Broadband Mode Converter Based on Photonic Crystal Fiber

In this letter, the scheme of a tapered mode-selective coupler based on photonic crystal fiber (PCF) is proposed. Three typical mode converters, such as LP01 to LP11a, LP01 to LP11b, and LP01 to LP21, are described and simulated in detail. The coupling loss and bandwidth is calculated to evaluate those mode converters. The results demonstrate that those mode converters are broadband and low-loss devices. In addition, those mode converters are insensitive to the orthogonal polarizations. They can be fabricated using PCF postprocessing technique and are useful for future mode-division multiplexing optical fiber communication systems.