本論文主旨為建構水下無線光通訊傳輸系統，利用在水裡傳輸損耗較小的450 nm藍光雷射當作光源，並使用長度為1.5公尺的水缸裝滿自來水將雷射光從水缸外側打入水缸，且架設反射面鏡使訊號光在水缸中來回反射，在有限距離內增長訊號光在水中傳輸的距離。經過本實驗架構傳輸損耗量測，光源進入水缸的入射角越大，所帶來的損耗也就越大，當入射角為30度時穿透傳輸損耗將大於1 dB，在1.5公尺的傳輸部分，經過實驗傳輸架構大約產生1.6 dB的損耗，在3公尺傳輸的部分產生4.4 dB的損耗，在6公尺傳輸的部分產生8.5 dB的損耗，在誤碼率方面，1.5公尺、3公尺與6公尺，功率償付值的差異大約為4 dB。而在傳輸通道干擾的實驗中，當傳輸通道為清澈時水流擾動對訊號接收幾乎不影響，接著水溫變化擾動實驗，以每5度為一間隔將水溫升高至攝氏50度與降低至攝氏10度，在升高水溫至40度時開始會對訊號接收產生影響，而在低水溫10度時對訊號光的接收效率影響不大，由於溫度越高熱對流明顯改變水的折射率，溫度分布不均導致訊號光傳輸路徑飄浮不定影響傳輸效率，接著是海水模擬傳輸實驗，在水中加入海水素模擬訊號光在海水中傳輸，結果顯示在海水中有許多細小微粒影響傳輸效率，其傳輸損耗為每公尺4 dB，接著分別將海水沉澱數小時與將沉水馬達開啟模擬水流擾動後量測誤碼率，發現較為混濁的海水進行水流擾動模擬時其影響傳輸效率明顯，其約有1dB的功率償付值，最後在以上的結果可以看出在通道間干擾時影響訊號光傳輸會是最大的，故實際應用時如何避免傳輸通道干擾會是無線傳輸的重要議題 。

The subject of this thesis is mainly to construct underwater wireless optical communication system. With the characteristics of low transmission loss in the water, the 450 nm blue-light laser is selected as the light source. Using the aquarium with the total length of 1.5 meter and filled with running water, we input the laser light from the lateral side of the aquarium, mount the reflective mirrors aside to make the incident light transmit back and forth in the aquarium and increase the transmission distance of the incident light in the water. According to the result of the transmission loss experiments, the bigger the incident angle of light into the aquarium is, the more the loss is. As the incident angle is 30 degrees, the transmission loss is more than 1 dB. There will be 1.6 dB, 4.4 dB, 8.5 dB corresponding to the transmission distance of 1.5 meter, 3 meters, 6 meters, respectively. Regarding the BER (Bit Error Ratio), the difference of power penalty is roughly 4 dB for the chosen transmission distances. In the experiment of the interruption to transmission routes, when the water is crystal clear, the perturbation resulted from water flow barely affect the signal reception. As for the experiment of the change of temperature in the water, we increase and decrease the temperature every 5 Celsius degrees between 10 and 50 Celsius. When the temperature is up to 40 degrees, it will affect the signal reception. But for the temperature down to 10 degrees, it has no clear impact on the efficiency of light reception. That is because as the temperature increases, the heat convection clearly changes the refractive index of the water and the uneven temperature distribution leads to the unstable route for light transmission. About the experiment of the simulation of transmission in the saltwater, we add the saltwater material to simulate the light transmission in the saltwater. The result shows that there are a variety of tiny particles that affect transmission efficiency and its transmission loss is 4 dB/m. With the precipitation of saltwater for hours and turning on the pump motor to simulate the perturbation of water flow to measure the BER, we find out that the phenomenon that the perturbation caused by water flow influences transmission efficiency in turbid saltwater is obvious, with 1 dB power penalty. Finally, from the above results, we can realize that the interruption in the route has the biggest impact on the light transmission. As a result, knowing how to avoid the interruption to the transmission routes is the important issue to wireless transmission in the real-world applications.

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