1. Fiber-Optic Communications
James N. Downing

2. Fiber and Cable Fabrication
Chapter 4
Fiber and Cable Fabrication

3. 4.1 Optical Fiber Fabrication
Fused Silica Glass
Medium of choice for fiber communications
Uses a silica soot that reacts with SiCl4 and produces GeO2. The GeO2 and P2O5 increase the refractive index.
The preform is a single, glass rod of about 1m by 2cm with the refractive index of the finished fiber.

4. 4.1 Optical Fiber Fabrication
Deposition Preform Methods
Rod-in-tube
A tube with a higher index is inserted into a lower index tube and the two are melted to make the preform.
Attenuation: 500 to 1000dB/km.
Double crucible method
Core and clad fibers are heated and pulled through nested platinum crucibles that are narrowed to fiber size.
Attenuation: 5 to 20dB/km

5. 4.1 Optical Fiber Fabrication
Deposition Preform Methods
Inside Vapor Deposition (IVD)
Deposits silica soot on inside wall of fused tube and then heated
Modified Chemical Vapor Deposition (MCVD)
SiCl4 and SiO2 are heated to 18000C, leaving a soot on the inside of the tube
Attenuation: 3dB/km at 85nm

6. 4.1 Optical Fiber Fabrication
Deposition Preform Methods
Plasma Chemical Vapor Deposition (PCVD)
Similar to MCVD except heat source is ionized electric charge instead of gas burner
More precise layering and refractive index profiling
Attenuation: 4dB/km at 850nm

7. 4.1 Optical Fiber Fabrication
Deposition Preform Methods
Outside Vapor Deposition (OVD)
Flame hydrolysis causes soot to be deposited on the outside of the rod. The rod is then removed and the resulting tube is collapsed to make the preform.
Attenuation: 1 to 2dB/km

8. 4.1 Optical Fiber Fabrication
Deposition Preform Methods
Axial Vapor Deposition (AVD)
Similar to OVD
Rod is drawn through soot trail several times to make the differing layers
Attenuation: 1 to 2dB/km

9. 4.1 Optical Fiber Fabrication
Fiber Drawing and Coating
The fiber can be “drawn” by heating the preform to 20000C and pulling the melting glass away from the preform at speed of about 1m/sec.
The fiber is coated by dipping, spraying, or electrostatic methods.

10. 4.2 Fiber Cable Fiber Cabling Considerations
Provide protection for ease of handling
Must withstand extremes of environment, installation forces, and stresses

11. 4.2 Fiber Cable Fiber Cable Construction
Buffer jacket around the fiber
Strength member provides mechanical support
Outer jacket provides protection from abrasion
Loose buffer to shield against environment issues
Tight buffer directly on the fiber

12. 4.2 Fiber Cable Types of Cables By installation
Simplex: one-way communication
Duplex: two-way communication
Multifiber: many fiber pairs in bundle
Ribbon: fibers in a row

13. 4.2 Fiber Cable Types of Cables By applications Light duty Heavy duty
Plenum: between walls
Riser: between floors
Indoor
Outdoor

14. 4.3 Connectors Connector Considerations Fiber and Cable Preparation
Tolerances are stringent
Precision alignment
Fiber and Cable Preparation
Ends must be smooth and clean
Cleaving: good enough for splices
Polishing: for all connectors

15. 4.3 Connectors Connector Installation
Depends on the connector and application
Flat finish: Used for multimode applications
Domed PC finish: Provides for good core contact
APC finish: Polished at 80 angle for matching purposes

16. 4.3 Connectors Types of Connectors Major Categories Sub Categories
Standard
Small
Sub Categories
Ferrule
Connection method
Number of fibers

17. 4.3 Connectors Standard Connectors: 2.5mm ceramic ferrule
FC: Earliest design with threaded coupling and adjustable keying to minimize loss
SC: Rectangular snap-in-plug in which the housing is not directly attached to the cable
ST: Evolved from copper connectors and the most popular; similar to FC but with quick connects and bayonet coupling and ½ turn keying

18. 4.3 Connectors Standard Connectors
FDDI: Two 2.5 mm ferrules stacked together
ESCON: IBM fiber optic based channel control
SFF:
MT: 12 single or multimode fibers
LC: doubles the count of standard connectors in same area. Used with RJ-45.
VF-45: contains a fiber holder, hinged door, and V-groove for alignment purposes

19. 4.4 Connector Losses Intrinsic Loss Extrinsic Loss
Caused by mismatches in
Numerical aperture
Core diameter
Core area
Extrinsic Loss
Caused by differences in connectors which cause misalignment

20. 4.4 Connector Losses Insertion Loss
The attenuation of any connector or component inserted inline
Used for power budget calculations

21. 4.5 Splices Mechanical Fusion
Can be installed in the field with minimum tools
Losses: 0.3db
Fusion
Junction must be heated
Special tools
Losses: 0.1dB

22. 4.5 Splices
Applications
Splice Tray: Secures a long row of splices and prevents them from moving inside the closure
Splice Panel: Provides sealed protection for splice trays
Splice closure: Used in aerial and underground telephone cable runs