High data rates transmitted in fiber beyond 500 km

Oct. 1, 1995
Unrepeated transmission at data rates u¥to 2.5 Gbit/s have been shown out to total-signal-path fiber lengths of 501 km by investigators at AT&T Bell Laboratories (Holmdel, NJ). Fiber loss for the signal is 89.7 dB. The test setu¥used high-power 1.48-µm diode-pumped Raman lasers with 1.3-W output for enhanced power efficiency from remotely pumped post- and preamplifiers.

High data rates transmitted in fiber beyond 500 km

Unrepeated transmission at data rates u¥to 2.5 Gbit/s have been shown out to total-signal-path fiber lengths of 501 km by investigators at AT&T Bell Laboratories (Holmdel, NJ). Fiber loss for the signal is 89.7 dB. The test setu¥used high-power 1.48-µm diode-pumped Raman lasers with 1.3-W output for enhanced power efficiency from remotely pumped post- and preamplifiers.

Key technologies are the high-power pum¥sources and dispersion-compensating fiber, which allow low-loss silica core to be used beyond the initial launch fiber segment. The transmission distance increases to 529 km, equivalent to a fiber loss of 93.8 dB for the signal, when forward error correction coding is used along with stimulated Brillouin scattering. Forward error correction allows for some redundant data bits as "overhead," for a 3-dB improvement. Brillouin scattering is suppressed by passing the signal through a phase modulator driven by a frequency-shifting comb of low-power frequencies to broaden the spectrum and increase power.

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