Connecting Fireface III and 1620 Pro

These are different standards for connecting MADI devices:
a) Optical connections (multimode up to 2 km, singlemode up to 20 km)
b) Coaxial connections (up to 100 m, sometimes up to 150 m possible)

to a) Optical connections:
RME uses two different connector standards for optical fiber: LC or SC.
The UFX III uses the larger SC connectors (fixed in the unit).
Default configuration is multimode; singlemode is available only as a special order option.

The M-1620 Pro uses an SFP-based transceiver with smaller LC connectors.
Here you can buy or replace the SFP transceiver to choose between multimode or singlemode operation.

The UFX III supports both optical and coaxial connections via word clock input/output, as well as Split Mode (32 channels optical + 32 channels coaxial at single speed). The M-1620 Pro also supports both optical and coaxial MADI.

I recommend using optical connections, as they provide galvanic isolation between the devices.
With the UFX III, you will need to use multimode fiber unless you specifically ordered the singlemode version.

For multimode operation, different optical fiber standards exist — OM3 and OM4.
They differ slightly in maximum supported network distances, which is irrelevant for MADI, but note one important point:
If you have structured in-house cabling with optical patch panels, never mix OM3 and OM4, as this increases attenuation.

The cables follow standardized color codes. I recommend OM4, which is now inexpensive and has a distinctive violet jacket.

Since the two devices (UFX III and M-1620 Pro) use different connector types — SC and LC — you need an OM4 multimode duplex cable (two fibers for transmit and receive) with an SC connector on one side and an LC connector on the other.

For the M-1620 Pro, I recommend purchasing the multimode SFP module directly from RME. Avoid third-party SFPs unless you are certain they use the correct wavelength (1310 nm) and are not vendor-locked (e.g. Cisco, Brocade, Intel).
It’s much safer to use modules known to work reliably with RME hardware.

When inserting the SFP module, be careful: it fits only in one orientation.
Insert it fully until it snaps into place.
Insertion sequence:
Insert SFP (bail up) → push fully in → lock bail down → connect LC duplex cable (check TX/RX orientation) → verify link.

You can use the UFX III as the clock master; the M-1620 Pro will operate as a clock slave, receiving clock via the MADI optical connection.

For additional information on clock synchronization, see my blog article:
https://www.tonstudio-forum.de/blog/ent … ios-en-de/