A large mode area optical fiber is configured to support multiple
transverse modes of signal radiation within its core region. The fiber is
a hybrid design that includes at least two axial segments having
different characteristics. In a first axial segment the transverse
refractive index profile inside the core is not radially uniform being
characterized by a radial dip in refractive index. The first segment
supports more than one transverse mode. In a second axial segment the
transverse refractive index profile inside the core is more uniform than
that of the first segment. The two segments are adiabatically coupled to
one another. Illustratively, the second segment is a terminal portion of
the fiber which facilitates coupling to other components. In one
embodiment, in the first segment M.sub.1.sup.2>1.0, and in the second
segment M.sub.2.sup.2<>1.0 and M.sub.2.sup.2.about.1.0. In another
embodiment, the optical fiber is coupled to a fiber stub.