Abstract: In order to satisfy the requirements of low complexity, capacity approaching performance and no error floor for the error correcting codes used in the optical transport network (OTN), a high-rate concatenated codes based on polar codes and low density generator matrix (LDGM) is proposed. The polar-LDGM coding scheme for the concatenated model is first described and the encoding complexity of the scheme is analyzed. And then, the concatenated decoding algorithm based on belief propagation (BP) algorithm is detailed according to the decoding structure of both codes. By reasonably using Gaussian approximation (GA) method, we derive the mean of message passed in the decoding structure, which results in the accurate prediction of the error probability for the Polar-LDGM codes. Simulation results show that the proposed scheme achieves the demands of the optical transport network (OTN).