-ADVANTAGES OF OPTICAL COMMUNICATION

  • Low transmission loss.

 Wide bandwidth.

 Small size and weight.

Immunity to interference (EMI & EMP).

 Electrical insulation (No arcing, sparking, ground loops, hazards).

 Signal security (banking, computer networks, military systems).

Abundant raw material

-نخلى بالنا بقى من المقارنتين اللى جايين دول عشان مهمين جدا وياريت نراجع عليهم يوم السبت بليل عشان مننسهاش

PROBLEMS

1-a)Using simple ray theory, describe the mechanism for the transmission of lightwithin an optical fiber.

b)Briefly discuss with the aid of a suitable diagram what ismeant by the acceptance angle for an optical fiber.

c)Show how this is related to thefiber numerical aperture and the refractive indices for the fiber core and cladding.

d)An optical fiber has a numerical aperture of 0.20 and a cladding refractive indexof 1.59. Determine:

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

(ii) The critical angle at the core–cladding interface.

Comment on any assumptions made about the fiber.

Solution

A)if the incident light on the interface by angle larger than then the light could be still bounded in the core till its end, while if Q< light will be lost in cladding

b)if Ө which will result in

which will cause unbounded ray so we can say that

ifwe'll have unbounded ray

c)راجع من الmid-term revisionالاثبات ده

d)using this rule NA= =

=

i-, ii-

2-The velocity of light in the core of a step index fiber is 2.01 × m s−1, and thecritical angle at the core–cladding interface is 80°. Determine the numerical apertureand the acceptance angle for the fiber in air, assuming it has a core diametersuitable for consideration by ray analysis. The velocity of light in a vacuum is2.998 × m s−1.

Solution

Using the rules NA= =

=

V=

Then NA=.238

=13.787 degree.

3-a) Define the relative refractive index difference for an optical fiber.

b) Show how itmay be related to the numerical aperture.

c)A step index fiber with a large core diameter compared with the wavelength of the transmitted light has an acceptance angle in air of 22° and a relative refractiveindex difference of 3%. Estimate the numerical aperture and the critical angle at thecore–cladding interface for the fiber.

Solution

a,b)so easy

c)= then NA==.3746=

But then

وبالتعويض عن قيمة تحت الجذر اقدر اجيب قيمة ومنها اجيب قيمة وبعدين من القانون ده =نلاقى ان

ملحوظة بس على المسألة دى

1-relative refractive index difference=

2-=fractional refractive index difference

5-Describe with the aid of simple ray diagrams:

(a) the multimode step index fiber;

(b) the single-mode step index fiber.

Compare the advantages and disadvantages of these two types of fiber for use as anoptical channel

Solution

وكمان معاها المقارنة اللى فى اول المراجعة .