Lecture 2: Optical Fiber

1. Lecture 2: Optical Fiber Iksan Bukhori, M.Phil.

2. Light Theorem • Geometric optical approach • Light creeps straight • Speed in a vacuum • Speed in another medium v = c / n; n is the index of refractive of the medium • - • air vacuum permit = • SNELL's law of reflection  The light comes, reflected light, and the normal line lies on the plane  Angle coming = reflected angle

3. Light Theorem - SNELL's law of refraction • Light continues to deflect close to normal • Light continues to deflect away from normal

4. Light Theorem • TIR (Total InternalReflection) Light comes from a Medium with a higher index of refraction Continued angle = 900 The angle is getting bigger, the light that keeps getting away from normal This condition of the coming angle is called a critical angle When the angle comes > a critical angle occurs TIR

5. Light Theorem • Approximation of EM Waves - Light: Waves EM f ~ 1014Hz

6. Light Theorem • Approximation of EM Waves - Polarization of EM waves

7. FRESNEL’S LAW (revision) • Field coming: plane perpendicular to boundary plane and through direction of light propagation. The electric field vector is perpendicular to the propagation of light • The parallel polarization of the field comes:

8. PERPENDICULAR POLARIZATION TO THE COMING PLANE

9. Reflectance: Critical Angle: Anti reflection:

12. LIGHT THEOREM • A quantum theory approach - Light is a series of discrete quantized energies called quanta or photons - Light energy depends on frequency - Can explain the phenomenon of disperse, emission, and absorption

13. Fiber Optic

16. Optical fiber structure

17. Optical Fiber Materials • Terms: - Must be long - Must be translucent  efficient - Allows to have a small refractive index difference between the core and the skin • Eligible: - Glass Fiber - Halide Glass Fiber - Active Glass Fiber - Plastic Skin Glass Fiber - Plastic Fiber

18. GLASS FIBER Mixed fusion of metal oxides, sulfides / selenides.

19. Example of fiber composition

20. HalideGlass Fiber • Fluoride glass found by Universite de Rennes researchers in 1970 • It has very low losses at infrared middle frequency (0.2 to 8 , lowest at 2.55 ) • The main element is called ZBLAN • For a lower refractive index one part is replaced by making it a ZHBLAN for the skin • The low attenuation gain is 0.001 to 0.01 dB / km • Losses difficult to make long because easy not to be glass (devitrification)

21. ZBLAN Key Element

22. ACTIVE GLASS FIBER

23. PLASTIC SKIN GLASS FIBER (PCS) • Silica nucleus • Plastic / polymeric skin (n = 1,405 at 850nm) or FEP (Ethylene Propylene Fluoride), n = 1,338 • Higher NA • Only step index fiber • Advantage is cheap & coupling with source is good • Disadvantage is high attenuation, and low quality • Only suitable for short distance communication

24. PLASTIC FIBER • Core and plastic skin • Example: - Polystyrene core (n = 1.60), methyl meta crylate skin (n = 1.49) - Methyl meta crylate core, copolymer skin (n = 1.40) • Advantages of large, cheap, easy to maintain, flexible angle acceptance  large core size 110 s / d 1400 μm fit in LED • Only suitable for a very short distance of 100 m

25. OPTICAL FIBER • How does light propagate in optical fiber?

26. OPTICAL FIBER (TYPES OF OPTICAL FIBERS) • Single Mode Step Index

27. OPTICAL FIBER (TYPES OF OPTICAL FIBERS) • Step Index Multimode

28. OPTICAL FIBER (TYPES OF OPTICAL FIBERS) • Graded Index Multimode

29. GRADED-INDEX MULTIMODE (GI MM) FIBERS

30. OPTICAL FIBER CHARACTERISTICS • Numerical Aparture Numerical Aperture is a fiber optic ability to collect light

31. OPTICAL FIBER CHARACTERISTICS

32. OPTICAL FIBER CHARACTERISTICS • Bandwidth-distance product - A measure of fiber optic information capacity, otherwise in MHz.Km • Example: • BW 400 MHz.Km, meaning 400 MHz signal can be sent for 1 Km, or it can mean anyway

33. OPTICAL FIBER CHARACTERISTICS

34. MULTI-STEP SINGLE MODE FIBERS

35. FIBER PARAMETERS: SUMMARY

36. FIBER PARAMETERS: SUMMARY