This paper aims to make understand the fundamentals and recent advancement in Dense Space Division Multiplexing (DSDM). Similar to Dense WDM (DWDM) with dense wavelength spacing and high count of over several tens of wavelength channels, it is shown that DSDM with high spatial density and large spatial multiplicity is effective for greatly expanding transmission capacity. Multicore fibers and few-mode fibers have potential application in realizing Dense Space Division Multiplexing system. As the main objective was to study the most important parameter that establishes the performance of optical fiber in distance and capacity. As in MCF, many cores tightly packaged together is inevitable that signals cause undesired effects from one core to another. Beside the physical space available for core, the maximum tolerated crosstalk dictates the maximum quantity of cores we can use. Design of single-mode 31 core fiber with Quasi Single Mode (QSM) core is demonstrated. Measurement of Spatial Channel Count (SCC) for different number of cores is studied. And to give the readers a glimpse of recent development in DSDM and MCF technology, some noticeable research papers have also been discussed.