We have codes like RS codes, turbo codes. With respect to modulation schemes like DPIM and DH-PIM, which codes are suitable to be used?
non-uniform and rate-compatible LDPC codes can achieve good results. These codes are hybrid codes.
What I read seems to say that turbocodes and low density parity check (LDPC) codes are about equally good, and surpass the others handily. LDPC seem to have gotten more attention lately, since the 2000s, whereas turbocodes were more in vogue perhaps in the 1990s.
The biggest advantage of LDPC is in lower complexity, compared with turbocodes. Aside from that, each outperforms the other in certain regions of Eb/No.
I don't think free space optical, as opposed to RF, should change the answer to your question.
I did a quick search and came up with two good articles. This first one is very complete.
http://www.ux.uis.no/norsig/norsig2003/Proceedings/papers/cr1020.pdf
This second article compares more types of code than just turbocodes and LDPC.
https://mns.ifn.et.tu-dresden.de/Lists/nPublications/Attachments/436/Zimmermann_E_VTCFALL_06.pdf
An interesting comment it makes is that this class of iterative codes suffers when data packets are very small, in which case you may be better off with a convolutional code.