As we all know, the internal temperature of the deposition tube is what matters, since the reaction is occurring on the inside. However, the process pyrometer is reading the external temperature. SG Controls offers a diameter control system, which controls and provides an optical measurement of the tube. This system is closed loop, with the pressurization system controlling tube back pressure with feedback from the diameter measurement and set-point. Having an automated system to control tube diameter is very important. While I’ve had some success controlling diameter manually, that approach is not nearly as reproducible as an automated system.

Larry Donalds

About Larry Donalds

Larry Donalds began his career at Fiber Optic Center (FOC) in 2017 as Business Development, Fiber Design and Manufacturing, Technical Sales. Larry brings more than 35 years of experience from 3M Company in St. Paul, MN, after recently retiring. During his time with 3M Company, he spent 24 years in the development and manufacture of specialty optical fiber utilizing “voice of the customer,” helping 3M design and produce optical fibers to meet specific customer applications and performance criteria. Projects included the development and production of PM, PZ, EDFA (Erbium Doped Fiber Amplifier) fiber, radiation-hardened fiber for gyroscopes, solution doping of preforms, patent development for Oxyfluoride Erbium fiber, organometallic rare earth deposition and a rare earth single mode fiber bend and position sensor. In his fiber position at 3M, Larry maintained and operated MCVD equipment from SG Controls Ltd of Cambridge, England, whom FOC has represented in North America for over 25 years. Larry has achieved several awards during his career including 3M Golden Step Award, Photonics Circle of Excellence Award, R&D 100 Award, 3M Circle of Technical Excellence Awards in 1983, 2001 and 2008 and the 3M Ideation Challenge award in 2017. Larry and his wife reside in Arizona. Outside of FOC, Larry’s hobbies include fishing, boating, snowmobiling, outdoor landscaping, and deck design and construction.