An integrated 1 × 4 high-speed optical switch and its applications to a time demultiplexer

A one-to-four optical switch was fabricated by integrating three interferometric modulators on a
z
-cut LiNbO
3
substrate. Each of three modulators consists of a symmetric Y-junction and an asymmetric X-junction as 3-dB input and output couplers, respectively, to function as a one-to-two light switching element. They are arranged so that the input light is switched at the first stage into two intermediate guides which are connected to two second stage elements where light signals are further divided into the final four output ports. The measured switching voltages were 6.6 and 13.3 V for the first- and second-stage elements respectively, for
TE
-mode at a 633-nm wayelength, and the maximum crosstalk ratio was -18 dB. The device was driven by a 1-GHz signal and the transmission characteristics for four output ports were measured. The device performs the function of demultiplexing an optical signal from 4 to 1 Gbit.