Fabrication and transmission characteristics of couplers using photonic crystal fibers

We have fabricated two types of fiber couplers using the photonic crystal fibers. The fabrication process of the PCF and the PCF coupler has been presented. With the 4 hole PCF coupler, the starting point of coupling could be obtained after pulling about 2.8 mm, and that of the 5 stack PCF was longer than that of the 4 hole PCF by two times. When the source of 1 mW was launched by a tunable laser diode, the sum of both outputs was about 3% of input power with the 5 stack PCF coupler. It was larger than that of the 4 hole PCF coupler. We have also observed that the peak wavelength of the output port 2 compared with the output port 1 was increased by about several pm with both couplers. In discussion, because the fusion splicing loss between the PCF and a single mode patch cord was about 5 dB, the sum of output power was rather small. If the coupling loss can be decreased, by using a well-designed PCF, these devices can be potentially useful for applications of optical communications.