Abstract: In a communications system, a generalized partial response signaling (GPRS) technique is employed to compensate for intersymbol interference. To this end, signal points representative of data to be transmitted are selected from a signal constellation. This signal constellation includes a multiplicity of signal points which are regularly spaced within a polygonal region having more than four sides. The selected signal points are precoded in the transmitter in accordance with the GPRS technique. Because of the particular choice of the signal constellation used, the precoded signal points for transmission occupies a region identical to the polygonal region.

Abstract: A hybrid fiber which, at the operating wavelength, has a desirable fiber dispersion characteristic and a relatively large effective area is provided. Hybrid fibers are constructed in accordance with the principles of the invention by splicing together a fiber with a large effective area but typically unsatisfactory fiber dispersion characteristics to a fiber having excellent dispersion characteristics but a smaller effective area. The resulting hybrid fiber has an increased effective area and desirable fiber dispersion characteristics at the low-loss operating wavelength.