Abstract

Fused tapered passive optical couplers are noted for their low optical loss and good reflectance properties.¹ Intrinsic to their evanescent wave coupling mechanism, however, is significant variability of the optical performance with wavelength. In a 1×2 or 2×2 fused biconic coupler, the standard method used to improve achromatic performance is to mismatch the two fibers in the coupling region by pre-tapering, pre-etching, or doping one of the fibers, resulting in performance as shown in Fig. I.² While this approach gives improved achromaticity, the coupling typically still shows significant variations over the wide passbands of interest in passive network applications.

© 1994 Optical Society of America