Generalizing about types of networks / systems. Compared with the Hardware / Software distinction in TheCityAsInformationSystem (OK, that's really the HerbertSimon distinction between HardwareComplexity and SoftwareComplexity : in hardware, the complexity is in the components (nodes) which have a rich repertoire of sophisticated behaviours, in software complexity, it's in the links, or more precisely, in the continuous changing and rewiring of the links.)
Here homogenous = the network contains only one type. Heterogenous means multiple types. Applies to both nodes (components) and arcs (links, flows, routes) Heterogenous arcs therefore means roughly that there are TypedLinks.
"Arcs connect" can refer to situations where arcs only connect one node to another, and situations where arcs can be higher level and connect nodes to arcs or arcs to arcs. This second situation is useful for SystemsThinking where we can imagine a system where arc is an output from a process which affects the flow-rate of another connection.