Wavelength Division Multiplexer

Abstract

The present disclosure provides a wavelength division multiplexer, comprising: an input optical waveguide for inputting an optical signal containing multiple wavelengths to be processed; a Mach-Zehnder interferometer module, including: a first Mach-Zehnder interferometer, a second Mach-Zehnder interferometer, an input port connected to a first output port of the first Mach-Zehnder interferometer; and a third Mach-Zehnder interferometer, an input port connected to a second output port of the first Mach-Zehnder interferometer; an output waveguide module, including multiple output optical waveguides; wherein, the first Mach-Zehnder interferometer, the second Mach-Zehnder interferometer and the third Mach-Zehnder interferometer all include a first multimode waveguide and a second multimode waveguide, the length of the first multimode waveguide is greater than the length of the second multimode waveguide, and the Mach-Zehnder interferometer module is a cascaded structure of second-order filters to cause the optical signal containing multiple wavelengths to interfere and then output from multiple output optical waveguides respectively, so as to achieve wavelength division multiplexing.

Description

Technical Field

[0001] The present disclosure relates to the field of optical communication technologies, and more particularly, to a wavelength division multiplexer. Background Art

[0002] Wavelength Division Multiplexing (WDM) technology has been widely used in the current field of optical communication, and is of great significance for improving communication capacity and data transmission speed.

[0003] Currently, common wavelength division multiplexers include Mach-Zehnder interferometers, Arrayed Waveguide Gratings (AWGs), and waveguide Bragg gratings. Among them, the wavelength division multiplexer based on a Mach-Zehnder interferometer has fewer channels, but has a flatter passband, smaller size, lower insertion loss, and crosstalk, and is often used in short-distance optical interconnections such as data centers. Most of the traditional wavelength division multiplexers based on cascaded Mach-Zehnder interferometers adopt a structure with non-equal arm lengths or non-equal arm widths, and the center wavelength position is very sensitive to manufacturing processes and operating temperatures, making it difficult to meet industrial actual requirements. Summary of the Invention

[0004] To solve at least one of the above-mentioned and other technical problems in the prior art, the present disclosure provides a wavelength division multiplexer, which includes a first Mach-Zehnder interferometer, a second Mach-Zehnder interferometer, and a third Mach-Zehnder interferometer. The first Mach-Zehnder interferometer, the second Mach-Zehnder interferometer, and the third Mach-Zehnder interferometer each include a first multimode waveguide and a second multimode waveguide, and the length of the first multimode waveguide is greater than the length of the second multimode waveguide. The Mach-Zehnder interferometer module is a two-stage filter cascaded structure to enable optical signals containing multiple wavelengths to interfere and then be output from multiple output optical waveguides respectively to achieve wavelength division multiplexing.

[0005] Embodiments of the present disclosure provide a wavelength division multiplexer, including: an input optical waveguide for inputting an optical signal containing multiple wavelengths to be processed; a Mach-Zehnder interferometer module including: a first Mach-Zehnder interferometer, a second Mach-Zehnder interferometer, an input port connected to a first output port of the first Mach-Zehnder interferometer; and a third Mach-Zehnder interferometer, an input port connected to a second output port of the first Mach-Zehnder interferometer; an output waveguide module including multiple output optical waveguides; wherein, the first Mach-Zehnder interferometer, the second Mach-Zehnder interferometer and the third Mach-Zehnder interferometer all include a first multimode waveguide and a second multimode waveguide, the length of the first multimode waveguide is greater than the length of the second multimode waveguide, and the Mach-Zehnder interferometer module is a cascaded structure of second-order filters to cause the optical signal containing multiple wavelengths to interfere and then output from multiple output optical waveguides respectively, so as to achieve wavelength division multiplexing.

[0006] According to some embodiments of the present disclosure, the lengths of the first multimode waveguide and the second multimode waveguide are related to the free spectral range of the wavelength division multiplexer, wherein, in response to the change of the lengths of the first multimode waveguide and the second multimode waveguide, the values of the free spectral ranges of the first Mach-Zehnder interferometer, the second Mach-Zehnder interferometer and the third Mach-Zehnder interferometer change respectively.

[0007] According to some embodiments of the present disclosure, the first Mach-Zehnder interferometer, the second Mach-Zehnder interferometer and the third Mach-Zehnder interferometer also all include: a first phase-shifting arm including a first mode converter, a second mode converter and the first multimode waveguide connected in sequence, wherein, the optical signal is converted from the fundamental mode to the first-order mode by the first mode converter in the first phase-shifting arm, and the optical signal is converted from the first-order mode to the fundamental mode by the second mode converter in the first phase-shifting arm, so that the optical signal is transmitted in the first multimode waveguide in the fundamental mode; and a second phase-shifting arm including a third mode converter, the second multimode waveguide, and a fourth mode converter connected in sequence, wherein, the optical signal is converted from the fundamental mode to the first-order mode by the third mode converter in the second phase-shifting arm, so that the optical signal is transmitted in the second multimode waveguide in the first-order mode, and the optical signal is converted from the first-order mode to the fundamental mode by the fourth mode converter.

[0008] According to some embodiments of the present disclosure, the above-mentioned first Mach-Zehnder interferometer, second Mach-Zehnder interferometer, and third Mach-Zehnder interferometer further include: a first bent directional coupler connected to the above-mentioned first phase shift arm and the above-mentioned second phase shift arm through a wired single-mode waveguide; and a second bent directional coupler connected to the above-mentioned first phase shift arm and the above-mentioned second phase shift arm through the above-mentioned wired single-mode waveguide; wherein, the above-mentioned first bent directional coupler and the above-mentioned second bent directional coupler are used to combine the above-mentioned optical signals and cause interference.

[0009] According to some embodiments of the present disclosure, both the above-mentioned first bent directional coupler and the above-mentioned second bent directional coupler include two input ports, two concentric arc structure waveguides, and two output ports. The centers of the two concentric arc structure waveguides of the above-mentioned first bent directional coupler are symmetric about the horizontal direction with the centers of the two concentric arc structure waveguides of the above-mentioned second bent directional coupler. The splitting ratios of the above-mentioned first bent directional coupler and the above-mentioned second bent directional coupler are both 50:50, achieving process tolerance.

[0010] According to some embodiments of the present disclosure, the above-mentioned first mode converter and the above-mentioned second mode converter are arranged in a mirror image with the connection point of the above-mentioned first mode converter and the above-mentioned second mode converter as the center. The above-mentioned first mode converter, the above-mentioned second mode converter, the above-mentioned third mode converter, and the above-mentioned fourth mode converter all include an input single-mode waveguide and an output multimode waveguide. The input single-mode waveguide and the output multimode waveguide form a waveguide coupling region, and the waveguide coupling region is used for mode conversion of the above-mentioned optical signal. Among them, the width of the input single-mode waveguide is equal to the width of the wired single-mode waveguide, and the width of the output multimode waveguide is equal to the widths of the above-mentioned first multimode waveguide and the above-mentioned second multimode waveguide.

[0011] According to some embodiments of the present disclosure, the above-mentioned first phase shift arm further includes a first tapered waveguide connected between the above-mentioned second mode converter and the above-mentioned first multimode waveguide and a second tapered waveguide connected between the above-mentioned first multimode waveguide and the above-mentioned wired single-mode waveguide. The above-mentioned second phase shift arm further includes a third tapered waveguide and a fourth tapered waveguide connected between the above-mentioned fourth mode converter and the above-mentioned wired single-mode waveguide. The above-mentioned third tapered waveguide and the above-mentioned fourth tapered waveguide are connected in sequence. The above-mentioned first tapered waveguide, the above-mentioned second tapered waveguide, the above-mentioned third tapered waveguide, and the above-mentioned fourth tapered waveguide are all isosceles trapezoid structures. The width of the upper base of the isosceles trapezoid structure is equal to the width of the wired single-mode waveguide, and the width of the lower base of the isosceles trapezoid structure is equal to the widths of the above-mentioned first multimode waveguide and the above-mentioned second multimode waveguide to achieve adiabatic change.

[0012] According to some embodiments of the present disclosure, the total length of the wired single-mode waveguide of the above-mentioned first phase shift arm is equal to the total length of the wired single-mode waveguide of the above-mentioned second phase shift arm.

[0013] According to some embodiments of the present disclosure, the widths of the above-mentioned first multimode waveguide and the above-mentioned second multimode waveguide are equal.

[0014] According to some embodiments of the present disclosure, the output multimode waveguides of the above-mentioned first mode converter, the above-mentioned second mode converter, the above-mentioned third mode converter, and the above-mentioned fourth mode converter are rectangular or trapezoidal.

[0015] A wavelength division multiplexer provided according to the present disclosure includes a first Mach-Zehnder interferometer, a second Mach-Zehnder interferometer, and a third Mach-Zehnder interferometer. The first Mach-Zehnder interferometer, the second Mach-Zehnder interferometer, and the third Mach-Zehnder interferometer each include a first multimode waveguide and a second multimode waveguide. The length of the first multimode waveguide is greater than the length of the second multimode waveguide. The Mach-Zehnder interferometer module is a cascaded structure of two-level filters to cause optical signals containing multiple wavelengths to interfere and then be output from multiple output optical waveguides respectively to achieve wavelength division multiplexing. Description of the Drawings

[0016] Figure 1 is a structural diagram of a wavelength division multiplexer according to a schematic embodiment of the present disclosure;

[0017] Figure 2 is Figure 1 a structural diagram of a part of the Mach-Zehnder interferometer module of the wavelength division multiplexer of the schematic embodiment shown;

[0018] Figure 3 is Figure 2 a structural diagram of the first bent directional coupler of the Mach-Zehnder interferometer module of the schematic embodiment shown;

[0019] Figure 4 is Figure 2 a structural diagram of a first mode converter of a schematic embodiment shown;

[0020] Figure 5 is Figure 2 a structural diagram of a first mode converter of another schematic embodiment shown;

[0021] In the above-mentioned drawings, the meanings of the reference numerals are specifically as follows:

[0022] 100, input optical waveguide;

[0023] 200, Mach-Zehnder interferometer module;

[0024] 210, first Mach-Zehnder interferometer;

[0025] 211, input port;

[0026] 212. First bending directional coupler;

[0027] 213. First phase shift arm;

[0028] 214. Second phase shift arm;

[0029] 215. Second bending directional coupler;

[0030] 216. First output port;

[0031] 217. Second output port;

[0032] 31. Wiring single-mode waveguide;

[0033] 32. First mode converter;

[0034] 33. Second mode converter;

[0035] 34. First tapered waveguide;

[0036] 35. First multimode waveguide;

[0037] 36. Second tapered waveguide;

[0038] 41. Third mode converter;

[0039] 42. Second multimode waveguide;

[0040] 43. Fourth mode converter;

[0041] 44. Third tapered waveguide;

[0042] 45. Fourth tapered waveguide;

[0043] 51. Bending waveguide coupling region;

[0044] 52. Output port;

[0045] 61. Input single-mode waveguide;

[0046] 62. Waveguide coupling region;

[0047] 63. Output multimode waveguide;

[0048] 220. Second Mach-Zehnder interferometer;

[0049] 230. Third Mach-Zehnder interferometer;

[0050] 300. Output waveguide module;

[0051] 301. First output optical waveguide;

[0052] 302. Second output optical waveguide;

[0053] 303. Third output optical waveguide;

[0054] 304. Fourth output optical waveguide. Detailed implementation manners

[0055] To make the objectives, technical solutions, and advantages of the present disclosure more clear and understandable, the following further describes the present disclosure in detail with reference to specific embodiments and the accompanying drawings.

[0056] The terms used herein are merely for describing specific embodiments and are not intended to limit the present disclosure. The terms "including", "comprising", etc. used herein indicate the presence of the described features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0057] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0058] In the case of using expressions such as "at least one of A, B, and C, etc.", generally, it should be interpreted according to the meaning commonly understood by those skilled in the art. For example, "a system having at least one of A, B, and C" should include, but is not limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C. In the case of using expressions such as "at least one of A, B, or C, etc.", generally, it should be interpreted according to the meaning commonly understood by those skilled in the art. For example, "a system having at least one of A, B, or C" should include, but is not limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C.

[0059] To make the objectives, technical solutions, and advantages of the present disclosure more clear and understandable, the following further describes the present disclosure in detail with reference to specific embodiments and the accompanying drawings.

[0060] Figure 1 is a structural diagram of a wavelength division multiplexer according to an exemplary embodiment of the present disclosure.

[0061] The wavelength division multiplexer provided according to an embodiment of the present disclosure, as Figure 1As shown, the wavelength division multiplexer includes an input optical waveguide 100, a Mach-Zehnder interferometer module 200, and an output waveguide module 300. Among them, the input optical waveguide 100 is used to input an optical signal containing multiple wavelengths to be processed. The Mach-Zehnder interferometer module 200 includes a first Mach-Zehnder interferometer 210, a second Mach-Zehnder interferometer 220, and a third Mach-Zehnder interferometer 230. The input port of the second Mach-Zehnder interferometer 220 is connected to the first output port 216 of the first Mach-Zehnder interferometer 210, and the input port of the third Mach-Zehnder interferometer 230 is connected to the second output port 217 of the first Mach-Zehnder interferometer 210. The output waveguide module 300 includes multiple output optical waveguides. Among them, the first Mach-Zehnder interferometer 210, the second Mach-Zehnder interferometer 220, and the third Mach-Zehnder interferometer 230 all include a first multimode waveguide 35 and a second multimode waveguide 42. The length of the first multimode waveguide 35 is greater than the length of the second multimode waveguide 42. The Mach-Zehnder interferometer module 200 is a cascaded structure of second-order filters to cause the optical signal containing multiple wavelengths to interfere and then output from multiple output optical waveguides respectively, so as to achieve wavelength division multiplexing.

[0062] According to an embodiment of the present disclosure, the widths of the first multimode waveguide 35 and the second multimode waveguide 42 are equal.

[0063] According to an embodiment of the present disclosure, the input optical waveguide 100 inputs the optical signal containing multiple wavelengths to be processed into the first Mach-Zehnder interferometer 210 through the input port 211.

[0064] According to an embodiment of the present disclosure, the output waveguide module 300 includes multiple output optical waveguides, which are a first output optical waveguide 301, a second output optical waveguide 302, a third output optical waveguide 303, and a fourth output optical waveguide 304 respectively.

[0065] According to the wavelength division multiplexer provided by the embodiment of the present disclosure, a cascaded structure of three Mach-Zehnder interferometers can achieve low loss and crosstalk, be insensitive to temperature, and have a large process tolerance.

[0066] According to an embodiment of the present disclosure, the lengths of the first multimode waveguide 35 and the second multimode waveguide 42 are related to the free spectral range of the wavelength division multiplexer. Among them, in response to the change of the lengths of the first multimode waveguide 35 and the second multimode waveguide 42, the values of the free spectral ranges of the first Mach-Zehnder interferometer 210, the second Mach-Zehnder interferometer 220, and the third Mach-Zehnder interferometer 230 change respectively.

[0067] According to an embodiment of the present disclosure, the free spectral range of the wavelength division multiplexer can be specifically expressed as:

[0068]

[0069] Among them, FSR represents the free spectral range, λ represents the central wavelength, and n g1 represents the group refractive index of the first multimode waveguide 35, and n g2 represents the group refractive index of the second multimode waveguide 42, L1 represents the length of the first multimode waveguide 35, and L2 represents the length of the second multimode waveguide 42.

[0070] Meanwhile, to achieve high process tolerance, the lengths of the first multimode waveguide 35 and the second multimode waveguide 42 also need to satisfy:

[0071]

[0072] Among them, n1 represents the effective refractive index of the first multimode waveguide 35, n2 represents the effective refractive index of the second multimode waveguide 42, W1 represents the waveguide width of the first multimode waveguide 35, and W2 represents the waveguide width of the second multimode waveguide 42.

[0073] Figure 2 is Figure 1 a structural diagram of a part of the Mach-Zehnder interferometer module 200 of the wavelength division multiplexer of the schematic embodiment shown.

[0074] According to an embodiment of the present disclosure, as Figure 2 shown, the first Mach-Zehnder interferometer 210, the second Mach-Zehnder interferometer 220, and the third Mach-Zehnder interferometer 230 all further include: a first phase shift arm 213, including a first mode converter 32, a second mode converter 33, and a first multimode waveguide 35 connected in sequence. Among them, the optical signal is converted from the fundamental mode to the first-order mode by the first mode converter 32 in the first phase shift arm 213, and the optical signal is converted from the first-order mode to the fundamental mode by the second mode converter 33 in the first phase shift arm 213, so that the optical signal is transmitted in the first multimode waveguide 35 in the fundamental mode; and a second phase shift arm 214, including a third mode converter 41, a second multimode waveguide 42, and a fourth mode converter 43 connected in sequence. Among them, the optical signal is converted from the fundamental mode to the first-order mode by the third mode converter 41 in the second phase shift arm 214, so that the optical signal is transmitted in the second multimode waveguide 42 in the first-order mode, and the optical signal is converted from the first-order mode to the fundamental mode by the fourth mode converter 43.

[0075] According to an embodiment of the present disclosure, by using the difference in the effective refractive indices of the fundamental mode and the first-order mode varying with the waveguide width, the offset caused by the change in the central wavelength with the waveguide width can be made close to zero, that is, it has high process tolerance.

[0076] According to an embodiment of the present disclosure, the structures of the first mode converter 32 and the second mode converter 33 of the first phase shift arm 213 are the same as those of the third mode converter 41 and the fourth mode converter 43 of the second phase shift arm 214, in order to eliminate the phase difference introduced by the mode converter and ensure that the phase difference between the first phase shift arm 213 and the second phase shift arm 214 is only determined by the first multimode waveguide 35 and the second multimode waveguide 42.

[0077] According to an embodiment of the present disclosure, phase differences are generated in the first phase shift arm 213 and the second phase shift arm 214 by using the fundamental mode and the first-order mode respectively, so as to achieve wavelength division multiplexing with high process tolerance.

[0078] According to an embodiment of the present disclosure, the first Mach-Zehnder interferometer 210, the second Mach-Zehnder interferometer 220, and the third Mach-Zehnder interferometer 230 further include: a first bent directional coupler 212 connected to the first phase shift arm 213 and the second phase shift arm 214 through a wired single-mode waveguide 31; and a second bent directional coupler 215 connected to the first phase shift arm 213 and the second phase shift arm 214 through a wired single-mode waveguide 31; wherein, the first bent directional coupler 212 and the second bent directional coupler 215 are used to combine optical signals and cause interference.

[0079] According to an embodiment of the present disclosure, using the first bent directional coupler 212 and the second bent directional coupler 215 as 3dB splitters has the characteristics of process insensitivity and wavelength insensitivity, further improving the process tolerance of the device and reducing the insertion loss and crosstalk of the device.

[0080] According to an embodiment of the present disclosure, the first phase shift arm 213 further includes a first tapered waveguide 34 connected between the second mode converter 33 and the first multimode waveguide 35 and a second tapered waveguide 36 connected between the first multimode waveguide 35 and the wired single-mode waveguide 31. The second phase shift arm 214 further includes a third tapered waveguide 44 and a fourth tapered waveguide 45 connected between the fourth mode converter 43 and the wired single-mode waveguide 31. The third tapered waveguide 44 and the fourth tapered waveguide 45 are connected in sequence. The first tapered waveguide 34, the second tapered waveguide 36, the third tapered waveguide 44, and the fourth tapered waveguide 45 are all isosceles trapezoid structures. The width of the upper base of the isosceles trapezoid structure is equal to the width of the wired single-mode waveguide 31, and the width of the lower base of the isosceles trapezoid structure is equal to the widths of the first multimode waveguide 35 and the second multimode waveguide 42, so as to achieve adiabatic change.

[0081] According to an embodiment of the present disclosure, the total length of the wired single-mode waveguide 31 of the first phase shift arm 213 is equal to the total length of the wired single-mode waveguide 31 of the second phase shift arm 214.

[0082] According to an embodiment of the present disclosure, the FSR of the first Mach-Zehnder interferometer 210 is 40 nm, and the FSRs of the second Mach-Zehnder interferometer 220 and the third Mach-Zehnder interferometer 230 are 80 nm. An optical signal containing four wavelengths of 1271 nm, 1291 nm, 1311 nm, and 1331 nm is input from the input optical waveguide 100. Two beams of light after passing through the first bent directional coupler 212 generate a phase difference in the first phase shift arm 213 and the second phase shift arm 214, and then are combined and interfered through the second bent directional coupler 215. The optical signals with wavelengths of 1271 nm and 1311 nm are output from the first output port 216 of the first Mach-Zehnder interferometer 210 and enter the second Mach-Zehnder interferometer 220. After a similar process, the optical signal with a wavelength of 1271 nm is output from the first output optical waveguide 301, and the optical signal with a wavelength of 1311 nm is output from the second output optical waveguide 302. Similarly, the optical signals with wavelengths of 1291 nm and 1331 nm are output from the second output port 217 of the first Mach-Zehnder interferometer 210 and enter the third Mach-Zehnder interferometer 230, and the optical signal with a wavelength of 1291 nm is output from the third output optical waveguide 303, and the optical signal with a wavelength of 1331 nm is output from the fourth output optical waveguide 304.

[0083] According to an embodiment of the present disclosure, by using a cascaded structure of three Mach-Zehnder interferometers, low loss and crosstalk, insensitivity to temperature, and large process tolerance can be achieved. Wavelength division multiplexing is realized on the premise of achieving high process tolerance. Wavelength division multiplexing means that optical signals containing multiple wavelengths are respectively output as optical signals with different wavelengths from different output optical waveguides.

[0084] Figure 3 Yes Figure 2 It is a structural diagram of the first bent directional coupler 212 of the Mach-Zehnder interferometer module 200 of the illustrated schematic embodiment.

[0085] According to an embodiment of the present disclosure, as Figure 3 shown, both the first bent directional coupler 212 and the second bent directional coupler 215 include two input ports 211, two concentric arc structure waveguides, and two output ports 52. The centers of the two concentric arc structure waveguides of the first bent directional coupler 212 are symmetric about the horizontal direction with respect to the centers of the two concentric arc structure waveguides of the second bent directional coupler 215. The splitting ratios of both the first bent directional coupler 212 and the second bent directional coupler 215 are 50:50, achieving process tolerance.

[0086] According to an embodiment of the present disclosure, the splitting ratios of the first bent directional coupler 212 and the second bent directional coupler 215 are both 50:50 and remain unchanged within a wide spectral range, having high process tolerance characteristics. The wide spectral range at least includes the range from the minimum wavelength to the maximum wavelength among the four wavelengths of the optical signals to be processed by the wavelength division multiplexer. It can also be two common bands in the field of optical communication, the O band (1260 nm - 1360 nm) and the C band (1530 nm - 1565 nm).

[0087] According to an embodiment of the present disclosure, the bending radii of the bending waveguide coupling regions 51 of the first bent directional coupler 212 and the second bent directional coupler 215 should be large enough, and an S-shaped bending waveguide is used to connect the input port 211 and the output port 52 to reduce the bending loss. By adjusting the bending radius and the bending angle, a splitting ratio of 50:50 within a wide spectral range can be achieved.

[0088] According to an embodiment of the present disclosure, for two concentric arc structure waveguides, the inner arc radius is R1, the outer arc radius is R2, the distance between the inner arc structure waveguide and the outer arc structure waveguide is G, and the waveguide width of the inner arc structure waveguide is F, then R2 = R1 + F + G.

[0089] Figure 4 Yes Figure 2 The structural diagram of the first mode converter 32 of a schematic embodiment shown Figure 5 Yes Figure 2 The structural diagram of the first mode converter 32 of another schematic embodiment shown

[0090] According to an embodiment of the present disclosure, as Figure 2 and Figure 4 shown, the first mode converter 32 and the second mode converter 33 are mirror - symmetrically arranged with the connection point of the first mode converter 32 and the second mode converter 33 as the center. The first mode converter 32, the second mode converter 33, the third mode converter 41, and the fourth mode converter 43 all include an input single - mode waveguide 61 and an output multimode waveguide 63. The input single - mode waveguide 61 and the output multimode waveguide 63 form a waveguide coupling region 62, and the waveguide coupling region 62 is used for mode conversion of optical signals. Among them, the width of the input single - mode waveguide 61 is equal to the width of the routing single - mode waveguide 31, and the width of the output multimode waveguide 63 is equal to the widths of the first multimode waveguide 35 and the second multimode waveguide 42.

[0091] According to an embodiment of the present disclosure, the input single - mode waveguide 61 and the output multimode waveguide 63 are placed in parallel at a certain interval, and the widths of the input single - mode waveguide 61 and the output multimode waveguide 63 satisfy the phase - matching condition.

[0092] According to an embodiment of the present disclosure, as Figure 4 andFigure 5 As shown, the output multimode waveguides 63 of the first mode converter 32, the second mode converter 33, the third mode converter 41, and the fourth mode converter 43 are rectangular or trapezoidal.

[0093] According to an embodiment of the present disclosure, when the output multimode waveguides 63 of the first mode converter 32, the second mode converter 33, the third mode converter 41, and the fourth mode converter 43 are trapezoidal, they have higher process tolerances.

[0094] According to an embodiment of the present disclosure, when the output multimode waveguides 63 of the first mode converter 32, the second mode converter 33, the third mode converter 41, and the fourth mode converter 43 are rectangular, since the waveguide width of the output multimode waveguide 63 is different from the waveguide width of the input single-mode waveguide 61, it can be defined as an asymmetric directional coupler. When the output multimode waveguides 63 of the first mode converter 32, the second mode converter 33, the third mode converter 41, and the fourth mode converter 43 are trapezoidal, the part of the input single-mode waveguide 61 in the waveguide coupling region 62 is rectangular. Since the shapes of the input single-mode waveguide 61 and the output multimode waveguide 63 at the position of the waveguide coupling region 62 are different, it can also be defined as an asymmetric directional coupler.

[0095] According to an embodiment of the present disclosure, the structure of an asymmetric directional coupler is adopted to realize the mutual conversion between the fundamental mode and the first-order mode.

[0096] It should also be noted that the directional terms mentioned in the embodiments, such as "up", "down", "front", "rear", "left", "right", etc., are only references to the directions in the drawings and are not used to limit the protection scope of the present disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. When it may cause confusion in the understanding of the present disclosure, the conventional structures or configurations will be omitted.

[0097] The embodiments of the present disclosure have been described above. However, these embodiments are only for illustrative purposes and not for limiting the scope of the present disclosure. Although the embodiments have been described separately above, this does not mean that the measures in each embodiment cannot be used advantageously in combination. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art can make various substitutions and modifications, and these substitutions and modifications should all fall within the scope of the present disclosure.

Claims

1. A wavelength division multiplexer, characterized in that, Comprising: An input optical waveguide for inputting an optical signal containing multiple wavelengths to be processed; A Mach-Zehnder interferometer module, comprising: A first Mach-Zehnder interferometer, A second Mach-Zehnder interferometer, the input port of which is connected to the first output port of the first Mach-Zehnder interferometer; A third Mach-Zehnder interferometer, the input port of which is connected to the second output port of the first Mach-Zehnder interferometer; An output waveguide module, comprising multiple output optical waveguides; The first Mach-Zehnder interferometer, the second Mach-Zehnder interferometer and the third Mach-Zehnder interferometer all comprise: A first phase-shift arm, comprising a first mode converter, a second mode converter and a first multimode waveguide connected in sequence. The optical signal is converted from the fundamental mode to the first-order mode by the first mode converter in the first phase-shift arm, and the optical signal is converted from the first-order mode to the fundamental mode by the second mode converter in the first phase-shift arm, so that the optical signal is transmitted in the first multimode waveguide in the fundamental mode; A second phase-shift arm, comprising a third mode converter, a second multimode waveguide and a fourth mode converter connected in sequence. The optical signal is converted from the fundamental mode to the first-order mode by the third mode converter in the second phase-shift arm, so that the optical signal is transmitted in the second multimode waveguide in the first-order mode, and the optical signal is converted from the first-order mode to the fundamental mode by the fourth mode converter. The length of the first multimode waveguide is greater than the length of the second multimode waveguide. The Mach-Zehnder interferometer module is a cascaded structure of two-stage filters to cause the optical signal containing multiple wavelengths to interfere and then be output from multiple output optical waveguides respectively, so as to achieve wavelength division multiplexing.

2. The wavelength division multiplexer according to claim 1, characterized in that, The lengths of the first multimode waveguide and the second multimode waveguide are related to the free spectral range of the wavelength division multiplexer. Wherein, in response to the change of the lengths of the first multimode waveguide and the second multimode waveguide, the values of the free spectral ranges of the first Mach-Zehnder interferometer, the second Mach-Zehnder interferometer and the third Mach-Zehnder interferometer change respectively.

3. The wavelength division multiplexer according to claim 1, wherein, The first Mach-Zehnder interferometer, the second Mach-Zehnder interferometer and the third Mach-Zehnder interferometer all further comprise: A first bent directional coupler connected to the first phase-shift arm and the second phase-shift arm through a wired single-mode waveguide; and A second bent directional coupler connected to the first phase-shift arm and the second phase-shift arm through the wired single-mode waveguide; Wherein, the first bent directional coupler and the second bent directional coupler are used to combine the optical signals and cause interference.

4. The wavelength division multiplexer according to claim 3, characterized in that, Both the first bent directional coupler and the second bent directional coupler include two input ports, two concentric arc structure waveguides and two output ports. The centers of the two concentric arc structure waveguides of the first bent directional coupler are symmetric about the horizontal direction with the centers of the two concentric arc structure waveguides of the second bent directional coupler. The splitting ratios of the first bent directional coupler and the second bent directional coupler are both 50:50 to achieve process tolerance.

5. The wavelength division multiplexer according to claim 3, characterized in that, The first mode converter and the second mode converter are arranged in a mirror image with the connection point of the first mode converter and the second mode converter as the center. The first mode converter, the second mode converter, the third mode converter, and the fourth mode converter all include an input single-mode waveguide and an output multimode waveguide. The input single-mode waveguide and the output multimode waveguide form a waveguide coupling region, and the waveguide coupling region is used for mode conversion of the optical signal. Among them, the width of the input single-mode waveguide is equal to the width of the wiring single-mode waveguide, and the width of the output multimode waveguide is equal to the width of the first multimode waveguide and the second multimode waveguide.

6. The wavelength division multiplexer according to claim 3, characterized in that, The first phase shift arm further includes a first tapered waveguide connected between the second mode converter and the first multimode waveguide and a second tapered waveguide connected between the first multimode waveguide and the wiring single-mode waveguide. The second phase shift arm further includes a third tapered waveguide and a fourth tapered waveguide connected between the fourth mode converter and the wiring single-mode waveguide. The third tapered waveguide and the fourth tapered waveguide are connected in sequence. The first tapered waveguide, the second tapered waveguide, the third tapered waveguide, and the fourth tapered waveguide are all isosceles trapezoid structures. The width of the upper base of the isosceles trapezoid structure is equal to the width of the wiring single-mode waveguide, and the width of the lower base of the isosceles trapezoid structure is equal to the width of the first multimode waveguide and the second multimode waveguide to achieve adiabatic change.

7. The wavelength division multiplexer according to claim 3, wherein The total length of the wiring single-mode waveguide of the first phase shift arm is equal to the total length of the wiring single-mode waveguide of the second phase shift arm.

8. The wavelength division multiplexer according to claim 3, wherein The width of the first multimode waveguide is equal to the width of the second multimode waveguide.

9. The wavelength division multiplexer according to claim 5, wherein The output multimode waveguides of the first mode converter, the second mode converter, the third mode converter, and the fourth mode converter are rectangular or trapezoidal.

Images