A method for manufacturing quartz glass, wherein (a) an appropriate liquid starting material is evaporated by spraying it into a vertically arranged evaporation chamber, (b) the vaporous starting material is oxidized to form SiO.sub.2, and the SiO.sub.2is collected. The method is characterized in that the starting material to be evaporated is sprayed in on the bottom of the evaporation chamber and the vaporous starting material is removed at the top end of the evaporation chamber, wherein the evaporation chamber is designed such that components depositing in the chamber accumulate on the bottom of the evaporator and are sprayed once again, as well as an evaporator for applying the method.

Monolithic optical structures include a plurality of layer with each layer having an isolated optical pathway confined within a portion of the layer. The monolithic optical structure can be used as an optical fiber preform. Alternatively or additionally, the monolithic optical structure can include integrated optical circuits within one or more layers of the structure. Monolithic optical structures can be formed by performing multiple passes of a substrate through a flowing particle stream. The deposited particles form an optical material following consolidation. Flexible optical fibers include a plurality of independent light channels extending along the length of the optical fiber. The fibers can be pulled from an appropriate preform.

A soot glass deposit body is manufactured by placing a starting rod and a burner 22 for producing glass particulates in a reaction container, introducing a source material gas to the burner 22 through a supplying pipe 26, producing glass particulates by a pyrolytic oxidation reaction of the source material gas in a flame formed by the burner 22, and depositing the produced glass particulates on the starting rod. At the time, the source material gas to be supplied to the burner 22 is a siloxane, the burner 22 is heated so that temperature of the burner 22 falls within the range of from 30 C. to +30 C. relative to the boiling point of the siloxane, and also temperature of the supplying pipe is controlled within the range of from the boiling point of the siloxane to the boiling point plus 30 C.