150860106054 150860106004 150860106045_150860106070_150860106010

ppt on optical fibre's total internal reflection,numerical aperture and acceptance angle.

1. . TOTAL INTERNAL REFLECTION, ACCEPTANCE ANGLE AND NUMERICAL APERTURE.

2. PRESENTED BY: ROLL NO. NAME ENROLL NO. 46 PRAJAPATI RIYA P. 150860106054 47 BARIA VAISHNAVI Y. 150860106004 48 PATEL MARTINA R. 150860106045 49 PATEL TIRTH H. 150860106070 50 CHAUDHARI RAJKUMAR M. 150860106010

3. OPTICAL FIBRE Optical fibre is made from thin strands of either glass or plastic It has little mechanical strength, so it must be enclosed in a protective jacket Often, two or more fibers are enclosed in the same cable for increased bandwidth and redundancy in case one of the fibers breaks It is also easier to build a full-duplex system using two fibers, one for transmission in each direction

4. Total internal reflection The transmission of light in an optical fibre involves the phenomena of total internal reflection at the interface between the core and cladding. When light enters one end of the glass fibre under right conditions, most of the light will propagate or move down the length of the fibre and exit from the far end. A small part of the light will escape through the side wall of the fibre, and some will also be lost due to internal absorption. But, a portion of the light will be contained and guided to the far end. Such a fibre is called a “light pipe” or “light guide”.

5. Conditions for Total internal reflection within fiber wall The refractive index n1 of the core must always be greater than the refractive index n2 of the cladding. The light must approach the wall with an angle of incidence Ø that is greater than the critical angle Øc. SinØc=n2/n1 ( when Ø = Øc , then by snells law, n1 sinØc =n2 sin90 or sinØc =n2/n1 )

6. Refraction and total internal reflection.

7. Acceptance angle Definition :Acceptance angle Acceptance angle of fiber Ømax is defined as the maximum value of angle of incidence at the entrance(air/fiber interface ) end of the fibre, at which the angle of incidence at the core-cladding interface is equal to critical angle of the core medium. Mathematically given as Where n1 and n2 are the refractive index of the core and cladding respectively.

8. Numerical aperture of optical fiber Numerical aperture (NA) is a figure of merit that is used to describe the light gathering or light collecting ability of an optical fiber. The large magnitude of (NA),the greater the amount of light accepted by the fibre from the external light source. Numerical aperture is mathematically define as the sine of the acceptance cone half angle. Thus,

9. The NA can also be expressed in term of normalized refractive index difference or relative refractive index( ). It is defined as the ratio of refractive index difference between core and cladding to the refractive index of core