This document discusses the key components in optical fiber communication systems. It describes the function of an optic source as converting electrical signals to optical signals for transmission through fiber. Common optic sources are LEDs, which emit incoherent light, and laser diodes, which emit coherent light. LED types include ELEDs and SLEDs, while factors like emission pattern and coupling efficiency differ. Fusion and mechanical splicing are outlined as methods to join optical fibers permanently. Reasons for splicing include repairs, extending runs, and reducing losses. The document also covers fiber optic connectors and splicing losses.

1. OPTICAL FIBER
COMMUNICATION
1

2. 2

3. 3

4. 4

5. 5

6. 6

7. 7

8. 8

9. 9

10. 10

11. 11

12. 12

13. 13

14. 14

15. 15

16. 16

17. 17

18. 18

19. 19

20. 20

21. 21

22. What is an Optic Source?
• The heart of a fiber optical data system
• A Hybrid Device
– Converts electrical signals into optical signals
– Launches these optical signals into an optical fiber
for data transmission.
• Device consists of an interface circuit, drive
circuit, and components for optical source.
(LEDs, ELEDs, SLEDs, LDs, etc)
22

23. LEDs – Light Emitting Diode
• Emits incoherent light through
spontaneous emission.
• Used for Multimode systems w/
100-200 Mb/s rates.
• Broad spectral width and wide
output pattern.
• 850nm region: GaAs and AlGaAs
• 1300–1550nm region: InGaAsP and
InP
• Two commonly used types: ELEDs
and SLEDs
23

24. SLEDs – Surface Emitting LEDs
• Primary active region is a small circular area located below the
surface of the semiconductor substrate, 20-50µm diameter and
up to 2.5µm thick.
• Emission is isotropic and in lambertian pattern.
• A well is etched in the substrate to allow the direct coupling of
emitted light to the optical fiber
• Emission area of substrate is perpendicular to axis of optical
fiber
• Coupling efficiency optimized by binding fiber to the substrate
surface by epoxy resin with matching refractive index
24

25. Surface Emitting LED
25

26. ELEDs – Edge Emitting LEDs
• Primary active region is a narrow strip that lies beneath the
semiconductor substrate
• Semiconductor is cut and polished so emission strip region runs
between front and back.
• Rear face of semiconductor is polished so it is highly reflective while
front face is coated with anti-reflective, light will reflect from rear
and emit through front face
• Active Regions are usually 100-150µm long and the strips are 50-
70µm wide which are designed to match typical core fibers of 50-
100µm.
• Emit light at narrower angle which allows for better coupling and
efficiency than SLEDs
26

27. Edge Emitting LED
27

28. LDs – Laser Diodes
• Emit coherent light through
stimulated emission
• Mainly used in Single Mode
Systems
• Light Emission range: 5 to 10
degrees
• Require Higher complex driver
circuitry than LEDs
• Laser action occurs from three
main processes: photon
absorption, spontaneous
emission, and stimulated
emission.
28

29. 29

30. 30

31. 31

32. 32

33. Splicing
There are several reasons for splicing a fiber cable,
these include:
To join two fibers due to a breakage.
To connect some of the cores straight through a
patch cabinet.
To extend a cable run.
To reduce losses, a fusion splice has much lower
losses than two connectorized cables joined
through a coupler.
Or to attach a pre-terminated pigtail.
33

34. Definitions
Splicer
mechanical device for joining two pieces of paper or
film or magnetic tape
Splice
joint made by overlapping two ends and joining them
Splicing
process of the permanent connection of two pieces of
optical fibers
34

35. Types of Splicing
• Mechanical
• Fusion (welding)
35

36. Fusion Splicing
• Fusing the two fibers
• Flame heating sources
- micro-plasma burners, oxy-
hydric micro-burners, electric
arc..
• Advantage
- consistent and easily controlled
heat with adaptability
• Possible drawback
- weakening of fiber in the vicinity
of splice
36

37. Mechanical Splicing
• bonding two fibers
together in an
alignment structure
• Transparent adhesive
- e.g. epoxy resin
• Commonly used
groove
- V-groove
• Alignment problems
37

38. Comparison
Mechanical splicing Fusion splicing
Reflection losses
(-45 db to -55 db)
No reflection losses
Insertion loss
(0.2 db)
Very low insertion loss
(0.1 db to .15 db)
cost – high Comparatively less
38

39. Fiber splicing
Fusion Splicing
39

40. V-groove optical fiber splicing
40

41. Optical Fiber Connectors
• Some of the principal requirements of a good
connector design are as follows:
1- low coupling losses
2- Interchangeability
3- Ease of assembly
4- Low environmental sensitivity
5- Low-cost and reliable construction
6- Ease of connection
41

42. Splicing Losses
• Intrinsic
- Freznel reflection
• Extrinsic
- foreign particles on surfaces
• Reflection
- incident and reflected beam travel on the same
path
42

43. 43

44. 44

45. 45

46. 46

47. Need of fiber optic communication
Fiber optic communication system has emerged as most
important communication system Compared to
traditional system because of following requirements:
• 1. In long haul transmission system there is need of low
loss transmission medium
• 2. There is need of compact and least weight
transmitters and receivers.
• 3. There is need of increased span of transmission.
• 4. There is need of increased bit rate-distrance product.
A fiber optic communication system fulfills these
requirements, hence most widely accepted
47