In this paper we successfully demonstrate the reach improvement of spectrum-sliced dense wavelength-division-multiplexed passive optical network (SS-DWDM PON) where amplified spontaneous emission (ASE) source is used as a seed light. Investigated optical system is built on the ITU-T DWDM frequency grid, defined in recommendation G.694.1 and therefore it is potentially much more compatible with other already existing WDM PON optical systems. In this way it is possible to replace the classic WDM PON system with our proposed extended-reach spectrum-sliced WDM PON system and reduce complexity of network architecture as well as cost per one user. The maximum reach of the spectrum-sliced dense wavelength-division-multiplexed passive optical network (SS-DWDM PON) system with data transmission speed 2.5 Gbit/s can be fairly limited by chromatic dispersion (CD) because of large optical bandwidth per channel compared to the bit rate. And therefore, dispersion degrades the performance of a SS-DWDM PON system more than it is observed in conventional laser-based system. This paper contains the investigation of high speed 8-channel spectrum-sliced DWDM PON system with efficient CD compensation methods like dispersion compensating fiber (DCF) and fiber Bragg grating (FBG). It is shown that CD compensation has an important role for guaranteed downstream optical link performance and maximum transmission line length of high speed SS-DWDM PON system. Results show that FBG used for CD compensation in high speed spectrum-sliced dense WDM PON systems provide better accumulated CD compensation and increase optical link length up to 150% while DCF fiber provides up to 130% reach improvement.