Although recent fiber-optic transmission experiments have shown impressive results in unrepeatered transmission distance at high data rates,1,2 only a small fraction of the information carrying capacity of the optical fiber has been utilized. To utilize fully the fiber bandwidth, it is desirable to use many closely spaced wavelength division multiplexed (WDM) channels in the minimum loss region ~1.5 μm. We report here the results of a ten-channel WDM system operating at 1.5-μm wavelength. The system was tested with 68.3 km of fiber and with a channel spacing and data rate of 1.35 nm and 2 Gbit/sec, respectively. The experimental setup is shown in Fig. 1. The lasers employed in this experiment were HRO distributed feedback (DFB) lasers.3 The pure single-longitudinal-mode operation, even under high-speed modulation, of these lasers was essential for achieving the narrow channel spacing, low cross talk, and error-free (<10−9-BER) operation. The laser wavelengths were between 1.529 and 1.561 μm and selected from several wafers with different design wavelengths.
© 1985 Optical Society of AmericaPDF Article