A GLC-SX-MM is an optical Small Form Pluggable (SFP) Gigabit Multimode SX Optical transceiver for Cisco switches. It can support up to 1km over laser-optimized 50 μm multimode fiber cable.

Multimode;

"Single-mode fiber gives you a higher transmission rate and up to 50 times more distance than multimode, but it also costs more."

A. G. Hanson has written:

'Optical waveguide communications glossary' -- subject(s): Fiber optics, Dictionaries

Rectangular Waveguide - TE10; (TM11 in case of TM waves)

Circular Waveguide - TE11;

There is a major difference in colors that separate a singlemode and a multimode. Single mode will be yellow or white. Multimode will be tan or black.