A communication system in which probabilistic signal shaping and FEC coding are jointly applied in a manner that enables the use of substantially any constellation template, e.g., a template in which the constellation symbols include a constellation symbol of zero amplitude and/or are arranged in an asymmetric manner. In an example embodiment, the transmitter's electronic encoder can be configured to apply two different respective shaping codes to the information bits and to the corresponding parity bits. The resulting shaped streams can then be appropriately multiplexed and transmitted over the optical communication channel to realize a significant shaping gain. Advantageously, the constellation template(s), two distribution matchers, and FEC code can be flexibly selected and/or adapted to achieve nearly optimal system operation under substantially arbitrary (e.g., arbitrarily bad) channel conditions.