Abstract: An isothermal, low pressure-based process of depositing material within a substrate has been developed and results in creating an extremely narrow reaction zone within which a more uniform and efficient deposition will occur. Sets of isothermal plasma operating conditions have been found that create a narrow deposition zone, assuring that the deposited material is clear glass rather than soot particles. The chemical delivery system, in one arrangement, utilizes rods of solid phase source material (which may otherwise be difficult to obtain in gaseous form). The operating conditions are selected such that the hot plasma does not transfer a substantial amount of heat to the substrate tube, where the presence of such heat has been found to result in vaporizing the reactant material (creating soot) and developing hot spots.

Abstract: A PCVD apparatus including an insulative covering disposed to surround at least a portion of the substrate tube and provide external heating of the substrate tube during the deposition process. The insulative covering functions to capture and retain the external thermal energy created by the plasma process. As a result, the areas of the substrate tube that are removed from the current location of the plasma absorb this captured thermal energy and remain at an essentially constant temperature until the next pass of the work coil.

Abstract: A method of making a microstructured optical fiber preform uses the plasma fusion of a powder layer deposited onto a substrate under conditions that prevent the deposited layer from completely densifying, thereby yielding the formation of bubbles within the layer. By systematic control of powder melt and delivery, while maintaining the process temperature below a temperature associated with densifying the deposited layer, the powder particles densify only partially on the substrate and create bubbles of a fairly narrow (and thus controllable) diameter range within a defined region of the preform. Upon drawing a fiber from the preform, the bubbles will extend into gas lines, forming a desired microstructure arrangement.

Abstract: An isothermal, low pressure-based process of depositing material within a substrate has been developed and results in creating an extremely narrow reaction zone within which a more uniform and efficient deposition will occur. Sets of isothermal plasma operating conditions have been found that create a narrow deposition zone, assuring that the deposited material is clear glass rather than soot particles. The chemical delivery system, in one arrangement, utilizes rods of solid phase source material (which may otherwise be difficult to obtain in gaseous form). The operating conditions are selected such that the hot plasma does not transfer a substantial amount of heat to the substrate tube, where the presence of such heat has been found to result in vaporizing the reactant material (creating soot) and developing hot spots.