In fiber optics, most of the literature says that single-mode (SM) fiber allows only 1 mode of light to propagate/travel within, then how the same SM fiber allows WDM or DWDM, which
エンドレスシングルモード・ラージモードエリアファイバー
Cut-off wavelength of single-mode and polarization-maintaining fibers
Use 1550nm/1310nm SFP Over MMF or 850nm SFP Over SMF?
Fiber Operating Wavelengths: Why so many? - Optical Systems DesignOptical Systems Design
a) Experimental of our multi-wavelength imaging system; SMF, single... | Download Scientific Diagram
Multiplexed single-mode wavelength-to-time mapping of multimode light | Nature Communications
Cut-off wavelength, explained by RP; modes, waveguide, single-mode fiber