On-chip dispersion compensator based on SOI micro-ring

Abstract

The invention discloses an on-chip dispersion compensator based on an SOI micro-ring. The on-chip dispersion compensator comprises a substrate and a core layer, the core layer is arranged at the top of the substrate; the core layer comprises a straight waveguide and four micro-rings; the arrangement direction of the straight waveguide is parallel to the transmission direction of incident light, along the incoming direction of the incident light, the left side of the straight waveguide is eccentrically nested and cascaded with a first micro-ring and a second micro-ring, the right side of the straight waveguide is eccentrically nested and cascaded with a third micro-ring and a fourth micro-ring, and the first micro-ring and the second micro-ring are respectively used for performing dispersion compensation on transmission wavelength signals; the radius of the first micro-ring is larger than that of the second micro-ring, and the radius of the third micro-ring is larger than that of the fourth micro-ring.

Description

Technical Field

[0001] The invention relates to the field of optical communication and optical information technology, and in particular to an on-chip dispersion compensator based on an SOI micro-ring. Background Art

[0002] Dispersion is a major damage mechanism in fiber-optic communication systems. It causes optical pulse broadening, which in turn causes inter-symbol crosstalk, reducing the transmission quality of optical signals and the overall performance of fiber-optic communication systems. With the rapid increase in data transmission rates and the continuous extension of transmission distances in current fiber-optic communication systems, the impact of dispersion has become increasingly significant, making it difficult to recover signals at the receiving end, thereby increasing the bit error rate and limiting the transmission distance and bandwidth utilization of the system. The solution is to use dispersion compensation technology, that is, introducing a negative dispersion device in the fiber link to offset the accumulated positive dispersion in the original link. Compared with other dispersion compensators, on-chip dispersion compensators have the advantages of small size, easy integration, low cost, and low power consumption.

[0003] In 2022, KYKOng et al. proposed a tunable dispersion compensator based on an upload-download microring resonator, which achieved a tunable dispersion compensator from +12.9×10 3 ps / nm to -12.3×10 3 After the device is used for compensation, the bit error rate of 25Gbit / s NRZ data after 20km single-mode fiber transmission is reduced from 10 -3 Down to 10 -11 , the signal quality is significantly improved. On-chip dispersion compensators show great application potential in the next generation of large-scale photonic integrated circuits, which can meet the needs of future high-speed communication and data processing.

[0004] At present, the reports on on-chip dispersion compensators mainly focus on their realization based on strip-slot hybrid optical waveguides, waveguide array gratings, waveguide Bragg gratings and photonic crystal waveguides.

[0005] However, from the perspective of engineering applications, the typical sizes of the above-mentioned photonic devices used as dispersion compensators usually range from hundreds of microns to several millimeters, and they cannot achieve larger group delays and high dispersion. These factors limit their application in high-density integration and miniaturized systems.

[0006] Therefore, it is necessary to provide an on-chip dispersion compensator based on SOI micro-ring to solve the problems mentioned in the above background technology. Summary of the invention

[0007] To achieve the above object, the present invention provides the following technical solution: an on-chip dispersion compensator based on SOI microring, comprising: a substrate and a core layer; the core layer is arranged on top of the substrate; The core layer includes a straight waveguide and four micro-rings; The straight waveguide is arranged in a direction parallel to the transmission direction of the incident light. Along the transmission direction of the incident light, the left side of the straight waveguide is eccentrically nested and cascaded with a first microring and a second microring, and the right side of the straight waveguide is eccentrically nested and cascaded with a third microring and a fourth microring, respectively used for dispersion compensation of a single-channel transmission wavelength signal; The radius of the first microring is greater than that of the second microring, and the radius of the third microring is greater than that of the fourth microring.

[0008] Preferably, the substrate is made of silicon dioxide; The core layer is made of silicon; Preferably, the core layer is coated with a silicon dioxide layer on its circumference.

[0009] Preferably, the thickness of the substrate is H=2μm±0.1μm; The thickness of the core layer is H=220nm±1nm.

[0010] Preferably, the width W of the straight waveguide, the first microring, the second microring, the third microring and the fourth microring are all 600 nm±1 nm.

[0011] Preferably, any node on the substrate plane is used as the coordinate origin, the straight waveguide extension direction is used as the X-axis direction, the horizontal and vertical transmission direction of the incident light is used as the Y-axis direction, and the second micro-ring and the fourth micro-ring are eccentrically nested in the first micro-ring and the third micro-ring respectively along the Y-axis direction.

[0012] Preferably, the shortest distance between the first microring and the second microring, and the shortest distance between the third microring and the fourth microring are both located on the side facing the straight waveguide.

[0013] Preferably, the shortest distance between the first microring and the second microring, and the shortest distance between the third microring and the fourth microring are both 0.09 μm-0.11 μm.

[0014] Preferably, the radii of the four micro-rings are different; The radius R of the first micro-ring 1 Greater than the radius R of the third micro-ring 3 ; Preferably, the radius R of the first micro-ring is 1 6.706μm-6.726μm; The radius R of the second micro-ring 2 4.785μm-4.805μm; The radius R of the third micro-ring 3 4.792μm-4.812μm; The radius R of the fourth micro-ring 4 It is 2.982μm-3.002μm.

[0015] Preferably, the distance between the straight waveguide and the first microring, and the distance between the straight waveguide and the third microring are All are at least 0.1μm.

[0016] Preferably, along the extension direction of the straight waveguide, the center distance G between the first micro-ring and the third micro-ring is 9.8 μm-10.2 μm.

[0017] Compared with the prior art, the present invention provides an on-chip dispersion compensator based on SOI microring, which has the following beneficial effects: In the present invention, the core layer includes a straight waveguide and four microrings with different radii. The straight waveguide is cascaded with two eccentrically nested microrings to ensure the application of the dispersion compensator in high-density integration and miniaturized systems. After optimization, the device size can be reduced to 25μm×27μm. Furthermore, by adjusting the radius of each microring and the spacing between the straight waveguide and the microring, a large group delay and high dispersion are achieved at the working wavelengths of 1550nm and 1545nm.

[0018] In the present invention, at the working wavelength of 1550nm, the maximum group delay value is 266.41ps, and the maximum negative dispersion value is -34611.6ps / nm; at the working wavelength of 1545nm, the maximum group delay value is -112.13ps, and the maximum negative dispersion value is -7567.1ps / nm. After the device of the present invention is used to perform dispersion compensation on the high-speed non-return-to-zero data transmitted at 30Gbit / s in a 100km single-mode optical fiber, the eye diagram is significantly improved, the Q factor after compensation is 18.48, and the bit error rate can be reduced to 10 -76 . BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall structure of an on-chip dispersion compensator based on SOI microring provided by the present invention; Figure 2 (a) is a mode field diagram of a straight waveguide of an on-chip dispersion compensator based on SOI microring provided by the present invention at a wavelength of 1550nm; Figure 2 (b) is a graph showing the variation of the effective refractive index of a straight waveguide of an on-chip dispersion compensator based on SOI microring provided by the present invention with respect to wavelength; Figure 3 (a) is a graph showing the variation of group delay and dispersion with wavelength of an on-chip dispersion compensator based on SOI microring provided by the present invention at an operating wavelength of 1550nm; Figure 3(b) is a graph showing the variation of group delay and dispersion with wavelength of an on-chip dispersion compensator based on SOI microring provided by the present invention at an operating wavelength of 1545 nm; Figure 4 (a) is an electric field distribution diagram of an on-chip dispersion compensator based on SOI microring provided by the present invention on the XOY plane; Figure 4 (b) is a mode field diagram of the input port of an on-chip dispersion compensator based on SOI microring provided by the present invention; Figure 4 (c) is an output mode field diagram of an on-chip dispersion compensator based on SOI microring provided by the present invention; Figure 5 It is a transmission spectrum of an on-chip dispersion compensator based on SOI microring provided by the present invention; Figure 6 (a) is a transmission spectrum and group delay variation with wavelength at 1550nm of an on-chip dispersion compensator based on SOI microring provided by the present invention; Figure 6 (b) is a transmission spectrum and group delay variation with wavelength of an on-chip dispersion compensator based on SOI microring provided by the present invention at 1545nm; Figure 7 This is a diagram of an experimental device for a dispersion compensation system provided by the present invention; Figure 8 (a) is a waveform diagram of an original signal of a dispersion compensation system provided by the present invention; Figure 8 (b) is an original signal eye diagram of a dispersion compensation system provided by the present invention; Figure 8 (c) is a signal waveform diagram before compensation of a dispersion compensation system provided by the present invention; Figure 8 (d) is a signal eye diagram before compensation of a dispersion compensation system provided by the present invention; Figure 8 (e) is a waveform diagram of a compensated signal of a dispersion compensation system provided by the present invention; Figure 8 (f) is a compensated signal eye diagram of a dispersion compensation system provided by the present invention; In the figure: 1. substrate; 2. core layer; 3. straight waveguide; 4. first microring; 5. second microring; 6. third microring; 7. fourth microring. DETAILED DESCRIPTION

[0020] See also Figure 1 The present invention provides an on-chip dispersion compensator based on SOI microring, comprising: a substrate 1 and a core layer 2; the core layer 2 is arranged on the top of the substrate 1; The core layer 2 includes a straight waveguide 3 and four micro-rings; The straight waveguide 3 is arranged in a direction parallel to the transmission direction of the incident light. Along the transmission direction of the incident light, the left side of the straight waveguide 3 is eccentrically nested and cascaded with a first microring 4 and a second microring 5, and the right side of the straight waveguide 3 is eccentrically nested and cascaded with a third microring 6 and a fourth microring 7, which are respectively used to perform dispersion compensation for single-channel transmission wavelength signals; The radius of the first micro-ring 4 is greater than that of the second micro-ring 5 , and the radius of the third micro-ring 6 is greater than that of the fourth micro-ring 7 .

[0021] It should be explained that cascading means connecting the straight waveguide 3 in series with the first microring 4 , the second microring 5 , the third microring 6 and the fourth microring 7 respectively, so as to achieve more accurate or more complex processing of the optical signal.

[0022] Furthermore, the substrate 1 is made of silicon dioxide; The core layer 2 is made of silicon; Preferably, the core layer is coated with a silicon dioxide layer on two circumferential sides.

[0023] Furthermore, the thickness of the substrate 1 is H=2 μm±0.1 μm; The thickness of the core layer 2 is H=220nm±1nm.

[0024] Furthermore, the widths W of the straight waveguide 3 , the first microring 4 , the second microring 5 , the third microring 6 and the fourth microring 7 are all 600 nm±1 nm.

[0025] Furthermore, taking any node on the plane of the substrate 1 as the coordinate origin, the extension direction of the straight waveguide 3 as the X-axis direction, and the horizontal and perpendicular transmission direction of the incident light as the Y-axis direction, the second microring 5 and the fourth microring 7 are eccentrically nested in the first microring 4 and the third microring 6 respectively along the Y-axis direction.

[0026] Furthermore, the shortest distance between the first microring 4 and the second microring 5 , and the shortest distance between the third microring 6 and the fourth microring 7 are both located on the side facing the straight waveguide 3 .

[0027] Furthermore, the shortest distance between the first micro-ring 4 and the second micro-ring 5 , and the shortest distance between the third micro-ring 6 and the fourth micro-ring 7 are both 0.09 μm-0.11 μm.

[0028] Furthermore, the radii of the four micro-rings are different; The radius R of the first micro-ring 4 1 Greater than the radius R of the third micro-ring 6 3 ; Preferably, the radius R of the first micro-ring 4 is 16.706μm-6.726μm; The radius R of the second micro-ring 5 2 4.785μm-4.805μm; The radius R of the third micro-ring 6 3 4.792μm-4.812μm; The radius R of the fourth micro-ring 7 4 It is 2.982μm-3.002μm.

[0029] Furthermore, the distance between the straight waveguide 3 and the first microring 4, and the distance between the straight waveguide 3 and the third microring 6 are All are at least 0.1μm.

[0030] Furthermore, along the extension direction of the straight waveguide 3 , the center distance G between the first micro-ring 4 and the third micro-ring 6 is 9.8 μm-10.2 μm.

[0031] In specific implementation, when the optical signal is input from the input port of the straight waveguide 3 and enters the coupling region of the micro-ring along the straight waveguide 3, a portion of the optical signal power will be coupled into the ring waveguide, and after circling around the micro-ring, it will be emitted from the output port of the straight waveguide 3. In this process, the micro-ring will modulate the optical signal, and by adjusting the parameters such as the resonant wavelength and coupling coefficient of the micro-ring, the transmission path and phase of the optical signal in the micro-ring can be changed, thereby achieving dispersion compensation for the optical signal.

[0032] like Figure 7 As shown, a dispersion compensation experiment is performed on the dispersion compensator of the present invention, and the specific parameters of the dispersion compensator experiment are: The thickness of substrate 1 is 0.1 μm; The thickness of core layer 2 is 220 nm; The widths of the straight waveguide 3, the first microring 4, the second microring 5, the third microring 6 and the fourth microring 7 are all 600 nm; The shortest distance between the first microring 4 and the second microring 5, and the distance between the third microring 6 and the fourth microring 7 are all 0.1 μm. The first microring 4 and the second microring 5 are located at the lower left of the straight waveguide 3, and the third microring 6 and the fourth microring 7 are located at the upper right of the straight waveguide 3. The radius R of the first micro-ring 4 1 is 6.716 μm, and the radius R of the second micro-ring 5 2 is 4.795 μm, and the radius R of the third micro-ring 6 is 3 is 4.802 μm, and the radius R of the fourth micro-ring 7 is 4 2.992μm; The distance between the straight waveguide 3 and the first microring 4 and the distance between the straight waveguide 3 and the third microring 6 are both 0.1 μm; Along the extending direction of the straight waveguide 3 , the center distance G between the first micro-ring 4 and the third micro-ring 6 is 10 μm.

[0033] The specific method is: a continuous laser is used to generate an optical signal with a central wavelength of 1550.04nm, and the signal is modulated at a rate of 30Gbit / s by a Mach-Zehnder modulator. 31 -1 pseudo-random binary sequence non-return-to-zero encoding. The modulated optical signal is adjusted by polarization controller and amplified by erbium-doped fiber amplifier (EDFA), and then transmitted in 100km single-mode optical fiber, where the optical fiber dispersion coefficient is 18ps·nm near the signal light wavelength. -1 km -1 . After long-distance transmission, the quality of the optical signal is degraded due to the influence of dispersion and loss. After the signal is amplified again by an erbium-doped fiber amplifier, dispersion compensation is performed by an on-chip dispersion compensator based on an SOI microring provided by the present invention. The compensated optical signal is received by a photodetector (PIN), and the received signal is then filtered out of high-frequency noise by a low-pass filter. Finally, the signal is input into a digital sampling oscilloscope and a bit error rate tester for measuring waveforms and eye diagrams, respectively.

[0034] The specific test results are as follows: like Figure 2 As shown, Figure 2 (a) It can be seen that the straight waveguide 3 only supports TE 0 mode, and the energy is well confined in the waveguide, due to Figure 2 (b) It can be seen that the TE in the straight waveguide 3 0 The effective refractive index of the mode is about 2.566 at the operating wavelength of 1550nm.

[0035] Figure 3 The graphs of group delay and dispersion of the on-chip dispersion compensator at the working wavelengths of 1550nm and 1545nm are shown as follows: Figure 3 (a) It can be seen that the group delay of the on-chip compensator reaches a maximum value of 266.41ps at a wavelength of 1550.032nm, and the negative dispersion reaches a maximum value of -34611.6ps / nm at a wavelength of 1550.034nm. Figure 3 (b) It can be seen that the group delay of the on-chip compensator reaches a minimum value of -112.13 ps at a wavelength of 1545.13 nm, and the negative dispersion reaches a minimum value of -7567.1 ps / nm at a wavelength of 1545.125 nm.

[0036] like Figure 4 The figures are respectively the XOY plane electric field distribution diagram, input port mode field diagram and output port mode field diagram of the on-chip dispersion compensator of the present invention. Figure 4(a) It can be seen that the large ring at the upper left corner and the small ring at the lower right corner of the on-chip compensator are in an over-coupled state, and the small ring at the upper left corner and the large ring at the lower right corner are in an under-coupled state. Figure 4 (b) and Figure 4 (c) It can be seen that compared with the input end, the mode field energy distribution at the output end after the light passes through the on-chip compensator remains basically unchanged, and the output is still in TE0 mode.

[0037] like Figure 5 The transmission spectrum of the on-chip dispersion compensator of the present invention is shown in Figure 1. The transmission spectrum has two minimum values ​​near 1545nm and 1550nm, both of which are much larger than -20dB. This shows that the cascaded nested microring is undercoupled at these two wavelengths, which meets the conditions for generating large dispersion values. In addition, the spectrum also shows that the insertion loss of the device is less than 0.44dB, which belongs to the low loss range.

[0038] Figure 6 The transmission spectrum and group delay of the on-chip dispersion compensator of the present invention at 1550nm and 1545nm vary with wavelength. Figure 6 (a) It can be seen that the group delay of the on-chip compensator reaches a peak of 266.41ps at the resonant wavelength of 1550nm. Figure 6 (b) It can be seen that the group delay of the on-chip compensator reaches a peak of -112.13ps at the resonant wavelength of 1545nm.

[0039] Figure 8 (a), (b), (c), (d), (e), and (f) are respectively an original signal waveform diagram, an original signal eye diagram, a signal waveform diagram before compensation, a signal eye diagram before compensation, a signal waveform diagram after compensation, and a signal eye diagram after compensation of a dispersion compensation system provided by the present invention. Figure 8 (c) and Figure 8 (d) It can be seen that after long-distance transmission, the dispersion effect causes serious signal distortion and the eye diagram is almost closed. Figure 8 (e) and Figure 8 (f) It can be seen that compared with Figure 8 (d), Figure 8 The eye opening shown in (f) is significantly larger. In addition, the Q factor after dispersion compensation is 18.48, and the minimum bit error rate is 10 -76 It shows that after the designed micro-ring dispersion compensation, the signal distortion is significantly reduced and the system performance is significantly improved.

[0040] What is described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An on-chip dispersion compensator based on SOI microring, characterized in that: include: A substrate (1) and a core layer (2); the core layer (2) is arranged on top of the substrate (1); The core layer (2) comprises a straight waveguide (3) and four micro-rings; The straight waveguide (3) is arranged in a direction parallel to the transmission direction of the incident light. Along the transmission direction of the incident light, the left side of the straight waveguide (3) is eccentrically nested with a first micro-ring (4) and a second micro-ring (5), and the right side of the straight waveguide (3) is eccentrically nested with a third micro-ring (6) and a fourth micro-ring (7), which are respectively used to perform dispersion compensation on the transmission wavelength signal. The radius of the first micro-ring (4) is greater than that of the second micro-ring (5), and the radius of the third micro-ring (6) is greater than that of the fourth micro-ring (7).

2. The on-chip dispersion compensator based on SOI microring according to claim 1, characterized in that: The substrate (1) is made of silicon dioxide; The core layer (2) is made of silicon; Preferably, the core layer (2) is coated with a silicon dioxide layer on its circumferential side.

3. The on-chip dispersion compensator based on SOI microring according to claim 1, characterized in that: The thickness of the substrate (1) is H=2 μm±0.1 μm; The thickness of the core layer (2) is H=220nm±1nm.

4. The on-chip dispersion compensator based on SOI microring according to claim 1, characterized in that: The width W of the straight waveguide (3), the first microring (4), the second microring (5), the third microring (6) and the fourth microring (7) are all 600 nm±1 nm.

5. The on-chip dispersion compensator based on SOI microring according to claim 1, characterized in that: With any node on the plane of the substrate (1) as the coordinate origin, the extension direction of the straight waveguide (3) as the X-axis direction, and the horizontal and perpendicular transmission direction of the incident light as the Y-axis direction, the second micro-ring (5) and the fourth micro-ring (7) are eccentrically nested in the first micro-ring (4) and the third micro-ring (6) respectively along the Y-axis direction.

6. The on-chip dispersion compensator based on SOI microring according to claim 5, characterized in that: The shortest distance between the first microring (4) and the second microring (5), and the shortest distance between the third microring (6) and the fourth microring (7) are both located on the side facing the straight waveguide (3).

7. The on-chip dispersion compensator based on SOI microring according to claim 1, characterized in that: The shortest distance between the first microring (4) and the second microring (5), and the shortest distance between the third microring (6) and the fourth microring (7) are both 0.09 μm-0.11 μm.

8. The on-chip dispersion compensator based on SOI microring according to claim 1, characterized in that: The radii of the four micro-rings are all different; The radius R1 of the first micro-ring (4) is greater than the radius R3 of the third micro-ring (6); Preferably, the radius R1 of the first micro-ring (4) is 6.706 μm-6.726 μm; The radius R2 of the second micro-ring (5) is 4.785 μm-4.805 μm; The radius R3 of the third micro-ring (6) is 4.792 μm-4.812 μm; The radius R4 of the fourth micro-ring (7) is 2.982 μm-3.002 μm.

9. The on-chip dispersion compensator based on SOI microring according to claim 1, characterized in that: The distance between the straight waveguide (3) and the first microring (4), and the distance between the straight waveguide (3) and the third microring (6) All are at least 0.1μm.

10. The on-chip dispersion compensator based on SOI microring according to claim 1, characterized in that: Along the extension direction of the straight waveguide (3), the center distance G between the first micro-ring (4) and the third micro-ring (6) is 9.8 μm-10.2 μm.

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