UV-induced polarisation-dependent loss (PDL) in tilted fibre Bragg gratings: application of a PDL equaliser

By using a zero-order-ed phase mask, tilted fibre Bragg gratings (FBG) were fabricated in standard telecommunications fibre that have a near constant polarisation-dependent loss (PDL) across a wide wavelength range (λ = 1500 to 1580 nm). The near constant PDL of the FBG device was produced by precise control of grating blaze angle, while the magnitude of the PDL was controlled through UV exposure conditions and device length. In this fashion a device with an arbitrary PDL value could be fabricated. By optically coupling the devices to an optical component or system requiring polarisation equalisation, the resultant PDLs of the systems were minimised by orienting the gratings of the PDL equaliser about its optical axis to lessen the inequality in output states of polarisations.