| 摘要 |
<p>The present document relates to passive optical networks (PON). In particular, the present document relates to an optical filter for Wavelength Division Multiplex (WDM) PONs. A Receiver Optical Subassembly (ROSA) for a WDM-PON ONU (151, 152) is described. The ROSA comprises a downstream filter (170) configured to isolate a first optical downstream signal (182) at a first downstream wavelength from an optical WDM downstream signal (183) comprising a plurality of downstream wavelengths. The downstream filter (170) comprises a first reflective plate (203) configured to let pass the optical WDM downstream signal (183) in a first propagation direction, and configured to reflect the optical WDM downstream signal (183) in a second propagation direction. The second propagation direction is opposite to the first propagation direction. Furthermore, the downstream filter (170) comprises a second reflector (202, 221) configured to reflect the optical WDM downstream signal (183) in the first propagation direction. The first reflective plate (203) and the second reflector (202, 221) form a resonator cavity having an optical path length (231). In addition, the downstream filter (170) comprises path length modification means configured to modify the optical path length (231) of the resonator cavity to adjust a pass band of the downstream filter (170) to the first downstream wavelength. The ROSA further comprises a photodetector (162) configured to convert the first optical downstream signal (182) into an electrical signal.</p> |
