This work deals with design of an optical switch device with optical-electrical conversion, used in optical test systems as an aid to automate testing procedure. It is well known that optical system could not be treated in such a simple way as electrical one. First problem one has to encounter is lack of simple components like relays or switches needed for designing the measuring setup. If one would like to automate any operation involving fibers there are only two choices: to use some pure optical components serving as computer controlled optical relays, or to convert the optical signal to electrical domain, and then deal with it in a suitable way before converting it back to the optical domain.The solution with optical-electrical conversion has been presented here. In order to get a better understanding of decisions and tradeoffs made during design, an overview of optical technology and components is given first, and then details of particular design are presented. Signal integrity issues like cross talk, ringing, and ground bounce make electrical devices complicated and expensive to design at high bit data rates. Construction of device is based on solid-state laser module containing Fabry-Perot laser and PIN diode, and signal switching is done in the electrical domain using high-speed LVPECL multiplexers. Laser modules and multiplexers are controlled by 8-bit microcontroller, which is capable to communicate with external computer through the RS-232 or RS-485 serial port.