Fig. 3: Optical property characterizations of the four-tube truncated double nested antiresonant nodeless fibre (tDNANF).
a Measured spectral propagation loss and macrobend loss under a bend radius (Rb) of 6 cm. b Extra loss real-time recorded in a quadrupolar winding. The coil length is 469 m, an amplified spontaneous emission (ASE) source of 40 nm bandwidth is implemented, and the innermost and the outermost radii of the fibre coil are 6 cm and 7.6 cm, respectively. c Fourier transform of the optical transmission spectrum of the 469 m quadrupolar-wound coil at 1550 nm measured by spatially and spectrally resolved (S2) imaging method. d Measured phase drifts over a 3 m polarization-maintaining fibre (PMF) and a 10 m four-tube tDNANF at 1550 nm with the temperature increasing from 25 to 55 °C, along with the fitted Shupe constants (S). e Measured principal axis offsets relative to the orientations at which minimum powers are detected in a crossed-polarizer setup at various temperatures. A 10 m four-tube tDNANF is measured in a 6 cm radius loop configuration. f Estimated extinction ratio between the two polarizations of the total integrated power from 1525 to 1565 nm based on the measured principal axis offset in (e) (black squares, see “Methods”), along with measured polarization extinction ratio (PER) of the 469 m coil by using an ASE source of 40 nm bandwidth and a commercial PER meter (red star).
