An optical fiber accessory includes a front housing, a rear housing sleeve, and a loopback module. The front housing defines two insertion slots extending in a front-rear direction and spaced apart from each other in a first direction perpendicular to the front-rear direction, and two core slots being respectively in spatial communication with the insertion slots. The rear housing sleeve is sleeved on a rear end of the front housing and defines a receiving space in spatial communication with the core slots. The loopback module is disposed in the rear housing sleeve, and includes two ferrules fixed onto the rear housing sleeve, and an optical fiber loop having two ends respectively connected to the ferrules and disposed in the receiving space. The ferrules project toward the front housing in the front-rear direction and extend respectively into the core slots.

An optical fiber loopback assembly includes a fiber optic connector and a loopback shell coupled to a boot of the fiber optic connector. The fiber optic connector can be a known connector, thereby avoiding the need for specialized components or modifications. The loopback shell includes a portion behind the boot of the connector, but can have a compact design that is still configured to store excess length of loopback optical fibers.