Channel-Polarized Multilevel Coding for Low-Complexity Forward Error Correction

Digital coherent optical fiber communication systems adopt forward error correction (FEC) and multilevel modulation in accordance with transmission distance, data rate, and power consumption requirements. Bit-interleaved coded modulation (BICM) is practical coded modulation because of the simplicity of applying a binary code to converted <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">binary-input memoryless channels</i> (B-MCs) under a random bit-interleaver. The power consumption of soft-decision (SD) FEC has recently become a challenge due to transceiver power constraints. The multilevel coding (MLC) scheme efficiently reduces the decoding complexity, while the code design and complexity reduction depend on the modulation order. In this paper, we propose new binary codes for channel-polarized multilevel coding (CP-MLC) that convert multiple B-MCs to unreliable and reliable bit-channels and apply only SD-FEC to unreliable bit-channel to reduce the decoding complexity without depending on the modulation order. Systematic CP-MLC can also be used in probabilistically-shaped signals by using it in the component code of a probabilistic amplitude shaping scheme.