Compact digital system for an iodine-stabilized laser

A compact digital control system based on an all-programmable system-on-chip iodine-stabilized laser is presented for realization of the meter. The system is composed of ZYNQ7000, peripheral circuits, and human–computer interaction, which can operate independently. An n th-harmonic extraction algorithm with less resource consumption is used in this system. The digital system overcomes the problems of complex debugging, large volume, and manual locking. Additionally, customers can set up, calibrate, and upgrade the system by themselves. Its stability is similar to that of the current analog system, with long-term stability of up to 10 − 13 . The repeatability of the two lasers with the digital system is approximately 1.5 × 10 − 11 , and the absolute frequencies satisfy the international recommendation.