Low Loss Splicing Between Double-Clad Fiber and Photonic Crystal Fiber Using Graded Index Fiber Lens

A novel approach of splicing between photonic crystal fiber (PCF) and double-clad fiber is demonstrated with the utilization of graded index fiber (GIF) and coreless fiber as fiber lens. The light beam in large core double-clad fiber is first enlarged by coreless fiber and then focused by GIF to match the small core PCF to realize the low loss splicing. The splicing losses versus the length of GIF, coreless fiber as well as the air hole collapsed region were investigated theoretically and experimentally. Through tailoring the length of GIF and coreless fiber precisely, a splicing loss as low as 0.5 dB was finally achieved between double-clad fiber and PCF with the mode field diameters of 18.7 and 3.9 μm, respectively. To the best of our knowledge, this is the first time to achieve such a low splicing loss between double-clad fiber and PCF.