Purely off the top of my head and not having done any physical plugging in of kit, the optical connection is shared with a 3.5mm stereo jack. So its one of those optical connectors in the tip of a 3.5mm jack plug type of connections.

I just need to find my lead of this type, or get an adaptor/new lead. Probably wait until I get around to ordering an SB3 or get some indication from M of their iPod dock capabilities.

Meridian owner since 1992
Prime & PSU, Focal Elear headphones, Roon (ROCK 8Gi5 NUC), Explorer 1 & 2, F80. 200/203, various Sonos (via Roon).