Compact optical-optical switches and wavelength converters by means of multimode interference mode converters
First Claim
1. A cross-phase-modulated optical--optical switch comprisinga mode splitter (111) having one or several waveguide inputs for an optical input signal (B) and for splitting said input signal into two arms (5, 6) of a Mach-Zender interferometer;
- a nonlinear optical material (114,
118) in at least one of said arms;
a phase shifter (115,
119) in at least one of said arms;
a first mode combiner (112) coupled to said arms for imaging the input signal (B) onto said arms of waveguides; and
a second mode combiner (113,
117) for coupling a control signal onto one of said arms, said second combiner comprising an multimode interferometer converter combiner.
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Abstract
New, compact optical--optical switches and/or wavelength converters manufacturable with good tolerances and evincing all or some of the following properties,
compactness
good ON/OFF switching ratios
possibility of cascading and bidirectional operation
polarization-independence feasibility
very fast switching
are being developed.
This requires developing components making use of different-order modes to mix the information signal and the control signal and to separate them. The compact Converter Combiner MMIs of the invention make possible:
1. converting a first fundamental mode into first-order modes,
2. superposing the first-order modes and the images of a second fundamental mode,
3. the MMI operates simultaneously as mode splitter for the participating modes.
Back-conversion of the generated modes of higher order into their initial modes also is possible.
The control signal generating not only a change in phase but also a change in intensity at the input signal, steps must be taken to achieve good ON/OFF switching ratios at the outputs. The problem of achieving good ON/OFF switching ratios is solved by using appropriate mode couplers having variably splitting ratios.
An alternative method for optical--optical switches and wavelength converters is discussed making no use of the optical mode converters of the invention but nevertheless evincing some or all the above properties.
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Citations
37 Claims
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1. A cross-phase-modulated optical--optical switch comprising
a mode splitter (111) having one or several waveguide inputs for an optical input signal (B) and for splitting said input signal into two arms (5, 6) of a Mach-Zender interferometer; -
a nonlinear optical material (114,
118) in at least one of said arms;a phase shifter (115,
119) in at least one of said arms;a first mode combiner (112) coupled to said arms for imaging the input signal (B) onto said arms of waveguides; and a second mode combiner (113,
117) for coupling a control signal onto one of said arms, said second combiner comprising an multimode interferometer converter combiner. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A cross-phase-modulated optical--optical switch comprising
a mode splitter (121) having a waveguide input for an optical input signal (B) and for splitting said input signal into two arms (5, 6) of a Michelson interferometer; -
a nonlinear optical material (124,
127) in at least one of said arms;a specular reflective surface for reversing signals in said arms; said mode splitter (121) operating as a first mode combiner for reflected signals from said arms and for imaging the input signal (B) onto two arms and one of two output waveguides; and a second mode combiner (122,
125) for coupling a control signal onto one of said arms, said second combiner comprising a multimode interferometer converter combiner. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A cross-phase modulation (XPM) optical--optical switch comprising
a first, outer Mach-Zehnder interferometer for receiving an optical input signal and having an input coupler (211) and an output coupler (212), said input and output couplers having matched splitting ratios and being coupled by optical arms; -
a second, inner Mach-Zehnder interferometer having a mode mixer (213) and a mode demixer (216), said mode mixer and said mode demixer having symmetric splitting ratios and being coupled by optical arms; optical non-linear regions in said optical arms between said mode mixer and said mode demixer and between said input and output couplers; and waveguides for coupling an input optical signal to said input coupler and an optical control signal to said mixer, discrimination between said input signal and said control signal at the demixer being accomplished by phase differences within said second, inner Mach-Zehnder interferometer. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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21. An optical--optical switch comprising
a middle section (163) containing at least one non linear medium and having a plurality of input and output waveguides coupled to input and output surfaces thereof; -
a mode splitter (161) having one or several waveguide inputs for an optical input signal (B) and for splitting said input signal into two arms that are guided into said middle section; and a mode combiner (162) connected to two waveguides from said middle section for imaging the input signal (B) onto the arms of output waveguides, said mode splitters and combiners comprising butterfly multimode interferometers with identical or substantially reciprocal splitting ratios.
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22. An optical--optical switch comprising an interferometer configuration including
first and second optical paths each having coupling elements and a non-linear optical medium, said paths having non-linearities different from each other, said coupling elements each having at least two optical inputs and at least two optical outputs; -
means for delivering an optical signal to one input of one of said coupling element optical inputs; an input mode coupler (171) comprising a 1×
2 multimode interferometer having a length L=(3Lc)/8 for receiving an input control signal (B) and for splitting said input control signal and delivering split signals to said coupling elements;an output mode coupler (172) comprising a 2×
2 multimode interferometer having a length L=(3Lc)/2 or L=(3Lc)/6 for receiving output signals from said coupling elements and for delivering split switched output signals.
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23. A cross-phase modulation (XPM) optical--optical switch comprising
mode coupler means (411, 415) for receiving an input signal and separating said input signal into two mode signals of different orders separated in time and sequentially coupling said two signals into a non-linear region; -
means for converting the two signals into fundamental modes; means for matching said two signals in time; a mode coupler (412,
416) for receiving and converting said time-matched signals and combining said signals so that they interfere; andmeans for coupling a resulting signal to an output. - View Dependent Claims (24)
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25. An optical--optical switch comprising an Mach-Zehnder interferometer configuration with
a mode splitter (511) having waveguide inputs for an optical input signal (B) and for splitting said input signal into two arms of a Michelson interferometer; -
sections with non-linear materials on each arm of said Michelson interferometer; a mode combiner (512) for combining the split twp parts of the input signals into an output guide with said splitters (511) and combiners (512) comprising multimode interference couplers having reciprocal splitting ratios.
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26. An optical--optical switch comprising
an Mach-Zehnder interferometer optical waveguide configuration with a 1× - 2 mode splitter (521) having one waveguide input for an optical input signal (B) and for splitting said input signal into the two arms of the Michelson interferometer;
two sections with differently operated non-linear material sections in each arm of the Michelson interferometer; and a mode combiner (522) for combining said split-up two input signals into an output guide.
- 2 mode splitter (521) having one waveguide input for an optical input signal (B) and for splitting said input signal into the two arms of the Michelson interferometer;
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27. A method of converting an optical signal of low-order mode into optical signals in higher order modes comprising the steps of
providing a multimode interferometer comprising a material having a known effective refractive index which is higher than an effective refractive index of surrounding material, the multimode interferometer having a first input surface, a second output surface and a length L between the first and second surfaces substantially equal to ##EQU1## wherein N is a number representative of a number of possible inputs and outputs, n is the effective refractive index of the multimode interferometer material, W is an equivalent width of the multimode interferometer in a direction perpendicular to the length, and λ - is the wavelength of an optical signal,
coupling a waveguide input to a selected location on the first surface of the multimode interferometer and at least one waveguide output to the second surface of the multimode interferometer, coupling an optical signal of a first, low-order mode into the waveguide input, and receiving an optical signal of order higher than the low-order mode into at least one waveguide output. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36)
- is the wavelength of an optical signal,
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37. An optical--optical switch comprising
a first multimode interferometer converter combiner (311) having a length L=3Lc /4 for converting a fundamental mode input signal (B) into first and zero order modes and for mapping a second zero order mode signal unchanged onto a zero order mode, wherein Lc equals (4nW2)/3λ - , W is the width of the multimode interferometer, n is the effective index of refraction and λ
is the wavelength in vacuum,an identical second multimode interferometer converter/combiner (312) for back-conversion of the first order mode into a fundamental mode and for coupling out the input signal and a control signal, input waveguides guided to the central input of said first converter combiner for said control signal, input waveguides guiding said signal to longitudinal edges of said first converter/combiner, three waveguides connecting the two converter/combiners with optical waveguides at upper and lower longitudinal edges of the converter/combiners and at the center, output waveguides for said input signal at the upper and lower longitudinal edges of said second converter/combiner, and an output waveguide for said control signal at the center position of said second converter/combiner.
- , W is the width of the multimode interferometer, n is the effective index of refraction and λ
Specification