHz. Each channel can be amplified by 30 dB in isolation. What are the channel gains when both channels are amplified simultaneously? Assume that Pin/Ps = , = 0.5 ns, and = 5.

18. Explain how an array of planar waveguides can be used for de-multiplexing WDM channels.

19. Sketchan opticalfiber communication system and explain the function of basic devices. 

20. Explain the three conditions of generating laser.

21. LD and LED are the two mainlightsourcein opticalfiber communication. Please the difference between them. 

22. Explain how a Mach–Zehnder interferometer works and deduce the formula of modulation for MZM.

23. Explain the gain mechanism in EDFAs.

24. The transfer function of an optical filter is given by . What is the impulse response of this filter?