CN117369167A - Optical switch and switching device based on multimode Bragg grating - Google Patents
Optical switch and switching device based on multimode Bragg grating Download PDFInfo
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- CN117369167A CN117369167A CN202311666248.7A CN202311666248A CN117369167A CN 117369167 A CN117369167 A CN 117369167A CN 202311666248 A CN202311666248 A CN 202311666248A CN 117369167 A CN117369167 A CN 117369167A
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/0009—Materials therefor
- G02F1/009—Thermal properties
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/35—Optical coupling means having switching means
- G02B6/351—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements
- G02B6/3534—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being diffractive, i.e. a grating
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/35—Optical coupling means having switching means
- G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
Abstract
The invention relates to the technical field of integrated photoelectrons and discloses an optical switch and a switching device based on multimode Bragg gratings. The optical switch includes: a multimode bragg grating filter comprising a multimode bragg grating and a mode multiplexer; the multimode Bragg grating adopts an antisymmetric multimode Bragg grating with positive dispersion and width gradually apodized according to a parabolic function, the mode multiplexer comprises an upper coupling waveguide and a lower coupling waveguide, the upper coupling waveguide is a light path main waveguide, the lower coupling waveguide is an uplink downlink waveguide, and the upper coupling waveguide is connected with the multimode Bragg grating; and a heating electrode for heating the multimode Bragg grating filter. The wide working wavelength range of the Bragg grating enables the optical switch to accommodate errors of technology, temperature, voltage and the like, and low crosstalk and low power consumption of the device are realized through the grating positive dispersion design and parabolic apodization.
Description
Technical Field
The invention relates to the technical field of integrated photoelectrons, in particular to an optical switch and a switching device based on multimode Bragg gratings.
Background
The integrated optical switch is widely applied to various photoelectric integrated chips as a basic component, and can also be applied to optical exchange, microwave photon beam forming and other systems by constructing a special optical switch array chip through large-scale cascading.
The conventional integrated optical switch is an MZI (mach-zehnder interferometer) structure (as shown in fig. 1 a) [ optics express, 2014, 22, 22707-22715], where the relationship between the switching state and the driving voltage is a continuously changing curve, and the optimal on state or off state corresponds to only a specific voltage value. As shown in fig. 1b, for the O1 outlet shown in fig. 1a, referring to the solid line in fig. 1b, the switch is in an on state under the condition of voltage V1, and the switch is in an off state under the condition of voltage V2, and deviates from the voltage values of V1 and V2, the switch deviates from the optimal switch state, and causes problems of crosstalk, loss and the like, so that the switch is very sensitive to voltage fluctuation. In addition, the optimal switching state voltage value is extremely sensitive to processing errors and temperature changes, so that the switching state voltage values of different switching devices on the same wafer are different, and the switching state voltage values of the same switching device at different temperatures are also different. In summary, the MZI optical switch has poor tolerance to driving voltage fluctuation, processing error and temperature variation, and in the practical application process, a complex high-precision real-time calibration control circuit is required to be provided. It can be seen that the existing MZI-type optical switch has the problem of poor tolerance.
Disclosure of Invention
The invention mainly aims to provide an optical switch and a switching device based on multimode Bragg gratings, and aims to solve the technical problem that the existing integrated optical switch is poor in tolerance.
To achieve the above object, the present invention provides an optical switch based on multimode bragg grating, comprising:
a multimode bragg grating filter comprising a multimode bragg grating and a mode multiplexer; the multimode Bragg grating adopts an antisymmetric multimode Bragg grating with positive dispersion and gradually apodized width according to a parabolic function, and the mode multiplexer comprises an upper coupling waveguide and a lower coupling waveguide, wherein the upper coupling waveguide is a light path main waveguide, the lower coupling waveguide is an uplink downlink waveguide, and the upper coupling waveguide is connected with the multimode Bragg grating;
and the heating electrode is used for heating the multimode Bragg grating filter.
In some embodiments, the heater electrode is configured to control the multimode bragg grating based optical switch to switch between a pass-through state and a cross-over state.
In some embodiments, the multimode bragg grating based optical switch is in the through state at normal temperature and in the cross state at high temperature.
In some embodiments, the multimode bragg grating comprises: and the main waveguide with constant width and the grating teeth with the width gradually becoming larger from two sides to the center according to a parabolic function, and the multimode Bragg grating is a positive dispersion characteristic grating.
In some embodiments, the multimode Bragg grating apodized according to a parabolic function has a period of 240nm, a period of 100, and a total length of 24 μm.
In some embodiments, the main waveguide is a silicon waveguide, and the thickness of the main waveguide is 220nm.
In some embodiments, the multimode bragg grating based optical switch has an operating wavelength of 1260nm to 1600nm and an operating bandwidth of 40 to 100nm.
In addition, to achieve the above object, the present invention also proposes a switching device including: a plurality of multimode bragg grating based optical switches as described above, the multimode bragg grating based optical switches being cascaded.
In some embodiments, the switching device comprises a first optical switch based on multimode bragg grating and a second optical switch based on multimode bragg grating; wherein,
the lower coupling waveguide of the first optical switch is connected in series with the upper coupling waveguide of the second optical switch, and one of the first optical switch and the second optical switch is in a heating state.
In some embodiments, the switching device comprises a first optical switch based on multimode bragg grating, a second optical switch based on multimode bragg grating, and a third optical switch based on multimode bragg grating; wherein,
the lower coupling waveguide of the first optical switch is connected in series with the upper coupling waveguide of the second optical switch, the output end of the light path main waveguide of the first optical switch is connected in series with the upper coupling waveguide of the third optical switch, the third optical switch and the first optical switch are in the same state, and the second optical switch and the first optical switch are in different states.
The invention provides an optical switch based on multimode Bragg grating, comprising: a multimode bragg grating filter comprising a multimode bragg grating and a mode multiplexer; the multimode Bragg grating adopts an antisymmetric multimode Bragg grating with positive dispersion and gradually apodized width according to a parabolic function, and the mode multiplexer comprises an upper coupling waveguide and a lower coupling waveguide, wherein the upper coupling waveguide is a light path main waveguide, the lower coupling waveguide is an uplink downlink waveguide, and the upper coupling waveguide is connected with the multimode Bragg grating; and the heating electrode is used for heating the multimode Bragg grating filter. In the invention, the wide working wavelength range of the Bragg grating enables the optical switch to accommodate errors of process, temperature, voltage and the like, low crosstalk and low power consumption of devices are realized through the grating positive dispersion design and parabolic apodization, and the technical problem of poor tolerance of the existing integrated optical switch is solved.
Drawings
FIG. 1a is a first schematic diagram of a conventional MZI type thermo-optic switch;
FIG. 1b is a schematic diagram of a spectrum of a conventional MZI type thermo-optic switch;
FIG. 1c is a schematic diagram of an embodiment of the present invention directed to a multimode Bragg grating based optical switch;
FIG. 1d is a schematic spectrum diagram of an embodiment of the present invention directed to a multimode Bragg grating based optical switch;
fig. 2a is a schematic structural diagram of a grating thermo-optical switch in a normal state according to an embodiment of the present invention;
FIG. 2b is a first spectral simulation diagram of a grating thermo-optic switch in a normal state according to an embodiment of the present invention;
FIG. 2c is a second spectral simulation diagram of a grating thermo-optic switch in a normal state according to an embodiment of the present invention;
FIG. 2d is a schematic diagram of a grating thermo-optical switch in a heating state according to an embodiment of the present invention;
FIG. 2e is a first spectral simulation of a grating thermo-optic switch in a heated state according to an embodiment of the present invention;
FIG. 2f is a second spectral simulation of a grating thermo-optic switch in a heated state according to an embodiment of the present invention;
FIG. 3a is a schematic diagram of an optical path of a grating thermo-optical switch according to an embodiment of the present invention;
FIG. 3b is a spectral simulation of the structure shown in FIG. 3 a;
FIG. 3c is a schematic diagram of an embodiment of the present invention directed to a width graded apodization and positive dispersion design for multimode Bragg grating based optical switches;
FIG. 3d is a spectral simulation of the structure shown in FIG. 3 c;
FIG. 4a is a graph comparing curves of Gaussian and parabolic functions;
FIG. 4b is a schematic diagram of a parabolic apodization structure for a multimode Bragg grating based optical switch according to an embodiment of the invention;
FIG. 4c is a schematic diagram of a conventional Gaussian apodization structure;
FIG. 4d is a graph showing the transmission spectrum of the parabolic apodization grating shown in FIG. 4 b;
FIG. 4e is a graph showing the transmission spectrum of the Gaussian apodization grating shown in FIG. 4 c;
FIG. 5a is a schematic diagram of a grating thermo-optic switch;
fig. 5b is a spectral simulation diagram of the structure of the grating thermo-optical switch of fig. 5a in normal (n=3.5) and high temperature (n= 3.626) states;
FIG. 5c is a second schematic diagram of a conventional MZI type thermo-optic switch;
FIG. 5d is a graph showing the change of refractive index of the MZI type thermo-optical switch shown in FIG. 5c with heating;
FIG. 6a is a first operational state diagram of an embodiment of the present invention involving a single grating thermo-optic switch;
FIG. 6b is a second operational state diagram of an embodiment of the present invention involving a single grating thermo-optic switch;
FIG. 6c is a spectrum corresponding to the structure shown in FIG. 6 a;
FIG. 6d is a spectrum corresponding to the structure shown in FIG. 6 b;
FIG. 7a is a first operational state diagram of an embodiment of the present invention involving a cascade of two grating thermo-optic switches;
FIG. 7b is a second operational state diagram of an embodiment of the present invention involving a cascade of two grating thermo-optic switches;
FIG. 7c is a spectral diagram corresponding to the structure shown in FIG. 7 a;
FIG. 7d is a spectrum corresponding to the structure shown in FIG. 7 b;
FIG. 8a is a first operational state diagram of an embodiment of the present invention involving three grating thermo-optic switch cascades;
FIG. 8b is a second operational state diagram of an embodiment of the present invention involving three grating thermo-optic switch cascades;
FIG. 8c is a spectral diagram corresponding to the structure shown in FIG. 8 a;
FIG. 8d is a spectral diagram corresponding to the structure shown in FIG. 8 b.
The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.
Furthermore, the description of "first," "second," etc. in this disclosure is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Aiming at the problem of poor tolerance of the existing MZI type optical switch, the embodiment of the invention provides a novel grating type optical switch, namely an optical switch based on multimode Bragg gratings (shown in a figure 1 c), which has a wider working voltage range, as shown in a figure 1d, for an O1 outlet shown in a figure 1c, referring to a solid line in a figure 1d, the switch is in an on state in a voltage range from V1 to V2, and in a voltage range from V3 to V4. The optical switch based on the multimode Bragg grating provided by the embodiment of the invention has a wide enough working voltage range, can accommodate errors such as processing errors, temperature changes, voltage fluctuation and the like, and ensures the working stability of the switch.
Referring to fig. 1c, fig. 1c is a schematic structural diagram of an optical switch based on multimode bragg grating according to an embodiment of the present invention.
As shown in fig. 1c, the multimode bragg grating-based optical switch includes:
a multimode bragg grating filter comprising a multimode bragg grating and a mode multiplexer; the multimode Bragg grating adopts an antisymmetric multimode Bragg grating with positive dispersion and gradually apodized width according to a parabolic function, and the mode multiplexer comprises an upper coupling waveguide and a lower coupling waveguide, wherein the upper coupling waveguide is a light path main waveguide, the lower coupling waveguide is an uplink downlink waveguide, and the upper coupling waveguide is connected with the multimode Bragg grating;
and the heating electrode is used for heating the multimode Bragg grating filter.
It should be noted that, in practical application, the heating electrode may be located at a distance above the multimode bragg grating filter, so as to heat the multimode bragg grating filter, and the heating electrode and the multimode bragg grating filter are not directly connected. In each drawing of the embodiment, the heating effect of the heating electrode on the multimode bragg grating filter is illustrated by connecting the multimode bragg grating with the voltage icon V, and the specific positional relationship between the heating electrode and the multimode bragg grating is not illustrated.
The embodiment provides an optical switch based on multimode Bragg gratings, wherein a multimode Bragg grating filter and a heating electrode are adopted to construct the grating type thermo-optical switch, and the optical switch can be controlled to be switched between an on state and an off state by controlling the voltage of the heating electrode. The Bragg grating has wider working bandwidth, so that the optical switch has wider working voltage range, and can accommodate various errors such as processing errors, temperature changes, voltage fluctuation and the like. In addition, through the positive dispersion design and the parabolic grating apodization, the low insertion loss and the low crosstalk can be realized through a smaller grating period number, the length of a grating device is greatly shortened, and the power consumption of the device is reduced. In addition, the extinction ratio of the switch can be further increased through cascading the optical switch, the extinction ratio can reach more than 40dB, and the requirements of various application scenes are met.
Specifically, the multimode bragg grating-based optical switch, i.e., the grating-type thermo-optical switch, is composed of a multimode bragg grating filter and a heating electrode. As shown in fig. 2a, the multimode bragg grating filter consists of 1 multimode bragg grating and 1 mode multiplexer. When light enters the filter from the I1 port of the filter, light of a particular wavelength will be reflected by the bragg grating and exit the O1 port, and light of the remaining wavelengths will exit the O2 port through the bragg grating. In the range of 1265nm to 1310nm, the optical transmittance of the O1 port is-0.1 dB (as shown in FIG. 2 c), and the optical transmittance of the O2 port is-40 dB (as shown in FIG. 2 b), which shows that the light in the interval exits from the O1 port, the loss is only 0.1dB, and the crosstalk generated on the O2 port is only-40 dB. Whereas in the 1310nm to 1350nm region, the optical transmittance of the O2 port is-0.1 dB (as shown in FIG. 2 c), and the optical transmittance of the O1 port is less than or equal to-20 dB (as shown in FIG. 2 b), which indicates that the loss of the light in this region from the O2 port is only 0.1dB, and the crosstalk generated on the O1 port is only less than or equal to-20 dB.
After a heating electrode is added above the multimode Bragg grating filter, a grating type thermo-optical switch is formed (as shown in figure 2 d). In the case where the heater electrode is not operating (e.g., the heater electrode is at 0V), the transmission spectra of the O1 and O2 ports are shown in fig. 2 b. When the heating electrode works, the electrode generates heat, so that the refractive index of the Bragg grating below is increased, the spectrum of the Bragg grating is shifted to a long wavelength, and the reflection forbidden band is shifted to a 1310 nm-1350 nm interval. As shown in fig. 2e and 2f, the optical transmittance of the O1 port is-0.1 dB in the 1310nm to 1350nm region (as shown in fig. 2 f), the optical transmittance of the O2 port is-40 dB (as shown in fig. 2 e), which means that the light having a wavelength ranging from 1310nm to 1350nm exits from the O1 port under heating, and the crosstalk generated at the O2 port is-40 dB.
In an embodiment, the heating electrode is configured to control the multimode bragg grating based optical switch to switch between a through state and a cross state. The multimode Bragg grating-based optical switch is in the straight-through state at normal temperature and is in the crossed state at high temperature.
It will be appreciated that the 1310nm to 1350nm range is selected as the operating wavelength range of the device, and that in the unheated condition, light exits the O2 port with a loss of 0.1dB, the O1 port receives crosstalk of-20 dB (as shown in fig. 2 b), exhibiting a pass-through state; under heating, light exits the O1 port with a loss of 0.1dB, and the O2 port receives crosstalk of-40 dB (as shown in fig. 2 d), representing a crossover state. It follows that it is possible to control whether light exits from the O1 port or from the O2 port by controlling the heater electrode to operate inactive.
In one embodiment, the multimode bragg grating comprises: and the main waveguide with constant width and the grating teeth with the width gradually becoming larger from two sides to the center according to a parabolic function, and the multimode Bragg grating is a positive dispersion characteristic grating. The period of the multimode Bragg grating apodized according to the parabolic function is 240nm, the period is 100, and the total length is 24 μm. The main waveguide is a silicon waveguide, and the thickness of the main waveguide is 220nm. The working wavelength of the multimode Bragg grating-based optical switch is 1260nm to 1600nm, and the working bandwidth is 40 to 100nm. The present embodiment is not limited to the specific range of the operating wavelength and the operating bandwidth of the multimode bragg grating-based optical switch.
As can be seen from fig. 2a to 2f, the optical switch based on the multimode bragg grating according to the present embodiment has an operating wavelength range of 1310nm to 1350nm, and an operating bandwidth of up to 40nm, where the operating bandwidth is wide enough to accommodate the shift of the central operating wavelength of the device caused by the refractive index change due to the process error, the driving voltage fluctuation, the temperature change, and the like. The center wavelength in the working wavelength range is selected as the ideal working wavelength of the device, and when the actual working wavelength drifts by +/-20 nm compared with the ideal working wavelength, the device still keeps working normally. For the grating device, the process error mainly comes from the fluctuation of the thickness of the waveguide, in the practical process line, the standard thickness of the silicon waveguide is 220nm, the maximum error is +/-10 nm, and the central working wavelength of the grating is deviated to +/-12 nm according to simulation calculation. The temperature change mainly comes from the application scene of different places and different temperatures of the laser chip and the switch chip, the temperature difference between the laser chip and the switch chip is assumed to be +/-50 ℃, and the wavelength deviation caused by +/-50 ℃ is considered to be +/-4 nm when the change quantity of the center wavelength of the optical switch based on the multimode Bragg grating along with the temperature in the embodiment is 0.08 nm/DEG C. In terms of voltage fluctuation, the central wavelength shift of the multimode Bragg grating-based optical switch is proportional to the power of the heater, the voltage of the heater varies by +/-5%, the power consumption varies by about +/-10%, and the central wavelength shift of the multimode Bragg grating-based optical switch is about +/-10% by 40nm plus or minus 4nm. It can be seen that the multimode Bragg grating-based optical switch can simultaneously accommodate the maximum process error, the temperature deviation of +/-50 ℃ and the voltage fluctuation of +/-5%, and the tolerance is good.
In some embodiments, the multimode bragg grating comprises: and the main waveguide with constant width and the grating teeth with the width gradually becoming larger from two sides to the center according to a parabolic function, and the multimode Bragg grating is a positive dispersion characteristic grating.
It should be noted that, as shown in fig. 3a, the structure of the multimode bragg grating is that the gratings on both sides of the main waveguide are all in dislocation distribution, that is, in antisymmetric distribution, and the antisymmetric distribution grating can enable TE0 mode light and TE1 mode light with specific wavelengths to be in reverse coupling. As shown in fig. 3a and 3b, after TE0 mode light in the 1265nm to 1310nm range (the working range shown by the dashed circle in fig. 3 b) enters from the I1 port, mode conversion and reflection occur under the action of the grating, and the reflected TE1 mode light is converted into TE0 mode light through the mode multiplexer and exits from the port O1. Whereas, after entering from the I1 port, the TE0 mode light in the 1310nm to 1350nm range passes directly through the grating and exits from the port O2 (as shown in fig. 3a and 3 b) due to the non-compliance with the coupling condition of the grating.
In order to suppress the coupling peak edge side lobe, the embodiment adopts an apodization mode with gradually changed grating tooth width and a positive dispersion design. As shown in fig. 3c, the width of the grating tooth gradually increases from two ends to the center, and the apodization with gradually changed grating tooth width can change the light coupling from weak to strong, so as to effectively suppress side lobes. However, considering the limitation of the line width of the process, the width of the grating at the entrance cannot be increased from 0 to 90nm or 130nm, and the suddenly-appearing grating teeth can generate stronger reflection to light, so that the effect of apodization on sidelobe suppression is weakened.
In order to further enhance the sidelobe suppression effect, the present embodiment adopts a positive dispersion design, as shown in fig. 3c, the main waveguide width is set to be a constant value, and when the grating width changes from small to large from the I1 entrance end to the center of the grating, the effective refractive index of the optical field mode also changes from small to large, so that short-wavelength light is mainly reflected in the area with small grating width, and long-wavelength light is mainly reflected in the area with large grating width. Since the light with a short wavelength travels in the grating in different paths, the light with a short wavelength comes out of the grating before the light with a long wavelength, and the effect of positive dispersion is exhibited. The positive dispersion design can realize the effect of single side lobe strong suppression. As shown in fig. 3d, the side lobe amplitude in the short wavelength direction of the coupling peak edge (near λ1 in fig. 3 d) is close to 0dB, while the side lobe amplitude in the long wavelength direction of the coupling peak edge (near λ3 in fig. 3 d) can be suppressed within-20 dB.
It should be noted that, in the grating switch, the power consumption of the grating in the heated state is a very critical performance index. The power consumption of the grating in the heated state is proportional to the total length of the grating, which depends on the number of periods of the grating. The present embodiment improves the function of grating apodization in order to reduce the number of grating periods while ensuring a strong coupling capability of the grating. In conventional grating designs, the apodization function is typically a gaussian-like function, as shown in fig. 4a, the curve change follows a slow-sharp-slow trend, and a grating apodized according to a gaussian function is shown in fig. 4 c. In this embodiment, in view of the characteristic of strong suppression of side lobes in the long wave direction caused by positive dispersion, parabolic apodization is creatively adopted, and as shown in fig. 4a, parabolic curve change is performed according to a sharp-slow trend. An apodized grating according to a parabolic function as shown in fig. 4b has the advantage that the width of the grating teeth can be increased rapidly, which has the disadvantage that the sidelobe suppression capability is weak, but this aspect can be exactly compensated by the strong suppression of the long-wave side lobes of the positive dispersion.
Specifically, fig. 4d shows a graph of the transmission spectrum of the O1 port of a grating apodized according to a parabolic function, with a period number of the grating of only 100. It can be seen from two aspects that the grating has achieved strong coupling of light, one is that the crosstalk in the forbidden band is only-40 dB, and the other is that the rising edge increasing from-40 dB to-0.1 dB is only 3nm (from 1308nm to 1312 nm) in the spectrum. Fig. 4e is a graph of the transmission spectrum of the O1 port of a grating apodized according to a gaussian function, with the solid line corresponding to the grating period number 100 and the dotted line corresponding to the grating period number 1000. In the case that the grating period number of the optical switch based on multimode Bragg grating is 100, the coupling capability of light is obviously weak, the crosstalk in the forbidden band reaches-20 dB, and the rising edge increasing from-20 dB to-0.1 dB is approximately 30nm (1292 nm to 1322 nm) in spectrum. In the case of a grating period of 1000, the coupling capacity of the Gaussian apodization grating to light can be equal to that of a parabolic apodization grating with a period of 100, the rising edge increasing from-20 dB to-0.1 dB is 3nm (1310 nm to 1313 nm) in spectrum, but the crosstalk in the forbidden band is still-20 dB. It can be seen that, under the condition of the same grating period number, the parabolic apodized grating provided by the embodiment is obviously stronger in light coupling capability than the traditional gaussian apodized grating. If the same coupling strength is maintained, the period number of the conventional Gao Siqie toe grating needs to be 10 times that of the parabolic apodized grating in the present embodiment, meaning that the power consumption is increased by 10 times. Therefore, the parabolic apodization grating in the optical switch based on the multimode Bragg grating has the advantages of strong coupling capability, low power consumption and low crosstalk.
It will be appreciated that the power consumption of the grating switch can be compared to that of a MZI-type thermo-optical switch. In this embodiment, the period of the grating in the grating switch is 240nm, the period of the grating is 100, and the total length of the grating is 24 μm (as shown in fig. 5 a). The refractive index of the silicon material in the normal state is 3.5, and the refractive index of the silicon material in the heated state is 3.626, and as shown in fig. 5b, the spectrum in the heated state is shifted by about 40nm in the long wavelength direction. In contrast, as shown in fig. 5c, the length of the phase-shifting arm of the MZI switch is also set to 24 μm, and the phase of the phase-shifting arm changes by approximately 2.9p as shown in fig. 5d when the same heat loss is applied to increase the refractive index of the silicon material from 3.5 to 3.626. In an MZI optical switch, one phase shift p can cause the switch to switch state once. Therefore, the power consumption of the optical switch based on multimode bragg grating, namely the grating type thermo-optical switch, is 2.9 times that of the MZI optical switch.
In order to further improve the extinction ratio of the optical switch, the embodiment also provides a switching device, and the switching device adopts a switching cascading mode.
It should be noted that, in the case of a single grating switch as shown in fig. 6a to 6d, in the normal state, as shown in fig. 6a, the heating electrode is not operated (as shown as "0" in fig. 6 a), light exits from the O2 port, and the spectrum diagram thereof is shown in fig. 6c, and the crosstalk of the O1 port is-20 dB; in the heated state, as shown in FIG. 6b (shown as "1" in FIG. 6 b), light exits from the O1 port, and the spectral diagram is shown in FIG. 6d, where the crosstalk at the O2 port is-40 dB. Assuming that the power consumption of the switch in the heating state is P, the power consumption of the switch is P.
In one embodiment, the switching device includes: at least two multimode bragg grating based optical switches as described above, said multimode bragg grating based optical switches being cascaded.
In an embodiment, the switching device comprises a first optical switch based on multimode bragg grating and a second optical switch based on multimode bragg grating; wherein,
the lower coupling waveguide of the first optical switch is connected in series with the upper coupling waveguide of the second optical switch, and one of the first optical switch and the second optical switch is in a heating state.
Specifically, the case of two grating switches cascaded is shown in fig. 7a to 7 d. As shown in fig. 7a, when the switch S1 (the first optical switch) is in a normal state (as shown by "0" in fig. 7 a) and the switch S2 (the second optical switch) is in a heated state (as shown by "1" in fig. 7 a), light exits from the O2 port, and the spectrum diagram thereof is as shown in fig. 7c, and the crosstalk of the O1 port is-60 dB; as shown in fig. 7b, when the switch S1 is in the heating state and the switch S2 is in the normal state, light exits from the O1 port, and the spectrum diagram is shown in fig. 7d, where the crosstalk of the O2 port is-40 dB. Since only one switch is in the heating state in both states, the power consumption of the switch is P.
In an embodiment, the switching device comprises a first optical switch based on multimode bragg grating, a second optical switch based on multimode bragg grating, and a third optical switch based on multimode bragg grating; wherein,
the lower coupling waveguide of the first optical switch is connected in series with the upper coupling waveguide of the second optical switch, the output end of the light path main waveguide of the first optical switch is connected in series with the upper coupling waveguide of the third optical switch, the third optical switch and the first optical switch are in the same state, and the second optical switch and the first optical switch are in different states.
In particular, the case of three grating switches cascaded is shown in fig. 8a to 8 d. As shown in fig. 8a, when the switch S1 (first optical switch) is in a normal state (as shown by "0" in fig. 8 a), the switch S2 (second optical switch) is in a heated state (as shown by "1" in fig. 8 a), and the switch S3 (third optical switch) is in a normal state (as shown by "0" in fig. 8 a), light exits from the O2 port, and the spectrum diagram thereof is shown in fig. 8c, and crosstalk of the O1 port is-60 dB; as shown in fig. 8b, when the switch S1 is in the heating state, the switch S2 is in the normal state, and the switch S3 is in the heating state, light exits from the O1 port, and the spectrum diagram is shown in fig. 8d, wherein the crosstalk of the O2 port is-80 dB. Since both switches are in the heating state in both states, the power consumption of the switch is 2P.
In summary, after cascade connection of the grating switches, crosstalk of the switches can be suppressed to below-60 dB, and the switching device provided in this embodiment basically meets all switching application scenarios.
In addition, technical details not described in detail in the embodiments of the present switching device may be referred to for application to the multimode bragg grating-based optical switch as described above in any embodiment of the present invention, which is not described herein.
It should be understood that the foregoing is illustrative only and is not limiting, and that in specific applications, those skilled in the art may set the invention as desired, and the invention is not limited thereto.
It should be noted that the above-described working procedure is merely illustrative, and does not limit the scope of the present invention, and in practical application, a person skilled in the art may select part or all of them according to actual needs to achieve the purpose of the embodiment, which is not limited herein.
Furthermore, it should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, article, or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, article, or system. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, article or system that comprises the element.
The foregoing embodiment numbers of the present invention are merely for the purpose of description, and do not represent the advantages or disadvantages of the embodiments.
The foregoing description is only of the preferred embodiments of the present invention, and is not intended to limit the scope of the invention, but rather is intended to cover any equivalents of the structures or equivalent processes disclosed herein or in the alternative, which may be employed directly or indirectly in other related arts.
Claims (10)
1. An optical switch based on multimode bragg grating, characterized in that it comprises:
a multimode bragg grating filter comprising a multimode bragg grating and a mode multiplexer; the multimode Bragg grating adopts an antisymmetric multimode Bragg grating with positive dispersion and gradually apodized width according to a parabolic function, and the mode multiplexer comprises an upper coupling waveguide and a lower coupling waveguide, wherein the upper coupling waveguide is a light path main waveguide, the lower coupling waveguide is an uplink downlink waveguide, and the upper coupling waveguide is connected with the multimode Bragg grating;
and the heating electrode is used for heating the multimode Bragg grating filter.
2. The multimode bragg grating-based optical switch of claim 1 wherein the heater electrode is configured to control the multimode bragg grating-based optical switch to switch between a pass-through state and a cross-over state.
3. The multimode bragg grating-based optical switch of claim 2 wherein the multimode bragg grating-based optical switch is in the through-state at normal temperature and in the cross-state at high temperature.
4. The multimode bragg grating-based optical switch of claim 1 wherein the multimode bragg grating comprises: and the main waveguide with constant width and the grating teeth with the width gradually becoming larger from two sides to the center according to a parabolic function, and the multimode Bragg grating is a positive dispersion characteristic grating.
5. The multimode bragg grating-based optical switch of claim 4 wherein the multimode bragg grating apodized according to a parabolic function has a period of 240nm, a period of 100, and a total length of 24 μm.
6. The multimode bragg grating-based optical switch of claim 4 wherein the main waveguide is a silicon waveguide and the thickness of the main waveguide is 220nm.
7. Multimode bragg grating-based optical switch according to any one of claims 1 to 6, characterized in that the multimode bragg grating-based optical switch has an operating wavelength of 1260nm to 1600nm and an operating bandwidth of 40 to 100nm.
8. A switching device, the switching device comprising: a plurality of multimode bragg grating based optical switches as claimed in any one of claims 1 to 7, the multimode bragg grating based optical switches being cascaded.
9. The switching device of claim 8, wherein the switching device comprises a first optical switch based on multimode bragg grating and a second optical switch based on multimode bragg grating; wherein,
the lower coupling waveguide of the first optical switch is connected in series with the upper coupling waveguide of the second optical switch, and one of the first optical switch and the second optical switch is in a heating state.
10. The switching device of claim 8, wherein the switching device comprises a first optical switch based on multimode bragg grating, a second optical switch based on multimode bragg grating, and a third optical switch based on multimode bragg grating; wherein,
the lower coupling waveguide of the first optical switch is connected in series with the upper coupling waveguide of the second optical switch, the output end of the light path main waveguide of the first optical switch is connected in series with the upper coupling waveguide of the third optical switch, the third optical switch and the first optical switch are in the same state, and the second optical switch and the first optical switch are in different states.
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