A model of a ring class B laser operating in two counterpropagating mo
des is considered. A set of reduced equations are derived which provid
e the simplest mathematical description of this model. Homoclinic bifu
rcations leading to the appearance of low-frequency regular and chaoti
c antiphase oscillations of the counterpropagating wave intensities ar
e described. The effect of symmetry breaking caused by weak backscatte
ring on the laser dynamics is discussed. (C) 1998 Published by Elsevie
r Science B.V.