Dense Wavelength Division Multiplexing (DWDM) is the correct choice as it allows for a greater number of wavelengths, or channels, over a single fiber, facilitating higher data throughput over long distances compared to other multiplexing technologies. DWDM can offer a significant expansion in bandwidth by utilizing extremely narrow wavelength intervals, thus supporting a high number of channels. Optical Time Division Multiplexing (OTDM), while using optical signals, relies on a different principle where signals are interleaved in time rather than differentiated by wavelength, and therefore does not inherently support the maximum bandwidth expansion provided by DWDM. Coarse Wavelength Division Multiplexing (CWDM) is a wavelength multiplexing technology similar to DWDM but with fewer channels due to wider wavelength intervals and hence less capacity, rendering it suboptimal for the scenario described. SONET/SDH, although they can be transported over DWDM systems, are multiplexing standards for the transmission of larger data volumes over fiber networks but don't fit the requirement of wavelength-based signal separation.