For the same link, the price difference between using a pair of optical modules and jumpers or using a DAC or AOC is quite large, but the three are not interchangeable casually. EB-LINK lists the alternative boundaries into a table according to the cable grades in the station. First measure the distance and then select the type.
Three ways to classify by distance
| Internet distance | general choice | alternative description |
|---|---|---|
| 1 to 3 meters in the same cabinet | DAC high speed cable | Can save two sections of module and jumper |
| 3 to 10 meters across cabinets | AOC active optical cable | Change the gear after exceeding the DAC. |
| More than tens of meters or across buildings | Optical module plus single-mode jumper | AOC is not suitable for long distance laying |
| 40G interface connected to 10G equipment | 40G to 10G branch line | Rates at both ends must be declared supported |
The gear position corresponds to the site specifications and is available for short distances.10G DAC high speed cable, look at wiring across cabinets25G AOC active optical cable, longer routes are still combined with optical modules and single-mode jumpers.
These three types of situations cannot be supported by cables.
- The opposite end is an electrical port or optical fiber transceiver. There is no corresponding high-speed port, and neither the DAC nor the AOC can be plugged in;
- Long-distance cable routing is required across the bridge, the AOC head end cannot be under tension, and the turning radius is also restricted;
- The port does not support branch split models.40G to 10G DAC high speed cableSuch branch lines may not be fully identified.
Two points that are easily overlooked when replacing
The first is identification information. Some switches will report unknown module alarms for non-certified cables, which need to be preset according to the equipment brand. Second, the ports and cable levels must be aligned. The 100G to 25G branch cable can only be used on the QSFP28 port that supports splitting. When connected to an ordinary 100G port, four 25G channels will not be generated. This type of mismatch occurs more during capacity expansion.
The notation is very short: look at the DAC within three meters, look at the AOC within ten meters, and still use optical modules and jumpers for further distances or across buildings. Measuring the actual measured length accurately before determining the type will save one round of construction compared with exchanging goods after they are put on the shelf, and also save one port resource rearrangement.