利用非歸零格式光數字訊號注入時鐘調變之垂直共振腔面射 型雷射進行歸零格式轉換

All-Optical Injection-Locking and NRZ-to-RZ Data-Format Conversion in Clock Modulated VCSEL

林嘉琪(Chia-Chi Lin)

指導教授 ： 林恭如

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.03293

摘要

在本論文中，我們使用2.5 GHz 的弦波時鐘訊號直接調變偏壓在臨界點之下的垂直共振腔面射型雷射(VCSEL)，實現OC-48 下全光之非歸零碼轉歸零碼的格式轉換。消光比為5 dB 的非歸零碼資料訊號外部注入到VCSEL，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9.2 dB。而在位元率2.5 Gbit/s 的操作下，轉換後歸零碼訊號的接收功率在-26.7dBm 時，仍可以獲得10-12 的誤碼率，並在傳輸25 km 後接收功率在-24.3 dBm 時，仍可以獲得10-9 的誤碼率。另外，我們也利用連續波及編碼調製波的光時鐘訊號分別注入垂直共振腔面射型雷射，進行轉換後歸零碼訊號的啾頻研究；理論分析顯示經由編碼調製波注入轉換後的訊號之啾嚬可以比連續波注入的結果還要明顯
降低2.2GHz (約為32 %)，然而脈衝寬也相對地加寬3.2 ps (劣化度17 %)。我們提出的利用光注入被時鐘訊號調變之垂直共振腔面射型雷射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。
此外，為因應高速高容量的需求，我們也利用10 GHz 脈衝時鐘取代弦波時鐘調變面射型雷射二極體，實現OC-192 下全光之非歸零碼轉歸零碼的格式轉換，我們使用脈衝式電梳訊號直接調變垂直共振腔面射型雷射，配合非歸零格式光訊號的注入不僅能提高垂直共振腔面射型雷射的調變頻寬，更可以在時域上透過注入鎖定效應有效地窄化其增益線寬。實驗結果顯示欲達成高位元率的操作，必須提高垂直共振腔面射型雷射的偏壓電流及增加反向電梳時鐘訊號調變功率。經過轉換之10 Gbit/s 歸零格式訊號擁有消光比約達7 dB，在接收功率抵達 -17.1 dBm 之下仍可以得到10-9 之誤碼率，相較於低位元率之轉換，訊號啁啾也明顯提升至 4.09GHz。

關鍵字

垂直共振腔面射型雷射 ； 暗梳直調 ； 注入鎖模 ； 增益切換 ； NRZ-to-RZ

並列摘要

Optically injection-locked single-wavelength gain-switching vertical cavity urface emitting laser (VCSEL) based all-optical converter is demonstrated to generate RZ data at 2.5 Gbit/s with bit-error-rate of 10-9 under receiving power of -29.3 dBm.A modified rate equation model is established to elucidate the optical injection induced gain-switching and NRZ-to-RZ data conversion in the VCSEL. The peak-to-peak frequency chirp of the VCSEL based NRZ-to-RZ is 4.5 GHz associated with a reduced frequency chirp rate of 178 MHz/ps at input optical NRZ power of -21 dBm, which is almost decreasing by a factor of 1/3 comparing with chirp on the SOA based NRZ-to-RZ converter reported previously. The power penalty of the BER measured back-to-back is about 2 dB from 1 Gbit/s to 2.5 Gbit/s.
Furthermore for the high bit rate, we proposed a novel OC-192 NRZ-to-RZ data format conversion based on VCSEL with a 10 GHz comb driven and external optical injection. As we know, the bandwidth of the TO-56-can package technology seems to limited up to 2.5 GHz. By using sinusoidal to 10 GHz directly modulated by the comb and external optical injection, the VCSEL resonance frequency is increased to 10 GHz. We can also increase the bias current and change the modulation shape for example to comb due to which support carrier can in short time immediately. We analyze the frequency chirp characteristic and the bit error rate (BER) performance under the different injection power and biased DC current. The peak-to-peak chirp is increased by increase the DC biased current and decrease the injection power which result from factor decreasing. Besides, the pulsewidth is reduced by increase the injection power and broaden by increase DC biased current with Δn’ add the phase shift. The peak-to-peak chirp of the optical signal with DC biased current 1.3 mA and injection power -5 dBm is 3.29 GHz. The BER of 10-9 is under receiving power –13 dBm, and the received power penalties improvement of 12dB from biased at lower DC biased current to higher DC biased current. Due to the threshold point left shift, the higher DC biased current has greater modulation depth compare to lower DC biased current, and further results the sharper shape on the transformed RZ signal. Besides, it also produces lager extinction ratio due to the part of comb shape under lasing is larger but has almost the same DC level, smaller chirp due to injection-locked improve the coherence of not only the signal but also the ASE and better timing jitter due to smaller phase noise from ASE. All of those can avoid the data format conversion’s sampling error. Therefore, the BER will be improved of 4-order is proposed. We also show the eye diagram of the converted RZ signal and different data stream. The signal to noise ratio, timing jitter, rising time, falling time and pulsewidth are measured 3.05, 7.14 ps, 120.5 ps, 132.2 ps and 97.8 ps, respectively.

並列關鍵字

Fiber optics communications ； Semiconductor optical amplifiers ； Optical data

參考文獻

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