Opt. Express 22, 22707–22715 (2014)

A reconfigurable optical delay line on a silicon chip has been fabricated by scientists in China. Such devices are needed in all-optical networks and optical information processing systems to perform data synchronization and buffering. The device designed and built by Jingya Xie and co-workers at Shanghai Jiao Tong University is based on a cascade of eight 2 × 2 Mach–Zehnder interferometer (MZI) switches. Variable optical time delays are introduced by selecting long or short optical paths in each MZI switch as desired. In this manner, a maximum time delay of up to 1.27 ns with a 10 ps resolution is achieved. The team says that given the long lengths of waveguides required to introduce the delay, it is important to minimize waveguide propagation loss. The device was fabricated using standard CMOS processes on a silicon-on-insulator wafer and has a footprint of 7.4 × 1.6 mm (11.8 mm2). Tests with data streams at 25 and 10 gigabits per second confirm its operation.