General Photonics' high-speed variable differential group delay (DGD) line provides a varied amount of group delay difference between two linear orthogonal polarization states. DGD is a key component in PMD emulation and compensation. This 40G DynaDelay is special designed for to meet the requirement of 40Gb/s systems. It can digitally switch the amount of DGD from 0 ps to 22.5 ps with a resolution of 0.36 ps (6-bit resolution) in less than 500 µs. With an integrated circuit board and software package, the device can easily be controlled with a computer or a microprocessor. In addition to PMD emulation and compensation, this patented device can also be used for precision TDM bit alignment.