Fiber-Optic Communications James N. Downing

Fiber and Cable Fabrication Chapter 4 Fiber and Cable Fabrication

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.

4.1 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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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