Super-separation thin film filtering for coexistence-type colorless WDM-PON networks

Two wavelength blocking filters (WBF) are designed to separate wavelength regions allocated for the Gigabit passive optical network (GPON) downstream and upstream signals. The designed WBFs guarantee high filter contrast factors achieved by steep transmission curves in the vicinity of cut-on/cut-off wavelengths of 1290 nm / 1330 nm and 1480 nm / 1500 nm. FBFs have pass passbands of less than ~5 dB ripple and reject wavelengths outside the widths of the passband at ~32 dB. The deployment of both WBFs could not only prevent the allocated wavelength bands from the undesirable interference with the future next-generations PON such as XG-PON, but it could also vacate wavelength space for future WDM or additional services re-allocation.