Broadband hitless bypass switch for integrated photonic circuits

A new microphotonic hitless switch is proposed. By enabling continuous, uninterrupted transition to a bypass path, it permits tuning of wavelength add-drop filters without disturbing intermediate channels. The scheme comprises two symmetrically actuated, 2 times 2 Deltabeta-type optical switches, antisymmetrically cascaded in a balanced Mach-Zehnder configuration, and a pi differential phase shift in the interferometer arms. By symmetry, it provides for wavelength-independent hitless operation before, during and after switch reconfiguration, permitting slow switching independent of bit rate. Compact implementations using high-index-contrast microelectromechanical-system (MEMS)-actuated switches are proposed