DWDM用途液晶式可調光濾波器

Abstract

高效能與經濟實惠的可調光濾波器對下一世代的動態波長區分多工系統與網路而言是非常必要的。對此，過去有許多的研究與設計被完成，例如Fabry-Perot干涉儀、Mach-Zehnder干涉儀、光纖布拉格光柵、聲光可調光濾波器，同樣的也有電光可調光濾波器，以及陣列波導光柵元件。工作在未達臨界電流狀態的雷射結構也是非常吸引人的主動濾波器候選。 在本論文中，我們提出了一個新型作為DWDM用途的可調濾波器結構，我們使用繞射光柵與一透鏡將光波依據波長的不同而展開於空間中，並使用一扭曲向列式液晶元件作為一空間調制器，在空間中經由將被選擇波長光波偏振態的改變與選擇而達到濾波的效果。我們在波長為830nm的波段展示了一5個頻道的可調濾波器，頻道寬度為約0.8nm，頻道阻隔約19dB，FWHM約0.43nm，調制時間約1秒。

High-performance and cost-effective tunable optical filters are essential for the next generation of dynamic WDM systems and networks. A number of designs have been implemented in the past, e.g., Fabry-Perot and Mach-Zehnder interferometers, Fiber Bragg Gratings, acousto-optic as well as electro-optical tunable filters (AOTF and EOTF), and arrayed waveguide grating (AWG) devices. Active filters based on laser structures operating below threshold are also attractive candidates. In this work, we propose a new configuration of tunable optical filter for DWDM applications. First-order diffracted signal light is directed to a lens and focused on to a transmission-type liquid crystal spatial light modulator (LC_SLM). Wavelength channels are selected by opening the appropriate pixels of the LC_SLM for transmission .We demonstrate the electrically tunable optical filter at a wavelength of 800 nm, with 5 channels, channel spacing of □ 0.8nm, channel isolation of 19dB, 3-dB bandwidth of □ 0.4 nm, and a tuning time of □ 1sec.