LOW-REFLECTIVITY IN-LINE VARIABLE ATTENUATOR UTILIZING OPTICAL FIBER TAPERS

We demonstrate a novel single-mode in-line variable optical attenuator utilizing optical fiber tapers. Optical attenuation control is achieved through axial separation between two tapers with beveled endfaces aligned within a ceramic sleeve. Increased axial separation causes increased coupling loss between the two taper fundamental modes. Insertion loss of < 0.5 dB, attenuation of > 75 dB with continuous 0.05 dB resolution, and reflection return loss of better than 58 dB have been realized. Theoretical studies indicate low polarization and wavelength dependence, and inherent insertion loss of < 0.1 dB. This design also exhibits simplicity of fabrication. © 1990 IEEE