Channel power equalizer for a wavelength division multiplexed system
AssigneeLucent Technologies Inc.
InventorChristopher Richard Doerr
Life of this patent
Estimating the term…
Abstract
A dynamically and chromatically variable transmissivity apparatus (e.g., a channel equalizer or an add-drop circuit) controls channel powers in wavelength-division multiplexed systems. The input WDM signal is split into two components, in one component a phase shift is added to the wavelengths needing equalizing, the two signal components are then recombined. The phase shift added at each wavelength determines the amount of equalization obtained for that wavelength. For a decrease in equalization (i.e., attenuation) range the apparatus exhibits a decrease in insertion loss.
Claims25
A chromatically variable transmissivity optical apparatus comprising
- a first coupler having an input port for receiving a Wavelength Division Multiplexed (WDM) signal and two output ports for outputting first and second WDM signals;
- a second coupler having two input ports and an output port for outputting an equalized WDM signal;
- a first optical path for coupling a first WDM signal from the first output port of said first coupler to a first input port of said second coupler;
- a second optical path for coupling the second WDM signal from a second output port of said first coupler to an input of a wavelength selective phase shifter apparatus for providing a phase shift to each of one or more wavelengths of said second WDM signal so as to change the level of the optical apparatus transmissivity at said one or more wavelengths;
- a third optical path for coupling the phase shifted second WDM signal from an output of said phase shifter apparatus to a second input port of said second coupler;
- wherein
- the effective optical path length of the first optical path is equal, to within a few wavelengths, to the sum of the effective optical path length of the second optical path plus the effective optical path length through the wavelength selective phase shifter apparatus plus the effective optical path length of the third optical path;
- and wherein
- said second coupler for combining said first WDM signal with the phase shifted second WDM signal to form the equalized WDM signal.
A chromatically variable transmissivity optical apparatus comprising
- a coupler having an input port for receiving a Wavelength Division Multiplexed (WDM) signal and two output ports for outputting first and second WDM signals;
- a first optical path for coupling said first WDM signal from a first output port of said coupler to only a reflective facet;
- said reflective facet for reflecting said first WDM signal back to the first output port of said coupler;
- a second optical path for coupling said second WDM signal from a second output port of said coupler to an input of a wavelength selective phase shifter apparatus for providing a phase shift to two or more wavelengths of the second WDM signal;
- said selective phase shifter apparatus including multiple phase shifters each coupled over a separate optical path to a second reflective facet;
- said second reflective facet for reflecting said phase shifted second WDM signal back to the phase shifter apparatus;
- and wherein
- said coupler combining said reflected first WDM signal with said reflected phase shifted second WDM signal to form an equalized WDM signal which is outputted at a second input port of said coupler.
A method of equalizing a WDM signal comprising the steps of:
- receiving a Wavelength Division Multiplexed (WDM) signal and forming therefrom a first and second WDM signals;
- providing an equal optical path length, to within a few wavelengths, for said first and second WDM signals;
- providing a phase shift to each of one or more wavelengths of said second WDM signal so as to change the level of the optical apparatus transmissivity at said one or more wavelengths;
- and
- combining said first WDM signal with the phase shifted second WDM signal received to form an equalized WDM signal.
Dependencies are inferred from the claim text.