WO2012099275A1 - Coupleur optique et procédé de contrôle de branchements - Google Patents

Coupleur optique et procédé de contrôle de branchements Download PDF

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Publication number
WO2012099275A1
WO2012099275A1 PCT/JP2012/051727 JP2012051727W WO2012099275A1 WO 2012099275 A1 WO2012099275 A1 WO 2012099275A1 JP 2012051727 W JP2012051727 W JP 2012051727W WO 2012099275 A1 WO2012099275 A1 WO 2012099275A1
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Prior art keywords
waveguide
refractive index
output
light
multimode
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PCT/JP2012/051727
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English (en)
Japanese (ja)
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松本　崇
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日本電気株式会社
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Publication of WO2012099275A1 publication Critical patent/WO2012099275A1/fr

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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
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/125—Bends, branchings or intersections
    • 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
    • G02F1/29—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 for the control of the position or the direction of light beams, i.e. deflection
    • G02F1/31—Digital deflection, i.e. optical switching
    • G02F1/313—Digital deflection, i.e. optical switching in an optical waveguide structure
    • G02F1/3132—Digital deflection, i.e. optical switching in an optical waveguide structure of directional coupler type
    • 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
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12133—Functions
    • G02B2006/12147—Coupler
    • 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
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
    • G02B6/2808—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using a mixing element which evenly distributes an input signal over a number of outputs
    • G02B6/2813—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using a mixing element which evenly distributes an input signal over a number of outputs based on multimode interference effect, i.e. self-imaging
    • 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
    • G02F1/01—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 for the control of the intensity, phase, polarisation or colour 
    • G02F1/0147—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 for the control of the intensity, phase, polarisation or colour  based on thermo-optic effects
    • 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
    • G02F1/01—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 for the control of the intensity, phase, polarisation or colour 
    • G02F1/21—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 for the control of the intensity, phase, polarisation or colour  by interference
    • G02F1/217—Multimode interference type

Definitions

  • the present invention relates to an optical coupler for branching a light wave transmitted through an optical waveguide and a branch control method thereof.
  • the 2 ⁇ 2 optical coupler divides light from an input port (waveguide) into two, and outputs each from two output ports (waveguides).
  • Examples of the 2 ⁇ 2 optical coupler include a directional coupler type (DC) shown in FIG. 12A and a Mach-Zehnder interferometer type (MZI: Mach-Zehnder Interferometer) shown in FIG.
  • the 2 ⁇ 2 coupler is required to be designed and manufactured so as to obtain a different branching ratio depending on the application.
  • coherent detection it is necessary to design and manufacture so that even if an optical signal is input from which input port, the optical signal is equally branched. This is because the accuracy of coherent detection and further the communication error rate are determined.
  • Optical couplers are required to have no complicated structure, be small, have low loss, have low wavelength dependency, and be resistant to manufacturing variations. More recently, the importance of optical couplers capable of performing optical branch control with high accuracy has been increasing. However, each of the above optical couplers has the following problems. In a DC type optical coupler, it is difficult to control the distance between two adjacent waveguides, and it is difficult to suppress manufacturing variations.
  • the MZI type optical coupler can control (trimming) the branching ratio by changing the optical path length between both arms.
  • an MZI type optical coupler needs to control the optical path length of about 10 nm and perform branching ratio control.
  • Patent Document 1 describes a multi-mode interferometer type optical coupler.
  • the control of the width of the MMI for obtaining a stable branching ratio is about 100 nm. Therefore, compared with the MZI type, the controllable region is about 10 times wider and the manufacturing tolerance is wider.
  • the wavelength characteristics are uniform and can be used over the entire optical communication wavelength band.
  • the MMI coupler is less wavelength dependent than the directional coupler, and a coupling rate of about 50% can be obtained in a wide wavelength range.
  • the optical coupler of the multimode interferometer described in Patent Document 1 needs to change the structure itself when the branching ratio is controlled. In other words, to arbitrarily control the branching ratio, the structure must be changed each time. Therefore, the optical coupler described in Patent Document 1 has a problem that the branching ratio cannot be easily controlled depending on the situation.
  • An object of the present invention is to provide an optical coupler that solves the above-described problems.
  • An optical coupler includes a multimode waveguide, at least two input waveguides that are connected to the multimode waveguide and input light, and at least two output waveguides that are connected to the multimode waveguide and output light. And a refractive index control unit that adjusts the refractive index of the multimode waveguide, and the refractive index control unit is arranged substantially parallel to the traveling direction of light.
  • the optical coupler in the present invention can arbitrarily change the branching ratio.
  • FIG. 1 is a top view of the optical coupler according to the first embodiment.
  • FIG. 2 shows a simulation result in which the refractive index is controlled in the first embodiment.
  • FIG. 3 is a top view of the optical coupler according to the second embodiment.
  • FIG. 4 is a top view when the refractive index at both ends of the multimode waveguide is increased in the second embodiment.
  • FIG. 5 shows a simulation result when the refractive indexes of both end portions of the multimode waveguide are increased in the second embodiment.
  • FIG. 6 is a top view when the refractive index of the central portion of the multimode waveguide is increased in the second embodiment.
  • FIG. 7 shows a simulation result when the refractive index of the central portion of the multimode waveguide is increased in the second embodiment.
  • FIG. 8 is a cross-sectional view of a multimode waveguide according to the second embodiment.
  • FIG. 9 is a diagram illustrating a state of input light and output light of the optical coupler.
  • FIG. 10 is a diagram illustrating a state of input light and output light of the optical coupler.
  • FIG. 11 is a diagram illustrating a coherent mixer including an optical coupler.
  • FIG. 12A is a schematic diagram showing a directional coupler type.
  • FIG. 12B is a schematic diagram showing a Mach-Zehnder interferometer type.
  • FIG. 1 is a top view of an optical coupler 1 in the present embodiment.
  • the optical coupler 1 in this embodiment includes a first input waveguide 2, a second input waveguide 3, a multimode waveguide 4, and a first output waveguide 5. And a second output waveguide 6 and a refractive index control unit 7.
  • the first input waveguide 2, the second input waveguide 3, the first output waveguide 5, and the second output waveguide 6 are waveguides that transmit light in a single mode.
  • the multimode waveguide 4 is a waveguide that transmits light in multimode.
  • the first input waveguide 2 and the second input waveguide 3 are connected to the multimode waveguide 4 from the same direction.
  • the first input waveguide 2 and the second input waveguide 3 input the propagated light to the multimode waveguide 4.
  • the multimode waveguide 4 is rectangular, and the first input waveguide 2 and the second input waveguide 3 are connected to the same side.
  • the light that has interfered in the multimode waveguide 4 forms a self-image and is output to the first output waveguide 5 and the second output waveguide 6, respectively.
  • first output waveguide 5 and the second output waveguide 6 are multimode waveguides on the side opposite to the side where the first input waveguide 2 and the second input waveguide 3 are connected to the multimode waveguide 4. It is connected to the waveguide 4.
  • the first input waveguide 2 and the first output waveguide 5 are provided at positions facing each other across the multimode waveguide 4.
  • the second input waveguide 3 and the second output waveguide 6 are provided at positions facing each other with the multimode waveguide 4 interposed therebetween.
  • the rate at which the light input from the first input waveguide 2 is output from the first output waveguide 5 is referred to herein as a bar port output.
  • the ratio at which the light input from the first input waveguide 2 is output from the second output waveguide 6 is referred to as a cross-port output.
  • the multimode waveguide 4 forms a refractive index distribution so as to be line symmetric with respect to the traveling direction of light.
  • the light traveling direction refers to the direction in which light entering from the first input waveguide 2 and the second input waveguide 3 travels as a whole. Specifically, the direction is from the first input waveguide 2 to the first output waveguide 5 or from the second input waveguide 3 to the second output waveguide 6.
  • the refractive index is uniformly formed with respect to the traveling direction of light.
  • the refractive index control unit 7 extends in the light traveling direction at the central portion on the multimode waveguide 4 or at both end portions on the side along the light traveling direction or in the vicinity thereof.
  • the refractive index control unit 7 is arranged at a position that is substantially parallel or line symmetric with respect to the light traveling direction, and controls the refractive index of the multimode waveguide 4.
  • the operation and action in this embodiment will be described.
  • the branching ratio of the light output from the multimode waveguide 4 to the first output waveguide 5 and the second output waveguide 6 depends on the width and length of the multimode waveguide 4 and the first input waveguide 2.
  • the second input waveguide 3, the first output waveguide 5, and the second output waveguide 6 are determined by the incident / exit position where the multimode waveguide 4 is connected.
  • the multimode waveguide 4 has a uniform refractive index, and under ideal conditions such that the multimode waveguide 4 is not bent downward or the like, the input light is converted into the first output waveguide 5. And can equally branch to the second output waveguide 6.
  • the width and length of the multimode waveguide 4 and the positional relationship between the input / output waveguides and the multimode waveguide 4 cannot be easily changed after they are determined in the manufacturing process. .
  • the optical coupler 1 in the present embodiment controls the refractive index distribution of the multimode waveguide 4 by disposing the refractive index control unit 7 at a position that is substantially parallel or line symmetric with respect to the light traveling direction.
  • FIG. 2 shows a simulation result in which the refractive index of the multimode waveguide 4 is changed by the refractive index control unit 7 provided in the central portion of the multimode waveguide 4 so as to extend in the light traveling direction. . As shown in FIG.
  • the bar port is higher than the cross port.
  • the ratio of the light input from the first input waveguide 2 to be output from the first output waveguide 5 disposed at the facing position is from the second output waveguide 6 disposed in the oblique direction. It becomes larger compared to the output ratio.
  • the horizontal axis in FIG. 2 indicates the difference in refractive index between the central portion and both end portions. Specifically, “0” indicates that the refractive index is the same at the center and both ends, the + side has a higher refractive index at the center than the both ends, and the ⁇ side has an opposite refractive index at the center.
  • the optical coupler 1 in the present embodiment controls the refractive index of the multimode waveguide 4 by the refractive index control unit 7 disposed substantially parallel to or in line symmetry with the light traveling direction. With the above structure, the branching ratio of light output from the multimode waveguide 4 can be easily controlled.
  • the branching ratio of the signals output from the multimode waveguide 4 to the first output waveguide 5 and the second output waveguide 6 depends on manufacturing variations in the manufacturing process and external factors. Even when the refractive index distribution is distorted or cannot be equally branched, the branching ratio can be easily controlled by controlling the refractive index of the multimode waveguide 4 with the refractive index control unit 7. Further, the branching ratio control of the refractive index control unit 7 in the present embodiment is not limited to the case where the refractive index distribution of the multimode waveguide 4 is distorted.
  • FIG. 3 is a top view of the optical coupler 1 in the present embodiment.
  • the optical coupler 1 in this embodiment uses a thin film heater 8 as the refractive index control unit 7.
  • Other structures and connection relationships are the same as those in the first embodiment, and the first input waveguide 2, the second input waveguide 3, the multimode waveguide 4, the first output waveguide 5, And a second output waveguide 6.
  • the thin film heater 8 is provided to extend in the light traveling direction at the central portion on the multimode waveguide 4, on both end portions on the side along the light traveling direction, or at least one of the vicinity thereof. . That is, the thin film heater 8 is disposed at a position that is substantially parallel or line symmetric with respect to the light traveling direction.
  • Each thin film heater 8 is preferably longer than the multimode waveguide 4.
  • Each thin film heater 8 includes electrodes 9 at both ends provided to extend, and generates heat when energized through the electrodes 9. Note that all three thin film heaters 8 are not necessarily required, but are illustrated in FIG. 3 for the sake of clarity.
  • FIG. 4 As shown in FIG. 4, at the time of manufacturing the optical coupler 1, the light input from the first input waveguide 2 is compared with the second output waveguide 6 positioned in the oblique direction.
  • the ratio of output from the first output waveguide 5 located in the opposing direction is large. That is, in the multimode waveguide 4, the ratio of output from the bar port is considered to be larger than the ratio of output from the cross port. (In FIG.
  • the refractive index at both ends of the multi-mode waveguide 4 can be increased by increasing the amount of current flowing through the thin film heaters 8 at both ends and raising the temperature at both ends.
  • the ratio output to the second output waveguide 6 can be increased, the ratio output to the first output waveguide 5 can be decreased, and the branching ratio can be made equal.
  • the horizontal axis in FIG. 5 indicates the amount of increase in the refractive index at both ends, and the vertical axis indicates the branching ratio. Before energization, that is, when the horizontal axis is 0, the branching ratio is 7: 3, but when the refractive index is increased to 10 ⁇ 10 ⁇ 4 , the branching ratio is 1: 1.
  • the branching ratio can be easily controlled by heating the multimode waveguide 4.
  • the refractive index temperature coefficient of a silica-type material is about 10 ⁇ -5 > / T, what is necessary is just to heat about 100 degreeC from normal temperature.
  • the temperature immediately below the thin film heater 8 becomes the highest temperature, and the temperature decreases as the distance from the thin film heater 8 increases. Therefore, a temperature gradient is formed in the multimode waveguide 4 in the direction perpendicular to the traveling direction.
  • the refractive index distribution can be corrected by this temperature gradient to obtain a desired distribution.
  • the light input from the first input waveguide 2 is obliquely compared with the first output waveguide 5 positioned in the opposite direction.
  • the ratio of the output from the second output waveguide 6 positioned at is large.
  • the multimode waveguide 4 is considered to have a higher rate of output from the cross port than a rate of output from the bar port. (In FIG. 7, it is 6: 4.)
  • distortion occurs in the refractive index distribution of the multimode waveguide due to manufacturing variations in the manufacturing process and external factors.
  • the refractive index of the multimode waveguide 4 is greater at both ends than at the center. It is thought that it became high. Therefore, as shown in FIG.
  • the multimode waveguide 4 has a flat refractive index distribution as shown by a broken line by energizing a thin film heater 8 provided at the center to heat the center of the multimode waveguide 4.
  • the thin film heaters 8 at both ends are not shown in FIG. 6 because they are unnecessary.
  • FIG. 7 by increasing the refractive index at the center of the multimode waveguide 4, the ratio of output to the first output waveguide 5 is increased and the ratio of output to the second output waveguide 6 is increased. , And the branching ratio can be made equal. That is, the branching ratio can be easily controlled by heating the multimode waveguide 4.
  • FIG. 7 shows that is, the branching ratio can be easily controlled by heating the multimode waveguide 4.
  • the horizontal axis represents the amount of increase in the refractive index at the center
  • the vertical axis represents the branching ratio.
  • the branching ratio control by the thin film heater 8 in the present embodiment is not limited to the case where the refractive index distribution of the multimode waveguide 4 is distorted.
  • the branching ratio deviates from equal branching due to factors other than refractive index distortion. Even in this case, the branching ratio can be easily controlled by controlling the refractive index of the multimode waveguide 4 with the thin film heater 8.
  • the branching ratio is controlled by changing the refractive index of the multimode waveguide 4 from the outside of the optical coupler 1 by heating using the thin film heater 8.
  • the refractive index of the multimode waveguide 4 it is not limited to the thin film heater 8, and a carrier plasma effect, an electro-optic effect, a magneto-optic effect, or the like can be used.
  • FIG. 8 is a cross-sectional view of the multimode waveguide 4.
  • the refractive index control unit 7 is the cladding thickness adjusting unit 10.
  • the multimode waveguide 4 is formed by laminating at least a lower cladding 13, a core 12, and an upper cladding 11 in order from the bottom.
  • the clad thickness adjusting unit 10 is provided on the multimode waveguide 4 and adjusts the thickness of the upper clad 11. When the thickness of the upper clad 11 is reduced, the refractive index of the multimode waveguide 4 is lowered. On the other hand, when the upper cladding 11 is thickened, the refractive index of the multimode waveguide 4 increases.
  • the clad thickness adjusting portion 10 is provided to extend in the light traveling direction at the central portion on the multimode waveguide 4 or at least one of both end portions in the direction perpendicular to the light traveling direction. That is, the cladding thickness adjusting unit 10 is disposed at a position that is substantially parallel or line-symmetric with respect to the light traveling direction.
  • an FIB (Focused Ion Beam) apparatus or the like can be considered. By irradiating the upper clad 11 with a focused ion beam such as gallium ions, the FIB apparatus can scrape off atoms on the surface. That is, the thickness of the upper clad 11 can be reduced.
  • vapor deposition can be performed by irradiating the upper cladding 11 with a metal such as Cu, Al, or Au as a low energy ion beam. That is, the thickness of the upper clad 11 can be increased.
  • the clad thickness adjusting unit 10 is not limited to this as long as the thickness of the upper clad 11 can be adjusted. [Description of Functions and Effects]
  • the clad thickness adjusting unit 10 is distorted in the refractive index distribution of the multi-mode waveguide 4 due to manufacturing variations in the manufacturing process and external factors in view of the branching ratio. Is estimated to be high, the thickness of the upper clad 11 provided at the center is reduced.
  • the branching ratio can be easily controlled by reducing the refractive index at the center.
  • the branching ratio can be easily controlled to be equal by increasing the refractive index at both ends of the multimode waveguide 4.
  • the clad thickness adjusting unit 10 is presumed that the refractive index distribution of the multimode waveguide 4 is distorted due to manufacturing variations in the manufacturing process and external factors in view of the branching ratio, and as a result, the central refractive index is low. In this case, the thickness of the upper clad 11 provided at both ends is reduced. Since the multimode waveguide 4 can reduce the refractive index when the thickness of the upper clad 11 is reduced, the refractive index distribution can be flattened by reducing the refractive indexes at both the upper and lower ends. In the above case, not only the thickness of the upper clad 11 provided at both ends of the multimode waveguide 4 may be reduced, but the center portion of the multimode waveguide 4 may be increased.
  • the branching ratio can be easily controlled to be equal by increasing the refractive index at the center of the multimode waveguide 4.
  • the irradiation ion beam amount is adjusted by the FIB apparatus, and the amount of cutting the upper clad 11 may be increased or decreased in the direction from the center portion to the end portion of the multimode optical waveguide 4.
  • the refractive index is changed, it is only necessary to perform additional machining once on the multimode waveguide 4, so that continuous power consumption can be reduced as compared with the thin film heater 8 described in the second embodiment.
  • the branching ratio can be controlled without the need.
  • the cladding thickness adjusting unit 10 is not limited to the cladding thickness adjusting unit 10 as long as the refractive index of the multimode waveguide 4 can be changed without requiring continuous power consumption, and is a method of controlling with an impurity. And a method of controlling by UV irradiation.
  • the branching ratio control by the cladding thickness adjusting unit 10 in the present embodiment is not limited to the case where distortion occurs in the refractive index distribution of the multimode mode waveguide 4. When the coupling from the multimode waveguide 4 to the first output waveguide 5 and the second output waveguide 6 is different between the two output waveguides, the branching ratio deviates from equal branching due to factors other than refractive index distortion.
  • FIGS. 9 and 10 are top views showing the states of input light and output light of the optical coupler 1.
  • the multimode waveguide 4 receives strong light from the first input waveguide 2 and weak light from the second input waveguide 3, strong light from the first output waveguide 5 Suppose that weak light is output from 6.
  • the ratio of barports is high.
  • the refractive index control unit 7 increases the refractive index at both ends of the multimode waveguide 4 or decreases the refractive index at the center by performing the above-described additional processing. That is, the rate at which the light input from the first input waveguide 2 is output to the first output waveguide 5 is decreased and the rate at which the light is output to the second output waveguide 6 is increased. As a result, the light output from the first output waveguide 5 becomes weak, and the light output from the second output waveguide 6 becomes strong, thereby realizing equal branching of the light output from the multimode waveguide 4. be able to.
  • the multimode waveguide 4 receives strong light from the first input waveguide 2 and weak light from the second input waveguide 3, weak light from the first output waveguide 5 Suppose that strong light is output from 6.
  • the refractive index control unit 7 lowers the refractive index at both ends of the multimode waveguide 4 or increases the refractive index at the center by performing the above-described additional processing.
  • FIG. 11 is a diagram illustrating a coherent mixer including the optical coupler 1.
  • the present embodiment includes an optical coupler 1, a splitter 14, a photodiode 15, and an amplifier 16.
  • the optical coupler 1 has the same structure and connection relationship as those of the first to third embodiments.
  • the optical coupler 1 has a first input waveguide 2, a second input waveguide 3, a multimode waveguide 4, and a first output waveguide.
  • a waveguide 5, a second output waveguide 6, and a refractive index control unit 7 are provided.
  • at least two splitters 14 are provided.
  • the signal light is incident on one splitter 14, and the local light that interferes with the signal light is incident on the other splitter 14 in order to demodulate the phase information.
  • the splitter 14 branches the incident signal light and local light.
  • at least two optical couplers 1 are provided.
  • One optical coupler 1 causes the signal light branched by the splitter 14 and the locally transmitted light to interfere with each other, and performs output in equal branches.
  • the other optical coupler causes the signal light branched by the splitter 14 and the locally transmitted light to interfere with each other and output in equal branches.
  • the two couplers have a difference of ⁇ / 4 in the optical path length of the waveguide that guides light from the splitter 14.
  • At least four photodiodes 15 are provided.
  • the photodiode 15 converts the four output lights output from the two optical couplers 1 into current signals.
  • the amplifier restores the current signal output from the photodiode 15 to a voltage signal.
  • the coherent mixer according to the present embodiment is a 90-degree optical hybrid interference that extracts phase information of a polarization-separated signal from a TE (Transverse Electric) optical signal and a TM (Transverse Magnetic) optical signal from the above configuration. It can be used for counting.
  • An important characteristic that affects the performance of a DP-QPSK receiver using a 90-degree optical hybrid interferometer is a characteristic called CMRR (Common-Mode Rejection Ratio). This is a measure of how much an input signal component common to two inputs can be removed in a differential amplifier circuit used for voltage conversion of a signal.
  • CMRR Common-Mode Rejection Ratio
  • the ideal branching characteristic of this optical coupler is that the branching ratio is 1: 1.
  • the optical coupler 1 in this embodiment can control the branching ratio of the output light to 1: 1 by providing the refractive index control unit 7. That is, the coherent mixer in the present embodiment can realize an amplifier having a high CMRR. As a result, since a high voltage offset can be applied, the influence of shot noise can be greatly reduced and high reception sensitivity can be realized.
  • the present invention has been described with reference to the above-described embodiment and examples, the present invention is not limited only to the configuration of the above-described embodiment and examples, and within the scope of the present invention. It goes without saying that various modifications and corrections that can be made by those skilled in the art are included. This application claims priority based on Japanese Patent Application No. 2011-011168 filed on Jan. 21, 2011, the entire disclosure of which is incorporated herein.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Nonlinear Science (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Abstract

La présente invention concerne un coupleur optique doté d'un guide d'ondes multimode, au moins deux guides d'ondes d'entrée connectés au guide d'ondes multimode pour y faire entrer de la lumière, au moins deux guides d'ondes de sortie connectés au guide d'ondes multimode pour en faire sortir de la lumière et une unité de commande d'indice de réfraction permettant d'ajuster l'indice de réfraction du guide d'ondes multimode, l'unité de commande de l'indice de réfraction étant agencée sensiblement parallèle à une direction de déplacement de la lumière.
PCT/JP2012/051727 2011-01-21 2012-01-20 Coupleur optique et procédé de contrôle de branchements WO2012099275A1 (fr)

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JP2011011168 2011-01-21
JP2011-011168 2011-05-18

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Citations (15)

* Cited by examiner, † Cited by third party
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JPH07110498A (ja) * 1993-10-14 1995-04-25 Oki Electric Ind Co Ltd 光スイッチ
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