This technical report describes the round robin measurement results for the group delay ripple (GDR)of tunable dispersion compensators (TDCs). It briefly explains the four typical TDCs measured and fourtypical methods of measuring group delay (GD), as well as the GDR round robin measurement resultsof TDCs, and an analysis of repeatability and differences among these measurement methods. Thisdocument also proposes suitable measurement parameters and a new parameter of phase rippleinstead of GDR.