Cascaded arrangement of two-mode Bragg gratings in multiplexing applications
Aspects described herein include an optical apparatus comprising an input port configured to receive an optical signal comprising a plurality of wavelengths, and a plurality of output ports. Each output port is configured to output a respective wavelength of the plurality of wavelengths. The optical apparatus further comprises a first plurality of two-mode Bragg gratings in a cascaded arrangement. Each grating of the first plurality of two-mode Bragg gratings is configured to reflect a respective wavelength of the plurality of wavelengths toward a respective output port of the plurality of output ports, and transmit any remaining wavelengths of the plurality of wavelengths.
1. An optical apparatus comprising:
an input port configured to receive an optical signal comprising a plurality of wavelengths;
a plurality of output ports, wherein each output port is configured to output a respective wavelength of the plurality of wavelengths; and
a first plurality of two-mode Bragg gratings in a cascaded arrangement, wherein each grating of the first plurality of two-mode Bragg gratings is configured to:
transmit a first mode of a respective wavelength of the plurality of wavelengths;
reflect a second mode of the respective wavelength toward a respective output port of the plurality of output ports; and
transmit any remaining wavelengths of the plurality of wavelengths.
2. The optical apparatus of claim 1 , wherein each grating of the first plurality of two-mode Bragg gratings comprises a silicon nitride or silicon oxynitride material.
3. The optical apparatus of claim 1 , further comprising:
a plurality of mode multiplexers, wherein each mode multiplexer of the plurality of mode multiplexers is configured to receive the respective wavelength reflected by a respective grating of the first plurality of two-mode Bragg gratings,
wherein each output port of the plurality of output ports is coupled with an output of a respective mode multiplexer of the plurality of mode multiplexers.
4. The optical apparatus of claim 3 , wherein each mode multiplexer is configured to propagate a fundamental mode along a first arm, and to propagate a reflected second-order mode along a second arm.
5. The optical apparatus of claim 1 , wherein a last grating of the cascaded arrangement is configured to:
reflect a second-to-last wavelength of the plurality of wavelengths toward a first output port of the plurality of output ports; and
transmit a last wavelength of the plurality of wavelengths to a second output port of the plurality of output ports.
6. The optical apparatus of claim 1 , wherein a last grating of the cascaded arrangement is configured to:
reflect a last wavelength of the plurality of wavelengths to a first output port of the plurality of output ports.
7. The optical apparatus of claim 1 , further comprising:
a second plurality of two-mode Bragg gratings, wherein each grating of the second plurality of two-mode Bragg gratings is configured to:
receive the respective wavelength reflected by a respective grating of the first plurality of two-mode Bragg gratings; and
reflect the respective wavelength toward the respective output port of the plurality of output ports.
8. The optical apparatus of claim 7 , further comprising:
a plurality of optical absorbers, wherein each grating of the second plurality of two-mode Bragg gratings has an output coupled with a respective optical absorber of the plurality of optical absorbers.
9. The optical apparatus of claim 1 , wherein the first plurality of two-mode Bragg gratings has non-overlapping passbands.
10. The optical apparatus of claim 1 , wherein the first plurality of two-mode Bragg gratings has partially overlapping passbands.
11. The optical apparatus of claim 10 , wherein each passband of the partially overlapping passbands has a center wavelength and an upper roll-off wavelength that are selected such that a range of the respective wavelength reflected by the respective grating is entirely included between the center wavelength and the upper roll-off wavelength.
12. The optical apparatus of claim 1 , wherein the first plurality of two-mode Bragg gratings are low-pass filters.
13. An optical apparatus comprising:
a plurality of receivers; and
a demultiplexer comprising:
an input port configured to receive an optical signal comprising a plurality of wavelengths;
a plurality of output ports, wherein each output port is configured to output a respective wavelength of the plurality of wavelengths to a respective receiver of the plurality of receivers; and
a first plurality of two-mode Bragg gratings in a cascaded arrangement, wherein each grating of the first plurality of two-mode Bragg gratings is configured to:
transmit a first mode of a respective wavelength of the plurality of wavelengths;
reflect a second mode of the respective wavelength toward a respective output port of the plurality of output ports; and
transmit any remaining wavelengths of the plurality of wavelengths.
14. The optical apparatus of claim 13 , wherein the demultiplexer is a coarse wavelength division multiplexing (CWDM) demultiplexer.
15. The optical apparatus of claim 13 , wherein each grating of the first plurality of two-mode Bragg gratings comprises a silicon nitride or silicon oxynitride material.
16. The optical apparatus of claim 13 , wherein the demultiplexer further comprises:
a plurality of mode multiplexers, wherein each mode multiplexer of the plurality of mode multiplexers is configured to receive the respective wavelength reflected by a respective grating of the first plurality of two-mode Bragg gratings,
wherein each output port of the plurality of output ports is coupled with an output of a respective mode multiplexer of the plurality of mode multiplexers, and
wherein each mode multiplexer is configured to propagate a fundamental mode along a first arm, and to propagate a reflected second-order mode along a second arm.
17. The optical apparatus of claim 13 , wherein the demultiplexer further comprises:
a second plurality of two-mode Bragg gratings, wherein each grating of the second plurality of two-mode Bragg gratings is configured to:
receive the respective wavelength reflected by a respective grating of the first plurality of two-mode Bragg gratings; and
reflect the respective wavelength toward the respective output port of the plurality of output ports.
18. The optical apparatus of claim 17 , further comprising:
a plurality of optical absorbers, wherein each grating of the second plurality of two-mode Bragg gratings has an output coupled with a respective optical absorber of the plurality of optical absorbers.
19. The optical apparatus of claim 13 , wherein the first plurality of two-mode Bragg gratings are bandpass filters.
20. The optical apparatus of claim 13 , wherein the first plurality of two-mode Bragg gratings are low-pass filters.