Novel relative frequency stabilization technique for multichanneloptical communication systems

An experimental demonstration of a relative frequency stabilization technique in which the FM sidebands of a frequency-modulated master laser are used as discrete frequency references is discussed. A frequency-shift-keying (FSK)-modulated DFB transmitter laser has been locked to the fundamental and each one of the 30 FM sidebands, which are spaced exactly 500 MHz apart. It is possible to generate a greater number of FM sidebands over a very large frequency range by using a master laser with larger output power and FM response. It is necessary, however, to select the FM index carefully and minimize residual intensity modulation in order to reduce the variations in the sideband heights