Published online by Cambridge University Press: 22 February 2011
The characterization of silica “sooting” torches used in optical waveguide manufacture by external flame-hydrolysis deposition processes such as Outside Vapor Deposition (OVD) and Vapor-phase Axial Deposition (VAD) prflents a formid.ble high temperature environment at > 2000°C in the presence of > 1012 particles/cm3 of silica. This paper describes the first application of Dynamic Light Scattering (DLS) to probe particle sizes in an actual lightguide burner following the “triple-flame” VAD design. DLS, also termed Photon Correlation Spectroscopy (PCS) or Diffusion Broadening Spectroscopy (DBS), was previously identified as a viable diagnostic tool for in-situ particle measurements in silica-sooting flames by W. L. Flower [1] and through an earlier collaboration between AT&T and the Sandia Combustion Research Facility. In applying DLS, however, our experience with the VAD torch reveals that a specialized experimental method will undoubtedly be required to deal with the inevitable presence of low frequency system instabilities in industrial systems.