  Although forward error-correction (FEC) coding is an essential part of modern
fiber-optic communication systems, it is impractical to implement and evaluate
FEC in transmission experiments and simulations. Therefore, it is desirable to
accurately predict the end-to-end link performance including FEC from
transmission data recorded without FEC. In this tutorial, we provide
ready-to-implement "recipes" for such prediction techniques, which apply to
arbitrary channels and require no knowledge of information or coding theory.
The appropriate choice of recipe depends on properties of the FEC encoder and
decoder. The covered metrics include bit error rate, symbol error rate,
achievable information rate, and asymptotic information, in all cases computed
using a mismatched receiver. Supplementary software implementations are
available.
