US Patent 7412132 Mini fiber optic isolator

A fiber optic array is miniaturized in a configuration that includes an input collimator, a first birefringence crystal, a waveplate, a Faraday rotator, a second birefringence crystal and a second collimator. The elements are aligned along a common optical axis. A light beam along the optical axis that is passed through the first collimator emerges off of the optical axis and through the remaining elements. It re-emerges from the fiber optic array on axis. The configuration provides substantial attenuation in a backward direction.