Double-pass polarization-independent signal processor and on-axis processing method

摘要

An apparatus includes a polarization beam splitter, at least two reflectors and first and second polarization rotation devices. The polarization beam splitter and the at least two reflectors are arranged in a loop that is capable of propagating a clockwise signal component and a counterclockwise signal component. The first polarization rotation device is located in the loop between the polarization beam splitter and a first reflector of the at least two reflectors. The second polarization rotation device is located in the loop between the polarization beam splitter and an additional reflector of the at least two reflectors. The first polarization rotation device includes a serial arrangement of a reciprocal rotator and a nonreciprocal rotator.