Primary standards of optical radiation total radiant flux are traditionally realized by absolute cryogenic radiometers  working on the principle of electrical substitution with a relative total uncertainty of 1e-4 in the power measurement. The current cryogenic radiometers though operate over a limited spectral range, usually from 350 nm to 800 nm and working with free space beam. For fibre optics telecom spectral range 1300 nm - 1650 nm this scale is then extended in several steps, typically via application of other standard detector systems such as spectrally flat room temperature pyro detectors  and spectrally dependent temperature stabilized solid state detectors , which adversely affects the scale accuracy by a factor of approximately one order of magnitude. The typical relative total uncertainty of state-of-the-art transfer standard fibre coupled detectors reaches 0.5 %.
Recently published results on planar electrical-substitution carbon nanotube cryogenic radiometer (PCBR)  brought the opportunities for using these systems as new absolute primary standards in telecom spectral range directly in fibre coupled configuration. This shortens the traceability chain, with a potential improvement in the total uncertainty to below 0.1 %. CMI in collaboration with NIST are developing the first prototypes of fibre coupled PCBR systems. First both free space and fibre coupled measurements have confirmed radiometric The paper will present both the core physical parameters of these PCBR electrical-substitution systems and initial results including the currently achieved agreement of traditional transfer standards with the PCBR at the level of 0.2 %.
The work reported in this abstract was partially funded by project EMPIR 14IND13 PhotInd. This project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme.
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Marek Šmíd, Geiland Porrovecchio, Malcolm G. White, Nathan A. Tomlin, Igor Vayshenker, Christopher S. Yung, and John H. Lehman, "Carbon nanotube planar absorber cryogenic bolometer as a novel primary absolute standard detector for optical power measurements for fibre optics and photonics (Conference Presentation)," Proc. SPIE 10683, Fiber Lasers and Glass Photonics: Materials through Applications, 106830Z (Presented at SPIE Photonics Europe: April 24, 2018; Published: 23 May 2018); https://doi.org/10.1117/12.2314835.5788853937001.
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