Research On A Photonic Crystal Fiber Used In FTTH Short Distance Transmission

In the construction of Fiber to the Home (FTTH), the cable is fixed in the junction box of theuser’s room after repeated bending, so that the bending loss caused by external force is the mainfactor which impacts FTTH performance. Transmission attenuation will proliferate if the currentordinary fiber is used, which unable to meet the signaling requirements. Photonic crystal fiber (PCF)provides a new way in the design of low bending loss fiber which aimed in FTTH short distancetransmission.In this paper, the bending characteristics and compatibility with single mode fiber (SMF) ofPCF are theoretical studied and numerical simulated by using the full vector finite element method(FEM) combined with bending index model of PCF and computer software COMSOL. A PCF withgermanium doped core is designed with excellent bend resistant characteristics due to the specialasymmetric cladding structure. The mode field distribution, bending characteristics, compatibilitywith SMF of PCF are analyzed by adjusting radius and density of doped core. Numerical resultsindicate that after the fiber bending, single mode propagation can still maintained when core radiuslarger than3.9μm and core index between1.4493~1.4530. Confinement loss of the fundamentalmode about0.014dB/km for a bending radius of5mm at a wavelength of1550nm is obtained.Furthermore, a mode field area of62.17μm2(corresponding a8.9μm mode field diameter) at awavelength of1550nm exhibits this PCF a high compatibility with SMF. The designed fibersustains a smaller bending radius and the properties of single mode propagation, low-bending-lossare simultaneously achieved.A FTTH transfer system based on PCF is designed according to the requirements of the opticalfiber network. Then, theoretical model while splice the fiber is discussed and the main factorswhich influence the splice loss between PCF and SMF are analyzed. Furthermore, FEM is used toanalyze the compatibility with SMF-28of PCF at different structural parameters. This fiber offersan efficient way to develop the low-bending-loss fibers for the application of fiber-to-the-home.