Optical switches are required to handle light signals with both vertical and horizontal polarisations – a technique known as polarisation-division multiplexing.
To achieve this dual transmission, a separate switch circuit must be used for each polarisation. In doing so, this doubles the size of the chip and increases the cost of the system.
The new device, referred to technically as a ‘fully integrated non-duplicate polarisation-diversity silicon-photonic switch’, consists of a single 8 x 8 grid of 2 x 2 element switches. The single grid with novel port assignments takes the place of two, and simultaneously manages both polarisations of light – a method known as polarisation diversity.
"In this way, the switch chip achieves polarisation ‘insensitivity’ without doubling the size and cost of the chip, which is important for broadening the practical application of such devices,” said lead author Ken Tanizawa.
"We believe that a silicon-photonic switch is a key device for achieving sustainable growth of traffic bandwidth in optical networks, including both telecommunications and data communications, and eventually computer communications."
The device also features polarisation splitter-rotators integrated onto the chip.
The researchers claim to have designed the device so that the distance travelled by any signal passing through the 8 x 8 grid is identical, regardless of its path. This means that the attenuation and delay of the signal are also the same, allowing for a consistently high quality signal.
These advances promise to not only enhance network flexibility, but also open up new possibilities for the use of optical switching in future energy efficient optical networks.
