The recent interest in precursors has been fuelled by the possibility of using them for the efficient transmission of information through absorbing media at radio or optical frequencies. Here we demonstrate that the low attenuation experienced by the Brillouin precursor is attributed to the inherently low absorption of dispersive media near DC, a characteristic already exploited with communications systems using the extremely low frequency (ELF) band. Pulses, regardless of their temporal width and carrier frequency, always obey Beer's law as long as they propagate in the linear time invariant regime. We conclude with an FDTD simulation of the Maxwell–Bloch equations that shows how optical coherent bleaching effects, which take place in the linear time variant regime of the Lorentz oscillator model, can cause sustained deviations from Beer's law over relatively long distances of water.

中文翻译：

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前体能否改善光频下的能量传输？

最近对前体的兴趣受到了使用它们通过无线电或光学频率的吸收介质有效传输信息的可能性的推动。在这里，我们证明了布里渊前体所经历的低衰减归因于 DC 附近色散介质的固有低吸收，这一特性已在使用极低频 (ELF) 频带的通信系统中得到利用。脉冲，无论其时间宽度和载波频率如何，只要它们在线性时不变机制中传播，就始终遵守比尔定律。我们以麦克斯韦-布洛赫方程的 FDTD 模拟结束，该模拟显示了在洛伦兹振荡器模型的线性时变机制中发生的光学相干漂白效应如何导致与 Beer' 的持续偏差