A method (200) of controlling compensation of chromatic dispersion in an optical transport network. The method comprises determining (202) whether a residual dispersion, RD, of a first path (3) within the network is within a defined RD range and if the RD of the first path is outside the defined RD range the method comprises identifying (204) a first tuneable dispersion compensation module, TDCM, crossed by the first path (3), configured to apply a respective value of dispersion compensation. The method also comprises determining (206) a different value of dispersion compensation to be applied by the first TDCM to bring the RD of the first path within the defined RD range; if (208) the first TDCM is crossed by at least one other path (1, 2), checking (210) that the respective RD of said at least one other path is within a respective defined RD range for said different value of dispersion compensation; and generating (212) a control signal comprising instructions configured to set the first TDCM to apply said different value of dispersion compensation.