Characteristics of optical fiber WDM with high isolation

A high isolation optical fiber WDM (wavelength division multiplexer) with isolation better than 40 dB was obtained by cascading fused biconic tapered (FBT) optical fiber. The fabricated multiplexer was compared with WDMs produced by a dielectric thin film interference method. The values of isolation and bandwidth for the cascading FBT were calculated analytically. In practice, a coiling method was employed to reduce the number of WDM components. The optical fiber WDM was optimized by calculating the insertion loss and isolation according to the diameter and wind number of the coil. The fabricated optical fiber WDM showed a 40.5 and 41.2 dB of isolation and 0.7 and 0.6 dB of insertion loss for 1310 nm and 1550 nm, respectively.