利用反向脈衝光時鐘注入半導體光放大器進行非歸零/歸零格式之轉換研究

Abstract

在本論文中，我們使用10 GHz的反向脈衝光時鐘訊號背向注入半導體光放大器，實現OC-192下全光之非歸零碼轉歸零碼的格式轉換。以消光比為7.13 dB非歸零碼資料訊號外部注入，在不需要放大的情況之下，經過半導體光放大器格式轉換器轉換後，歸零碼資料訊號的消光比可提升到13.6 dB。而在位元率10 Gbit/s的操作下，轉換後歸零碼訊號的接收功率在-18.3 dBm時，仍可以獲得小於10-12的誤碼率，獲得功率補償為-3.7 dB的改善。另外，我們也利用多波長及單波長的反向脈衝光時鐘訊號分別注入半導體光放大器，進行轉換後歸零碼訊號的啾頻研究；理論分析顯示多波長的反向脈衝光時鐘訊號注入，不僅能在時域上縮短半導體光放大器中的增益窗口，更可以在頻域上有效地窄化其增益線寬，進而降低轉換後訊號的啾嚬。實驗結果顯示在高位元率的操作下，必須提高半導體光放大的電流及增加反向脈衝光時鐘訊號注入功率。經由多波長注入轉換後的訊號之啾嚬可以比單波長注入的結果還要明顯降低2.1GHz (約為16 %)，然而脈衝寬也相對地加寬1 ps (劣化度3 %)。我們提出的反向脈衝光時鐘訊號注入半導體光放大器實現全光非歸零碼轉歸零碼的格式轉換器，具有簡單的架構，而且轉換後的歸零碼訊號其波長與資料極性皆與輸入的非歸零碼訊號一致。

In this thesis, we use a semiconductor optical amplifier (SOA) backward injected with a dark-optical-comb pulse-train at 10 GHz to demonstrate a 10Gbit/s all-optical non-return-to-zero (NRZ) to return-to-zero (RZ) format conversion of an incoming optical pseudorandom binary sequence (PRBS) data-stream. Without any pre-amplification on the degraded optical NRZ PRBS data, its extinction ratio is greatly improved from 7.13 dB to 13.6 dB after converting into a RZ PRBS data. Low bit-error-rate (BER) of 10-12 at data rate up to 10 Gbit/s is obtained with a received optical power of -18.3 dBm. To date, the converted RZ PRBS data exhibits a negative power penalty of >3.7 dB at a BER of 10-12 in comparison with the NRZ PRBS data. The characteristics in our proposed experiment include simple architecture and both of the polarity and wavelength of converted RZ data as same as the incoming NRZ data during the format conversion process. Furthermore, by spectrally and temporally reshaping the gain-window of a SOA with a backward injected multi- or single-wavelength dark-optical-comb, we also theoretically and experimentally investigate the dynamic frequency chirp of the all-optical 10GBit/s RZ data-stream format-converted from the SOA under strong cross-gain depletion scheme. The multi-wavelength dark-optical-comb injection effectively depletes the SOA gain spectrally and temporally, remaining a narrow gain-window and a reduced spectral linewidth and provide a converted RZ data with a smaller peak-to-peak frequency chirp of 11.1 GHz. Even at high dark-optical-comb injection power and highly biased current for improving the operational bit-rate, the chirp of the multi-wavelength injection converted RZ pulse is still 2.1 GHz smaller than that obtained by using single-wavelength injection at a cost of slight pulsewidth broadening by 1 ps.