) An optical fiber has a core refractive index of 1.4. Two lengths of thefiber with smooth and perpendicular (to the core axes) end faces arebutted together. Assuming the fiber axes are perfectly aligned, calculatethe optical loss in decibels at the joint (due to Fresnel reflection) whenthere is a small air gap between the fiber end faces. ---- 2 marks
Question
) An optical fiber has a core refractive index of 1.4. Two lengths of thefiber with smooth and perpendicular (to the core axes) end faces arebutted together. Assuming the fiber axes are perfectly aligned, calculatethe optical loss in decibels at the joint (due to Fresnel reflection) whenthere is a small air gap between the fiber end faces. ---- 2 marks
Solution
The Fresnel reflection, R, at an interface between two media with refractive indices n1 and n2 is given by:
R = ((n1 - n2) / (n1 + n2))^2
In this case, n1 is the refractive index of the fiber core (1.4) and n2 is the refractive index of air (approximately 1.0).
So,
R = ((1.4 - 1.0) / (1.4 + 1.0))^2 = 0.04
The optical loss in decibels is given by:
Loss (dB) = -10 log10(1 - R)
Substituting R = 0.04 into this equation gives:
Loss (dB) = -10 log10(1 - 0.04) = 0.17 dB
So, the optical loss at the joint due to Fresnel reflection when there is a small air gap between the fiber end faces is 0.17 dB.
Similar Questions
Show how this is related to the fiber numerical aperture and the refractive indices for the fibercore and cladding. An optical fiber has a numerical aperture of 0.20 and a cladding refractive index of1.59. 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. Comment on any assumptions made about thefiber.
How the numerical aperture (NA) of an optical fibre is related tothe refractive index of core and relative refractive index difference(delta) between core and cladding?
A multimode step-index fiber has a core refractive index of 1.5 and relative refractive index difference of 1%. The length of the optical link is 6 km. Estimate the RMS pulse broadening due to intermodal dispersion on the link.a. a.86.7 nsb. b.69.3 nsc. c.92.6 nsd. d.68.32 ns
The optical source used in a fiber is an injection laser with a relative spectral width σλ/λ of 0.0011 at a wavelength of 0.70μm. Estimate the RMS spectral width.
The velocity of light in the core of a step index fibre is 2 × 108 ms−1 ,and the critical angle at the core–cladding interface is 70°. Determine thenumerical aperture and the acceptance angle for the fibre in air, assumingit has a core diameter suitable for consideration by ray analysis. ( 3 marks)The velocity of light in a vacuum is 3 × 108 ms−
Upgrade your grade with Knowee
Get personalized homework help. Review tough concepts in more detail, or go deeper into your topic by exploring other relevant questions.