Reflective optical non-reciprocal devices

An optical non-reciprocal device for coupling light beams between a plurality of ports, the device comprising at least a first port and a second port at one end of the device, mirror means at an opposite end of the device and, disposed between the plurality of ports and the mirror means, a optical elements for spatially separating first and second polarization components of a light beam leaving said first port, conveying the first and second polarization components non-reciprocally to and from the minor means such that the first and second polarization components travel along first and second paths, respectively, recombining said first and second polarization components and coupling the recombined light beam to the second port, the optical elements being configured such that a second light beam leaving the second port will be separated into first and second polarization components, and the first and second polarization components of the second light beam will travel along third and fourth paths, respectively, and be recombined at a position at said one end of the device, which position is spaced from both the first port and the second port in a plane extending through the first and second ports.