10-Gbit/s system transmits 100 km without dispersion compensation

Oct. 1, 2001

Ioannis Tomkos and coworkers at Corning Incorporated's Photonic Research and Test Center (Somerset, NJ) and NTT Electronics Corp. (Ibaraki, Japan) demonstrated transmitting a 10-Gbit/s 1.55-µm signal from a directly modulated distributed-feedback laser over 100 km of fiber without any dispersion compensation.1 They managed the feat—the longest transmission distance for such a system yet reported—using a commercially available nonzero dispersion-shifted fiber that has a negative dispersion over the entire bandwidth from 1280 to 1620 nm.

Commercially available 1.55-µm directly modulated distributed-feedback lasers are attractive for use in metropolitan-area networks because they supply enough power to transmit 80 to 100 km. The frequency chirp of the lasers, however, severely limits the distance over standard single-mode fiber at bit rates of 10 Gbit/s and faster, and it precludes the use of wavelength-division multiplexing.

The group uses negative-dispersion fiber to balance the "positive" dispersion in the frequency chirp. They investigated transmission performance of the 1.55-µm 10-Gbit/s modulated laser at different biases and driving conditions. When the laser bias current was 55 mA and the modulation voltage was 2 V (peak-to-peak), the extinction ratio was 5 dB, and the measured peak-to-peak transient chirp was about 19 GHz. When transmitted over 100 km of the MetroCor negative-dispersion fiber and run through a preamplifier, the resulting signal had a bit-error rate of less than 10-15 (or a Q of 9.4 dB). This corresponds to a dispersion-length product of about 750 ps/nm.

With this remarkably high value for the dispersion-length product, and the group's previous WDM experiments, they believe that similar performance could be achieved for channels across the C- and L-bands amplified by erbium-doped fiber amplifiers.

For more information contact Ioannis Tomkos at [email protected].

Yvonne Carts-Powell

REFERENCE

  1. I. Tomkos et al., IEEE Photon. Tech. Lett. 13, 735 (July 2001).

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