弱共振腔法布里珀羅雷射二極體鎖模環光纖雷射之特性與脈 衝壓縮之研究

Characteristic Analysis and Pulse Compression of the Weak-Resonat-Cavity Fabry-Perot Laser Diode Mode-Locked Fiber Ring

彭國璿(Guo-Hsuan Peng)

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.2008.01684

摘要

我們研究反向光注入弱共振腔Fabry-Perot雷射二極體光纖雷射系統輸出特性。藉由10GHz暗脈衝光注入的方式調變Fabry-Perot雷射二極體，使其光纖雷射產生10GHz鎖模脈衝。本文共分成三大方向探討：
首先，研究影響此脈衝特性的因數。光注入弱共振腔的Fabry-Perot雷射二極體達成環形光纖鎖模雷射，其環腔內的迴授能量大小控制了波長飄移、啁啾大小、脈衝寬度以及線寬。在強的光暗脈衝注入或是強的回授耦合比例時，我們可以觀察到輸出脈衝的波長峰值會產生波長紅移，飄移的範圍從1536奈米到1542奈米、脈衝寬度由27皮秒降低到19皮秒、頻譜線寬由10奈米降低到6奈米。除此之外，由於線寬的降低使得峰值對峰值的頻率啁啾由3.5G赫茲降低至1.8G赫茲。接著，研究色散補償光纖長度對脈衝壓縮之特性變化。在光注入10%反射率的弱共振腔Fabry-Perot雷射二極體而產生的環形光纖鎖模雷射的脈衝輸出來達成全新的光的分時多工載波和200GHz頻道(1.6奈米模間距)的分波多工的訊號源，而色適當長度(55公尺)的色散補償光纖可將啁啾由9.7GHz降低至4.3GHz和脈衝寬度由19微微秒減少至10.5微微秒，但是長度若超過最佳補償長度(55公尺)則脈衝就會劣化，理論與實驗的結果相符合。最後，我們試著利用高功率摻鉺光纖放大器產生非線性光孤子效應，將鎖模雷射壓縮至1.4皮秒等級的脈衝寬度，產生10GHz的超短脈衝訊號源。在光纖環腔內加入可調式頻段選擇器可以達到 12皮秒與重複率10GHz的脈衝輸出，而且進一步的被壓縮為1.4皮秒的脈衝寬度。而在沒有可調式頻段選擇器的情況下，脈衝寬度變寬至21皮秒，不過經由色散補償的線性壓縮後，也可達12皮秒的脈衝輸出。這個五階的非線性光孤子壓縮因素，最後可被非線性自我向位調變的壓縮方式壓縮至2.1皮秒等級。同時，鎖模線寬也從2.4奈米增加至3.8奈米

關鍵字

弱共振腔Fabry-Perot 雷射二極體 ； 暗脈衝光 ； 頻率啁啾 ； 色散補償 ； 非線性光孤子效應

並列摘要

In this thesis, we discussed the characteristics of optical injection mode-locking of a weak-resonant-cavity Fabry-Perot laser diode based fiber ring. The 10 GHz mode-locking pulse was generated by using the 10 GHz dark-optical comb injection. The thesis has three mainly parts:
First, the optical injection mode-locking of a weak-resonant-cavity Fabry-Perot laser diode based fiber ring with an intra-cavity power controlled wavelength shift and a reducing chirp linewidth at high intra-cavity coupling ratio condition is demonstrated. Both the strong dark-optical comb and strong feedback coupling contribute to the wavelength spectrum shift toward longer wavelength, a wavelength shift from 1536 to 1542 nm of the weak-resonant-cavity FPLD based fiber ring associated with its pulsewidth and linewidth also reduced from 27 to 19 ps and from 10 to 6 nm, respectively, can be observed. Furthermore, the peak-to-peak frequency chirp reduced from 3.5 to 1.8 GHz was caused by the shrink of linewidth. Second, a novel optical TDM pulsed carrier from optically injection-mode-locked weak-resonant-cavity Fabry-Perot laser diode (FPLD) with 10%-end-facet reflectivity is demonstrated with tunable mode spacing matching ITU-T DWDM channels. The FPLD exhibits relatively weak cavity modes and a gain profile covering > 33.5 nm with intracavity mode spacing of 1.6 nm. The mode-spacing spacing was tunable by adjusting length of the fiber ring cavity. The least multiple between the longitudinal modes of ring cavity and FPLD result in 12 lasing modes with channel spacing of 200 GHz and a mode-locking pulsewidth up to 19 ps. The operating wavelength can further extend from 1520 to 1553.5 nm. After channel filtering, each selected longitudinal mode component give rises to shortened pulsewidth of 12 ps due to reduced group velocity dispersion. By linear dispersion compensating with 55 m long dispersion compensation fiber (DCF), the pulsewidth can be further compressed to 8.5 ps with corresponding chirp reducing from 9.7 to 4.3 GHz. Final, 1.4-picosecond nonlinear pulse compression of a backward dark-optical-comb injection harmonic-mode-locked semiconductor optical amplifier based fiber laser (SOAFL) is demonstrated. With the tunable bandpass filter (TBF) in the fiber ring, shortest mode-locked SOAFL pulsewidth of 12 ps at 10 GHz is generated, which can further be compressed to 1.4 ps after nonlinear soliton compression. A maximum pulsewidth compression ratio for the compressed fifth-order mode-locked SOAFL is reported. The fifth-order soliton can be obtained by injecting the amplified pulse with peak power of 10.8 W into a 400m-long single-mode fiber (SMF). The tolerance in SMF length is relatively large (400-700 m) for obtaining <2 ps mode-locked SOAFL pulsewidth. However, without the TBF in fiber ring, the mode-locked SOAFL linewidth can be broadened to 2.4 nm and the pulsewidth were broaden to 21 ps. It can be linear compensated to 12 ps by passing through the 70m-long dispersion compensation fiber (DCF). It can be further compressed to 2.1 ps after fifth-order soliton compression, at the same time, the linewidth of mode-locked SOAFL broadened from 2.4 to 3.8 nm.

並列關鍵字

weak-resonant-cavity Fabry-Perot laser diode ； dark-optical comb ； frequency chirp ； dispersion compensation ； nonlinear soliton compression effect.

參考文獻

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