9E-1 Limitation and Improvement of Collinear Beam Acousto-Optic Tunable Filters

Based on the analysis of the theoretical and practical limitations of resolution and sidelobe obtainable by using apodization, a new design of the CBAOTF for WDM is proposed. Experimental results of a 65 degree apodized CBAOTF measured at 1550 nm include 3 db bandwidth less than 0.4 nm and sidelobe level of -25 dB at 0.8 nm away from the center wavelength. The specified sidelobe level of -35 db for the 100 GHz channel spacing can be met by using two apodized CBAOTF in cascade. Other practical limitations include the tight tolerance required in the fabrication and the strong temperature dependent properties of the CBAOTF.A new filter configuration for overcoming these deficiencies is described.