Abstract: A circulator includes a polarization beam splitter, a first reflector, a first non-reciprocal device, a second non-reciprocal device, and a second reflector. The first reflector is coupled with the polarization beam splitter. The first non-reciprocal device is coupled to the first reflector. The second non-reciprocal device is coupled to the polarization beam splitter. The second reflector is coupled with the polarization beam splitter.

Abstract: An optical circulator has a first collimator; a first block of birefringent material; a first compound polarization rotator; a light angle deflector (e.g., Wollaston prism); a second compound polarization rotator; a second block of birefringent material; and a second collimator. Light from the first fiber exits the first collimator along a first path into a first collimated beam that first hits the central plane on a crossing line between the interface and the central plane such that the first collimated beam exits the light angle deflector along a second path substantially parallel to the longitudinal direction and is received by the second fiber. Light from the second fiber exits the second collimator along the second path into a second collimated beam that exits the light angle deflector along a third path and is received by the third fiber.

Abstract: A wavelength division multiplexer includes a filter, a first lens, a second lens, a first holder, and a second holder. The pass-band of the filter is dependent on the incident angle of light incident upon the filter. The first lens is positioned on a first side of the filter. The second lens is positioned on a second side of the filter. The first holder is configured to hold at least first, second, third, and fourth fibers proximate to the first lens. The first holder is also configured to hold a center of the second and the fourth fibers on opposite sides of a line connecting a center of the first and the third fibers. The second holder is configured to hold at least fifth and sixth fibers proximate to the second lens.

Abstract: An optical circulator has a first collimator; a first block of birefringent material; a first compound polarization rotator for rendering mutually parallel polarizations orthogonal and mutually orthogonal polarizations parallel; a light angle deflector (e.g., Wollaston prism); a second compound polarization rotator for rendering mutually parallel polarizations orthogonal and mutually orthogonal polarizations parallel; a second block of birefringent material; and a second collimator. Light from the first fiber exits the first collimator along a first path into a first collimated beam that first hits the central plane on a crossing line between the interface and the central plane such that the first collimated beam exits the light angle deflector along a second path substantially parallel to the longitudinal direction and is received by the second fiber.

Abstract: A system and method for a four-port circulator. The four-port circulator includes a polarization beam splitter, a first reflector, a first non-reciprocal device, a second non-reciprocal device, and a second reflector. The first reflector is coupled with the polarization beam splitter. The first non-reciprocal device is coupled to the first reflector. The second non-reciprocal device is coupled to the polarization beam splitter. The second reflector is coupled with the polarization beam splitter.