An open and flexible digital phase-locked loop for optical metrology

TL;DR

This paper introduces an open-source, FPGA-based digital phase-locked loop platform for optical metrology, enabling flexible laser stabilization with high bandwidth and low latency, demonstrated through fiber noise cancellation.

Contribution

The paper presents a customizable, low-cost digital PLL platform on Red Pitaya with remote control and measurement tools, optimized for optical metrology applications.

Findings

Achieved noise cancellation over 30 kHz bandwidth

Total latency of 565 ns limits control bandwidth to ~225 kHz

Demonstrated fiber noise canceler over 400 m fiber link

Abstract

This paper presents an open and flexible digital phase lock loop optimized for laser stabilization systems. It is implemented on a cheap and easily accessible FPGA-based digital electronics platform (Red Pitaya) running a customizable open-source firmware. A PC-based software interface allows controlling the platform and optimizing the loop parameters remotely. Several tools are included to allow measurement of quantities of interest smoothly and rapidly. To demonstrate the platform's capabilities, we built a fiber noise canceler over a $400$~m fiber link. Noise cancellation was achieved over a $30$~kHz bandwidth, a value limited mainly by the delays introduced by the actuator and by the round-trip propagation over the fiber link. We measured a total latency of $565$~ns for the platform itself, limiting the theoretically achievable control bandwidth to approximately 225 kHz.