Optical band splitter/combiner device comprising a three-arms interferometer
View Patent ↗A three-arm-Mach-Zehnder interferometer for splitting/combining first and second wavelength bands is provided, wherein the optical device includes first and second optical splitting/combining elements; a differential optical delay device comprising first, second and third optical paths; the first, second and third optical paths of the differential optical delay device are configured to introduce, at a wavelength λ z within the first optical band, a phase delay of 2πm.
1. An optical device for splitting/combining first and second optical wavelength bands, the optical device comprising:
first and second optical splitting/combining elements, each comprising first, second and third optical paths; and
a differential optical delay device comprising first, second and third optical paths respectively interposed between and optically coupled to the first and second optical splitting/combining elements, wherein:
each of the splitting/combining elements is of the (25-50-25%)λx/(0-0-100%)λy type, wherein λx is a wavelength within the first optical band and λy is a wavelength within the second optical band, and
the first, second and third optical paths of the differential optical delay device are configured to introduce, at a wavelength λz within the first optical band, a phase delay Δφ of 2πm to optical radiation propagating through the first optical path, wherein m is an integer other than zero.
2. The optical device of claim 1 , wherein the parameter m, in absolute value, is 2 to 5.
3. The optical device of claim 2 , wherein the parameter m, in absolute value, is equal to 3 or 4.
4. The optical device of claim 1 , wherein the optical device is a planar optical waveguide device.
5. The optical device of claim 4 , comprising three optical waveguides suitably arranged to form the first and the second optical splitting/combining elements and the differential optical delay device.
6. The optical device of claim 4 , comprising a waveguide core-to-cladding refractive index contrast greater than or equal to 1%.
7. The optical device of claim 6 , wherein the waveguide core-to-cladding refractive index contrast is greater than 2%.
8. The optical device of claim 6 , wherein the waveguide core-to-cladding refractive index contrast is lower than 4.5%.
9. The optical device of claim 1 , wherein the first and the second optical splitting/combining element and the differential optical delay device are configured so as to form a three-arm Mach-Zehnder interferometer structure.
10. The optical device of claim 1 , wherein a first, second and third optical paths of the differential optical delay device have optical lengths L 1 , L 2 , and L 3 , respectively, wherein L 3 is equal to about L 0 , L 2 is equal to about L 0 +ΔL and L 1 is equal to about L 0 +2ΔL, wherein ΔL is equal to M*λz.
11. An optical apparatus for splitting/combining a first and a second optical wavelength band, comprising a first and a second optical device according to claim 1 , optically connected in cascade.
12. The optical apparatus of claim 11 , wherein the first and the second optical devices each have an input port and a through port, the input port of the second optical device being connected to the through port of the first device.
13. An optical unit comprising:
an optical device for splitting/combining a first and a second optical wavelength band according to claim 1 ;
a receiver optically connected to the optical device and adapted to receive a first optical signal having a wavelength within one of the first and second optical bands; and
an optical transmitter optically connected to the optical device and adapted to transmit a second optical signal having a wavelength within the other of the first and second optical bands.
14. The optical unit of claim 12 , further comprising a demultiplexer device optically connected to and interposed between the optical device and the optical receiver.
15. The optical unit of claim 14 , wherein the demultiplexer device receives an output from the optical device and separates the first optical signal and a third optical signal, the third optical signal having a wavelength within the same optical band of the first optical signal.
16. The optical unit of claim 15 , comprising a further optical receiver adapted to receive the third optical signal from the demultiplexer device.
17. An optical network comprising a central station, a plurality of terminal stations, each comprising an optical unit according to claim 13 , and a plurality of optical links connecting the terminal stations to the central station.
18. A method of splitting/combining first and second optical wavelength bands using first and second optical splitting/combining elements, the method comprising:
introducing, at a wavelength λz within the first optical band, a phase delay Δφ of 2πm to optical radiation propagating through a first optical path with respect to optical radiation propagating through a second optical path and to optical radiation propagating through the second optical path with respect to optical radiation propagating through a third optical path, wherein m is an integer other than zero, and wherein each of the splitting/combining elements is of the (25-50-25%)λx/(0-0-100%)λy type, and λx is a wavelength within the first optical band and λy is a wavelength within the second optical band.
19. The method of claim 18 , wherein the parameter m, in absolute value, is 2 to 5.
20. The method of claim 18 , wherein the parameter m, in absolute value, is equal to 3 or 4.