We demonstrate a 4 x 2.5 Gb/s cold-start WDM system using a synchronized etalon filter. This system automatically operated its transmitter lasers at the standardized wavelengths of 1547.82 +n x 0.8 nm (193.686 -n x 0.100 THz), where n is the channel number, to an accuracy of 1 GHz. The output power of each laser was also adjusted to be 0 +/- 0.1 dBm simultaneously. Error-free transmission (BER <10(-9)) was achieved within 20 s after turning on the system's power supply.