Can single-mode SFP modules run over an old 200 m multimode fibre?
4
The poster had an existing multimode fibre run of about 200 m that could not be replaced and only single-mode SFP modules available. The question was whether a 1G single-mode SFP pair would establish a stable link over multimode fibre, and what the practical limits were. The thread also raised the reverse case (multimode optics over single-mode fibre).
- Transceivers: 1G single-mode SFP (1310 nm), 1G multimode SFP
- Form factor: SFP
Symptoms / messages:
fibre type mismatch
uncertain link stability
Comments 3
Several users reported it working in practice at 195-400 m for months or years; at gigabit speed over 50/125 fibre the standard allows up to about 500 m, and the core-diameter mismatch effectively acts as an attenuator.
The reverse case (multimode SFP into single-mode fibre) does not work because of very large coupling loss.
Use mode-conditioning patch cords for a cleaner launch into multimode fibre; the safer answer is still to buy multimode SFPs.