Research on optical fiber transmission method for ultra-high intermediate frequency signals in terahertz polarimeter-interferometer

The Tokamak experimental hall presents a highly complex electromagnetic environment, where conventional cable transmission of multiple high-speed signals is prone to interference and attenuation, limiting measurement accuracy. To address this issue, this paper develops a high-speed optical fiber transmission system based on FPGA technology for the EAST terahertz polarimeter–interferometer (POINT). The system first employs a high-speed analog-to-digital converter (ADC) to perform dual-channel, high-resolution sampling of the original signals. The digitized data are then processed through the FPGA’s GT module, packaged into parallel format, and transmitted via dual-channel SFP optical fiber interfaces to the receiving FPGA. On the receiving side, the data are restored by digital-to-analog conversion (DAC) and subsequently delivered to a digital phase demodulator (DPD), enabling real-time computation of electron density and Faraday rotation angle. Experimental validation demonstrates that the proposed scheme achieves high throughput, low latency, and strong reliability, making it well suited for polarimetric interferometry and other plasma diagnostics requiring high signal integrity.