A three-mode multiplexer and an adjustable-mode multiplexer

Abstract

The present invention discloses a three-mode multiplexer and a tunable mode multiplexer. The tunable mode multiplexer includes a multimode interferometer, a phase shifter, and a three-mode multiplexer. The three-mode multiplexer includes a first waveguide, a second waveguide, and a third waveguide. The second waveguide is located between the first waveguide and the third waveguide. The first waveguide, the second waveguide, and the third waveguide form a coupling region. The width of the second waveguide gradually increases from narrow to wide along a first direction, and the widths of the first waveguide and the third waveguide gradually decrease from wide to narrow along the first direction. The first output port of the multimode interferometer is connected to the first port of the three-mode multiplexer, and the second output port of the multimode interferometer is connected to the third port of the three-mode multiplexer. A phase shifter is provided between the first port or the third port of the three-mode multiplexer and the multimode interferometer. By using the tunable mode multiplexer of the present invention, through phase regulation, the TE0 mode can be converted into the TE1 mode or the TE2 mode, realizing controllable adjustment of mode conversion.

Description

Technical Field

[0001] The present invention relates to the field of integrated optoelectronic technology, and more particularly to a three-mode multiplexer and a tunable mode multiplexer. Background Art

[0002] With the development of technologies such as big data and cloud computing, the communication data traffic has increased sharply, and the communication technology is upgrading to ultra-wideband. Wavelength division multiplexing technology and mode multiplexing technology are considered two main ways to increase the communication bandwidth. At present, wavelength division multiplexing technology has been widely applied, but mode multiplexing technology is still in the research stage, and its bottleneck lies in the generation and regulation of modes.

[0003] In mode multiplexing technology, multiple signals need to be coupled into one channel. To avoid coherence, the multiple signals coupled into the same channel need to exist in different modes, so a mode multiplexer is required. The structure of a common mode multiplexer based on directional coupling is as Figure 1 shown. The TE0 mode light of a certain channel is coupled into the main channel through the mode multiplexer, and at the same time its mode is changed from the TE0 mode to the TE1 mode. Based on this directional-coupling mode multiplexer, the multiplexing and demultiplexing of multiple modes such as TE0, TE1, and TE2 can already be realized. However, in these mode multiplexers, a certain stage of mode multiplexer can only realize the conversion from TE0 to a certain specific high-order mode, and cannot be changed to other high-order modes. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art, and provides a three-mode multiplexer and a tunable mode multiplexer. Through phase regulation, the TE0 mode can be converted into the TE1 mode or the TE2 mode, realizing the controllable adjustment of mode conversion.

[0005] The technical solution of the present invention is implemented as follows: The present invention discloses a three-mode multiplexer, which includes a first waveguide, a second waveguide, and a third waveguide. The second waveguide is located between the first waveguide and the third waveguide, and the first waveguide, the second waveguide, and the third waveguide form a coupling region. The width of the second waveguide gradually becomes wider along a first direction, and the widths of the first waveguide and the third waveguide gradually become narrower along the first direction;

[0006] One end of the second waveguide is connected to a second port, and the other end of the second waveguide is connected to a fourth port. One end of the first waveguide close to the second port is connected to a first port, and one end of the third waveguide close to the second port is connected to a third port;

[0007] The first direction is the direction pointing from the second port to the fourth port.

[0008] Further, the lengths of the first waveguide, the second waveguide, and the third waveguide extend along the first direction.

[0009] Further, the first waveguide, the second waveguide, and the third waveguide are arranged side by side; the gap width between the second waveguide and the first waveguide remains unchanged along the first direction, the gap width between the second waveguide and the third waveguide remains unchanged along the first direction, and the gap width between the second waveguide and the first waveguide is equal to the gap width between the second waveguide and the third waveguide.

[0010] Further, the gap width between the second waveguide and the first waveguide and the gap width between the second waveguide and the third waveguide are both 200 - 300 nm;

[0011] Or / and,

[0012] The length of the coupling region is 30 - 100 μm.

[0013] Further, the first waveguide, the second waveguide, and the third waveguide are all tapered waveguides;

[0014] Or / and,

[0015] The first waveguide is exactly the same as the third waveguide, and the coupling region is symmetrically arranged along the longitudinal center line of the second waveguide.

[0016] Further, when TE0 mode light is input at the second port, TE0 mode light is output at the fourth port; when TE0 mode light is input at the first port and the third port simultaneously, and the two TE0 mode lights have a phase difference of π, TE1 mode light is output at the fourth port; when TE0 mode light is input at the first port and the third port simultaneously, and the two TE0 mode lights are in phase, only TE2 mode light is output at the fourth port;

[0017] When TE0 mode light is input at the fourth port, TE0 mode light is output at the second port; when TE1 mode light is input at the fourth port, TE0 mode light is output at the first port and the third port, and the two beams of light have a phase difference of π; when TE2 mode light is input at the fourth port, TE0 mode light is output at the first port and the third port, and the two beams of light are in phase.

[0018] The present invention discloses an adjustable mode multiplexer, which includes an equal - power splitter coupler, a phase shifter, and the three - mode multiplexer as described above. The equal - power splitter coupler is provided with a first input port, a second input port, a first output port, and a second output port. The first output port of the equal - power splitter coupler is connected to the first port of the three - mode multiplexer, the second output port of the equal - power splitter coupler is connected to the third port of the three - mode multiplexer, and a phase shifter is provided between the first port and / or the third port of the three - mode multiplexer and the equal - power splitter coupler.

[0019] Further, the adjustable mode multiplexer of the present invention further includes a TE1 mode filter, and one end of the TE1 mode filter is connected to the second port of the three - mode multiplexer.

[0020] Further, the TE1 mode filter includes a section of curved waveguide for filtering out the high-order modes emerging from the second port of the three-mode multiplexer.

[0021] Further, the phase shifter is used to generate a phase difference of π or 0 between the first port and the third port of the three-mode multiplexer for the signal.

[0022] Further, the equal-power splitter coupler is a two-in-two-out multimode interferometer. A phase shifter is provided between the first port of the three-mode multiplexer and the first output port or the second output port of the multimode interferometer. When the phase shift amount of the phase shifter is such that the first optical signal of TE0 mode input from the second port of the three-mode multiplexer remains the TE0 mode optical signal when output from the fourth port of the three-mode multiplexer; the second optical signal of TE0 mode input from the first input port of the multimode interferometer becomes the TE2 mode optical signal when output from the fourth port of the three-mode multiplexer; the third optical signal of TE0 mode input from the second input port of the multimode interferometer becomes the TE1 mode optical signal when output from the fourth port of the three-mode multiplexer;

[0023] When the phase shift amount of the phase shifter is such that the first optical signal of TE0 mode input from the second port of the three-mode multiplexer remains the TE0 mode optical signal when output from the fourth port of the three-mode multiplexer; the second optical signal of TE0 mode input from the first input port of the multimode interferometer becomes the TE1 mode optical signal when output from the fourth port of the three-mode multiplexer; the third optical signal of TE0 mode input from the second input port of the multimode interferometer becomes the TE2 mode optical signal when output from the fourth port of the three-mode multiplexer;

[0024] When the phase shift amount of the phase shifter and the optical signals of TE0 / TE1 / TE2 modes are all input from the fourth port of the three-mode multiplexer simultaneously, the input TE0 mode optical signal will be output from the second port of the three-mode multiplexer and remains the TE0 mode, becoming the first optical signal; the input TE2 mode optical signal will be output from the first input port of the multimode interferometer and becomes the TE0 mode, becoming the second optical signal; the input TE1 mode optical signal will be output from the second input port of the multimode interferometer and becomes the TE0 mode, becoming the third optical signal;

[0025] When the phase shift amount of the phase shifter When, and when the lights of TE0 / TE1 / TE2 three modes are simultaneously input from the fourth port of the three-mode multiplexer, the input TE0-mode light will be output from the second port of the three-mode multiplexer and remains in the TE0 mode, becoming the first optical signal; the input TE1-mode light will be output from the first input port of the multimode interferometer and is converted to the TE0 mode, becoming the second optical signal, and the input TE2-mode light will be output from the second input port of the multimode interferometer and is converted to the TE0 mode, becoming the third optical signal.

[0026] Further, the equal-power splitter coupler is a two-in-two-out multimode interferometer, and a phase shifter is provided between the third port of the three-mode multiplexer and the second output port of the multimode interferometer. When the phase shift amount of the phase shifter When, the TE0-mode first optical signal input from the second port of the three-mode multiplexer remains in the TE0 mode when output from the fourth port of the three-mode multiplexer; the TE0-mode second optical signal input from the first input port of the multimode interferometer is converted to the TE1 mode when output from the fourth port of the three-mode multiplexer; the TE0-mode third optical signal input from the second input port of the multimode interferometer is converted to the TE2 mode when output from the fourth port of the three-mode multiplexer;

[0027] When the phase shift amount of the phase shifter When, the TE0-mode first optical signal input from the second port of the three-mode multiplexer remains in the TE0 mode when output from the fourth port of the three-mode multiplexer; the TE0-mode second optical signal input from the first input port of the multimode interferometer is converted to the TE2 mode when output from the fourth port of the three-mode multiplexer; the TE0-mode third optical signal input from the second input port of the multimode interferometer is converted to the TE1 mode when output from the fourth port of the three-mode multiplexer;

[0028] When the phase shift amount of the phase shifter When, and when the lights of TE0 / TE1 / TE2 three modes are simultaneously input from the fourth port of the three-mode multiplexer, the input TE0-mode light will be output from the second port of the three-mode multiplexer and remains in the TE0 mode, becoming the first optical signal; the input TE1-mode light will be output from the first input port of the multimode interferometer and is converted to the TE0 mode, becoming the second optical signal; the input TE2-mode light will be output from the second input port of the multimode interferometer and is converted to the TE0 mode, becoming the third optical signal;

[0029] When the phase shift amount of the phase shifter When, and when the lights of TE0 / TE1 / TE2 modes are simultaneously input from the fourth port of the three-mode multiplexer, the input TE0-mode light will be output from the second port of the three-mode multiplexer and remain in the TE0 mode, becoming the first optical signal; the input TE2-mode light will be output from the first input port of the multimode interferometer and be converted to the TE0 mode, becoming the second optical signal, and the input TE1-mode light will be output from the second input port of the multimode interferometer and be converted to the TE0 mode, becoming the third optical signal.

[0030] Compared with the prior art, the present invention has the following beneficial effects: The three-mode multiplexer of the present invention is composed of three adjacent tapered waveguides and can achieve mode conversions of TE0-TE0, TE0-TE1, and TE0-TE2.

[0031] The tunable mode multiplexer of the present invention includes a three-mode multiplexer, a 2x2 MMI (multimode interferometer), a TE1 mode filter, and a phase shifter. This device can achieve multiplexing and demultiplexing of TE0, TE1, and TE2 modes, and by controlling the phase shift amount of the phase shifter, the TE0 mode can be converted to the TE1 mode or the TE2 mode, realizing controllable adjustment of mode conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic diagram of a conventional mode multiplexer;

[0033] Figure 2 is a schematic structural diagram of the three-mode multiplexer provided by an embodiment of the present invention;

[0034] Figure 3 is a schematic diagram of the optical mode change between the second port and the fourth port of the three-mode multiplexer provided by an embodiment of the present invention;

[0035] Figure 4 is a schematic diagram of the change between the first port, 3, and the fourth port of the three-mode multiplexer provided by an embodiment of the present invention between TE0 and TE1 modes;

[0036] Figure 5 is a schematic diagram of the change between the first port, 3, and the fourth port of the three-mode multiplexer provided by an embodiment of the present invention between TE0 and T2 modes;

[0037] Figure 6 is the phase shift amount of the phase shifter is a schematic diagram of the three-mode multiplexing of the tunable mode multiplexer when the phase shift amount of the phase shifter is π / 2;

[0038] Figure 7 is the phase shift amount of the phase shifter is a schematic diagram of the mode distribution when the signal 1 input from the fifth port of the tunable mode multiplexer reaches the fourth port when the phase shift amount of the phase shifter is π / 2;

[0039] Figure 8 is the phase shift amount of the phase shifter When it is π / 2, it is a schematic diagram of the mode distribution when the signal 2 input from the sixth port of the tunable mode multiplexer reaches the fourth port;

[0040] Figure 9 is the phase shift amount of the phase shifter When it is π / 2, it is a schematic diagram of the mode distribution when the signal 3 input from the seventh port of the tunable mode multiplexer reaches the fourth port;

[0041] Figure 10 is the phase shift amount of the phase shifter When it is -π / 2, it is a schematic diagram of three-mode multiplexing of the tunable mode multiplexer;

[0042] Figure 11 is the phase shift amount of the phase shifter When it is -π / 2, it is a schematic diagram of the mode distribution when the signal 1 input from the fifth port of the tunable mode multiplexer reaches the fourth port;

[0043] Figure 12 is the phase shift amount of the phase shifter When it is -π / 2, it is a schematic diagram of the mode distribution when the signal 2 input from the sixth port of the tunable mode multiplexer reaches the fourth port;

[0044] Figure 13 is the phase shift amount of the phase shifter When it is -π / 2, it is a schematic diagram of the mode distribution when the signal 3 input from the seventh port of the tunable mode multiplexer reaches the fourth port;

[0045] Figure 14 is the phase shift amount of the phase shifter When it is π / 2, it is a schematic diagram of three-mode demultiplexing of the tunable mode multiplexer;

[0046] Figure 15 is the phase shift amount of the phase shifter When it is π / 2, it is a schematic diagram of the distribution when the TE0 mode light input from the fourth port of the tunable mode multiplexer becomes the signal 1, signal 2, and signal 3 of the TE0 mode when reaching the fifth, sixth, and seventh ports;

[0047] Figure 16 is the phase shift amount of the phase shifter When it is π / 2, it is a schematic diagram of the distribution when the TE1 mode light input from the fourth port of the tunable mode multiplexer becomes the signal 1, signal 2, and signal 3 of the TE0 mode when reaching the fifth, sixth, and seventh ports;

[0048] Figure 17 is the phase shift amount of the phase shifter Schematic diagram of the distribution of signal 1, signal 2, and signal 3 in TE0 mode when the TE2 mode light input at the fourth port of the tunable mode multiplexer becomes TE0 mode when reaching the fifth, sixth, and seventh ports when the phase shift amount is π / 2;

[0049] Figure 18 is the phase shift amount of the phase shifter Schematic diagram of the demultiplexing of three modes of the tunable mode multiplexer when the phase shift amount is -π / 2;

[0050] Figure 19 Phase shift amount of the phase shifter Schematic diagram of the distribution of signal 1, signal 2, and signal 3 in TE0 mode when the TE0 mode light input at the fourth port of the tunable mode multiplexer becomes TE0 mode when reaching the fifth, sixth, and seventh ports when the phase shift amount is -π / 2;

[0051] Figure 20 Phase shift amount of the phase shifter Schematic diagram of the distribution of signal 1, signal 2, and signal 3 in TE0 mode when the TE1 mode light input at the fourth port of the tunable mode multiplexer becomes TE0 mode when reaching the fifth, sixth, and seventh ports when the phase shift amount is -π / 2;

[0052] Figure 21 Phase shift amount of the phase shifter Schematic diagram of the distribution of signal 1, signal 2, and signal 3 in TE0 mode when the TE2 mode light input at the fourth port of the tunable mode multiplexer becomes TE0 mode when reaching the fifth, sixth, and seventh ports when the phase shift amount is -π / 2.

[0053] In the attached drawings, 1 is the first waveguide, 2 is the second waveguide, and 3 is the third waveguide. Detailed implementation manners

[0054] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with the attached drawings and specific implementation manners.

[0055] Unless otherwise defined, technical or scientific terms used in this invention shall have the ordinary meanings as understood by those of ordinary skill in the field to which this invention pertains. The "first", "second" and similar terms used in this invention do not denote any order, quantity or importance, but are merely used to distinguish different components. Similarly, terms such as "a", "an" or "the" do not denote a limitation of quantity, but rather indicate the presence of at least one. Words such as "comprising" or "including" mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Upper", "lower", "left", "right", etc. are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0056] In the respective drawings, the same elements are denoted by like reference numerals. For the sake of clarity, not all parts in the drawings are drawn to scale. In addition, some well-known parts may not be shown in the figures.

[0057] Many specific details of this invention are described hereinafter, such as the structure, materials, dimensions, processing techniques and technologies of components, in order to understand this invention more clearly. However, as those skilled in the art can understand, this invention can be implemented without these specific details.

[0058] Embodiment 1

[0059] Refer to Figures 2 to 5 , an embodiment of this invention provides a three-mode multiplexer, which includes a first waveguide 1, a second waveguide 2 and a third waveguide 3. The second waveguide 2 is located between the first waveguide 1 and the third waveguide 3. The first waveguide 1, the second waveguide 2 and the third waveguide 3 form a coupling region. The width of the second waveguide becomes wider along a first direction, and the widths of the first waveguide and the third waveguide become narrower along the first direction.

[0060] This three-mode multiplexer has 4 ports. Among them, one end of the second waveguide is connected to the second port, and the other end of the second waveguide is connected to the fourth port. One end of the first waveguide close to the second port is connected to the first port, and one end of the third waveguide close to the second port is connected to the third port;

[0061] The first direction is the direction pointing from the second port to the fourth port.

[0062] Further, the first waveguide, the second waveguide and the third waveguide are arranged side by side, and the lengths of the first waveguide, the second waveguide and the third waveguide extend along the first direction.

[0063] Furthermore, the gap width between the second waveguide and the first waveguide remains unchanged along the first direction, the gap width between the second waveguide and the third waveguide remains unchanged along the first direction, the gap width between the first waveguide and the third waveguide becomes wider from narrow along the first direction, and the gap width between the second waveguide and the first waveguide is equal to the gap width between the second waveguide and the third waveguide.

[0064] The core part of the three-mode multiplexer of the present invention is a coupling region composed of three adjacent waveguides. The coupling region is symmetrically arranged along the longitudinal center line of the second waveguide (i.e., the center line along the length direction). The first waveguide, the second waveguide, and the third waveguide are all tapered waveguides. And the first waveguide and the third waveguide are exactly the same.

[0065] Furthermore, the gap width between the second waveguide and the first waveguide and the gap width between the second waveguide and the third waveguide are of the same width W5. The gap width W5 is 200 - 300 nm.

[0066] Furthermore, the length of the coupling region is 30 - 100 um.

[0067] In some embodiments, the minimum width W1 of the second waveguide in the coupling region is 920 nm, and the maximum width W2 is 1900 nm. The minimum width W4 of the first waveguide and the third waveguide in the coupling region is 220 nm, and the maximum width W3 is 650 nm.

[0068] The optical transmission characteristics of the three-mode multiplexer of the present invention are as Figures 3 to 5 shown. First, consider the case where light enters from the left port and exits from the right port. When TE0 mode light is input at the second port, TE0 mode light is output at the fourth port; when TE0 mode light is input at the first port and the third port simultaneously, and the two TE0 mode lights have a phase difference of π, TE1 mode light is output at the fourth port; when TE0 mode light is input at the first port and the third port simultaneously, and the two TE0 mode lights have the same phase, only TE2 mode light is output at the fourth port;

[0069] The three-mode multiplexer of the present invention has optical path reversibility. When TE0 mode light is input at the fourth port, TE0 mode light is output at the second port; when TE1 mode light is input at the fourth port, TE0 mode light is output at the first port and the third port, and the two beams of light have a phase difference of π; when TE2 mode light is input at the fourth port, TE0 mode light is output at the first port and the third port, and the two beams of light have the same phase.

[0070] Embodiment 2

[0071] See Figure 6 and Figure 10, an embodiment of the present invention discloses an adjustable mode multiplexer, which includes an equal-power splitter coupler, a phase shifter, and a three-mode multiplexer as described in Embodiment 1. The equal-power splitter coupler is provided with a first input port, a second input port, a first output port, and a second output port. The first output port of the equal-power splitter coupler is connected to the first port of the three-mode multiplexer, and the second output port of the equal-power splitter coupler is connected to the third port of the three-mode multiplexer. A phase shifter is provided between the first port or / and the third port of the three-mode multiplexer and the equal-power splitter coupler, for enabling an adjustable phase difference of π or 0 to be generated between the first port and the third port of the three-mode multiplexer for signals.

[0072] In the present invention, the first input port of the equal-power splitter coupler is the sixth port of the adjustable mode multiplexer, and the second input port of the equal-power splitter coupler is the seventh port of the adjustable mode multiplexer.

[0073] The equal-power splitter coupler is used to divide the signal input from the first input port of the equal-power splitter coupler into two paths and output them respectively from the first output port and the second output port, and the signal output from the second output port has a phase larger than that of the signal output from the first output port by π / 2.

[0074] The equal-power splitter coupler is used to divide the signal input from the second input port of the equal-power splitter coupler into two paths and output them respectively from the first output port and the second output port, and the signal output from the first output port has a phase larger than that of the signal output from the second output port by π / 2.

[0075] Further, the equal-power splitter coupler may be, but is not limited to, a 2x2 multimode interferometer (2x2 MMI). The equal-power splitter coupler may also be a 2x2 3dB directional coupler and other optical 3dB power splitters, etc.

[0076] Further, the adjustable mode multiplexer of the present invention further includes a TE1 mode filter. One end of the TE1 mode filter is connected to the second port of the three-mode multiplexer, and the other end of the TE1 mode filter is the fifth port.

[0077] Further, the TE1 mode filter includes a section of curved waveguide for filtering out high-order modes coming out of the second port of the three-mode multiplexer.

[0078] When signals 1, 2, and 3 in TE0 mode enter from the fifth port, the sixth port, and the seventh port of the adjustable mode multiplexer respectively, the adjustable mode multiplexer can implement an optical mode adjustable mode multiplexing function. Three optical signals (i.e., the first optical signal, the second optical signal, and the third optical signal) can be transmitted simultaneously, realizing the transmission of the three optical signals in three modes of TE0 / TE1 / TE2 in the same waveguide, that is, realizing mode multiplexing.

[0079] In some embodiments, the equal-power splitter / combiner is a two-input two-output multimode interferometer. A phase shifter is provided between the first port of the three-mode multiplexer and the first output port of the multimode interferometer. When the phase shift amount of the phase shifter is, the first optical signal of TE0 mode input from the second port of the three-mode multiplexer remains TE0 mode when output from the fourth port of the three-mode multiplexer; the second optical signal of TE0 mode input from the first input port of the multimode interferometer becomes TE2 mode when output from the fourth port of the three-mode multiplexer; the third optical signal of TE0 mode input from the second input port of the multimode interferometer becomes TE1 mode when output from the fourth port of the three-mode multiplexer;

[0080] When the phase shift amount of the phase shifter is, the first optical signal of TE0 mode input from the second port of the three-mode multiplexer remains TE0 mode when output from the fourth port of the three-mode multiplexer; the second optical signal of TE0 mode input from the first input port of the multimode interferometer becomes TE1 mode when output from the fourth port of the three-mode multiplexer; the third optical signal of TE0 mode input from the second input port of the multimode interferometer becomes TE2 mode when output from the fourth port of the three-mode multiplexer;

[0081] When the phase shift amount of the phase shifter and the light of TE0 / TE1 / TE2 three modes are simultaneously input from the fourth port of the three-mode multiplexer, the input TE0 mode light will be output from the second port of the three-mode multiplexer and remains TE0 mode, becoming the first optical signal; the input TE2 mode light will be output from the first input port of the multimode interferometer and becomes TE0 mode, becoming the second optical signal; the input TE1 mode light will be output from the second input port of the multimode interferometer and becomes TE0 mode, becoming the third optical signal;

[0082] When the phase shift amount of the phase shifter is, and the light of TE0 / TE1 / TE2 three modes are simultaneously input from the fourth port of the three-mode multiplexer, the input TE0 mode light will be output from the second port of the three-mode multiplexer and remains TE0 mode, becoming the first optical signal; the input TE1 mode light will be output from the first input port of the multimode interferometer and becomes TE0 mode, becoming the second optical signal, and the input TE2 mode light will be output from the second input port of the multimode interferometer and becomes TE0 mode, becoming the third optical signal.

[0083] In some other embodiments, the equal-power splitter / combiner is a two-input two-output multimode interferometer. A phase shifter is provided between the third port of the three-mode multiplexer and the second output port of the multimode interferometer. When the phase shift amount of the phase shifter When the phase shift amount of the phase shifter is

[0084] When the phase shift amount of the phase shifter is the first optical signal of TE0 mode input from the second port of the three-mode multiplexer remains the TE0 mode optical signal when output from the fourth port of the three-mode multiplexer; the second optical signal of TE0 mode input from the first input port of the multimode interferometer is converted into the TE1 mode optical signal when output from the fourth port of the three-mode multiplexer; the third optical signal of TE0 mode input from the second input port of the multimode interferometer is converted into the TE2 mode optical signal when output from the fourth port of the three-mode multiplexer;

[0085] When the phase shift amount of the phase shifter is and the optical signals of TE0 / TE1 / TE2 modes are all input from the fourth port of the three-mode multiplexer simultaneously, the input TE0 mode optical signal will be output from the second port of the three-mode multiplexer and remains the TE0 mode, becoming the first optical signal; the input TE1 mode optical signal will be output from the first input port of the multimode interferometer and is converted into the TE0 mode, becoming the second optical signal; the input TE2 mode optical signal will be output from the second input port of the multimode interferometer and is converted into the TE0 mode, becoming the third optical signal.

[0086] When the phase shift amount of the phase shifter is and the optical signals of TE0 / TE1 / TE2 modes are all input from the fourth port of the three-mode multiplexer simultaneously, the input TE0 mode optical signal will be output from the second port of the three-mode multiplexer and remains the TE0 mode, becoming the first optical signal; the input TE2 mode optical signal will be output from the first input port of the multimode interferometer and is converted into the TE0 mode, becoming the second optical signal, and the input TE1 mode optical signal will be output from the second input port of the multimode interferometer and is converted into the TE0 mode, becoming the third optical signal.

[0087] As Figure 6 shown, the equal-power splitter coupler in this embodiment is a two-in-two-out multimode interferometer (2x2 MMI). A phase shifter is provided between the first output port of the 2x2 MMI and the first port of the three-mode multiplexer. When the phase shift amount of the phase shifter is When the signal 2 input from the first input port of the 2x2 MMI passes through the 2x2 MMI, it is divided into path 1 (i.e., the path between the first output port of the 2x2 MMI and the first port of the three-mode multiplexer) and path 2 (i.e., the path between the second output port of the 2x2 MMI and the third port of the three-mode multiplexer). Due to the phase characteristics of the 2x2 MMI, the phase of path 2 is larger than that of path 1 by π / 2. After passing through the phase shifter, since the phase shifter adds π / 2 to path 1, the phases of the signal 2 when reaching the first port and the third port of the three-mode multiplexer are the same. As Figure 5 shown, when two TE0 signals with the same phase enter the first port and the third port of the three-mode multiplexer respectively, the fourth port will output TE2 mode light. Therefore, Figure 6 the light of the signal 2 in

[0088] becomes TE2 mode at the fourth port. Figure 4 From the second input port of the 2x2 MMI, after the signal 3 passes through the 2x2 MMI, the phase of path 1 is larger than that of path 2 by π / 2. After passing through the phase shifter, the phase on path 1 increases by another π / 2. Therefore, the phases of the signal 3 when reaching the first port and the third port of the three-mode multiplexer differ by π. As Figure 6 shown, when two TE0 signals with a phase difference of π enter the first port and the third port of the three-mode multiplexer respectively, the fourth port will output TE1 mode light. Therefore,

[0089] the light of the signal 3 in Figure 3 becomes TE1 mode at the fourth port. Figure 6 The signal 1 in TE0 mode remains in TE0 mode after passing through the TE1 mode filter. As Figure 3 shown, when the light in TE0 mode enters the second port of the three-mode multiplexer, the light output from the fourth port remains in TE0 mode. Therefore, Figure 6 the light of the signal 1 in

[0090] Figures 7 - 9 respectively illustrate the phase shift amounts of the phase shifter when the mode ratios of the signals 1, 2, and 3 at the fourth port are shown. Specifically, Figure 7 illustrates the phase shift amount of the phase shifter when it is π / 2, the mode distribution of the signal 1 input from the fifth port of the tunable mode multiplexer when reaching the fourth port. Figure 8 illustrates the phase shift amount of the phase shifter when it is π / 2, the mode distribution of the signal 2 input from the first input port of the 2x2 MMI when reaching the fourth port. Figure 9 illustrates the phase shift amount of the phase shifter when it is π / 2, the mode distribution of the signal 3 input from the second input port of the 2x2 MMI when reaching the fourth port. From Figure 7It can be seen that the signal 1 is mainly in the TE0 mode at the fourth port. The insertion loss of the signal 1 in the TE0 mode within the entire O-band of 1260 nm - 1360 nm is 0.3 dB. At the same time, about -12.5 dB of the light of the signal 1 will be converted into the TE2 mode. The light of this part of the signal 1 will cause crosstalk to the signal 2 that is also converted into the TE2 mode, and the crosstalk intensity is -12.5 dB. From Figure 8 it can be seen that the signal 2 is mainly in the TE2 mode at the fourth port. The maximum insertion loss of the signal 2 in the TE2 mode within the entire O-band of 1260 nm - 1360 nm is 1.2 dB. At the same time, about -12.8 dB of the light of the signal 2 will be converted into the TE0 mode. The light of this part of the signal 2 will cause crosstalk to the signal 1 that is also in the TE0 mode, and the crosstalk intensity is -12.8 dB. From Figure 9 it can be seen that the signal 3 is mainly in the TE1 mode at the fourth port. The maximum insertion loss of the signal 3 in the TE1 mode within the entire O-band of 1260 nm - 1360 nm is 0.8 dB. At the same time, about -40 dB of the light of the signal 2 will be converted into the TE2 mode. Although this part of the light will also cause crosstalk to the signal 2 in the TE2 mode, since the crosstalk is too small, it can be ignored.

[0091] When the phase shift amount of the phase shifter is Figure 10 as shown, after the signal 2 input from the first input port of the 2x2 MMI passes through the 2x2 MMI and the phase shifter, the phase difference when reaching the first port and the third port of the three-mode multiplexer is π. Therefore, Figure 10 the light of the signal 2 in Figure 10 becomes the TE1 mode at the fourth port. After the signal 3 input from the second input port of the 2x2 MMI passes through the 2x2 MMI and the phase shifter, the phase difference when reaching the first port and the third port of the three-mode multiplexer is 0. Therefore, Figure 10 and Figure 6 the light of the signal 3 in Figure 11 becomes the TE2 mode at the fourth port. The path of the signal 1 in and Figure 12 remains unchanged, so it still remains in the TE0 mode. shows the mode distribution of the signal 1 input from the fifth port of the tunable mode multiplexer when reaching the fourth port when the phase shift amount of the phase shifter Figure 13 is -π / 2. shows the mode distribution of the signal 2 input from the first input port of the 2x2 MMI when reaching the fourth port when the phase shift amount of the phase shifter Figure 11It can be seen that signal 1 is mainly in the TE0 mode at the fourth port. The insertion loss of signal 1 in the TE0 mode within the entire O band from 1260 nm to 1360 nm is 0.3 dB, and at the same time, it will cause -12.5 dB of crosstalk to signal 3 in the TE2 mode. From Figure 12 It can be seen that signal 2 is mainly in the TE1 mode at the fourth port. The maximum insertion loss of signal 2 in the TE1 mode within the entire O band from 1260 nm to 1360 nm is 0.8 dB, and the crosstalk to other signals is less than -40 dB and can be ignored. From Figure 13 It can be seen that signal 3 is mainly in the TE2 mode at the fourth port. The maximum insertion loss of signal 2 in the TE1 mode within the entire O band from 1260 nm to 1360 nm is 1.2 dB, and at the same time, it will cause -12.8 dB of crosstalk to signal 1 in the TE0 mode.

[0092] When the light in the TE0, TE1, and TE2 modes enters from the fourth port of the tunable mode multiplexer, the tunable mode multiplexer can realize the tunable mode demultiplexing function.

[0093] When the phase shift amount of the phase shifter is Figure 14 as shown, the TE0 mode optical signals coming out of the fifth, sixth, and seventh ports are defined as signals 1, 2, and 3. When the light containing the TE0, TE1, and TE2 modes enters the tunable mode multiplexer from the fourth port, the light in the TE0 mode becomes signal 1, the light in the TE2 mode becomes signal 2, and the light in the TE1 mode becomes signal 3. Figure 15 Schematically shows that when the phase shift amount of the phase shifter is π / 2, the distribution of the TE0 mode light input at the fourth port of the tunable mode multiplexer becoming signals 1, 2, and 3 in the TE0 mode when reaching the fifth, sixth, and seventh ports. Figure 16 Schematically shows that when the phase shift amount of the phase shifter is π / 2, the distribution of the TE1 mode light input at the fourth port of the tunable mode multiplexer becoming signals 1, 2, and 3 in the TE0 mode when reaching the fifth, sixth, and seventh ports. Figure 17 Schematically shows that when the phase shift amount of the phase shifter is π / 2, the distribution of the TE2 mode light input at the fourth port of the tunable mode multiplexer becoming signals 1, 2, and 3 in the TE0 mode when reaching the fifth, sixth, and seventh ports. From Figure 15 It can be seen that most of the TE0 mode light entering from the fourth port is converted into signal 1, with a loss of about 0.3 dB. At the same time, -12.8 dB of light is converted into signal 2, forming crosstalk to signal 2. From Figure 16It can be seen that most of the TE1 mode light entering the fourth port is converted into signal 3, with a loss of about 0.8 dB. At the same time, light with a power less than -40 dB is converted into signal 2, forming crosstalk to signal 2. This crosstalk is too small to be ignored. From Figure 17 It can be seen that most of the TE2 mode light entering the fourth port is converted into signal 2, with a loss of about 1.2 dB. At the same time, light with a power less than -12.5 dB is converted into signal 1, forming crosstalk to signal 1.

[0094] When the phase shift amount of the phase shifter is Figure 18 as shown, the light of TE0 mode becomes signal 1, the light of TE1 mode becomes signal 2, and the light of TE2 mode becomes signal 3. Figure 19 Illustrates the phase shift amount of the phase shifter is -π / 2, the distribution of the TE0 mode light input from the fourth port of the tunable mode multiplexer becoming signal 1, signal 2, and signal 3 of TE0 mode when reaching the fifth port, sixth port, and seventh port. Figure 20 Illustrates the phase shift amount of the phase shifter is -π / 2, the distribution of the TE1 mode light input from the fourth port of the tunable mode multiplexer becoming signal 1, signal 2, and signal 3 of TE0 mode when reaching the fifth port, sixth port, and seventh port. Figure 21 Illustrates the phase shift amount of the phase shifter is -π / 2, the distribution of the TE2 mode light input from the fourth port of the tunable mode multiplexer becoming signal 1, signal 2, and signal 3 of TE0 mode when reaching the fifth port, sixth port, and seventh port. It can be seen from Figure 19 that most of the TE0 mode light entering the fourth port is converted into signal 1, with a loss of about 0.3 dB. At the same time, -12.8 dB of light is converted into signal 3, forming crosstalk to signal 3. It can be seen from Figure 20 that most of the TE1 mode light entering the fourth port is converted into signal 2, with an insertion loss of about 0.8 dB. At the same time, light with a power less than -40 dB is converted into signal 3, forming crosstalk to signal 3. This crosstalk is too small to be ignored. It can be seen from Figure 21 that most of the TE2 mode light entering the fourth port is converted into signal 3, with a loss of about 1.2 dB. At the same time, light with a power less than -12.5 dB is converted into signal 1, forming crosstalk to signal 1.

[0095] Table 1 lists the insertion loss and crosstalk performance of this tunable mode multiplexer during mode multiplexing and demultiplexing. Due to the optical path reversibility of the device, the insertion loss and crosstalk performance of the device during mode multiplexing and demultiplexing are the same. First, in the mode multiplexing scenario, when the phase shifter At this time, signals 1, 2, and 3 are in TE0, TE2, and TE1 modes respectively at the fourth port, with insertion losses of 0.3 dB, 1.2 dB, and 0.8 dB respectively. Among them, there is approximately -13 dB of crosstalk between signal 1 and signal 2; when the phase shifter is in a certain state, signals 1, 2, and 3 are in TE0, TE1, and TE2 modes respectively at the fourth port, with insertion losses of 0.3 dB, 0.8 dB, and 1.2 dB respectively. Among them, there is approximately -13 dB of crosstalk between signal 1 and signal 3. Summarizing the performance of this device in the mode multiplexing scenario, the following two points can be obtained: 1. Signals 1, 2, and 3 in the TEO mode can be transformed into TE0, TE1, and TE2 modes after passing through the adjustable mode multiplexer, completing multi-mode combining; 2. By adjusting the phase shift amount of the phase shifter, the modes of signal 2 and signal 3 at the output fourth port can be controlled. When the phase shifter is in a certain state, signal 2 is in TE2 and signal 3 is in TE1. When the phase shifter is in a certain state, signal 2 is in TE1 and signal 3 is in TE2. It can be seen that this adjustable mode multiplexer can achieve mode multiplexing of three signals, and can control whether the modes of two of the signals after multiplexing are TE1 or TE2.

[0096] Secondly, in the mode demultiplexing scenario, when the phase shifter is in a certain state, the lights in TE0, TE1, and TE2 modes respectively become signal 1, 3, and 2 in TE0 mode, with insertion losses of 0.3 dB, 0.8 dB, and 1.2 dB respectively. Among them, there is approximately -13 dB of crosstalk between signal 1 and signal 2; when the phase shifter is in a certain state, the lights in TE0, TE1, and TE2 modes respectively become signal 1, 2, and 3 in TE0 mode, and the insertion losses are still 0.3 dB, 0.8 dB, and 1.2 dB respectively. Among them, there is approximately -13 dB of crosstalk between signal 1 and signal 3. Summarizing the performance of this adjustable mode multiplexer during the demultiplexing process, the following two points can be obtained: 1. The lights in TE0, TE1, and TE2 modes can be transformed into the TEO mode after passing through the adjustable mode multiplexer, and are output from the fifth port, sixth port, and seventh port, completing mode transformation and splitting; 2. By adjusting the phase shift amount of the phase shifter, it can be controlled whether the lights in TE1 and TE2 modes come out from the sixth port or the seventh port. When the phase shifter is in a certain state, the light in TE1 mode becomes signal 3 and comes out from the seventh port, and the light in TE2 mode becomes signal 2 and comes out from the sixth port. When the phase shifter is in a certain state, the light in TE1 mode becomes signal 2 and comes out from the sixth port, and the light in TE2 mode becomes signal 3 and comes out from the seventh port.

[0097] Table 1

[0098]

[0099]

[0100] It is understood that the above embodiments are merely exemplary embodiments adopted for the purpose of illustrating the principles of the present invention. However, the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims

1. A three-mode multiplexer, characterized in that : comprising a first waveguide, a second waveguide and a third waveguide, wherein the second waveguide is located between the first waveguide and the third waveguide, the first waveguide, the second waveguide and the third waveguide form a coupling region, the width of the second waveguide changes from narrow to wide along a first direction, and the width of the first waveguide and the third waveguide changes from wide to narrow along the first direction; the first waveguide is exactly the same as the third waveguide, and the coupling region is symmetrically arranged along the longitudinal center line of the second waveguide; One end of the second waveguide is connected to the second port, the other end of the second waveguide is connected to the fourth port, one end of the first waveguide close to the second port is connected to the first port, and one end of the third waveguide close to the second port is connected to the third port; The first direction is a direction from the second port to the fourth port; When the second port inputs TE0 mode light, the fourth port outputs TE0 mode light; when the first port and the third port input TE0 mode light at the same time, and the two TE0 mode lights differ in phase by π, the fourth port outputs TE1 mode light; when the first port and the third port input TE0 mode light at the same time, and the two TE0 mode lights are the same in phase, the fourth port only outputs TE2 mode light; When the fourth port inputs TE0 mode light, the second port outputs TE0 mode light; when the fourth port inputs TE1 mode light, the first port and the third port output TE0 mode light, and the two beams of light have a phase difference of π; when the fourth port inputs TE2 mode light, the first port and the third port output TE0 mode light, and the two beams of light have the same phase.

2. The three-mode multiplexer according to claim 1, characterized in that: The first waveguide, the second waveguide, and the third waveguide are arranged side by side; the gap width between the second waveguide and the first waveguide remains unchanged along the first direction, the gap width between the second waveguide and the third waveguide remains unchanged along the first direction, and the gap width between the second waveguide and the first waveguide is equal to the gap width between the second waveguide and the third waveguide.

3. The three-mode multiplexer according to claim 2, characterized in that: The gap width between the second waveguide and the first waveguide and the gap width between the second waveguide and the third waveguide are both 200-300 nm; or / and, The length of the coupling region is 30-100um.

4. The three-mode multiplexer according to claim 1, 2 or 3, characterized in that: The first waveguide, the second waveguide and the third waveguide are all tapered waveguides.

5. An adjustable mode multiplexer, characterized in that : comprising an equal power division coupler, a phase shifter and a three-mode multiplexer as claimed in any one of claims 1 to 4, wherein the equal power division coupler is provided with a first input port, a second input port, a first output port and a second output port, the first output port of the equal power division coupler is connected to the first port of the three-mode multiplexer, the second output port of the equal power division coupler is connected to the third port of the three-mode multiplexer, and a phase shifter is provided between the first port or / and the third port of the three-mode multiplexer and the equal power division coupler.

6. The adjustable mode multiplexer according to claim 5, characterized in that: Also includes a TE1 mode filter, one end of the TE1 mode filter is connected to the second port of the three-mode multiplexer; The TE1 mode filter includes a curved waveguide and is used to filter out the high-order mode coming out of the second port of the three-mode multiplexer.

7. The adjustable mode multiplexer according to claim 5, characterized in that: The phase shifter is used to make the signal generate a phase difference of π or 0 between the first port and the third port of the three-mode multiplexer.

8. The adjustable mode multiplexer according to claim 5 or 7, characterized in that: The equal power division coupler is a two-input and two-output multimode interferometer. A phase shifter is provided between the first port of the three-mode multiplexer and the first output port of the multimode interferometer. When the phase shift amount of the phase shifter is When the first optical signal of the TE0 mode input from the second port of the three-mode multiplexer is output from the fourth port of the three-mode multiplexer, it is still the TE0 mode light; the second optical signal of the TE0 mode input from the first input port of the multimode interferometer is converted into the TE2 mode light when it is output from the fourth port of the three-mode multiplexer; the third optical signal of the TE0 mode input from the second input port of the multimode interferometer is converted into the TE1 mode light when it is output from the fourth port of the three-mode multiplexer; When the phase shifter When the first optical signal of the TE0 mode input from the second port of the three-mode multiplexer is output from the fourth port of the three-mode multiplexer, it is still the TE0 mode light; The second optical signal of the TE0 mode input from the first input port of the multimode interferometer is converted into the TE1 mode light when output from the fourth port of the three-mode multiplexer; the third optical signal of the TE0 mode input from the second input port of the multimode interferometer is converted into the TE2 mode light when output from the fourth port of the three-mode multiplexer; When the phase shifter When the three modes of light, TE0 / TE1 / TE2, are input from the fourth port of the three-mode multiplexer at the same time, the input TE0 mode light will be output from the second port of the three-mode multiplexer and remain in the TE0 mode, becoming the first optical signal; the input TE2 mode light will be output from the first input port of the multimode interferometer and converted into the TE0 mode, becoming the second optical signal; The input TE1 mode light will be output from the second input port of the multimode interferometer and converted into TE0 mode to become a third optical signal; When the phase shifter When the TE0 / TE1 / TE2 modes of light are input from the fourth port of the three-mode multiplexer at the same time, the input TE0 mode light will be output from the second port of the three-mode multiplexer and remain in the TE0 mode, becoming the first optical signal; the input TE1 mode light will be output from the first input port of the multimode interferometer and converted into the TE0 mode, becoming the second optical signal; the input TE2 mode light will be output from the second input port of the multimode interferometer and converted into the TE0 mode, becoming the third optical signal.

9. The adjustable mode multiplexer according to claim 5 or 7, characterized in that: The equal power division coupler is a two-input and two-output multimode interferometer. A phase shifter is provided between the third port of the three-mode multiplexer and the second output port of the multimode interferometer. When the phase shift amount of the phase shifter is When the first optical signal of the TE0 mode input from the second port of the three-mode multiplexer is output from the fourth port of the three-mode multiplexer, it is still the TE0 mode light; The second optical signal of the TE0 mode input from the first input port of the multimode interferometer is converted into the TE1 mode light when output from the fourth port of the three-mode multiplexer; the third optical signal of the TE0 mode input from the second input port of the multimode interferometer is converted into the TE2 mode light when output from the fourth port of the three-mode multiplexer; When the phase shifter When the first optical signal of the TE0 mode input from the second port of the three-mode multiplexer is output from the fourth port of the three-mode multiplexer, it is still the TE0 mode light; the second optical signal of the TE0 mode input from the first input port of the multimode interferometer is converted into the TE2 mode light when it is output from the fourth port of the three-mode multiplexer; the third optical signal of the TE0 mode input from the second input port of the multimode interferometer is converted into the TE1 mode light when it is output from the fourth port of the three-mode multiplexer; When the phase shifter When the three modes of light, TE0 / TE1 / TE2, are input from the fourth port of the three-mode multiplexer at the same time, the input TE0 mode light will be output from the second port of the three-mode multiplexer and remain in the TE0 mode, becoming the first optical signal; the input TE1 mode light will be output from the first input port of the multimode interferometer and converted into the TE0 mode, becoming the second optical signal; the input TE2 mode light will be output from the second input port of the multimode interferometer and converted into the TE0 mode, becoming the third optical signal; When the phase shifter When the TE0 / TE1 / TE2 modes of light are input from the fourth port of the three-mode multiplexer at the same time, the input TE0 mode light will be output from the second port of the three-mode multiplexer and remain in the TE0 mode, becoming the first optical signal; the input TE2 mode light will be output from the first input port of the multimode interferometer and converted into the TE0 mode, becoming the second optical signal, and the input TE1 mode light will be output from the second input port of the multimode interferometer and converted into the TE0 mode, becoming the third optical signal.

Images