We report significant advances in the development of simple all-fiber, tunable acousto-optic spectral filters based on null couplers. The performance agrees well with theoretical predictions and is attributed to improved control of the coupler uniformity. Furthermore, using a double-pass arrangement, we demonstrate filter bandwidth reduction and improved sidelobe suppression of -20 dB . The double-pass configuration is also shown to double the frequency shifts that are obtainable from such devices.
© 1997 Optical Society of America
D. O. Culverhouse, S. H. Yun, D. J. Richardson, T. A. Birks, S. G. Farwell, and P. St.J. Russell, "Low-loss all-fiber acousto-optic tunable filter," Opt. Lett. 22, 96-98 (1997)