Definition of a FPGA-Based SoC Architecture for PRBS Transmission in Optical Spectroscopy

Optical spectroscopy is a well-known tool typically employed for characterizing the properties of materials by analyzing their iteration with light. One of the most spread techniques is the dual comb spectroscopy, since it accomplishes ultra-high resolution and high sensitivity measurements with a relatively simple platform including a single, relatively narrow-band photodetector. The employed optical dual comb can be implemented through electro-optic (EO) modulation driven by pseudo-random binary sequences (PRBSs) at high data rates, commonly in the range of tens of gigabit per second. For that purpose, the run-time generation and transmission of adaptive PRBS are still an open challenge, often involving expensive and not flexible high-speed digital systems, with a few commercially available solutions that sometimes do not match the application requirements efficiently. In this context, this work describes the definition and implementation of a system-on-chip (SoC) architecture, based on a field-programmable gate array (FPGA) device, capable of generating and transmitting two PRBS for a dual comb, at a data rate up to 5 Gb/s. The architecture can be configured and its operation modified in run time, thanks to the general-purpose processor involved, in charge of managing an Ethernet link to receive new PRBS to be transmitted or set up certain parameters. The proposed design has been validated experimentally on a dual comb spectroscopy measurement, where the absorption of a hydrogen cyanide (HCN) gas cell has been successfully characterized.