High-speed switching characteristics of integrated optoelectronic crossbar switch

Optoelectronic (OE) switching is a promising approach for routing signals in fibre optic networks. Recently, the integration of a 4x4 MSM array with optical surface waveguides has been reported. This technique greatly simplifies the packaging of an OE switch. The on-chip polyimide optical waveguides perform the optical signal distribution to a matrix of MSMs which are responsible for the switching operation itself. Photoresponse bandwidths exceeding 4 GHz have been demonstrated. Another important characteristic of a switch is the switching speed since it determines the reconfiguration time. Mechanical and thermal optical waveguide switches offer switching speeds of the order of milliseconds which is sufficient for network traffic management but too slow for packet switching. We report measurements on the switching characteristics of a 4x4 optoelectronic switch performed in both the frequency and time domain. In the time domain, the individual crosspoints exhibit a rise time of 3 ns. However, a sizeable overshoot and ringing settles only after 35 ns. This constitutes the reconfiguration time at present. This is confirmed by measurements in the frequency domain of the electrical transmission from control line to output line. The 3-dB switching bandwidth is a few hundred megahertz. The 35 ns reconfiguration time indicates that it is already suitable for packer switching in a 10 Mb/s network. Switching speed measurements on individual MSMs suggests that modifications to the switch circuit could improve the switching time. The switch could also find application as a component in the wavelength conversion circuit of a WDM fibre optic network.