Applied Physics Dept, GHRCE



G. H. Raisoni College Of Engineering, Nagpur

APPLIED PHYSICS

UNIT IV

OPTICAL FIBER

1. An optical fiber has NA of 0.20 and a cladding refractive index of 1.59. Determine the acceptance angle for the fiber in water which has RI of 1.33. Sum-2011,Sum2012 (4)

2. Determine the critical angle for a ray traveling from water (n=1.333) to air.

3. The core has RI 1.6 and the cladding RI is 1.3. What is the value of critical angle? What is the angle of cone of acceptance (2θo)? (WK9) (4) [W-2012] (3)

4. The numerical aperture of an optical fiber is 0.5 and core refractive index is 1.54. Find the refractive index of the cladding. (SK10) (3)

5. A silica optical fiber with a core diameter large enough to be considered by ray theory analysis has a core refractive index of 1.5 & cladding refractive index of 1.47. Determine a) critical angle at the core-cladding interface b) N. A. for the fiber c) The acceptance angle in the air for the fiber.

6. A typical relative refractive index difference for an optical fiber designed for long distance transmission is 1% Estimate N.A. when the core index is 1.46, calculate the (c.

7. A single mode step index fiber, which is designed for operation at a wavelength of 1.34(m, has a core and cladding refractive indices of 1.447 and 1.442 resp. when the core diameter is 7.2 (m confirm that the fiber will permit single-mode transmission and estimate the range of wavelength over which this will occur.

8. A single mode fiber has a core refractive index of 1.47. Find the relative refractive index diff for the fiber to operate at 1.3(m. Determine whether the fiber remains single mode at a transmission wavelength 0.85(m when its core radius is 4.5(m.

9. An optical fiber has a Numerical aperture of 0.2 and a cladding refractive index of 1.59. Determine

a) The acceptance angle for the fiber in water which has a refractive index of 1.33,

b) The critical angle at the core cladding interface.

10. The velocity of light in the core of a step index fiber is 2.01 x 108 m/s, and the critical angle at the core-cladding interface is 80o. Determine the Numerical aperture and the acceptance angle for fiber in air, assuming it has a core diameter suitable for consideration by ray analysis. The velocity of light in vacuum is 2.998 x 108 m/s.

11. Calculate the velocity of light in the optically active region of a substance at 850 nm. Also complete the corresponding wavelengths. Given RI of the substance at 850nm is 3.6 & at 1300nm is 3.4 velocity of light in free space = 3x 108 m/sec.

12. Calculate the refractive indexes at the core & cladding material of a fiber from the following data NA = 0.22, ( = 0.02. (WK7) (3)

13. A single mode step index fiber has a core diameter of 7(m and a core refractive index of 1.49. Estimate the shortest wavelength of light, which allows single mode operation when the relative refractive index difference for the fiber is 1%.

14. A step index optical fiber of diameter 50 (m has a NA of 0.23. If the wavelength of input light energy is 0.82 (m, determine the number of modes in the cable.

15. Calculate the cut-off parameter and also the number of mode for a fiber operating wavelength = 0.85 (m.

16. Compute the maximum radius allowed for a fiber having core refractive index 1.47 and cladding refractive index 1.46. The fiber is to support only one mode at a wavelength of 1300(m.

17. Calculate the fractional refractive index change and the largest core size for single mode propagation of a GRIN fiber having a parabolic profile with n1 = 1.465, n2 =1250 nm.

18. Complete the cut-off parameter and the number of modes supported by a fiber n1 (core) = 1.54 and n2 (cladding) = 1.5 core radius 25 (m & operating wavelength is 1300nm.

19. Compute the maximum value of ( = (n1 – n2)/n1 and n2 (cladding of a single mode fiber of core diameter 10(m and core refractive index 1.5. The fiber is couple to a light source with a wavelength of 1.3 (m. V out off for single mode propagation is 2.405. Also calculate the acceptance angle.

20. Calculate the wavelength of a light wave in free space for a frequency of 600GHz, velocity = 3x108 m/s.

21. Find the fractional refractive index and numerical aperture for an optical fiber with refractive indices of core and cladding as 1.5 and 1.49 respectively. (SK6) (4)

22. Calculate ( for a step index fiber having core & cladding refractive index 1.48 & 1.46 respectively. If ( = 1.5 calculate the velocity of light in glass.

23. Find n2 if ( = 1% & n = 1.48 what is the critical angle for this material if the light travels from glass into air.

24. A single mode fiber with V = 2.3 and mode of fused Silica (core) of n1 = 1.458. The numerical aperture of the fiber is 0.10. Compute the following.

a) n2 and radius of the core.

b) Number of mode in the fiber for operation at 820nm.

26. Calculate the numerical aperture and acceptance angle for an optical fibre whose core R. I. is 1.48 and cladding R.I. is 1.39.(S-14) (3)

27. Calculate Numerical Aperture and Acceptance angle for an optical fiber from the following data: (1 (core)=1.55 and (2 (cladding)= 1.50 (SK6) (4)

28. A multimode graded index fiber has an acceptance angle of 8o in air in air. Estimate the relative refractive index difference between the core axis and the cladding when the refractive index at the core axis is 1.52.

29. A graded index fiber with parabolic index profile supports propagation of 742 guided modes. NA in air is 0.3 and the core diameter is 70 (m. Determine Wavelength of light propagating& Maximum diameter of the fiber that gives single mode operation.

30. A graded index fiber with a core axis refractive index of 1.5 has a characteristic index profile of 1.90, a relative index difference of 1.3% and a core diameter of 40 (m. Estimate the number of guided modes propagating in the fiber when the transmitted light has wavelength of 1.55 (m and determine the out-off value of normalized freq for single mode transmission fiber.

31. A multimode step index fiber has a relative refractive index difference of 1.1%, and a core refractive index of 1.5. The no. of modes propagating at a wavelength of 1.3 (m is 1100. Estimate the diameter of the fiber core. (SK9) (4)

32. Estimate the maximum core diameter for an optical fiber with relative refractive index difference 1.5% and core refractive index 1.48 in order that it may be suitable for single mode operation. The operating wavelength 0.85 (m. Further estimate the new maximum core diameter for single mode operation when the relative refractive index difference is reduced by a factor of 10.

33. A 15km optical fiber link uses fiber with a loss of 1.5 dB/km; the fiber is jointed every km with connectors which give an attenuation of 0.8dB each. Determine the minimum mean optical power which must be launched into the fiber in order to maintain a mean optical power level of 0.3 (w of the detector.

34. When the mean optical power launched into an 8 km length of fiber is 120 (w, the mean optical power at the fiber output is 3 (w. Determine, a) overall signal attenuation or loss in decibels through the fiber assuming there are no connection or splitters. b) The signal attenuation per km for the fiber .c) the overall signal attenuation for a 10 km optical link using the same fiber with splitters at 1 km intervals, each giving an attenuation of 1 dB. d) The numerical input/output power ratio.

35. The mean optical power launched into an optical fiber link is 1.5(w and the fiber has attenuation of 0.5 dB/km. Determine the maximum possible link length without repeaters when the minimum mean optical power level required at the detector is 2(w.

36. The numerical input/output mean optical power ratio in a 1km length of optical fiber is found to be 2.5. Calculate the received mean optical power when a mean optical power of 1mw is launched into a 5 km length of fiber.

37. Calculate the numerical aperture and acceptance angle for a cable with a core index of refraction of 1.45 and a cladding index of refraction of 1.30. (WK8) (4), S-2013 (3)

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ANJUMAN COLLEGE OF ENGINEERING & TECHNOLOGY, NAGPUR

BE –Second Semester

ADVANCED PHYSICS

Unit- IV - Optical fibre & Nanoscience (Numerical)

• MOTION OF CHARGE PARTICLE IN UNIFORM ELECTRIC & MAGNETIC FIELD

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