This paper describes a prototype of an optoelectronic oscillator delivering a microwave signal with a power of 5 dBm at 10.52 GHz, promised to be compacted. It is evaluated in terms of its phase noise performance, and the associated ±2 dB uncertainty at 2 σ is calculated according to the international standards enacted for metrology.

Summary form only given: Recent approach is used to calculate uncertainty for an microwave and optoelectronic system. The deduced global uncertainty on spectral density of phase noise in the range of 2 dB is improved.

International comparisons play a critical role in ensuring precision, accuracy, consistency, and trust in the global metrology system. The Comité International des Poids et Mesures (CIPM) established the Mutual Recognition Arrangement (MRA) in 1999 to facilitate global trade. This paper gives an overview of the critical role of international comparisons to National Metrology Institutes (NMIs), industrial calibration laboratories, and research laboratories in fostering global measurement equivalence and the CIPM MRA. NMIs rely on Key and Supplementary Comparisons to ensure the mutual recognition of calibration and reference material certificates, vital for global trade and regulatory compliance. Industrial calibration laboratories participate in inter-laboratory or international comparisons to validate their calibration and measurement capability (CMC) and balance their risk management. Research laboratories push the frontiers of measurement science and validate their measurement result via international comparisons. Through some examples of comparisons, the paper illustrates how measurement result discrepancies uncovered in comparisons drive technical improvements, uncertainty component identification, and measurement technique refinement. International comparisons enhance scientific credibility, build public trust, support industrial innovation, and drive evolution in measurement science. As technological demands grow, fostering broader participation in international comparisons by various metrology and research laboratories remains crucial to maintain a robust and reliable global metrology system.

Modern approach according to recent standards is used to determine uncertainty on phase noise for an optoelectronic measurement system. Deduced global uncertainty on the spectral density of phase noise is 1.6 dB.

The use of a shorter delay line in a optoelectronic phase noise measurement system working in X-band, allow a characterization of the phase noise far from the carrier. Fourier frequency analysis can be extended from 10⁵ to 2.10⁶ Hz by introducing a 100 m delay line in addition of a 2 km optical fiber.