  We examine collisions of moving solitons in a fiber Bragg grating with a
triplet composed of two closely set repulsive defects of the grating and an
attractive one inserted between them. A doublet (dipole), consisting of
attractive and repulsive defects with a small distance between them,is
considered too. Systematic simulations demonstrate that the triplet provides
for superior results, as concerns the capture of a free pulse and creation of a
standing optical soliton, in comparison with recently studied traps formed by
single and paired defects, as well as the doublet: 2/3 of the energy of the
incident soliton can be captured when its velocity attains half the light speed
in the fiber (the case most relevant to the experiment), and the captured
soliton quickly relaxes to a stationary state. A subsequent collision between
another free soliton and the pinned one is examined too, demonstrating that the
impinging soliton always bounces back, while the pinned one either remainsin
the same state, or is kicked out forward, depending on the collision velocity
and phase shift between the solitons.
