Abstract A study of optical fibre power metre calibrations is presented based on comparison with fibre-coupled cryogenic radiometry. Three nearly identical cryogenic radiometers are used together with a free-space absolute spectral responsivity measurement facility. The results show that the dominant sources of uncertainty originate not from the radiometers or the transfer standard detector, but from the optical path components used to convey light from the source to the detector. The properties of the optical radiation, defined by wavelength, polarization, and modal quality, together with system components such as optical fibres, fibre switches, fibre splitters, polarization controllers, and external influences including temperature and vibration, limit the achievable uncertainty. Measurements are performed at optical power levels near 100 µW, a regime in which the underlying measurement technology has matured over several decades. The absolute uncertainty ranges from approximately 0.0010 A W −1 to 0.0043 A W −1 , depending on the wavelength and components. The results provide a quantitative basis for assessing the limits of uncertainty reduction in fibre-based optical power measurements and are relevant to future uncertainty analyses of fibre-coupled single-photon detector efficiency in quantum communications and quantum technologies in general.
Passive daytime radiative cooling (PDRC) is an emerging, electricity-free cooling approach that can achieve sub-ambient temperatures by emitting thermal radiation through the atmospheric transparency window (8-13 mu m). It therefore offers a promising route to mitigate the growing demand for cooling across a broad range of applications. As the number of reported PDRC materials and demonstrations increases rapidly, robust and broadly comparable figures of merit (FoMs) and testing protocols are increasingly needed to assess performance and to translate laboratory results to diverse outdoor conditions. However, commonly used FoMs and experimental methods are often reported inadequately or without key experimental information, which hampers reproducible benchmarking and cross-study comparison. This perspective critically reviews the main classes of spectral and thermally derived FoMs. In doing so, it discusses numerical and experimental testing approaches by highlighting recurring limitations that drive discrepancies between studies. Building on this analysis, we propose a metrological framework for the classification and comparison of PDRC materials and provide a minimum reporting checklist to enable efficient inter-laboratory comparison and more reliable performance assessment.
Proper and regular calibration of eye-tonometers is crucial, as inaccurate intraocular pressure measurements can lead to both underdiagnosis and overtreatment of glaucoma. Ensuring measurement accuracy is therefore vital for safe and reliable clinical practice. The article focuses on regional cooperation in ensuring the metrological traceability of eye-tonometers in Central European countries. It describes the joint activities aimed at exchanging expertise and improving the quality of intraocular pressure measurements. The cooperation also included a study the developed reference (transfer-standard) devices, the results of which contribute to enhanced reliability of clinical measurements and to the promotion of unified metrological standards within the region. The cooperation will gradually have a direct impact on clinical practice and patient safety. More accurate and comparable intraocular pressure measurements will enable better diagnosis and monitoring of glaucoma, optimization of treatment procedures, and reduced risk of misinterpretation of results.
Digital real-time oscilloscopes are increasingly of interest for metrological applications, e.g., for measurements of digital signal properties, in electromagnetic interference detection, and also for calibration applications. The traceable calibration of these instruments is normatively only established for the property rise time, i.e. the speed of the oscilloscope's step response to a fast pulse, which can be transferred to the rise time of other, slower pulsed signals. The application of full waveform metrology to this type of instrument could allow for signal reconstruction of more complex signals as well as for analysis of complete pulses instead of only the rise time. This paper proposes the validation of proposed correction methods using a model-based approach as well as a comparison of modeled and measured waveforms using different instruments.
