New configuration of polarisation-independent isolator using a polarisation-dependent one

A simple effective method to realise polarisation-independent optical isolators is proposed. The isolator consists of spatial walk-off polarisers, half-wave plates, and a conventional polarisation-dependent isolator. The measured forward loss of the assembled isolator is 0.38dB and 0.32db at 1.3dB and 1.55μm wavelengths, respectively. The backward loss is 55.5dB and 63.5dB at 1.3 and 1.55μm wavelengths, respectively.