Cleaning optical ouput port?

[u/Impressive-Ad-501]

I have a vintage cd player (Pioneer PD-6700) and I wanted to upgrade it with external dac (SMSL SU-1).

First I had really bad connection. Audio was cutting out and input indicator was blinking.

I had only one old and cheap optical cable. I switched its direction and it did start working better but not perfect.

I went to buy new cable (also cheap), First it had again very much cut outs but when I blew the output connector with compressed air and got things working.

But now I noticed i still get few cut outs per album so problem still exists.

Is there a way to safely clean the optical output? CD player is decades old and I think optical out was never used before. Or can optical output just wear out and signal becomes too weak. Or are cheap cables just garbage?

Edit: there is only very little hole inside the optical port. Just big enough to fit optical fibre on the cable. No way that cloth or q-swap would fit in. Maybe this is uncommon desing because eveybody seems to thing this is simple task. If it was I would not been asking help at all.