Underwater optical communications systems. Part 2: basic design considerations
Underwater optical communications systems. Part 2: basic design considerations
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DOI：
10.1109/milcom.2005.1605919
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发表时间：
2005-10
期刊：
影响因子：
--
通讯作者：
J. Giles;I. Bankman
中科院分区：
文献类型：
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作者：
J. Giles;I. Bankman
声学系统可以提供合适的水下通信，因为声音在水中传播良好。然而，这些系统在浅海水域的最大数据传输速率约为每秒10千比特（kbps），这只能在小于100米的距离内实现。虽然水下（u/w）无线光通信系统可以有更短的范围，由于更大的衰减光通过水传播，他们可以提供更高的带宽（高达几百kbps）通信以及覆盖度。为了充分利用这些潜在的优势，我们在本文中考虑了光/w通信系统的基本设计问题。除了具有环境噪声的u/w光通信的基本物理特性外，我们还考虑了一些最先进的商用现货（COTS）组件的系统性能，这些组件有望将u/w光通信系统置于具有低功耗和重量的小封装中。我们讨论了有希望用于u/w光发射器的光源，如激光二极管（ld）和发光二极管（led）。输出频率移至500- 650纳米范围的激光二极管每脉冲可以比led发射更多的能量，但更昂贵。目前，led发出大量的光，而且通常非常便宜。此外，COTS光电二极管可以用作探测器，可以响应几纳秒宽的脉冲。讨论了考虑指向的发射机广播角度和探测器视场。当发射机广播角度和检波器视场都较窄时，接收到的脉冲信噪比较高，但对发射机和接收机的指向精度影响较大。然而，如果发射机广播角度和/或探测器视场较宽，指向不那么关键，但信噪比较低，可能会失去一些隐蔽性。考虑了透射光在各种清澈的海洋和浑浊的沿海水域类型中的传播，并估计了一些COTS光源和探测器的距离。我们还考虑了环境噪声的影响，如背景太阳辐射，这通常限制了这些系统的性能
Acoustic systems may provide suitable underwater communications because sound propagates well in water. However, the maximum data transmission rates of these systems in shallow littoral waters are ~10 kilobits per second (kbps) which may be achieved only at ranges of less than 100 m. Although underwater (u/w) wireless optical communications systems can have even shorter ranges due to greater attenuation of light propagating through water, they may provide higher bandwidth (up to several hundred kbps) communications as well as covertness. To exploit these potential advantages, we consider the basic design issues for u/w optical communications systems in this paper. In addition to the basic physics of u/w optical communications with environmental noise, we consider system performance with some state-of-the-art commercial off-the-shelf (COTS) components, which have promise for placing u/w optical communications systems in a small package with low power consumption and weight. We discuss light sources which show promise for u/w optical transmitters such as laser diodes (LDs) and light emitting diodes (LEDs). Laser diodes with their output frequency shifted into the 500- to 650-nm range can emit more energy per pulse than LEDs but are more expensive. Currently, LEDs emit substantial amounts of light and are typically very inexpensive. Also, COTS photodiodes can be used as detectors which can respond to pulses several nanoseconds wide. Transmitter broadcast angles and detector fields of view (FOVs) with pointing considerations are discussed. If the transmitter broadcast angle and the detector FOV are both narrow, the signal-to-noise ratio (SNR) of the received pulse is higher but the pointing accuracy of transmitter and receiver is critical. If, however, the transmitter broadcast angle and/or the detector FOV is wide, pointing is less critical but SNR is lower and some covertness may be lost. The propagation of the transmitted light in various clear oceanic and turbid coastal water types is considered with range estimates for some COTS light sources and detectors. We also consider the effects of environmental noise such as background solar radiation, which typically limits performance of these systems