What was the original form factor for removable transceivers used in Gigabit interfaces?

The original form factor for removable transceivers used in Gigabit interfaces is the Gigabit Interface Converter (GBIC). Introduced in the late 1990s, GBIC was designed to support 1 Gbps connections and was a significant advancement in modular transceiver technology, allowing network administrators to easily swap and replace transceivers to accommodate different types of media or interfaces without replacing the entire interface card.

While other options such as SFP+ and XFP also serve similar purposes in newer generations of networking equipment, they were developed later. SFP+ was an evolution of the SFP design that supports data rates of up to 10 Gbps, while XFP was developed to manage 10 Gbps links in a slightly different form factor. QSFP+ is designed for even higher speeds (up to 40 Gbps) and is used for aggregating multiple channels. However, GBIC remains the original standard for Gigabit interfaces, marking it as the first modular transceiver type widely adopted in the industry.