A 42 km single-mode fibre has been observed by an OTDR at 1.55 ¿m wavelength utilising a semiconductor laser and a Ge-PIN photodiode cooled to 77 K with liquid nitrogen together with a feedback resistor of a transimpedance amplifier. The dark current and the thermal noise have been drastically decreased.
Published in:
Electronics Letters
(Volume:20
,
Issue:
6
)
Date of Publication: March 15 1984