A transceiver is the correct answer because it is the Layer 1 (Physical Layer) component that physically terminates and converts fiber-optic signals on an SFP-capable switch. In CompTIA Network+ N10-009 objectives, transceivers—such as SFP, SFP+, QSFP, and QSFP+ modules—are explicitly identified as physical interface components that handle signal transmission and reception. These modules convert electrical signals from the switch into optical signals for fiber cabling (and vice versa), enabling communication over different media types and distances.

A modem is also a Layer 1 device, but its purpose is to modulate and demodulate signals for WAN technologies such as DSL or cable—it does not terminate fiber connections on switches. An Ethernet NIC provides network access for end devices like computers and servers and typically terminates copper Ethernet, not modular fiber interfaces on switches. A repeater regenerates and amplifies signals to extend cable distances but does not provide fiber termination or media conversion at a switch port.

According to Network+ standards, SFP transceivers are essential for flexible network design, allowing administrators to select appropriate fiber types (single-mode or multi-mode), wavelengths, and distances while remaining compliant with physical layer requirements.