Cooling an optical fiber to 4.5 K by indirect thermal contact with a liquid-helium flow and spectroscopic temperature measurements.
We have made it possible to cool a 10-m-long optical fiber to 4.5 K in a compact helium-flow cryostat. The cryostat is vacuum loaded and the cooling principle is based on thermal contact with a copper holder cooled by the liquid-helium flow. To measure the temperature directly, we employed two different spectroscopic methods depending on the temperature regions. One was photon-counting Raman spectroscopy and the other was Brillouin spectroscopy. We used certain devices to improve the cooling efficiency and confirmed that the fiber was uniformly cooled to 4.5 K.
Hashimoto
Daisuke
D
NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198, Japan. hashidai@will.brl.ntt.co.jp
Shimizu
Kaoru
K