Exfo E.O. Engineering Inc.'s IQ-2600 tunable laser source is capable of >60-dB sidemode suppression, making it suitable for spectral characterization of dense WDM components. Based on an erbium-doped fiber laser cavity, it is continuously tunable from 1520 to 1570 nm at a 0.01-nm tuning resolution. A 10% monitoring output provides a wavelength meter connection. An optional ASE broadband output also is available.