| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce influences of narrow band filtering in a high-density wavelength division multiplexing (WDM) communication system. <P>SOLUTION: A transmitter of a WDM communication system is equipped with a Mach-Zehnder modulator (MZM) for dealing with a duobinary data stream. A three-level electrical signal is applied to the MZM to modulate the light. At the second signal level, the modulator substantially blocks light transmission. At the first and third levels, the modulator transmits light corresponding to the duobinary "-1" and "+1" bits, respectively such that a relative phase shift between the optical bits is different from 180 degrees, i.e., the phase shift value employed in prior-art optical duobinary modulation. By appropriately selecting voltages for the first and third levels, the relative phase shift between the optical bits can be adjusted to reduce harmful effects of optical bandpass filtering typically present in the WDM communication system, thereby reducing the number of decoding errors at the receiver. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
