The JHN 9401-2 standard is a set of rules that specify the physical characteristics of fiber-optic connectors and the minimum performance levels that the connectors must meet in order to be certified for use in fiber-optic networks. It covers both single-mode and multi-mode fiber-optic connector types, including SC, ST, FC, LC, MT-RJ, and MU connectors. It also includes requirements for optical, mechanical, and environmental performance, as well as restrictions on the design and material of the connector. The standard also provides guidance on coding and color conventions for fiber-optic connectors.