本論文致力於提升高容量無線光通訊系統之總傳輸容量，並將系統用於接取網路及橋樑備用路由。本無線光通訊系統以單模光纖接取並用透鏡組縮擴束收發光訊號；為提高傳輸容量將系統應用在分波多工傳輸，傳輸距離10公尺，系統最佳傳輸及對光損耗約為4.3 dB，傳輸雙向共20通道，每一通道傳輸速度達到10 Gb/s。而針對系統作傳輸品質誤碼率量測中，其結果在誤碼率為10-9的標準下功率償付值在波長1549.21 nm 傳輸單向約為0.37 dB、雙向約為0.41 dB，在波長1550.71 nm單向約為0.4 dB、雙向約為0.43 dB，並對系統進行傳輸通道干擾測試，在系統傳輸時於傳輸通道間加入熱空氣使氣流產生擾動，得到當空氣擾動下，誤碼率在10-5會出現錯誤平層，造成傳輸品質下降。
而為驗證本無線光通訊系統具有設置便利及機動性，能應用於光纖鋪設不易地帶作為接取技術，故設計一個分波多工被動光網路系統，並嘗試與本無線光通訊鏈結觀察其傳輸品質，其次為補償光訊號在經過光纖傳輸時的損耗，採用遠端泵激光源的方式進行訊號放大，並在實驗架構分別使用1、2、3、4公尺的摻鉺光纖進行分析，最後發現在泵激光源為85 mW經過一段距離傳輸之後剩餘34.5 mW時，4公尺的摻鉺光纖可使訊號光達到最大的增益輸出，並對於其傳輸品質進行誤碼率測試，在鏈結無線光通訊系統的功率償付值較未鏈結時，傳輸8通道只增加約0.41 dB，傳輸4通道時只增加約0.37 dB。
無線光通訊也可應用於光纖通訊系統作備用鏈結，我們設計以本論文無線光通訊系統用光開關切換當橋樑光纖備用鏈結，並於光纖路徑上加入光纖光柵反射訊號光供給橋樑受力監控用，且利用不同長度摻鉺光纖補償上下路徑功率差，經實驗得到通過本切換架構之上下路徑之訊號光功率差小於1 dB；而監控用訊號光在回傳50 km及60 km後之光訊雜比皆大於20 dB；傳輸品質在光纖總傳輸距離75 km及85 km誤碼率量測10-9情況下，中間切換為10公尺無線光通訊路徑接收功率比起為10公尺光纖路徑分別只差約0.41 dB及0.75 dB。

In this thesis, we studied on enhancing the total transmission data rate, as well as the quality of free-space optical (FSO) transmission. The proposed schemes are based on an advanced dense wavelength division multiplexing (DWDM) in bidirectional point-to-point FSO system. The wavelength ranges from 1545.98 to 1565.40 nm with channel spacing of 200 GHz (1.6 nm). Then each channel is externally modulated by data rate of 10 Gbit/s in non-return-to-zero (NRZ) formats. The 10 m losses induce by free space and coupling is only 4.3 dB. In the bidirectional system, the transmission capacity is 10 Ch x 10 Gb/s for each direction. We measured the bit error rate (BER) performance at both 1549.21- and 1550.71 nm wavelengths. For unidirectional transmission, the power penalties are 0.37 dB and 0.4 dB, respectively, as compared to the back-to-back transmission. For bidirectional transmission, the power penalties are 0.41 dB and 0.43 dB, respectively, for the same wavelengths. We also investigated the system performance under atmospheric turbulence effect. The measured system performance is strongly affected by the turbulence and results in an error floor of about 10-5.
To verify whether the proposed FSO scheme is suitable for optical communication, especially an area where optical fiber is difficult to deploy, we designed a passive optical network (PON) and compared system performance at the receiving end of a PON with or without 10 m FSO scheme. It is found that extra power penalties are only 0.37 and 0.41 dB, individually, for 4 and 8 channels transmission.
The FSO scheme is also used as a backup module for crossing-bridge transmission. To demonstrate the proposed FSO could play as an alternative for fiber transmission, we compared system performance of both wire and wireless optical transmission by parallel linking the proposed 10 m FSO scheme using an optical switch. In case the fiber link is failure due to unpredictable destroyed, then the 10 m FSO scheme could acts as the backup router. The power difference between fiber and 10 m FSO path is about 1 dB. Bit error rate (BER) performance of 10 m FSO path were measured with extra power penalties of 0.41 dB and 0.75 dB for 75 km and 85 km transmission, respectively, when compared to fiber wired router. The measured results confirm the proposed FSO scheme is feasible for FSO communications.

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