Low-Loss Fusion Splicing Photonic Crystal Fibers and Double Cladding Fibers by Controlled Hole Collapse and Tapering.

We demonstrate a novel method for low-loss splicing photonic crystal fibers (PCFs) and double cladding fibers (DCFs) by controlled hole collapse and tapering using a conventional fusion splicer. Through controlled hole collapse, two center rings of holes were collapsed to expand the core of the PCF, while the cladding diameter of the PCF was almostly not changed. The mode field diameter (MFD) and inner cladding diameter of the DCFs were decreased by tapering. So an optimum mode field and cladding match at the interface of PCF-DCF and an adiabatic mode field variation in the longitudinal direction of the PCF and DCF can be achieved. This is the first time, to our knowledge, to realize low-loss splicing between the DCFs and PCFs. Splice losses as low as 0.65 dB were achieved between a PCF and a DCF with MFDs of 5.8 and 26.5 μm, and with the inner cladding diameters of 125 and 250 μm, respectively. [ABSTRACT FROM PUBLISHER]