Fiber optics use total internal reflection to transmit light through optical fibers. Fibers come in different materials and have either step index or graded index refractive index profiles. They can operate in single mode or multi-mode. Common light sources are LEDs and lasers, while detectors include photodiodes and PIN diodes. Loss mechanisms in fibers include attenuation, dispersion, and bending loss. Fibers are used in communication systems and sensors can measure temperature and displacement.

1. FIBER OPTICS

2. Principle and propagation of light in optical fibers

5. Total internal reflection

6. Numerical aperture and Acceptance angle Numerical aperture / Light collecting capacity NA = ( n12 - n22 ) ½ Acceptance angle = Sin -1 (NA)

7. Types of optical fibers Material Mode Refractive index profile

8. Material Glass fiber Plastic fiber

9. Glass fiber

10. Plastic fiber core cladding polyurethene methyl methacrylate Poly methyl metha co-polymer crylate

11. Mode Single mode Multi mode

13. Multimode

14. Refractive index profile Step index Graded index

16. Double crucible technique of fiber drawing Platinum crucible

17. Fiber manufacture

18. Splicing

19. connector

20. Loss in optical fiber Attenuation coefficient Po is the power emitted from the source fiber Pi is the power accepted by the connected fiber

21. Dispersion Dispersion chromatic intermodal dispersion

22. Bending loss

23. Fiber optical communication system (Block diagram)

24. Light sources LED LASER

25. LED

27. LASER

28. Detectors PHOTO-DIODE P-I-N DIODE

29. Photo diode When a photon of sufficient energy strikes the diode, it excites an electron, thereby creating a mobile electron and a positively charged electron hole.

30. Photodiode

31. P-I-N diode The intrinsic "i" region is flooded with charge carriers from the "p" and "n" regions. Its function is similar to filling up a water bucket with a hole on the side. If,water reaches the hole's level it will begin to pour out. Similarly the Pin diode will conduct where the number of electrons is equal to the number of holes in the intrinsic region

34. Fiber optic sensors – temperature & displacement

35. Endoscope