Got told my fiber handoffs were causing jitter and had to redo half my network

A customer ran a 3-day latency test and sent me the results showing 15ms spikes every hour. I had to switch from single-mode to multi-mode transceivers on our Cisco gear and the problem vanished. Anyone else have a client call you out on something obvious you missed?

2 comments

2 Comments

simon_coleman3h ago

Used to think single-mode was always the better choice for everything, figured multi-mode was old tech. A similar thing happened to me on an MPLS handoff where the optics were just too sensitive for the distance and kept flipping bits. Swapped to multi-mode transceivers on both ends and the red errors dropped to zero, real eye opener how much the hardware specs actually matter in the real world.

patkelly11m ago

Yeah so that's not quite how the optics work. The issue with singlemode on short runs isn't that it's "too sensitive" in the way you're describing. Singlemode transceivers are designed for long distances, and if you plug one into a short patch cable, the light can actually be too strong and overwhelm the receiver, causing errors. That's why you'll sometimes see folks using attenuators on short singlemode links. Multimode handles that better because it's built for shorter distances and the light scatters more, so you don't get that overload problem. Good catch swapping them out though, sometimes the fix is just using the right tool for the distance.