An on-chip dispersion compensator based on SOI microring

Abstract

The invention discloses an on-chip dispersion compensator based on SOI microring, comprising a substrate and a core layer; the core layer is arranged on the top of the substrate; the core layer comprises a straight waveguide and four microrings; the arrangement direction of the straight waveguide is parallel to the transmission direction of the incident light, and 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, which are respectively used for dispersion compensation of the 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.

Description

Technical Field

[0001] The present invention relates to the field of optical communication and optical information technology, and particularly relates to a chip-based dispersion compensator based on an SOI microring. Background Art

[0002] Dispersion is a major impairment mechanism in fiber optic communication systems. It causes optical pulse broadening, which leads to inter-symbol interference, reduces the transmission quality of optical signals and the overall performance of fiber optic communication systems. With the rapid increase in data transmission rate and continuous extension of transmission distance in current fiber optic communication systems, the impact of dispersion becomes increasingly significant, making it difficult to recover signals at the receiving end, increasing the bit error rate, and limiting the transmission distance and bandwidth utilization of the system. The solution is to adopt dispersion compensation technology, that is, to introduce a negative dispersion device in the fiber optic link to cancel the positive dispersion accumulated in the original link. Compared with other dispersion compensators, chip-based dispersion compensators have the advantages of small size, easy integration, low cost, and low power consumption.

[0003] In 2022, K.Y.K. Ong et al. proposed a tunable dispersion compensator based on an upload-download type microring resonator, achieving a dispersion compensation range from +12.9×10 3 ps / nm to -12.3×10 3 ps / nm. After being compensated by this device, the bit error rate of 25Gbit / s NRZ data after transmission in a 20-kilometer single-mode fiber drops from 10 -3 to 10 -11 , and the signal quality is significantly improved. Chip-based dispersion compensators show great application potential in next-generation large-scale photonic integrated circuits and can meet the needs of future high-speed communication and data processing.

[0004] Currently, reports on chip-based dispersion compensators mainly focus on implementation 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 several hundred micrometers to several millimeters; and they cannot achieve larger group delays and high dispersion. These factors limit their application effects in high-density integration and miniaturized systems.

[0006] Therefore, it is necessary to provide a chip-based dispersion compensator based on an SOI microring to solve the problems mentioned in the above background art. Summary of the Invention

[0007] To achieve the above object, the present invention provides the following technical solution: A chip-based dispersion compensator based on an SOI microring, comprising: a substrate and a core layer; the core layer is disposed on top of the substrate;

[0008] The core layer includes a straight waveguide and four micro - rings;

[0009] The layout direction of the straight waveguide is parallel to the incident light transmission direction. Along the incident light incoming direction, the first micro - ring and the second micro - ring are eccentrically nested and cascaded on the left side of the straight waveguide, and the third micro - ring and the fourth micro - ring are eccentrically nested and cascaded on the right side of the straight waveguide, respectively used for dispersion compensation of the single - path transmission wavelength signal;

[0010] 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.

[0011] Preferably, the substrate preparation material is silicon dioxide;

[0012] The core layer preparation material is silicon;

[0013] Preferably, the core layer is coated with a silicon dioxide layer on its periphery.

[0014] Preferably, the thickness H of the substrate is 2μm ± 0.1μm;

[0015] The thickness H of the core layer is 220nm ± 1nm.

[0016] Preferably, the widths W of the straight waveguide, the first micro - ring, the second micro - ring, the third micro - ring and the fourth micro - ring are all 600nm ± 1nm.

[0017] Preferably, taking any node on the substrate plane as the coordinate origin, the straight waveguide extension direction as the X - axis direction, and the direction perpendicular to the incident light transmission direction horizontally as the Y - axis direction, 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.

[0018] Preferably, the shortest distances between the first micro - ring and the second micro - ring, and between the third micro - ring and the fourth micro - ring are both on the side facing the straight waveguide.

[0019] Preferably, the shortest distances between the first micro - ring and the second micro - ring, and between the third micro - ring and the fourth micro - ring are both 0.09μm - 0.11μm.

[0020] Preferably, the radii of the four micro - rings are all different;

[0021] The radius R of the first micro - ring 1 is larger than the radius R of the third micro - ring 3 ;

[0022] Preferably, the radius R of the first micro - ring 1 is 6.706μm - 6.726μm;

[0023] The radius R of the second micro-ring 2 is 4.785 μm - 4.805 μm;

[0024] The radius R of the third micro-ring 3 is 4.792 μm - 4.812 μm;

[0025] The radius R of the fourth micro-ring 4 is 2.982 μm - 3.002 μm.

[0026] Preferably, the distance between the straight waveguide and the first micro-ring, and the distance between the straight waveguide and the third micro-ring are both at least 0.1 μm.

[0027] Preferably, along the extending 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.

[0028] Compared with the prior art, the present invention provides a on-chip dispersion compensator based on an SOI micro-ring, having the following beneficial effects:

[0029] In the present invention, the core layer includes a straight waveguide and four micro-rings with different radii. By cascading two eccentrically nested micro-rings through the straight waveguide, the application of the dispersion compensator in a high-density integrated and miniaturized system is ensured. The optimized device size can be reduced to 25 μm × 27 μm. Further, by adjusting the radii of each micro-ring and the distance between the straight waveguide and the micro-ring, a large group delay and high dispersion are achieved at the working wavelengths of 1550 nm and 1545 nm.

[0030] In the present invention, at the working wavelength of 1550 nm, the maximum group delay value is 266.41 ps, and the maximum negative dispersion value is -34611.6 ps / nm; at the working wavelength of 1545 nm, the maximum group delay value is -112.13 ps, and the maximum negative dispersion value is -7567.1 ps / nm. After the dispersion compensation of the 30 Gbit / s high-speed non-return-to-zero data transmitted in a 100 km single-mode optical fiber by the device of the present invention, the eye diagram is significantly improved, and the compensated Q factor is 18.48, and the bit error rate can be reduced to 10 -76 . Description of the Drawings

[0031] Figure 1 is the overall structural schematic diagram of a on-chip dispersion compensator based on an SOI micro-ring provided by the present invention;

[0032] Figure 2 (a) is the mode field diagram of the straight waveguide of a on-chip dispersion compensator based on an SOI micro-ring provided by the present invention at the wavelength of 1550 nm;

[0033] Figure 2 (b) is the graph of the effective refractive index of the straight waveguide of the on-chip dispersion compensator based on SOI microring provided by the present invention varying with wavelength;

[0034] Figure 3 (a) is the graph of the group delay and dispersion of the on-chip dispersion compensator based on SOI microring provided by the present invention varying with wavelength at the working wavelength of 1550 nm;

[0035] Figure 3 (b) is the graph of the group delay and dispersion of the on-chip dispersion compensator based on SOI microring provided by the present invention varying with wavelength at the working wavelength of 1545 nm;

[0036] Figure 4 (a) is the electric field distribution diagram of the on-chip dispersion compensator based on SOI microring provided by the present invention in the XOY plane;

[0037] Figure 4 (b) is the input port mode field diagram of the on-chip dispersion compensator based on SOI microring provided by the present invention;

[0038] Figure 4 (c) is the output port mode field diagram of the on-chip dispersion compensator based on SOI microring provided by the present invention;

[0039] Figure 5 is the transmission spectrum of the on-chip dispersion compensator based on SOI microring provided by the present invention;

[0040] Figure 6 (a) is the graph of the transmission spectrum and group delay of the on-chip dispersion compensator based on SOI microring provided by the present invention varying with wavelength at 1550 nm;

[0041] Figure 6 (b) is the graph of the transmission spectrum and group delay of the on-chip dispersion compensator based on SOI microring provided by the present invention varying with wavelength at 1545 nm;

[0042] Figure 7 is the experimental setup diagram of the dispersion compensation system provided by the present invention;

[0043] Figure 8 (a) is the original signal waveform diagram of the dispersion compensation system provided by the present invention;

[0044] Figure 8 (b) is the original signal eye diagram of the dispersion compensation system provided by the present invention;

[0045] Figure 8 (c) is the signal waveform diagram before compensation of the dispersion compensation system provided by the present invention;

[0046] Figure 8 (d) is the pre - compensation signal eye diagram of a dispersion compensation system provided by the present invention;

[0047] Figure 8 (e) is the post - compensation signal waveform diagram of a dispersion compensation system provided by the present invention;

[0048] Figure 8 (f) is the post - compensation signal eye diagram of a dispersion compensation system provided by the present invention;

[0049] In the figure: 1. Substrate; 2. Core layer; 3. Straight waveguide; 4. First micro - ring; 5. Second micro - ring; 6. Third micro - ring; 7. Fourth micro - ring. Specific embodiments

[0050] Please refer to Figure 1 , the present invention provides a on - chip dispersion compensator based on SOI micro - rings, including: a substrate 1 and a core layer 2; the core layer 2 is disposed on top of the substrate 1;

[0051] The core layer 2 includes a straight waveguide 3 and four micro - rings;

[0052] The layout direction of the straight waveguide 3 is parallel to the incident light transmission direction. Along the incident light incoming direction, the first micro - ring 4 and the second micro - ring 5 are eccentrically nested and cascaded on the left side of the straight waveguide 3, and the third micro - ring 6 and the fourth micro - ring 7 are eccentrically nested and cascaded on the right side of the straight waveguide 3, respectively for performing dispersion compensation on the single - path transmission wavelength signal;

[0053] 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.

[0054] It should be explained that cascading means connecting the straight waveguide 3 in series with the first micro - ring 4, the second micro - ring 5, the third micro - ring 6 and the fourth micro - ring 7 respectively to achieve more precise or more complex processing of the optical signal.

[0055] Furthermore, the material for preparing the substrate 1 is silicon dioxide;

[0056] The material for preparing the core layer 2 is silicon;

[0057] Preferably, the core layer 2 is coated with a silicon dioxide layer on its circumferential side.

[0058] Furthermore, the thickness H of the substrate 1 is 2μm ± 0.1μm;

[0059] The thickness H of the core layer 2 is 220nm ± 1nm.

[0060] Further, the widths W of the straight waveguide 3, the first micro-ring 4, the second micro-ring 5, the third micro-ring 6, and the fourth micro-ring 7 are all 600 nm ± 1 nm.

[0061] Further, taking any node on the plane of the substrate 1 as the coordinate origin, the extending direction of the straight waveguide 3 as the X-axis direction, and the direction perpendicular to the incident light transmission direction horizontally 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 along the Y-axis direction respectively.

[0062] Further, the shortest distances between the first micro-ring 4 and the second micro-ring 5, and between the third micro-ring 6 and the fourth micro-ring 7 are both on the side facing the straight waveguide 3.

[0063] Further, the shortest distances between the first micro-ring 4 and the second micro-ring 5, and between the third micro-ring 6 and the fourth micro-ring 7 are both 0.09 μm - 0.11 μm.

[0064] Further, the radii of the four micro-rings are all different;

[0065] The radius R of the first micro-ring 4 1 is greater than the radius R of the third micro-ring 6 3 ;

[0066] Preferably, the radius R of the first micro-ring 4 1 is 6.706 μm - 6.726 μm;

[0067] The radius R of the second micro-ring 5 2 is 4.785 μm - 4.805 μm;

[0068] The radius R of the third micro-ring 6 3 is 4.792 μm - 4.812 μm;

[0069] The radius R of the fourth micro-ring 7 4 is 2.982 μm - 3.002 μm.

[0070] Further, the distances between the straight waveguide 3 and the first micro-ring 4, and between the straight waveguide 3 and the third micro-ring 6 are both at least 0.1 μm.

[0071] Further, 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 9.8 μm - 10.2 μm.

[0072] In specific implementation, when an 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 part of the optical signal power will be coupled into the ring waveguide, and after circulating in the micro-ring for one week, it will be emitted from the output port of the straight waveguide 3. During this process, the micro-ring will modulate the optical signal. By adjusting 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 realizing the dispersion compensation of the optical signal.

[0073] As Figure 7 shown, a dispersion compensation experiment is carried out on the dispersion compensator of the present invention. The specific parameters of the dispersion compensator experiment are as follows:

[0074] The thickness of the substrate 1 is 0.1 μm;

[0075] The thickness of the core layer 2 is 220 nm;

[0076] The widths of the straight waveguide 3, the first micro-ring 4, the second micro-ring 5, the third micro-ring 6, and the fourth micro-ring 7 are all 600 nm;

[0077] The shortest distance between the first micro-ring 4 and the second micro-ring 5, and the distance between the third micro-ring 6 and the fourth micro-ring 7 are both 0.1 μm. The first micro-ring 4 and the second micro-ring 5 are located at the lower left of the straight waveguide 3, and the third micro-ring 6 and the fourth micro-ring 7 are located at the upper right of the straight waveguide 3;

[0078] The radius R of the first micro-ring 4 1 is 6.716 μm, the radius R of the second micro-ring 5 2 is 4.795 μm, the radius R of the third micro-ring 6 3 is 4.802 μm, the radius R of the fourth micro-ring 7 4 is 2.992 μm;

[0079] The distances between the straight waveguide 3 and the first micro-ring 4, and between the straight waveguide 3 and the third micro-ring 6 are both 0.1 μm;

[0080] 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 10 μm.

[0081] The specific method is as follows: An optical signal with a central wavelength of 1550.04 nm is generated by a continuous laser. This signal is modulated by a Mach-Zehnder modulator at a rate of 30 Gbit / s, and the modulation signal uses a 2 31 -1 pseudorandom binary sequence non-return-to-zero coding. The modulated optical signal is adjusted in polarization by a polarization controller and then amplified by an erbium-doped fiber amplifier (EDFA), and then enters a 100-km single-mode fiber for transmission. Among them, the fiber dispersion coefficient near the signal light wavelength is 18 ps·nm -1 ·km -1After long-distance transmission, affected by dispersion and loss, the quality of the optical signal deteriorates. After the signal is amplified again by an erbium-doped fiber amplifier, it is dispersion-compensated by a 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 by a low-pass filter to remove high-frequency noise. Finally, the signal is input into a digital sampling oscilloscope and a bit error rate tester, which are used to measure the waveform and the eye diagram respectively.

[0082] The specific test results are as follows:

[0083] As Figure 2 shown, Figure 2 (a) It can be seen that the straight waveguide 3 only supports the TE 0 mode, and the energy is well confined in the waveguide. From Figure 2 (b), it can be seen that the effective refractive index of the TE 0 mode in the straight waveguide 3 is about 2.566 at the working wavelength of 1550 nm.

[0084] Figure 3 Figs. are the graphs of the group delay and dispersion of the on-chip dispersion compensator varying with wavelength at the working wavelengths of 1550 nm and 1545 nm. From Figure 3 (a), it can be seen that the group delay of the on-chip compensator reaches the maximum value of 266.41 ps at the wavelength of 1550.032 nm, and the negative dispersion reaches the maximum value of -34611.6 ps / nm at the wavelength of 1550.034 nm. From Figure 3 (b), it can be seen that the group delay of the on-chip compensator reaches the minimum value of -112.13 ps at the wavelength of 1545.13 nm, and the negative dispersion reaches the minimum value of -7567.1 ps / nm at the wavelength of 1545.125 nm.

[0085] As Figure 4 shown are the XOY plane electric field distribution diagram, the input and output port mode field diagrams of the on-chip dispersion compensator of the present invention respectively. From Figure 4 (a), it can be seen that the large ring in the upper left corner and the small ring in the lower right corner of the on-chip compensator are in an over-coupled state, and the small ring in the upper left corner and the large ring in 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 of the optical signal passing through the on-chip compensator remains basically unchanged, and the output is still the TE0 mode.

[0086] As Figure 5The transmitted spectrum diagram of the on-chip dispersion compensator of the present invention is shown. The transmitted spectrum has two minima near 1545 nm and 1550 nm respectively, both of which are much greater than -20 dB. This indicates that the cascaded nested micro-ring is in an under-coupled state at these two wavelengths, meeting the conditions for generating a large dispersion value. In addition, this spectral line can also show that the insertion loss of this device is less than 0.44 dB, belonging to the low-loss range.

[0087] Figure 6 The transmitted spectrum and group delay versus wavelength diagrams of the on-chip dispersion compensator of the present invention at 1550 nm and 1545 nm are shown. From Figure 6 Figure (a), it can be seen that the group delay of the on-chip compensator reaches a peak value of 266.41 ps at the resonant wavelength of 1550 nm. From Figure 6 Figure (b), it can be seen that the group delay of the on-chip compensator reaches a peak value of -112.13 ps at the resonant wavelength of 1545 nm.

[0088] Figure 8 In Figures (a), (b), (c), (d), (e), and (f) are respectively the original signal waveform diagram, original signal eye diagram, signal waveform diagram before compensation, signal eye diagram before compensation, signal waveform diagram after compensation, and signal eye diagram after compensation of a dispersion compensation system provided by the present invention. From Figure 8 Figure (c) and Figure 8 Figure (d), it can be seen that after long-distance transmission, the dispersion effect causes the signal to be severely distorted and the eye diagram to be almost closed. From Figure 8 Figure (e) and Figure 8 Figure (f), it can be seen that compared with Figure 8 Figure (d), Figure 8 the eye diagram opening in Figure (f) increases significantly. 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 degree of signal distortion is significantly reduced and the system performance is significantly improved.

[0089] The above-mentioned is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered within 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 microring (4) and a second microring (5), and the right side of the straight waveguide (3) is eccentrically nested with a third microring (6) and a fourth microring (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); 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 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; 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).

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; 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: 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.

6. 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); 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.

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

8. 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 microring (4) and the third microring (6) is 9.8 μm-10.2 μm.

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