What Does Gigabit Interface Converter (GBIC) Mean?
A gigabit interface converter (GBIC) is a transceiver that converts optical signals to electrical signals and vice versa in a gigabit Ethernet or fiber to the home (FTTH) configuration. These interface converters were most common in early 2000s. GBIC is not obsolete, but has been largely replaced by a smaller and more lightweight version.
Techopedia Explains Gigabit Interface Converter (GBIC)
A gigabit interface converter (GBIC) is an electrical interface that makes the gigabit port capable of supporting a large number of physical media through hundreds of kilometers. The transceiver is connected at the end of the Ethernet cable to facilitate signal conversion. A later variation of the GBIC, the small form-factor pluggable transceiver (SFP), is also called a mini-GBIC. The SFP performs the same functions but with a smaller form factor. The transceiver module is easily configurable and can be upgraded in opto-electrical systems without shutting off the system (hot swappable).