Process optical fibers

Vapor-Phase Processing. Optical fiber preforms are prepared by vapor-phase techniques because of the superior clarity of the products. 

Precision alignment and attachment of optical fibers to couple them with lenses, transmitter and receiver components, and laser diodes is stiU largely a manual, labor-intensive process. Optical fibers must be aligned to insure that the optimum amoimt of light is transmitted between the fiber on the outside and the laser, photodiode, or other optical component on the inside of a package. Alignment may be active or passive. ... 

Fig. 21. Schematic illustration of the four primary vapor-phase deposition processes used in optical-fiber fabrication outside vapor deposition (OVD), modified chemical vapor deposition (MCVD), plasma vapor deposition (PVD), and vapor axial deposition (VAD) (115).

Two major processes are available for the production of optical fibers (or liquid phase) and CVD. Solgel is being evaluated but has yet to evolve into a viable production process for that application. 

The direct melt process economically produces thick optical fibers (250-400 pm in diam.), which is advantageous, but their relatively high attenuation (3-20 dB/km) due to impurities is not. As a result, they are limited to short distance multimode applications. 

Developing better processes for deposition and coating of thin films. An integrated circuit, in essence, is a series of electrically coimected thin films. Thin films are the key stractural feature of recording media and optical fibers, as well. 

The medium used for the transmission of information and data over distances has evolved from copper wire to optical fiber. It is quite likely that no wire-based information transmission systems will be installed in the future. The manufacture of optical fibers, like that of microcircuits, is almost entirely a chemical process. 

There are four principal processes that may be used to manufacture the glass body that is drawn into today s optical fiber. "Outside" processes—outside vapor-phase oxidation and vertical axial deposition— produce layered deposits, of doped silica by varying the concentration of SiCl4 and dopants passing through a torch. The resulting "soot" of doped silica is deposited and partially sintered to form a porous silica boule. Next, the boule is sintered to a pore-free glass rod of exquisite purity and transparency. 

Light wave technologies provide a number of special challenges for polymeric materials. Polymer fibers offer the best potential for optical communications in local area network (LAN) applications, because their large core size makes it relatively cheap to attach connectors to them. There is a need for polymer fibers that have low losses and that can transmit the bandwidths needed for LAN applications the aciylate and methacrylate polymers now under study have poor loss and bandwidth performance. Research on monomer purification, polymerization to precise molecular-size distributions, and weU-controlled drawing processes is relevant here. There is also a need for precision plastic molding processes for mass prodnction of optical fiber connectors and splice hardware. A tenfold reduction in the cost of fiber and related devices is necessaiy to make the utilization of optical fiber and related devices economical for local area networks and tlie telecommunications loop. 

For optical fibers, improved control over the stracture of the thin films in the preform will lead to fibers with improved radial gradients of refractive index. A particnlar challenge is to achieve this sort of control in preforms created by sol-gel or related processes. 

A challenge related to the problems of reactor design and engineering is the modehng and study of the fundamental chemistry occtrrring in manufactrrring processes for semiconductors, optical fibers, magnetic media, and interconnection. 

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