High speed analog fiber optical transmission link based on voltage to frequency converter technique for ITER-India Gyrotron test facility

Electron Cyclotron (EC) system is one of the RF auxiliary heating and current drive systems, based on high power, high frequency Gyrotron sources, is used for fusion plasma applications. To test a Gyrotron, various auxiliary systems like super conducting magnet, High Voltage Power Supplies (HVPS), auxiliary power supplies, cooling water system, waveguide components and a Local Control Unit (LCU) are required. LCU plays very crucial role for safe and reliable operation of the Gyrotron system. The LCU consists of Sequence & real time control, Interlock protection, Real time Data acquisition and signal conditioning. A reliable high speed, precise and high frequency analog signal conditioning/transmission in harsh Electro Magnetic Interference (EMI) environment with ground & high voltage isolation and filtering are utmost requirements for some critical operational parameter transmission; provided by this analog fiber optical link. The critical field signals will be coming from various sub-systems such as high voltage power supplies (-55kV Main HVPS and 35kV Body Power supply) and Gyrotron diagnostic system (RF power, arc signals etc.). It is important to develop a high speed and precision analog fiber optic transmission link for monitoring and acquisition of such critical parameter analysis during operation and post processing. A prototype modular fiber optic analog transmission link has been designed and developed indigenously based on the technology of Voltage-to-Frequency (V/F) and Frequency-to-Voltage (F/V) conversion and successfully tested in laboratory environment. This paper presents requirements, approach, detail design, features and performance test results.