A digitally controlled grating delay switch and an adjustable optical delay line

Abstract

This invention discloses a numerically controlled optical grating delay switch and an adjustable optical delay line. The numerically controlled optical grating delay switch includes a first numerically controlled optical grating switch with one input and two outputs, and a second numerically controlled optical grating switch with two inputs and two outputs. The first numerically controlled optical grating switch includes a first Bragg grating, a first mode multiplexer, and a first port, a second port, and a third port. The second numerically controlled optical grating switch includes a second Bragg grating, a second mode multiplexer, a third mode multiplexer, and a fourth port, a fifth port, a sixth port, and a seventh port. The seventh port is connected to an optical absorber. The second port is connected to the sixth port via a first delay waveguide, and the third port is connected to the fourth port via a second delay waveguide. The first and second numerically controlled optical grating switches operate in opposite states. The numerically controlled optical grating switch of this invention achieves controllable adjustment of the delay and has excellent performance characteristics such as small delay error, small insertion loss, low power consumption, small fluctuations in insertion loss and power consumption, low crosstalk, good tolerance, and high stability.

Description

Technical Field

[0001] This invention relates to the field of integrated optoelectronics technology, and more specifically to a digitally controlled grating delay switch and an adjustable optical delay line. Background Technology

[0002] Tunable optical delay lines have important applications in optical communication data buffering, optically controlled phased array radar, and microwave photonic filters. Currently, tunable optical delay line chip types include MZI switch delay lines, micro-ring delay lines, and Bragg grating delay lines, among which MZI switch delay lines have advantages in bandwidth and delay accuracy, and are therefore the most popular. However, due to the poor tolerance of MZI switches, MZI switch delay lines require complex real-time calibration control circuits, thus limiting their practical application.

[0003] The digitally controlled optical switch based on the broadband Bragg grating filter has high tolerance, allowing for a certain range of errors in the driving voltage, and has advantages such as high stability, good environmental adaptability, and simple driving circuit. Figure 1 This is a schematic diagram of a 2x2 digitally controlled optical switch based on a Bragg grating filter. The digitally controlled optical switch includes a Bragg grating filter and a heater. The heater is used to heat the Bragg grating filter and control the switching of the digitally controlled optical switch based on the broadband Bragg grating filter between a normal state and a heated state. Figure 2 and Figure 3 These are the spectral diagrams of the switch in its normal (V=0) and heated (V=1) states, respectively. When the operating wavelength is in the range of 1312-1354nm, in the normal state, light enters from I2 and exits from O1; in the heated state, light enters from I2 and exits from O2. The state of the switch can be changed by the driving voltage. Figure 4 By connecting this 2x2 digitally controlled grating switch and delay waveguide in multiple stages in series, an tunable optical delay line can be formed. Figure 4 However, this type of adjustable delay line will face the following problems in practical applications:

[0004] 1. Delay error introduced by the switch itself

[0005] like Figure 1 As shown, when I2 enters and O2 exits, the light is reflected at the grating, and this reflection is concentrated in the entrance region of the grating, so the delay caused by the grating is very small; while when I2 enters and O1 exits, the light has to pass through the entire grating, and the grating causes a large delay. Therefore, the two switching states will introduce a certain delay difference.

[0006] 2. High crosstalk from the switch.

[0007] like Figure 2 As shown, the crosstalk of the switch is about -20dB, which is greater than the -30dB required by many application scenarios.

[0008] 3. Insertion loss fluctuations introduced by the switch itself

[0009] like Figure 1 As shown, in the case of I2 input and O2 output, the insertion loss of the switch mainly comes from the incomplete reflection of light and the insertion loss of one mode multiplexer; while in the case of I2 input and O1 output, the insertion loss of light mainly comes from the transmission loss of the grating waveguide and the insertion loss of two mode multiplexers. It can be seen that the insertion loss of the switch is different in different switching states.

[0010] 4. Power consumption fluctuations caused by switching

[0011] like Figure 1 As shown, under normal conditions, light enters from I2 and exits from O1, generating no power consumption; under heating conditions, light enters from I2 and exits from O2, generating power consumption. Therefore, the power consumption of the optical switch is different in the two states, and this fluctuation in power consumption is detrimental to the stability of the driving voltage. Summary of the Invention

[0012] The present invention aims to solve at least one of the technical problems existing in the prior art, and proposes a numerically controlled grating delay switch and an adjustable optical delay line.

[0013] The technical solution of this invention is implemented as follows: This invention discloses a numerically controlled optical grating delay switch, including a first numerically controlled optical grating switch with one input and two outputs, and a second numerically controlled optical grating switch with two inputs and two outputs. The first numerically controlled optical grating switch includes a first Bragg grating, a first mode multiplexer, and a first port, a second port, and a third port. The first port is the input port of the numerically controlled optical grating delay switch. The second numerically controlled optical grating switch includes a second Bragg grating, a second mode multiplexer, a third mode multiplexer, and a fourth port, a fifth port, a sixth port, and a seventh port. The fifth port is the output port of the numerically controlled optical grating delay switch, and the seventh port is connected to a light absorber. The second port of the first numerically controlled optical grating switch is connected to the sixth port of the second numerically controlled optical grating switch through a first delay waveguide, and the third port of the first numerically controlled optical grating switch is connected to the fourth port of the second numerically controlled optical grating switch through a second delay waveguide. The first numerically controlled optical grating switch and the second numerically controlled optical grating switch maintain opposite operating states.

[0014] Furthermore, the first CNC grating switch is in a direct-through state under normal conditions and in a reflective state under heating conditions. When the first Bragg grating is in the direct-through state, the first mode light entering from the first port passes directly through the first Bragg grating and exits from the third port. When the first Bragg grating is in the reflective state, the first mode light entering from the first port undergoes mode conversion and reflection under the action of the first Bragg grating. The reflected second mode light is converted back into first mode light by the first mode multiplexer and exits from the second port.

[0015] Furthermore, the second CNC grating switch is in a direct-through state under normal conditions and in a reflection state under heating conditions. When the second Bragg grating is in the direct-through state, the first mode light entering from the sixth port passes directly through the second Bragg grating and exits from the fifth port. The first mode light entering from the fourth port is converted into the second mode light after passing through the third mode multiplexer. The second mode light passes through the second Bragg grating and then through the second mode multiplexer. The second mode multiplexer converts the second mode light into the first mode light and exits from the seventh port.

[0016] When the second Bragg grating is in a reflective state, the first mode light entering from the fourth port is converted into the second mode light by the third mode multiplexer, and then undergoes mode conversion and reflection under the action of the second Bragg grating. The reflected first mode light is emitted from the fifth port. The first mode light entering from the sixth port undergoes mode conversion and reflection under the action of the second Bragg grating. The reflected second mode light is converted back into the first mode light by the second mode multiplexer and emitted from the seventh port.

[0017] Furthermore, the first mode light is the TE0 mode light; the second mode light is the TE1 mode light.

[0018] Furthermore, the first mode multiplexer includes a first coupling waveguide and a second coupling waveguide. One end of the first coupling waveguide is a first port, and the other end of the first coupling waveguide is connected to the first end of the main waveguide of the first Bragg grating. One end of the second coupling waveguide is a second port, which is connected to the first end of the first delay waveguide.

[0019] Furthermore, the first numerically controlled grating switch also includes a third coupling waveguide, one end of which is connected to the second end of the main waveguide of the first Bragg grating, and the other end of which is a third port connected to the first end of the second delay waveguide.

[0020] Furthermore, the second-mode multiplexer includes a fourth coupling waveguide and a fifth coupling waveguide. One end of the fourth coupling waveguide is a sixth port, which is connected to the second end of the first delay waveguide. The other end of the fourth coupling waveguide is connected to the second end of the main waveguide of the second Bragg grating. One end of the fifth coupling waveguide is a seventh port, which is connected to the optical absorber.

[0021] Furthermore, the third-mode multiplexer includes a sixth coupling waveguide and a seventh coupling waveguide. One end of the sixth coupling waveguide is the fifth port, and the other end of the sixth coupling waveguide is connected to the second end of the main waveguide of the second Bragg grating. One end of the seventh coupling waveguide is the fourth port, which is connected to the second end of the second delay waveguide.

[0022] Furthermore, the first and second delay waveguides have different lengths, which in turn creates a delay difference between the two switching states.

[0023] The present invention also discloses an adjustable optical delay line, comprising at least two numerically controlled grating delay switches as described above, wherein the numerically controlled grating delay switches are connected in series.

[0024] Compared with the prior art, the present invention has the following beneficial effects: The numerically controlled grating delay switch of the present invention includes a 1x2 (one-input two-output) and a 2x2 (two-input two-output) numerically controlled grating switch, as well as a first delay waveguide and a second delay waveguide of different lengths. The 1x2 numerically controlled grating switch includes a mode multiplexer and a Bragg grating, and has three ports: the first port, the second port, and the third port. The first port serves as the input port of the entire switch. The 2x2 numerically controlled grating switch includes two mode multiplexers and a Bragg grating, and has four ports: the fourth port, the fifth port, the sixth port, and the seventh port. The fifth port serves as the output port of the entire switch, the seventh port is connected to a light absorber, the fourth port is connected to the third port via the second delay waveguide, and the sixth port is connected to the second port via the first delay waveguide. The 1x2 and 2x2 numerically controlled grating switches maintain different operating states, such as... Figure 5 When the 1x2 digitally controlled grating switch is in its normal state (0) and the 2x2 digitally controlled grating switch is in its heated state (1), light passes through the second delay waveguide within the switch; as Figure 6 When the 1x2 CNC grating switch is in the heated state and the 2x2 CNC grating switch is in the normal state, light passes through the first delay waveguide within the switch. In both switching states, firstly, the light travels through the second delay waveguide and the first delay waveguide respectively, thus achieving adjustable delay; secondly, within the 1x2 and 2x2 CNC grating switches... Figure 5 and Figure 6 In both switching states, the light travels through a direct path and a reflection path. Therefore, the delay introduced by the switch is a constant and will not cause delay errors due to changes in the switching state. Furthermore, since the light travels through a direct path and a reflection path in both switching states, the insertion loss is the same, as shown below. Figure 8 and 11 The insertion loss remained around 0.2dB in both switching states, exhibiting low insertion loss and minimal difference. Furthermore, due to the asynchronous operation of the 1x2 and 2x2 CNC grating switches, in both switching states, one switch is in the normal state while the other is in the heating state. Therefore, the power consumption consistently remains the same as that of the heating switch, achieving power consumption stability. Finally, as... Figure 7 and 10 In both switching states, crosstalk was suppressed to below -60dB, which is nearly three times lower than the -20dB crosstalk of a single switch.

[0025] In summary, the numerically controlled grating switch proposed in this invention achieves controllable adjustment of delay and has excellent performance characteristics such as small delay error, small insertion loss, low power consumption, small fluctuations in insertion loss and power consumption, low crosstalk, good tolerance, and high stability. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a 2x2 digitally controlled optical switch based on a Bragg grating filter;

[0027] Figure 2 The spectrum of a 2x2 digitally controlled optical grating switch under normal operating conditions;

[0028] Figure 3 The spectrum of a 2x2 digitally controlled optical grating switch in the heated state;

[0029] Figure 4 This is a schematic diagram of an adjustable delay line based on a 2x2 digitally controlled grating switch;

[0030] Figure 5 This is a schematic diagram of a switching state of a symmetrical delay switch based on a numerically controlled optical grating switch;

[0031] Figure 6 This is a schematic diagram of another switching state of a symmetrical delay switch based on a numerically controlled grating switch;

[0032] Figure 7 In order to be in Figure 5 Transmission spectrum of port 5 in switch state;

[0033] Figure 8 In order to be in Figure 5 A magnified view of the transmission spectrum at the fifth port in the switch state;

[0034] Figure 9 In order to be in Figure 5 Transmission spectrum of port 7 in switch state;

[0035] Figure 10 In order to be in Figure 6 Transmission spectrum of port 5 in switch state;

[0036] Figure 11 In order to be in Figure 6 A magnified view of the transmission spectrum at the fifth port in the switch state;

[0037] Figure 12 In order to be in Figure 6 Transmission spectrum of port 7 in switch state;

[0038] Figure 13 This is a schematic diagram of a 3-bit delay line constructed by a numerically controlled grating delay switch.

[0039] In the attached diagram, 1 is the first numerically controlled grating switch, 11 is the first Bragg grating, 12 is the first mode multiplexer, 13 is the first port, 14 is the second port, 15 is the third port, 2 is the second numerically controlled grating switch, 21 is the second Bragg grating, 22 is the second mode multiplexer, 23 is the third mode multiplexer, 24 is the fourth port, 25 is the fifth port, 26 is the sixth port, 27 is the seventh port, 3 is the first delay waveguide, 4 is the second delay waveguide, and 5 is the light absorber. Detailed Implementation

[0040] 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 with reference to the accompanying drawings and specific embodiments.

[0041] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms "an," "a," or "the" do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. The terms "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up," "down," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0042] In the various figures, the same elements are represented by similar reference numerals. For clarity, not all parts in the figures are drawn to scale. Furthermore, some well-known parts may not be shown in the figures.

[0043] Many specific details of the invention, such as the structure, materials, dimensions, processing methods, and techniques of the components, are described below to provide a clearer understanding of the invention. However, as those skilled in the art will understand, the invention may be implemented without following these specific details.

[0044] Example 1

[0045] See Figure 5 and Figure 6This invention provides a numerically controlled grating delay switch, including a first numerically controlled grating switch 1 (i.e., a 1x2 numerically controlled grating switch) with one input and two outputs, and a second numerically controlled grating switch 2 (i.e., a 2x2 numerically controlled grating switch) with two inputs and two outputs. The first numerically controlled grating switch 1 includes a first Bragg grating 11, a first mode multiplexer 12, and a first port 13, a second port 14, and a third port 15. The first port 13 is the input port of the numerically controlled grating delay switch. The second numerically controlled grating switch 2 includes a second Bragg grating 21, a second mode multiplexer 22, and a third mode multiplexer 25. The multiplexer 23 includes a fourth port 24, a fifth port 25, a sixth port 26, and a seventh port 27. The fifth port 25 is the output port of the numerically controlled grating delay switch, and the seventh port 27 is connected to the light absorber 5. The second port 14 of the first numerically controlled grating switch 1 is connected to the sixth port 26 of the second numerically controlled grating switch 2 through the first delay waveguide 3. The third port 15 of the first numerically controlled grating switch 1 is connected to the fourth port 24 of the second numerically controlled grating switch 2 through the second delay waveguide 4. The first numerically controlled grating switch 1 and the second numerically controlled grating switch 2 operate in opposite states.

[0046] This invention designs a symmetrically structured numerically controlled optical grating delay switch based on a numerically controlled optical grating switch. Figure 5 and Figure 6 These represent the two states of the switch, corresponding to light passing through the second delay waveguide 4 and the first delay waveguide 3, respectively, enabling two delay states. The design concept of this numerically controlled grating delay switch is that, regardless of which delay waveguide the light travels through within the switch, it always passes through a direct path and a reflection path. Figure 5 and Figure 6 (Middle dashed line) to achieve consistent delay and loss. The seventh port 27 is connected to the optical absorber 5 to eliminate crosstalk signals within the switch.

[0047] Furthermore, the first CNC grating switch 1 and the second CNC grating switch 2 are in a direct-on state under normal conditions and in a reflective state under heating conditions.

[0048] When the first CNC grating switch 1 is in the through state and the second CNC grating switch 2 is in the reflection state, the light passes through the second delay waveguide 4 in the CNC grating delay switch. When the first CNC grating switch 1 is in the reflection state and the second CNC grating switch 2 is in the through state, the light passes through the first delay waveguide 3 in the CNC grating delay switch.

[0049] Furthermore, when the first Bragg grating 11 is in the through state, the first mode light entering from the first port 13 passes directly through the first Bragg grating 11 and is emitted from the third port 15. When the first Bragg grating 11 is in the reflection state, the first mode light entering from the first port 13 undergoes mode conversion and reflection under the action of the first Bragg grating 11. The reflected second mode light is converted back into first mode light by the first mode multiplexer 12 and emitted from the second port 14.

[0050] Furthermore, when the second Bragg grating 21 is in the through state, the first mode light entering from the sixth port 26 passes directly through the second Bragg grating 21 and exits from the fifth port 25. The first mode light entering from the fourth port 24 is converted into the second mode light after passing through the third mode multiplexer 23. The second mode light then passes through the second Bragg grating 21 and passes through the second mode multiplexer 22. The second mode multiplexer 22 converts the second mode light into the first mode light and exits from the seventh port 27.

[0051] When the second Bragg grating 21 is in a reflective state, the first mode light entering from the fourth port 24 is converted into the second mode light by the third mode multiplexer 23, and then undergoes mode conversion and reflection under the action of the second Bragg grating 21. The reflected first mode light is emitted from the fifth port 25. The first mode light entering from the sixth port 26 undergoes mode conversion and reflection under the action of the second Bragg grating 21. The reflected second mode light is converted into the first mode light again by the second mode multiplexer 22 and emitted from the seventh port 27.

[0052] Furthermore, the first mode light is the TE0 mode light; the second mode light is the TE1 mode light.

[0053] Furthermore, the first mode multiplexer 12 includes a first coupling waveguide and a second coupling waveguide. One end of the first coupling waveguide is a first port 13, and the other end of the first coupling waveguide is connected to the first end of the main waveguide of the first Bragg grating 11. One end of the second coupling waveguide is a second port 14, which is connected to the first end of the first delay waveguide 3. The other end of the second coupling waveguide is in an unused state, such as... Figure 5 and Figure 6 As shown.

[0054] Furthermore, the first numerically controlled grating switch 1 also includes a third coupling waveguide, one end of which is connected to the second end of the main waveguide of the first Bragg grating 11, and the other end of which is a third port 15, which is connected to the first end of the second delay waveguide 4.

[0055] Furthermore, the second-mode multiplexer 22 includes a fourth coupling waveguide and a fifth coupling waveguide. One end of the fourth coupling waveguide is a sixth port 26, connected to the second end of the first delay waveguide 3. The other end of the fourth coupling waveguide is connected to the second end of the main waveguide of the second Bragg grating 21. One end of the fifth coupling waveguide is a seventh port 27, connected to the optical absorber 5. The other end of the fifth coupling waveguide is in an unused state, such as... Figure 5 and Figure 6 As shown.

[0056] The third-mode multiplexer 23 includes a sixth coupling waveguide and a seventh coupling waveguide. One end of the sixth coupling waveguide is the fifth port 25, and the other end is connected to the second end of the main waveguide of the second Bragg grating 21. One end of the seventh coupling waveguide is the fourth port 24, which is connected to the second end of the second delay waveguide 4. The other end of the seventh coupling waveguide is in an unused state. Figure 5 and Figure 6 As shown.

[0057] Furthermore, the first delay waveguide 3 and the second delay waveguide 4 have different lengths, which will produce different delays, thus creating an adjustable delay. In this embodiment, the length of the first delay waveguide 3 is longer than the length of the second delay waveguide 4.

[0058] The first port 13 is a through port, the second port 14 is a coupling port, the third port 15 is a through port, the fourth port 24 is a coupling port, the fifth port 25 is a through port, the sixth port 26 is a through port, and the seventh port 27 is a coupling port.

[0059] Under normal circumstances, such as Figure 5 1x2 CNC grating switch When the heater in the switch is not working, the 1x2 CNC grating switch is in a straight-through state. TEO mode light entering through the first port 13 can directly pass through the first Bragg grating 11; this path is defined as a straight-through path. Then, it passes through the second delay waveguide 4 and enters the 2x2 CNC grating switch. In the heated state, as... Figure 6 In the 1x2 CNC grating switch, '①' indicates that the heater in the switch is in working state. At this time, the 1x2 CNC grating switch is in reflection state. When the TEO mode light entering through the first port 13 passes through the first Bragg grating 11, TEO-TE1 mode coupling reflection occurs. The reflected TE1 mode light passes through the first mode multiplexer 12 and becomes TE0 mode again, exiting from the second port 14. This path is defined as the reflection path, and then enters the 2x2 CNC grating switch through the first delay waveguide 3.

[0060] Under normal circumstances, such as Figure 6The 2x2 CNC grating switch is in a pass-through state. The TEO mode light entering through port 26 can remain in TEO mode throughout the entire switch and exit through port 25. The TEO mode light entering through port 24 becomes TE1 mode after passing through the third mode multiplexer 23, then remains in TE1 mode throughout the second Bragg grating 21, and then passes through the second mode multiplexer 22, becoming TE0 mode and exiting through port 27 before being eliminated by the light absorber 5.

[0061] In a heated state, such as Figure 5 The 2x2 digitally controlled grating switch is in reflection mode. TEO mode light entering through port 24 is converted to TE1 mode by the third mode multiplexer 23, and then undergoes TEO-TE1 mode coupling reflection in the second Bragg grating 21. The reflected TE0 mode light exits from port 25. Meanwhile, TEO mode light entering through port 26 undergoes TEO-TE1 mode coupling reflection when passing through the second Bragg grating 21. The reflected TE1 mode light is converted to TE0 mode by the second mode multiplexer 22 and exits from port 27, where it is then eliminated by the light absorber 5.

[0062] exist Figure 5 In the process, after light enters the digitally controlled optical grating switch, most of the light passes through the 1x2 digitally controlled optical grating switch and then travels through the second delay waveguide 4, exiting from the output port (port 5, 25). Only a small portion of the light passes through the 1x2 digitally controlled optical grating switch and travels through the first delay waveguide 3. This portion of light is considered crosstalk. When this crosstalk passes through the 2x2 digitally controlled optical grating switch, it mainly follows a reflection path. Therefore, most of this crosstalk is eliminated by the light absorber 5 after reaching port 7, 27. Only a small portion travels a straight path and exits from the output port (port 5, 25), causing crosstalk to the signal light at the output port. Thanks to the low crosstalk performance (-20dB) of both the 1x2 and 2x2 digitally controlled optical grating switches and the absorption of crosstalk by port 7, 27 of the 2x2 digitally controlled optical grating switch, the crosstalk at the output end is reduced to an extremely low level. Figure 7 and Figure 8 As shown, the crosstalk signal after passing through the first delay waveguide 3 is reduced to below -60dB. Figure 7 The signal insertion loss after passing through the second delay waveguide 4 is only 0.2dB. Figure 8 ). Figure 9 The crosstalk signal coming from port 7 (27) is eliminated by optical absorber 5. (Comparison) Figure 9 and Figure 2 It can be observed that, Figure 2 Crosstalk and Figure 9 The crosstalk signal strength from the seventh port 27 is basically the same, indicating that most of the crosstalk will be eliminated by the optical absorber 5.

[0063] exist Figure 6In the circuit, after light enters the switch, most of the light passes through the 1x2 digitally controlled grating switch and then travels through the first delay waveguide 3, exiting from the output port (port 5, 25). Only a small portion of the light passes through the 1x2 digitally controlled grating switch and then travels through the second delay waveguide 4. This portion of light is considered crosstalk signal. When passing through the 2x2 digitally controlled grating switch, it mainly takes a straight-through path. Therefore, most of this light is eliminated by the light absorber 5 after reaching port 7, 27. Only a small portion takes a reflection path and exits from the output port (port 5, 25), causing crosstalk to the signal light at the output port. Figure 10 and Figure 11 As shown, the crosstalk signal after passing through the second delay waveguide 4 is reduced to below -60dB. Figure 10 The signal insertion loss after passing through the first delay waveguide 3 is only 0.2dB. Figure 11 ). Figure 12 For the crosstalk signal coming from port 27, compare Figure 12 and Figure 2 It can be observed that most of the crosstalk will come out from port 7, 27, and then be eliminated by the optical absorber 5.

[0064] Finally, the delay error, insertion loss, power consumption, and crosstalk performance of the numerically controlled grating delay switch with a symmetrical structure were comprehensively evaluated.

[0065] First, compare Figure 5 and Figure 6 In both switching states, the light travels through the second delay waveguide 4 and the first delay waveguide 3, respectively. However, in the 1x2 and 2x2 digitally controlled grating switches, the light in both switching states travels through a direct path and a reflection path. Therefore, the delay introduced by the switch is a constant value and will not cause delay error due to changes in the switching state.

[0066] Secondly, in both switching states, since the light travels through a direct path and a reflection path, the insertion loss is the same. Figure 8 and Figure 11 It can also be seen that the insertion loss remains at around 0.2dB in both switching states.

[0067] In addition, in both switching states, one is in a normal state and the other is in a heating state, so the power consumption is always the power consumption of a heating switch, thus achieving power consumption stability.

[0068] Finally, in both switching states, from Figure 7 and Figure 10 As can be seen, crosstalk was suppressed to below -60dB, which is nearly three times lower than the -20dB crosstalk of a single switch.

[0069] In summary, the numerically controlled grating switch proposed in this patent achieves controllable adjustment of delay and has excellent performance in terms of small delay error, small insertion loss error, small power consumption fluctuation, and small crosstalk.

[0070] Example 2

[0071] See Figure 13 The present invention also provides an adjustable optical delay line, including at least two digitally controlled grating delay switches as described in Embodiment 1, wherein the digitally controlled grating delay switches are connected in series.

[0072] In some embodiments, the length of the first delay waveguide 3 of the plurality of numerically controlled grating delay switches increases sequentially along the direction of light transmission. Of course, the present invention is not limited to the above embodiments, and the length of the first delay waveguide 3 of the plurality of numerically controlled grating delay switches can be set as needed.

[0073] See Figure 13 One embodiment of the adjustable optical delay line includes three numerically controlled grating delay switches as described in Embodiment 1, connected in series. Connecting the three numerically controlled grating delay switches in series achieves a 3-bit delay. Figure 13 As shown, the delay differences between the two delay waveguides in the first, second, and third stage delay switches are Δt, 2*Δt, and 4*Δt, respectively. Then... Figure 13 The delay line in the middle will have an adjustable delay amount of 0-7*Δt, or step Δt.

[0074] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled 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 considered to be within the scope of protection of the present invention.

Claims

1. A digitally controlled grating delay switch, characterized by The application relates to a first in-out numerical control grating switch and a second in-in numerical control grating switch, the first numerical control grating switch comprises a first Bragg grating, a first mode multiplexer and a first port, a second port and a third port, the first port is an input port of the numerical control grating delay switch, the second numerical control grating switch comprises a second Bragg grating, a second mode multiplexer, a third mode multiplexer and a fourth port, a fifth port, a sixth port and a seventh port, the fifth port is an output port of the numerical control grating delay switch, and the seventh port is connected with a light absorber; the second port of the first numerical control grating switch is connected with the sixth port of the second numerical control grating switch through a first delay waveguide, and the third port of the first numerical control grating switch is connected with the fourth port of the second numerical control grating switch through a second delay waveguide; the first numerical control grating switch and the second numerical control grating switch are kept in different states, one of the first numerical control grating switch and the second numerical control grating switch is in a normal state, and the other is in a heating state; the first numerical control grating switch and the second numerical control grating switch are in a straight-through state in the normal state and in a reflection state in the heating state.

2. The digitally controlled grating delay switch of claim 1, wherein: When the first Bragg grating is in the straight-through state, first mode light entering from the first port directly passes through the first Bragg grating and is emitted from the third port; when the first Bragg grating is in the reflection state, first mode light entering from the first port is subjected to mode conversion and reflection under the action of the first Bragg grating, second mode light reflected back passes through the first mode multiplexer and is converted into first mode light which is emitted from the second port.

3. The digitally controlled grating delay switch of claim 1, wherein: the first and second grating delay lines are formed on a same substrate; and the first and second grating delay lines are formed of the same material. When the second Bragg grating is in the straight-through state, first mode light entering from the sixth port directly passes through the second Bragg grating and is emitted from the fifth port, first mode light entering from the fourth port is converted into second mode light through the third mode multiplexer, and the second mode light passes through the second Bragg grating and the second mode multiplexer, then the second mode light is converted into first mode light by the second mode multiplexer and is emitted from the seventh port; When the second Bragg grating is in the reflection state, first mode light entering from the fourth port is converted into second mode light through the third mode multiplexer, and then the second mode light is subjected to mode conversion and reflection under the action of the second Bragg grating, first mode light reflected back is emitted from the fifth port; First mode light entering from the sixth port is subjected to mode conversion and reflection under the action of the second Bragg grating, and second mode light reflected back is converted into first mode light which is emitted from the seventh port.

4. A digitally controlled grating delay switch as claimed in claim 2 or 3, characterized in that: The first mode light is TE0 mode light, and the second mode light is TE1 mode light.

5. The digitally controlled grating delay switch of claim 1, wherein: the first and second grating delay lines are formed on a same substrate. The first mode multiplexer comprises a first coupling waveguide and a second coupling waveguide, one end of the first coupling waveguide is the first port, and the other end of the first coupling waveguide is connected with a first end of a main waveguide of the first Bragg grating, and one end of the second coupling waveguide is the second port and is connected with a first end of the first delay waveguide.

6. The digitally controlled grating delay switch of claim 5, wherein: The first number-controlled grating switch further comprises a third coupling waveguide, one end of the third coupling waveguide is connected with the second end of the main waveguide of the first Bragg grating, and the other end of the third coupling waveguide is a third port and is connected with the first end of the second delay waveguide.

7. The digitally controlled grating delay switch of claim 1, wherein: the first and second grating delay lines are formed on a single substrate. The second mode multiplexer comprises a fourth coupling waveguide and a fifth coupling waveguide, one end of the fourth coupling waveguide is a sixth port and is connected with the second end of the first delay waveguide, and the other end of the fourth coupling waveguide is connected with the second end of the main waveguide of the second Bragg grating, one end of the fifth coupling waveguide is a seventh port and is connected with the light absorber.

8. The digitally controlled grating delay switch of claim 1, wherein: The third mode multiplexer comprises a sixth coupling waveguide and a seventh coupling waveguide, one end of the sixth coupling waveguide is a fifth port, the other end of the sixth coupling waveguide is connected with the second end of the main waveguide of the second Bragg grating, and one end of the seventh coupling waveguide is a fourth port and is connected with the second end of the second delay waveguide.

9. The digitally controlled grating delay switch of claim 1, wherein: The first delay waveguide and the second delay waveguide are different in length.

10. An adjustable optical delay line characterized by The number-controlled grating delay switch comprises at least two number-controlled grating delay switches as claimed in any one of claims 1 to 9, and the number-controlled grating delay switches are connected in series.

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