Hyphenation of a phrasal attributive with an open compound: "A B to C noun"

I'm wondering how to properly hyphenate (or en-dash) the following phrase:

fiber optic to BNC converter

That is to say, a device that converts "fiber optic" to BNC. If it didn't contain an open compound, I'd simply write "optic-to-BNC converter; but I'm not sure how the open compound "fiber optic" might affect the situation. I prefer not to write "fiber optic–BNC converter", as this could cause confusion in some contexts if the reader doesn't read "–" as "to". I also thought about

fiber optic–to–BNC converter

, but that looks too strange to me.

My best guess is

fiber-optic to BNC converter

. I think this expresses that "fiber" and "optic" are related but "BNC" and "converter" are not. Is this the right way, or is there a better solution?

Note: this is actually an example of poor writing because fiber optic is essentially a transmission medium, while BNC refers to a connector type. So I actually solved my problem by writing "optical-to-electrical converter" (and afterward, "optoelectronic converter"). Nonetheless, the basic question remains. Another example phrase that exemplifies the problem is "surface area to volume ratio", for which I've found evidence of a variety of hyphenation styles.