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
Single Mode vs. Multimode Fiber | SERVPAC
Single-mode optical fiber - Wikipedia
The difference between single-mode fiber and multi-mode fiber
Understand the different single-mode & multi-mode fiber optic cable types
Single Mode vs Multimode Fiber: What are the Differences?
Single Mode vs Multimode Fiber: What are the Differences?
OS2 Single Mode Fiber Optic Cable | FutureFLEX® Air Blown Fiber
Fiber Optic Cable Types: Single Mode vs. Multi-mode… - AddOn Networks