Low-crosstalk balanced bridge interferometric-type optical switch for optical signal routing

Crosstalk is one of the significant measures of an optical cross-bar switch. In this paper, we describe a configuration for crosstalk suppression of a balanced-bridge interferometric type optical switch and its application to an optical-signal routing device. Since crosstalk of the optical switch originates from imbalance in the amplitude of a lightwave propagating within the arm of the interferometer, additional Mach-Zehnder structures were embedded for trimming the amplitude of the light. By adjusting the transmittance of the trimmers, crosstalk of less than -56 dB is achieved for dc voltage. Also, for high-frequency voltages, a crosstalk estimation procedure was developed, and crosstalk at 10-GHz sinusoidal voltage was evaluated to be -48 dB. Furthermore, based on the transient response measurement, its switching time was evaluated to be 26 ps. For a demonstration utilizing extremely low crosstalk and quick response, a guard-time-free optical signal routing experiment is also described.