The Poisson channel is a popular direct-detection model in optical communication. In this paper, we study efficient data communication over the on-off keyed (OOK) modulated Poisson channel. We first analyze the channel capacity, and based on the analysis we study the application of low-density parity-check (LDPC) codes on such channels. The asymmetric density evolution (ADE) method is used to determine the decoding threshold of an LDPC ensemble, and it is demonstrated that optimized LDPC ensembles have near-capacity performance, for various code rates. We also point out that the robustness of LDPC codes for the Poisson channel, i.e. a certain optimized LDPC ensemble remain (essentially) optimal over a wide range of channel conditions, making LDPC codes an attractive forward correcting coding (FEC) scheme for optical communication.