A tunable laser source that characterizes optical components for WDM transmission systems has been released by Anritsu Co. The MG9541A covers the 1510- to 1640-nm range and analyzes passive and active optical components used in C- and L-band applications. The first of its three ports has an optical attenuator with a variable output level of 0 to -30 dBm and a dynamic range of >70 dB when used with an optical spectrum analyzer in tracking mode, making it suitable for characterizing optical filters. Port 2, suitable for optical amplifier evaluation, can output a signal of better than +7 dBm in the 1530- to 1580-nm range and better than +6 dBm extending into the L-band. The third port offers a signal-to-noise-ratio output of 70 dB and can be used with a power meter to characterize passive devices.