Ultra-High-Capacity Optical Communications and Networking: High-Performance Electrooptic Tunable Filters for Dense Wavelength Division Multiplexing

0123367 Eknoyan该提案是应NSF 01-65“超高容量光通信和网络”的要求提交的。“该项目的目标是使用最近开发的设计原理和制造方法，在密集波分复用（WDM）的电光可调谐滤波器中展示前所未有的调谐范围和速度。该滤波器将在LiNbO 3衬底上生产，预计将提供比以前任何可调谐滤波器技术中实现的更快的调谐（50 ns）和更宽的调谐范围（10 THz）的组合。调谐是通过改变波导双折射的外加电场来实现的，因此改变了相位匹配频率，在该频率下发生了接近完全的偏振转换。 由于TE、TM和TM、TE耦合是相互作用的过程，这些器件具有固有的偏振无关性，德克萨斯大学的研究成果将被纳入这些器件中，包括：（1）使用空间周期性的SiO2条带，通过应变光学效应诱导光的偏振耦合。SiO2在升高的温度下沉积在LiNbO 3衬底上并在室温下图案化，使得纵向应变由热膨胀失配引起。(2)一种新的滤波器设计，消除了对偏振分束器的需要，从而在制造过程中提供了额外的自由度。(3)利用稀疏变迹应变光栅实现偏振耦合。这给滤波器响应提供了类似标准具的周期性，其中零点在频率上几乎均匀间隔。这种设计技术应该使它有可能扩大光谱范围的数量级超过以前的EOTF designs.Preliminary实验室工作，对LiNbO 3电路元件的优化已经准备了所提出的研究的方式。在波长为1537 nm的直波导中实现了TE、TM和TM TE转换效率均为99.3%的相位匹配偏振耦合，并在15 nm（2 THz）范围内实现了峰值转换波长的电光调谐。偏振转换的响应速度测量为52 ns。本项目研制了分束比为25 dB的偏振分束器和适用于EOTF的非偏振分束器，并在LiNbO 3基片上制作了通道间距为50 GHz和100 GHz的四端口光谱分割滤波器、二端口带通滤波器和四端口分插滤波器。滤波器的光谱和时间响应及其调谐范围将被表征。

0123367EknoyanThis proposal was submitted in response to the solicitation NSF 01-65 on "Ultra-High Capacity Optical Communications and Networking." The goal of this project is to demonstrate unprecedented tuning range and speed in electrooptic tunable filters for dense wavelength division multiplexing (WDM) using recently developed design principles and fabrication methods. The filters, which will be produced on LiNb03 substrates, are expected to provide a combination of faster tuning ( 50 ns) and wider tuning range ( 10 THz) than has previously been achieved in any tunable filter technology.Optical frequency selection in the proposed filters is based upon phase-matched polarization mode conversion by a spatially periodic strain perturbation in a single mode optical waveguide. Tuning is accomplished by an applied electric field which alters the waveguide birefringence, and hence the phase-match frequency at which near-complete polarization conversion occurs. The devices are inherently polarization independent because the TE TM and TM TE coupling are reciprocal processes.Innovations from the research at Texas A&M which will be incorporated into these devices include: (1) The use of spatially periodic strips of SiO2 to induce polarization coupling of light via the strain-optic effect. The SiO2 is deposited at an elevated temperature on the LiNb03 substrates and patterned at room temperature, so that longitudinal strain results from thermal expansion mismatch. (2) A new filter design which eliminates the need for polarizing beam splitters and thus gives an extra degree of freedom in the fabrication process. (3) The use of a sparse, apodized strain grating to achieve polarization coupling. This gives an etalon-like periodicity to the filter response, with nulls which are almost evenly spaced in frequency. This design technique should make it possible to extend the spectral range by an order of magnitude over previous EOTF designs.Preliminary laboratory work directed towards the optimization of LiNb03 circuit elements has prepared the way for the proposed research. Phase-matched polarization coupling with 99.3% efficiency for both TE TM and TM TE conversion has been achieved in straight waveguides at a wavelength of 1537 nm, and electrooptic tuning of the peak conversion wavelength over a range 15 nm (2 THz) was also demonstrated. Response speed for polarization conversion was measured to be 52 ns. Both polarizing beam splitters with splitting ratios 25 dB and non-polarizing beam splitters suitable for EOTF application have been produced and characterized.Under this project, four-port spectral slicing filters, two-port bandpass filters, and four-port add-drop filters with 50 GHz and 100 GHz channel spacing will be fabricated on LiNb03 substrates. Spectral and temporal response of the filters and their tuning range will be characterized.