In this paper, we study two types of optical wireless channels under average-intensity constraints. One is called the Gaussian optical intensity channel, where the channel output models the converted electrical current corrupted by the additive white Gaussian noise. The other one is the Poisson optical intensity channel, where the channel output models the number of received photons corrupted by the positive dark current. When the average input intensity $\mathcal{E}$ is small, the capacity of the Gaussian optical intensity channel is shown to scale as $\mathcal{E}\sqrt{\frac{\log\frac{1}{\mathcal{E}}}{2}}$, and the capacity of the Poisson optical intensity channel as $\mathcal{E}\log\log\frac{1}{\mathcal{E}}$, which close the existing capacity gaps in these two channels.

翻译：本文研究两种在平均强度约束下的光无线信道。其一为高斯光强度信道，其信道输出模拟了叠加加性高斯白噪声的转换电流；其二为泊松光强度信道，其信道输出模拟了受正暗电流干扰的接收光子数。当平均输入强度$\mathcal{E}$较小时，高斯光强度信道的容量与$\mathcal{E}\sqrt{\frac{\log\frac{1}{\mathcal{E}}}{2}}$成比例，泊松光强度信道的容量与$\mathcal{E}\log\log\frac{1}{\mathcal{E}}$成比例，这一结果填补了这两种信道现有容量分析中的空白。