Variable optical attenuator based on rare earth doped glass
A variable optical attenuator including a loss element and a rare earth doped gain element in optical communication with the loss element, the rare earth doped gain element having a gain responsive to an optical pump.
1 . A variable optical attenuator, comprising:
a loss element; and
a rare earth doped gain element in optical communication with the loss element, the rare earth doped gain element having a gain responsive to an optical pump.
2 . The variable optical attenuator of claim 1 , in which the loss element comprises one of a rare earth doped waveguide, an un-doped waveguide, and a neutral density filter.
3 . The variable optical attenuator of claim 1 , in which the loss element is doped with Er 3+ in the range of 5 to 30 wt %.
4 . The variable optical attenuator of claim 3 , in which the loss element is additionally doped with Yb 3+ in the range of 7 to 35 wt %.
5 . The variable optical attenuator of claim 1 , in which the rare earth doped gain element is doped with Er 3+ in the range of 5 to 30 wt %.
6 . The variable optical attenuator of claim 5 , in which the rare earth doped gain element is additionally doped with Yb 3+ in the range of 7 to 35 wt %.
7 . The variable optical attenuator of claim 1 , additionally comprising:
a waveguide including a core and a cladding, the cladding at least partially surrounding the core, in which the core is doped with at least one species of rare earth ion in the range of 5 to 75 wt %; and
a coupling region in optical communication with the waveguide, the coupling region connected to receive an optical pump and provide the optical pump to at least a portion of the waveguide;
in which the waveguide includes the loss element and the rare earth doped gain element.
8 . The variable optical attenuator of claim 7 , in which the core is doped with Er 3+ in the range of 5 to 30 wt %.
9 . The variable optical attenuator of claim 8 , in which the core is additionally doped with Yb 3+ in the range of 7 to 35 wt %.
10 . The variable optical attenuator of claim 7 , in which the cladding is doped with Er 3+ in the range of 5 to 30 wt %.
11 . The variable optical attenuator of claim 10 , in which the cladding is additionally doped with Yb 3+ in the range of 7 to 35 wt %.
12 . The variable optical attenuator of claim 7 , in which the core includes silver atoms.
13 . The variable optical attenuator of claim 7 , in which the coupling region is located at an intermediate portion along the waveguide.
14 . The variable optical attenuator of claim 7 , in which the coupling region of the optical pump comprises one of a diffractive coupler, a y-branch coupler, a directional coupler, a grating coupler, a fused optical fiber coupler, and a combination thereof.
15 . The variable optical attenuator of claim 7 , in which the coupling region comprises coupling regions connected to receive respective optical pumps.
16 . A method of varying optical attenuation, comprising:
optically connecting a loss element in series with a rare earth doped gain element;
passing an optical signal through the loss element and the gain element;
attenuating the optical signal in the loss element; and
illuminating the gain element with optical pump power having an intensity that defines the attenuation.
17 . The method of claim 16 , in which the illuminating comprises:
co-propagating the optical signal and the optical pump power within the rare earth gain element.
18 . The method of claim 16 , in which the passing comprises:
coupling the optical signal to the loss element;
coupling the optical signal from the loss element to the rare earth gain element.
19 . The method of claim 16 , in which the passing comprises:
coupling the optical signal to the rare earth gain element;
coupling the optical signal from the rare earth gain element to the loss element.
20 . The method of claim 19 , additionally comprising:
filtering pump power between the loss element and the rare earth gain element.