| 摘要 |
A polarisation dependent loss (PDL) compensator for receiving from a transmission system radiation having TM and TE polarisation components comprises a waveguide structure for separating the TM and TE polarisation components, the reference numerals denoting the TM mode axis and the TE mode axis corresponding to the TM and TE fundamental mode heights within the waveguide structure. Differential coupling losses are introduced by positioning the ends of input/output fibres relative to the axes to generate a required amount of coupling PDL, that is for applying a first loss to the TM polarisation component and a second loss to the TE polarisation component. If the waveguide structure has positive PDL (TE mode loss greater than TM mode loss), for example, the output fibre may be aligned with the TE mode axis to reduce TE coupling loss relative to TM coupling loss, thus inducing a negative coupling PDL. Such a compensator is capable of applying compensating losses such that the total losses are the same for the two polarisation modes. As a result the PDL is reduced substantially to zero, and the received power will be substantially constant regardless of polarisation changes in the signal. |
