Theoretical simulation of compound ring cavity filter for single longitudinal mode fiber laser
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摘要: 提出了一种用于单纵模激光器选模的基于光纤耦合器的光纤复合环腔(CRC)滤波器的仿真方法,利用该方法对两种新型双耦合器双环CRC (DCDR-CRC)滤波器及三耦合器双环CRC (TCDR-CRC)滤波器进行了理论仿真,通过引入游标原理,分析了两种滤波器在不同环长差下的滤波特性,并通过调整DCDR-CRC及TCDR-CRC的耦合比、环长及环长差,对有效自由光谱范围 (FSR)、抑制比 (SR)及主透射峰带宽进行优化,计算结果表明优化后环腔的有效FSR可有效抑制波长选择器传输通带内的增益竞争,较低的SR可以抑制CRC滤波器相邻透射峰之间的增益竞争,较窄的主透射峰可以保证仅有一个激光器的纵模被选择。Abstract: A method for simulating the optical-coupler-based fiber compound ring cavity (CRC) filter for mode selection of the single longitudinal mode fiber laser is proposed. With this method, we theoretically simulated two types of novel dual-coupler double ring CRC (DCDR-CRC) filter and tri-coupler double ring CRC (TCDR-CRC) filter. By introducing the Vernier effect, the transmittance characteristics of the proposed two filters under different cavity length differences are analyzed. The effective free spectral range (FSR), suppression ratio (SR) and bandwidth of the main transmission peak of CRC filters are optimized by adjusting the coupling ratios, cavity length and cavity length difference of the DCDR-CRC and TCDR-CRC filters. The simulated results show that the optimized effective FSR of the ring cavity can effectively suppress the gain competition in the transmission passband of the wavelength selector. Furthermore the lower SR can suppress the gain competition between the adjacent transmission peaks of the CRC filter, and the narrower bandwidth of the main transmission peak can ensure that only one longitudinal mode of the laser can be selected.
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Key words:
- filter /
- single longitudinal mode /
- dual-coupler double ring /
- tri-coupler double ring /
- Vernier effect
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图 7 环长及环长差固定,不同耦合比下仿真所得TCDR的传输谱, 内插图分别为一个FSR内TCDR传输谱的放大图及最高透射峰传输谱放大图
Figure 7. Transmission spectra of the TCDR compound cavity at different coupling ratios with certain cavity length and cavity length difference, where the insets are the zoomed-in transmission spectra over one FSR and the highest transmission peak of the simulated TCDR, respectively
图 8 耦合比及环长差固定,不同腔长下仿真所得TCDR传输谱, 内插图分别为一个FSR内TCDR传输谱的放大图及最高透射峰传输谱放大图
Figure 8. Transmission spectra of the TCDR compound cavity at different cavity lengths and certain coupling ratio and cavity length difference, where the insets are the zoomed-in transmission spectra over one FSR and the highest transmission peak of the simulated TCDR, respectively
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