Application of optical fiber in monitoring long-distance transmission: single-mode multi-mode, splicing and optical modules
When is fiber optic needed
The PoE effective distance of Category 5e/Category 6 network cable is about 100 meters. If it exceeds, you need to relay or change the medium. It is recommended to directly connect to optical fiber in the following situations: cross-building backbones in the park, perimeter points exceeding 150 meters, Strong electromagnetic interference environments (near substations and computer rooms), and open areas sensitive to lightning risk.
How to choose between single-mode and multi-mode
| Type | Transmission distance | Cost | Applicable |
|---|---|---|---|
| Multi-mode OM3/OM4 | 300～550 meters | Optical modules are cheap | In-building backbone and intra-machine room interconnection |
| Single-mode OS2 | 10~40 kilometers | Optical fiber is cheap, modules are slightly expensive | Park backbone, long-distance points |
It is recommended to use single-mode in security projects: the price difference of optical fiber itself is very small. Single-mode has almost no restrictions on distance, and there is no need to change lines for later expansion.
Optical modules and jumpers
- The wavelength, speed, and transmission distance of the module must match the switch port. Gigabit multi-mode modules cannot be directly plugged into single-mode optical fiber.
- The interface type (LC/SC) is the same as the jumper. Mixed use requires an adapter flange, which will add a fault point.
- It is recommended to choose modules of the same brand and batch. Cross-brand compatibility issues are very common in actual projects.
Welding and acceptance
Welding point loss should be controlled within 0.3 dB, the entire link (including welding points, flanges, jumpers) The total loss is generally required to be single mode less than 3 dB. Use an optical power meter for actual measurement during acceptance acceptance. And keep test records - when the link is interrupted later, this record can quickly distinguish whether it is fiber degradation or equipment failure.
Attention should be paid to outdoor optical cables: choose water-blocking type, armored direct burial or pipe laying, and make waterproof connector boxes at both ends. And indicate the location of the welding package on the as-built drawing.