I’ve put together some simple ocaml-arrow library. It works reasonably well and is quite battle tested but definitely needs a bit of cleanup as the bits under src/ are deprecated in favor of the ones under c_api/. There is also a ppx to automatically convert ocaml records to/from arrow. Some examples using this can be seen in the tests directory.
If there is some interest, I can certainly push up on cleaning this and make an actual opam package.