Crossing over between worlds isn’t just something that John Edward does.
Inside Plant (ie active equipment such as switches, routers, multiplexers, etc) is typically managed using Inventory Management software or Configuration Management Databases (CMDB). In this paradigm, a “circuit” is a single link between two entities such as ports on a multiplexer.
Outside Plant (eg pits, pipes, cables, splice enclosures, etc) is often managed by GIS (Geographic Information Systems) or similar, where a circuit can comprise of a single fibre.
The dilemma for many products lies in the fact that a single point-to-point link between inside plant (1 circuit) is underpinned by a pair of fibres (2 transmit/receive pairs as separate circuits) in the outside plant world. Similarly, on the inside plant, there is often a transmit connector and a receive connector that are collectively seen by it’s management systems as being just a single port. The single port actually has two fibre or frame appearances, making seamless cross-over between inside plant and outside plant the domain of only the most “spiritual” of OSS products