Experimental and theoretical results on the characteristics of a compact three cavity transmitter configuration are presented. The configuration consists of a 1.3-μm semiconductor laser with external resonators on each side. One resonator is a spherical reflector positioned at the rear facet for sidemode suppression to about 30 dB. The other resonator at the front facet is a semitransparently gold coated grin-rod lens for linewidth reduction to about 1 MHz. The whole configuration has a length of less than 2 cm.