The RightWave tunable dispersion-compensating module enables transmission systems to operate at ultrahigh data rates of 40 Gb/s. Its manufacturer, OFS, Specialty Photonics Div. of Somerset, N.J., says that the module eliminates the adverse effects of the time-dependent temporal broadening of optical signals caused by chromatic dispersion.A specially designed fiber Bragg diffraction grating, coupled to a tapered thin-film microheater, comes in an isothermal package that protects it from air currents, changes in ambient RightWave's design enables a wide dispersion tuning range in a compact, low-loss, low-power, all-fiber device. Its primary use is to compensate for variations in the chromatic dispersion of optical links, which would otherwise limit the length of the link and/or the transmission rate. The device also may be used in nonlinear fiber devices as a temporal-pulse-compressing element.RightWave has no moving parts, and its low thermal mass makes for efficient operation. The high surface-area-to-volume ratio of the microheater leads to a high rate of passive cooling, so that the tuning speed is sufficient to compensate for fluctuations in network dispersion.