Lanthanide upconversion (UC) luminescent nanocrystals exhibit a uniquely sharp multiband emission over a broad spectral bandwidth covering the ultraviolet region to the near-infrared (NIR) region when subjected to NIR excitation, which is vital for multichannel optical communication using wavelength-division multiplexing to achieve high transmission rates. In this study, we experimentally and theoretically investigated the spectral and spatial characterization of a single NaYF