本文主要在探討全光式增益箝制(Gain-Clamped)技術於摻鉺光纖放大器(EDFA)的最佳化設計。分成三種架構來討論，第一種架構是利用兩個光循環器結合光帶通濾波器及可調光衰減器構成環形光迴路。此迴路具有自我調制功能，當波道數增加，則光回饋量減少；反之，波道數減少，則光回饋量增加，如此來達到增益箝制效果。第二種架構是利用單一或雙光纖光柵(Fiber Bragg Grating, FBG)來反射殘餘放大自發性輻射(Amplified Spontaneous Emission, ASE)，以調制訊號增益，此種架構同樣具有自我調制功能。光纖光柵中心波長及頻寬選擇可以控制增益箝制強度，達到最佳增益及可接受雜訊指數。最後第三種架構與第一種環形光迴路類似，不同之處，在於它是一種8-字形光迴路架構，可以同時對C-band 與L-band進行調制，此迴路它共用光帶通濾波器及可調光衰減器。光帶通濾波器之濾波通道選擇在C-band 與L-band交界帶，此可避免與通訊波道衝突，且適當調整可調光衰減器的衰減量，即可獲得C-band 與L-band等增益輸出。

In this paper, we investigate the optimal design of optically gain-clamped (GC) erbium-doped fiber amplifier (EDFA). Three configurations under discussion, the first uses two optical circulators (OC), one optical band pass filter (OBPF), and one variable optical attenuator (VOA), to form ring cavity. Such ring cavity can regulate itself: when the channel numbers increase, the amounts of optical feedback decrease; contrarily, when the channel numbers decrease, the amounts of optical feedback increase. So it has the gain-clamped ability. The second employs one or double fiber Bragg grating (FBG) to reflect the residual Amplified Spontaneous Emission (ASE) for regulating the signal gain, such configurations have the same self-regulation as before. The choice of center wavelength and bandwidth of FBG can control the signal gain to reach the optimal gain and fairly low noise figure (NF). The third configuration is similar to the first; the difference is that the third with figure-8 cavity, which uses a common OBPF and VOA, can regulate the gain of C- and L-bands at the same time. The choice of OBPF is just located within the dead-zone between the C- and L-bands, where no WDM channels can be transmitted. If we choose suitable loop attenuation, we can get an equal signal gain of C- and L-bands’ channels.

Chapter 1 Introduction
1.1 Brief Introduction of Gain-Clamping
1.2 Components of Fiber-Optic Communication Systems
1.2.1 Wavelength Division Multiplexer (WDM)
1.2.2 Isolators
1.2.3 Circulators
1.2.4 Attenuators
1.2.5 Filters
1.2.6 Fiber Bragg Grating (FBG)
1.3 Erbium-Doped Fiber Amplifiers (EDFAs)
1.4 Amplified Spontaneous Emission (ASE)
1.5 The Dissertation Organization
Chapter 2 Principles of Gain Clamping
2.1 Principles of Optical Amplifiers
2.2 Principles of Gain Clamping
2.3 Summary
Chapter 3 Gain Clamping of L-band EDFA Using a Ring Cavity
3.1 L-Band GC-EDFA Configuration and Modeling
3.2 GC-EDFA Design and Comparison in terms of Single- and Multiple- Channel Operations
3.2.1 Single-Channel-Based Design
3.2.2 Multiple-Channel-Based Design
3.3 Characteristic Comparison of GC-EDFA by Using a Saturation Tone
and Multiple Channels
3.4 Discussion
3.5 Summary
Chapter 4 Gain Clamping of L-band EDFA Using a Linear Cavity
4.1 Optimal EDFA Design in Multiple-Channel Operation
4.2 L-Band GC-EDFA Incorporating a Fiber Bragg Grating
4.3 Discussion
4.4 Summary
Chapter 5 Gain Clamping in Wideband EDFA Using a Common
Feedback Loop Ring Cavity
5.1 Experimental Setup
5.2 Experimental Results and Discussions
5.3 Summary
Chapter 6 Conclusions

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