Single-mode fiber guides one ray of light down a hair-thin core, and that constraint is what buys distance: where multimode measures reach in hundreds of metres, single-mode measures it in kilometres. GRT single-mode transceivers are designated SM and typically work at 1310 nm and 1550 nm wavelengths, spanning the module families — SFP for gigabit access, SFP+ at 10G, SFP28 at 25G and QSFP28 at 100G. The F1102EBPLR bypass card’s bundled modules are single-mode parts rated for 10 km, a useful anchor for what the class delivers.
Specifying single-mode is mostly about the loss budget: connector count, splice quality and total distance decide whether a standard-reach module suffices. It is also the future-proof choice — single-mode plant installed today carries every rate generation, which is why new campus and riser builds overwhelmingly choose it even when today’s links are short.
Choose single-mode when
- Links leave the room: risers, campus, metro, leased spans
- You are installing new fiber plant (rate-proof for decades)
- Links must exceed a few hundred metres at any speed
What wavelengths do GRT single-mode modules use?
Typically 1310 nm and 1550 nm, per the single-mode modules in the catalogue. BiDi variants use one of each, one per direction.
Can single-mode and multimode modules be mixed on a link?
No. Both ends and the fiber between them must be the same discipline. Mode mixing is the most common cause of "mystery" link failures.