Contents 1. Introduction
Tunable dispersion compensation is regarded as a key enabling technology for 40 Gb/s optical transmission systems. Furthermore, with the increase in transmission distances as well as the introduction of wavelength dependent routing. even 10 Gb/s systems are beginning to require this functionality. Numerous approaches have been demonstrated including fiber Bragg gratings[1], Virtual Phased Arrays[2], integrated optical filters[3], [4]and others. The first two approaches have experienced the widest success to date, and are currently reaching the product stage. However, challenges to improving device performance remain, such as providing multi-channel compensation (in the case of the FBG device which is single channel), reducing Group Delay Ripple (GDR), reducing insertion loss (in the case of the VIPA), increasing bandwidth (limited by waveguide bending radii in the all-pass ring filter case, for example), and reducing size and complexity (as in the case of lattice filters that typically reQuire many tuning elements for a single device).
