These are link parts. Specify the far end and the medium, then the module or the injector. Tradinor treats a bare SFP cage or a PoE logo as incomplete.
SFP: medium, wave, distance
State the data rate, single-mode or multimode, wavelength, and the distance you need with the fiber you have. A 10 km single-mode module is the wrong part for a 50 m multimode patch. Bidirectional modules need a matched pair. Write both ends. If the switch vendor locks the cage, say you need a coded module or a vendor-approved one. Do not assume a generic module will be accepted.
PoE: class and the device
State the standard and the class the powered device asks for. A camera that needs a higher class will boot and then brown out on a low-power port. Cable type and length belong on the note because the loss is real. An injector is a reasonable buy for one device. A switch is the buy when many devices share a rack. Either way, write the watts at the device, the input voltage of the injector, and whether the data speed is 100 megabit or gigabit. Some injectors are not gigabit.
- SFP: rate, fiber type, wavelength, distance, connector.
- Both ends of a bidirectional pair.
- PoE: standard, class, and power at the device.
- Data speed through the injector, not only the power.
- Who approves a third-party module if the switch is locked.
| Part | Matching line | Common miss |
|---|---|---|
| SFP | SM or MM, nm, km | Multimode fiber, single-mode optic |
| PoE injector | Class and gigabit or not | A 100 megabit injector on a gigabit camera |
| PoE switch | Budget in watts for all ports at once | Adding ports until the budget collapses |
On delivery, read the SFP label for wavelength and distance before you patch it. Read the injector for the class and the data rate. A link light is not a power check. If the far device resets under load, compare its class with the port before you replace the device.
What to lock on the order
Write each link as a pair. For fiber, name the module at each end, the fiber type, and the patch length. For PoE, name the powered device and the class it requests, then the switch or injector that must provide it. Add the data rate. A power-only match that drops the link to 100 megabit will be discovered after the cameras are up. If the switch vendor publishes an optic list, attach it and say whether a coded third-party module is acceptable to your network owner. Put the total PoE budget on the switch line, summing the classes you will use at once, not the average. On delivery, read the optic label before it goes into a cage, and read the injector rate before it goes above a ceiling. A link light plus a device that reboots under load is a power-class problem. Compare the class before you replace the camera or the phone.
Questions buyers actually ask
Will any SFP fit any switch?
The cage may be the same. The switch still has an approved list, a speed, and a fiber type. A single-mode module will not light a multimode run just because it seats.
How much power does PoE really give the device?
The class and the standard say the power at the powered device after cable loss. The injector wattage headline is not that number.
Do I need a managed switch?
Not for a single camera or phone if an injector of the right class is acceptable. You do need the class, the voltage, and a cable that meets the standard you cite.