Key points of distance classification for metropolitan area network optical modules from 10KM to 80KM

Metropolitan area network link classification: how to choose modules from 10KM to 80KM

Published: 2026-05-16 EB-LINK Views: 1267 Distance binning, loss margin, optical module selection, attenuator, metropolitan area network

The most common selection misunderstanding for batch projects is to use the straight-line distance on the map to correspond to the module level. The actual loss of a metropolitan area network link is determined by the fiber core, connectors and distribution frame termination. The gear selection should be based on the loss budget rather than the number of kilometers.

First measure the measured attenuation and then set the gear.

Use an OTDR or light source optical power meter to get the full loss, plus the termination loss of the connectors at both ends and the distribution frame, to get the design value. Conventional access link distance is shorter,SFP Gigabit single mode dual fiber 10KM optical moduleIt is usually sufficient; the cross-region aggregation section determines whether to increase to the 40KM level based on the actual measured value, for exampleSFP 2.5G single mode dual fiber 40KM optical module.

It is recommended to leave a margin of 3dB

The proportion of design attenuation to the upper limit of the gear range is generally controlled at about 70%, leaving about 3dB margin for subsequent termination and aging.
The margin is not to shorten the gear to save costs, but to cope with the microliter welding loss in winter and the reading fluctuation after cleaning.
For ultra-long sections, it is better to use the 80KM gear to increase the attenuation, rather than forcefully run at the critical value.

Commonly used in suburban rings and county linksSFP 2.5G single mode dual fiber 80KM optical module, this level has high transmitting power, and it is necessary to check whether the receiving end is overloaded at the same time.

Short links use overload control instead of shifting

When long-distance modules are used on short links, excessive light collection will increase bit errors or even damage the receiving device. The correct approach is to add fixed attenuators at both ends to push the received power back within the range, rather than temporarily switching to low-end modules, which are more likely to break the link when distance and loss fluctuate.

EB-LINK can provide binning suggestions and supporting attenuation parts according to the project port table. For specific calculations, please contact 0755-83179002.