Cabling Things by Wentz Wu, CISSP/ISSMP/ISSAP/ISSEP,CCSP,CSSLP,CISM,PMP,CBAP

ANSI/TIA-568-D

As of 2020, the revision status of the standard is ANSI/TIA-568-D, published 2015, which replaced TIA/EIA-568-C of 2009, revision B of 2001, and revision A of 1995, and the initial issue of 1991, which are now obsolete.
Source: Wikipedia

TIA/EIA-568

TIA/EIA-568 defines structured cabling system standards for commercial buildings, and between buildings in campus environments. The bulk of the standards define cabling types, distances, connectors, cable system architectures, cable termination standards and performance characteristics, cable installation requirements and methods of testing installed cable.

TIA/EIA-568-D.1 defines general requirements,

TIA-568-D.2 focuses on components of balanced twisted-pair cable systems

TIA-568-D.3 addresses components of fiber optic cable systems, and

TIA-568-D.4, addressed coaxial cabling components.

Source: TIA.FOTC

Optical Fiber

Why Run Multimode at All?

The answer to this comes down primarily to budget and applications. Single mode cable requires single mode transceivers, and those tend to be far more expensive than multimode equivalents. The difference in electronics can bring single mode system costs far above those of multimode, even if the per foot cost of single mode cable is low. This is one of the primary reasons we’ll generally recommend multimode before single mode fiber in lower-distance applications.

However, there are still times when single mode may be recommended for short cable runs. It depends on the installation!
Source: cleerlinefiber.com