- 學位論文
光電反饋式渾沌通訊於光纖微波系統應用之研究
Chaotic Communication in Radio-over-Fiber System Based on Optoelectronic Feedback Semiconductor Laser
摘要
在本論文中，渾沌通訊 (chaotic communication) 被論證可以應用在 Radio-over-Fiber (RoF) 系統中。此無線通訊系統擁有許多優點，如更有效的利用頻寬，高傳輸速率，長距離傳輸，以及保密性。渾沌通訊是利用兩個同步化 (synchronization) 的半導體雷射所完成。而渾沌載波 (chaotic carrier) 可經由半導體雷射利用光電回饋 (optoelectronic feedback) 的機制而產生。經由不同的加密方式，如 ACM (Additive Chaotic Modulation) 和 OOSK (On-Off Shift Keying)，可以達到保密通訊的效果。 本論文研究了渾沌通訊在不同系統下的效能，例如 back-to-back 系統、光纖傳輸系統，以及無線傳輸頻道。在光纖系統中，我們考慮了衰減、非線性 (nonlinearity)、色散 (dispersion)、ASE (Amplifier Spontaneous Emission) 雜訊等影響。其中我們計算系統的誤碼率 (bit error rate) 來量化其通訊品質。在無線頻道裡，則考慮路徑衰減、白色高斯雜訊 (additive white Gaussian noise)，以及多重路徑等現象。之後更進一步把光線傳輸及無線頻道的現象一起考慮，來完成對 RoF 系統之整體研究。 利用半導體雷射的光電回饋機制驗證了渾沌通訊可應用在 RoF 系統中，其傳輸速率可到達每秒109位元。其中， OOSK 之編碼方式比較適合應用在 RoF 系統裡，並且可以達到超過100公里的遠距離傳輸，而ACM則是在光纖系統裡擁有比較好的效能。
並列摘要
Chaotic communication in Radio-over-Fiber (RoF) system has been demonstrated and numerically investigated. The advantages of this system include efficient use of bandwidth, high-bit rate, long-distance transmission, and security of the wireless communications. The implementation of this chaotic communication system is based on the synchronization two identical lasers, where chaotic carrier is generated with an optoelectronic feedback (OEF) scheme. With different message encoding schemes, including the additive chaotic modulation (ACM) and the on-off shift keying (OOSK), the secured communication in RoF system can be achieved. The performance of chaotic communication system in back-to-back configuration, fiber channel, and radio channel has been investigated respectively. In fiber transmission module, influences of fiber attenuation, nonlinearity, dispersion, and amplifier spontaneous emission (ASE) noise have been taken into accounts. The system bit-error-rate (BER) for different fiber transmission distances and message bit rate is calculated. The effects of the radio channel including path loss, additive white Gaussian noise (AWGN), and multipath are considered. Moreover, the RoF system is achieved after combing the fiber channel with the radio channel. Chaotic communication in RoF system at a bit rate of Gbit/s level is investigated numerically using optoelectronic feedback semiconductor lasers. The OOSK scheme is shown to be more suitable for the RoF system, which it can provide long-distance transmission to above 100 km. On the other hand, the ACM scheme only shows moderate performance in the fiber transmission.