The transmission performance of WDM transmission systems is influenced by many effects according to the type of optical fiber employed in the system. Japanese high-speed transmission systems use dispersion-shifted fiber (DSF). It is well known that the transmission distance of WDM systems employing DSF is restricted by fiber four-wave mixing (FWM). Unequally spaced channel allocation (USCA) was proposed to mitigate the FWM effect. However, if no FWM light is allowed to fall on any optical channel, the number of channels is limited. This paper proposes a new method to extend the number of USCA channels to more than 16 under the optical bandwidth limitation. This method determines channel allocation by considering the distribution of the zero-dispersion wavelength of the optical fiber. The transmission performance of a WDM transmission system employing the proposed USCA methodology is clarified by numerical simulation to confirm that the optical bandwidth requirements can be reduced without degrading transmission performance. As a result, for 16 2.5 Gbit/s, if the fiber input power ranges from -3 dBm/ch to 3 dBm/ch, the achievable transmission distance is 700 km; the fluctuation in zero-dispersion wavelength is assumed to have the standard deviation of 5 nm. For 16 10 Gbit/s, if the fiber input power ranges from 0 dBm/ch to 3 dBm/ch, the achievable transmission distance is 400 km.

A simple method of compensating the DC drift of LiNbO3 Mach-Zehnder intensity modulators for very high speed optical transmission systems is proposed. This method adds low frequency perturbation to the modulator driving signal, and controls the bias voltage using the detected envelope of the modulator output signal. The control circuit is successfully demonstrated to work with less than a 0. 1-dB power penalty.

BP-LDD n+ self-aligned GaAs-MESFETs with Au/WSiN bilayer gate have been fabricated on 3-indiameter GaAs substrate which demonstrates the splendid potentiality of GaAs-MESFET technology. The 0.3-µm gate GaAs-MESFETs show a peak extrinsic transconductance of 550 mS/mm with a threshold voltage of -1.4 V. From S-parameter measurement, the MESFETs demonstrate a peak cutoff frequency of 56 GHz and a maximum oscillation frequency of 120 GHz. Moreover, a monolithic distributed amplifier has been fabricated using the four GaAs-MESFETs with 0.3 µm gate length. The amplifier has achieved a high gain of 7.3 dB with a 3-dB down frequency bandwidth of 0.5-30 GHz.