RFoF Connector Challenge

RF Over Fiber or RF Over Glass technology is commonly used when a RF (Radio Frequency) signal can’t be transported using regular coax cable due to distance, weight or other reasons. There are various RFoF modules that can support various frequency ranges up to 40 GHz or even beyond.

Vendors offer RFoF modules with various RF and optical connectors. During brand new deployments installers ensure that the fiber and coax cables have the mating connectors to fit the RFoF modules. However, things get a little messy when RFoF modules need to be deployed using existing cable infrastructure.

Optical connectors

According to Wikipedia there are 30+ optical connector types.
Most common ones are:

• SC- Square Connector or Subscriber Connector
• FC- Ferrule Connector or Fiber Channel
• LC- Lucent connector or Little Connector
• ST- Straight Tip

To complicate matters further each connector comes finished as APC (Angled Physical Contact) or UPC (Ultra Physical Contact). Most vendors furnish RFoF modules with FC or SC connectors and to reduce back reflection connectors typically have APC polish

So, what happens when there is a mismatch between the connectors of RFoF modules and cables. One solution is to reterminate the cable with the appropriate connector. However, expensive splicing equipment and skillful technician are needed for that route. Another option is to use adapter patch cables. So, for example what happens if your RFoF module has SC/APC connector but the existing cable has LC/UPC connector. You can use a short patch cable with SC/APC connector at one end and LC/UPC at the other end. Since RFoF modules have female connectors and cables have always male connectors, you can connect the cable’s male SC/APC connector to the female SC/APC connector of the RFoF module. Now the connectors on the installed cable and the patch cable will match. However, since they will both be male connectors, now a coupler or a patch panel needs to be used to connect these 2 cables to each other

Another important aspect to keep in mind in the RFoF deployment is the mode of the fiber cable which can be multi-mode (MM)or single-mode (SM). Since RFoF technology only works with SM fiber, special attention must be given that all connectors and cables used are SM

RF Connectors

Again, according to Wikipedia there are tens of RF connector types. But the most commons are: SMA, BNC, N-Type

Most RFoF vendors provide modules with SMA connectors. To convert RF connectors from one type to another is easier than converting the optical connectors because RF adapters are readily available and there is no need for patch cables and couplers although they can be used if preferred

As most suppliers RFOptic modules have FC/APC or SC/APC optical connectors and SMA RF connector. However, to help our customers with their deployment needs we stock optical adapter patch cables with various connector combinations and associated couplers