Numerical control grating delay switch and adjustable light delay line

Abstract

The invention discloses a numerical control grating time delay switch and a dimmable time delay line, and the numerical control grating time delay switch comprises a first numerical control grating switch with one inlet and two outlets and a second numerical control grating switch with two inlets and two outlets, the first numerical control grating switch comprises a first Bragg grating, a first mode multiplexer, a first port, a second port and a third port, and the second numerical control grating switch comprises a second Bragg grating, a second mode multiplexer, a third mode multiplexer, a fourth port, a fifth port, a sixth port and a seventh port. The seventh port is connected with the light absorber; the second port is connected with the sixth port through the first delay waveguide, and the third port is connected with the fourth port through the second delay waveguide; and the first numerical control grating switch and the second numerical control grating switch keep working in different states. According to the numerical control grating switch, controllable adjustment of time delay is achieved, and the numerical control grating switch has the excellent performance of being small in time delay error, small in insertion loss, small in power consumption, small in insertion loss and power consumption fluctuation, small in crosstalk, good in tolerance and high in stability.

Description

Technical Field

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

[0002] Adjustable optical delay lines have important applications in optical communication data caching, optically controlled phased array radar, microwave photon filters, etc. At present, the types of adjustable optical delay line chips include MZI switch delay line, micro-ring delay, Bragg grating delay, etc. Among them, MZI switch delay line has advantages in bandwidth and delay accuracy, so it has attracted the most attention. However, due to the poor tolerance of MZI switches, MZI switch delay lines need to be equipped with complex real-time calibration control circuits, so MZI switch delay lines have not been put into practical use.

[0003] The digitally controlled optical switch based on the broadband Bragg grating filter has a high tolerance, allowing a certain range of errors in the driving voltage. It has the advantages of high stability, good environmental adaptability, and simple driving circuit. Figure 1 The schematic diagram of a two-input and two-output (2x2) digitally controlled optical switch based on a Bragg grating filter is shown. The digitally controlled optical switch includes a Bragg grating filter and a heater, wherein the heater is used to heat the Bragg grating filter and control the digitally controlled optical switch based on the broadband Bragg grating filter to switch between a normal state and a heated state. Figure 2 and Figure 3 They are the spectrum diagrams of the switch in the normal state (V=0) and the heated state (V=1). When the working wavelength is in the range of 1312-1354nm, in the normal state, light enters from I2 and exits from O1, and in the heated state, light enters from I2 and exits from O2. The state of the switch can be changed by driving voltage. Figure 4 By connecting this 2x2 digitally controlled grating switch and delay waveguide in series, an adjustable optical delay line can be formed ( Figure 4 ), but this adjustable delay line will face the following problems in practical application:

[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 area of ​​the grating, so the delay caused by the grating is very small; when I2 enters and O1 exits, the light has to pass through the entire grating, and the grating brings a larger delay, so the two switching states will introduce a certain delay difference.

[0006] 2. The crosstalk of the switch is large

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

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

[0009] like Figure 1 As shown in the figure, when I2 is in and O2 is out, the switch insertion loss mainly comes from the incomplete reflection of light and the insertion loss of a mode multiplexer; while when I2 is in and O1 is out, the light insertion loss mainly comes from the transmission loss of the grating waveguide and the insertion loss of the 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 in the figure, in the normal state, light enters from I2 and exits from O1, and no power consumption is generated; in the heating state, light enters from I2 and exits from O2, and power consumption is generated. Therefore, the power consumption of the optical switch in the two states is different, and this fluctuation in power consumption is not conducive 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 digitally controlled grating delay switch and an adjustable optical delay line.

[0013] The technical solution of the present invention is implemented as follows: The present invention discloses a digitally controlled grating delay switch, comprising a first digitally controlled grating switch with one input and two outputs and a second digitally controlled grating switch with two inputs and two outputs, wherein the first digitally controlled grating switch comprises a first Bragg grating, a first mode multiplexer, and a first port, a second port, and a third port, wherein the first port is an input port of the digitally controlled grating delay switch, and the second digitally controlled 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, wherein the fifth port is an output port of the digitally controlled grating delay switch, and the seventh port is connected to a light absorber; the second port of the first digitally controlled grating switch is connected to the sixth port of the second digitally controlled grating switch through a first delay waveguide, and the third port of the first digitally controlled grating switch is connected to the fourth port of the second digitally controlled grating switch through a second delay waveguide; the first digitally controlled grating switch and the second digitally controlled grating switch maintain an anomalous operation.

[0014] Furthermore, the first numerically controlled grating switch is in a straight-through state in a normal state and in a reflective state in a heated state. When the first Bragg grating is in the straight-through state, the 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 reflective state, the first mode light entering from the first port undergoes mode conversion and reflection under the action of the first Bragg grating, and the reflected second mode light is converted into the first mode light through the first mode multiplexer and is emitted from the second port.

[0015] Furthermore, the second digitally controlled grating switch is in a straight-through state in a normal state and in a reflective state in a heated state. When the second Bragg grating is in the straight-through state, the first mode light entering from the sixth port directly passes through the second Bragg grating and is emitted 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, and keeps the second mode and passes through the second Bragg grating and passes through the second mode multiplexer. The second mode multiplexer converts the second mode light into the first mode light and then emits 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 through the third mode multiplexer, and then undergoes mode conversion and reflection under the action of the second Bragg grating, and the reflected first mode light is emitted from the fifth port; the first mode light entering from the sixth port is converted into mode and reflected under the action of the second Bragg grating, and the reflected second mode light is converted into the first mode light through the second mode multiplexer and emitted from the seventh port.

[0017] Furthermore, the first mode light is TE0 mode light; and the second mode light is 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, the other end of the first coupling waveguide is connected to the first end of the main waveguide of the first Bragg grating, and one end of the second coupling waveguide is a second port connected to the first end of the first delay waveguide.

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

[0022] Furthermore, the first delay waveguide and the second delay waveguide have different lengths, thereby generating a delay difference between the two states of the switch.

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

[0024] Compared with the prior art, the present invention has the following beneficial effects: the digital controlled grating delay switch of the present invention includes a one-input and two-output (1x2) and a two-input and two-output (2x2) digital controlled grating switch and a first delay waveguide and a second delay waveguide of different lengths, wherein the 1x2 digital controlled grating switch includes a mode multiplexer and a Bragg grating, and has three ports, namely a first port, a second port, and a third port, wherein the first port serves as the input port of the entire switch, and the 2x2 digital controlled grating switch includes two mode multiplexers and a Bragg grating, and has four ports, namely a fourth port, a fifth port, a sixth port, and a seventh port, wherein the fifth port serves as the output port of the entire switch, the seventh port is connected to the 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 digital controlled grating switch and the 2x2 digital controlled grating switch maintain heterogeneous operation, such as Figure 5 , when the 1x2 digitally controlled grating switch is in the normal state (0) and the 2x2 digitally controlled grating switch is in the heated state (1), light passes through the second delay waveguide in the switch; Figure 6 When the 1x2 CNC grating switch is in the heating state and the 2x2 CNC grating switch is in the normal state, the light passes through the first delay waveguide in the switch. In the two switching states, first, the light passes through the second delay waveguide and the first delay waveguide respectively, thereby achieving adjustable delay; secondly, in the 1x2 CNC grating switch and the 2x2 CNC grating switch, Figure 5 and Figure 6 In both switching states, the light passes through a straight path and a reflection path, so the delay introduced by the switch is a constant value, and there will be no delay error due to the change of the switch state. Again, in both switching states, since the light passes through a straight path and a reflection path, the insertion loss is the same, such as Figure 8 and 11 In both switching states, the insertion loss is kept at about 0.2dB, with small insertion loss and small difference. In addition, since the 1x2 CNC grating switch and the 2x2 CNC grating switch work in different states, in both switching states, one switch is in the normal state and the other is in the heating state, so the power consumption is always the power consumption of a heating switch, achieving the stability of power consumption. Finally, Figure 7 and 10 In both switching states, the crosstalk is suppressed to below -60dB, which is nearly three times lower than the -20dB crosstalk of a single switch.

[0025] In summary, the digitally controlled grating switch proposed in the present invention realizes controllable adjustment of delay, and has excellent performances such as small delay error, small insertion loss, small power consumption, small fluctuation of insertion loss and power consumption, small crosstalk, good tolerance and high stability. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0027] Figure 2 This is the spectrum diagram of the 2x2 CNC grating switch under normal conditions;

[0028] Figure 3 This is the spectrum diagram of the 2x2 CNC grating switch in the heating state;

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

[0030] Figure 5 A schematic diagram of a switching state of a symmetrical delay switch based on a digitally controlled grating switch;

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

[0032] Figure 7 For Figure 5 Transmission spectrum of the fifth port in the switch state;

[0033] Figure 8 For Figure 5 A magnified view of the transmission spectrum of the fifth port in the switch state;

[0034] Fig. 9 For Figure 5 Transmission spectrum of the seventh port in the switch state;

[0035] Fig.10 For Figure 6 Transmission spectrum of the fifth port in the switch state;

[0036] Fig.11 For Figure 6 A magnified view of the transmission spectrum of the fifth port in the switch state;

[0037] Fig.12 For Figure 6 Transmission spectrum of the seventh port in the switch state;

[0038] Fig.13 Schematic diagram of a 3-bit delay line constructed by digitally controlled grating delay switches.

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

[0040] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0041] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, similar words such as "one", "one" or "the" do not indicate quantity restrictions, but indicate that there is at least one. Similar words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Similar words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described target changes, the relative positional relationship may also change accordingly.

[0042] In each of the accompanying drawings, identical elements are represented by similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not all drawn to scale. In addition, some well-known parts may not be shown in the drawings.

[0043] Many specific details of the present invention are described below, such as component structures, materials, dimensions, processing techniques and technologies, in order to more clearly understand the present invention. However, as those skilled in the art will appreciate, the present invention may be implemented without following these specific details.

[0044] Embodiment 1

[0045] See also Figure 5 and Figure 6The embodiment of the present invention provides a digitally controlled grating delay switch, comprising a first digitally controlled grating switch 1 with one input and two outputs (i.e., a 1x2 digitally controlled grating switch) and a second digitally controlled grating switch 2 with two inputs and two outputs (i.e., a 2x2 digitally controlled grating switch), wherein the first digitally controlled grating switch 1 comprises a first Bragg grating 11, a first mode multiplexer 12, a first port 13, a second port 14, and a third port 15, wherein the first port 13 is an input port of the digitally controlled grating delay switch, and the second digitally controlled grating switch 2 comprises a second Bragg grating 21, a second mode multiplexer 22, a third mode multiplexer 23, a first port 13, a second port 14, and a third port 15. A multiplexer 23 and a fourth port 24, a fifth port 25, a sixth port 26 and a seventh port 27, wherein 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, and 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 maintain an abnormal operation.

[0046] The present invention designs a digital controlled grating delay switch with a symmetrical structure based on the digital controlled grating switch. Figure 5 and Figure 6 The two states of the switch correspond to the light passing through the second delay waveguide 4 and the first delay waveguide 3, respectively, and two delay states can be realized. The design concept of the digital controlled grating delay switch of the present invention is that no matter which delay waveguide the light passes through in the switch, it passes through a switch direct path and a switch reflection path ( Figure 5 and Figure 6 The seventh port 27 is connected to the optical absorber 5 to eliminate the crosstalk signal in the switch.

[0047] Furthermore, the first digitally controlled grating switch 1 and the second digitally controlled grating switch 2 are in a through state in a normal state and in a reflective state in a heated state.

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

[0049] Furthermore, when the first Bragg grating 11 is in a through state, the first mode light entering from the first port 13 directly passes through the first Bragg grating 11 and is emitted from the third port 15. When the first Bragg grating 11 is in a reflective 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, and the reflected second mode light is converted into the first mode light through the first mode multiplexer 12 and is emitted from the second port 14.

[0050] Further, when the second Bragg grating 21 is in the straight-through state, the first mode light entering from the sixth port 26 directly passes through the second Bragg grating 21 and then is emitted from the fifth port 25, and 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, and keeps the second mode and passes through the second Bragg grating 21 and then passes through the second mode multiplexer 22, and the second mode light is converted into the first mode light by the second mode multiplexer 22 and then is emitted 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 through the third mode multiplexer 23, and then undergoes mode conversion and reflection under the action of the second Bragg grating 21, and the reflected first mode light is emitted from the fifth port 25; the first mode light entering from the sixth port 26 is converted into mode and reflected under the action of the second Bragg grating 21, and the reflected second mode light is converted into the first mode light through the second mode multiplexer 22 and emitted from the seventh port 27.

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

[0053] Further, 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, the other end of the first coupling waveguide is connected to the first end of the main waveguide of the first Bragg grating 11, and 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 empty state, such as Figure 5 and Figure 6 shown.

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

[0055] Further, 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, and 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 empty state, as shown in FIG. Figure 5 and Figure 6 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 a fifth port 25, the other end of the sixth coupling waveguide is connected to the second end of the main waveguide of the second Bragg grating 21, and one end of the seventh coupling waveguide is a 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 empty state, as shown in FIG. Figure 5 and Figure 6 shown.

[0057] Furthermore, the first delay waveguide 3 and the second delay waveguide 4 have different lengths, which will produce different delays, thereby producing 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 coupled port, the third port 15 is a through port, the fourth port 24 is a coupled port, the fifth port 25 is a through port, the sixth port 26 is a through port, and the seventh port 27 is a coupled port.

[0059] Under normal circumstances, Figure 5 1x2 CNC grating switch Indicates that the heater in the switch is not working. At this time, the 1x2 CNC grating switch is in a straight-through state. The TEO mode light entering the first port 13 can directly pass through the first Bragg grating 11. This path is defined as a straight-through path, and then enters the 2x2 CNC grating switch through the second delay waveguide 4. In the heating state, Figure 6 In the 1x2 CNC grating switch, '①' represents 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 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 then changes to TE0 mode and comes out from the second port 14. This path is defined as the reflection path, and then passes through the first delay waveguide 3 to enter the 2x2 CNC grating switch.

[0060] Under normal circumstances, Figure 6, the 2x2 digitally controlled grating switch is in a straight-through state. The TEO mode entering the sixth port 26 can maintain the TEO mode to pass through the entire switch and exit from the fifth port 25. The TEO mode light entering the fourth port 24 changes to the TE1 mode after passing through the third mode multiplexer 23, and then maintains the TE1 mode to pass through the entire second Bragg grating 21, and then passes through the second mode multiplexer 22, changes to the TE0 mode, and exits from the seventh port 27 and is eliminated by the light absorber 5.

[0061] In the heated state, Figure 5 , the 2x2 digital controlled grating switch is in the reflection state. The TEO mode light entering the fourth port 24 is converted to TE1 mode by the third mode multiplexer 23, and then TEO-TE1 mode coupling reflection occurs in the second Bragg grating 21, and the reflected TE0 mode light comes out from the fifth port 25. When the TEO mode light entering the sixth port 26 passes through the second Bragg grating 21, TEO-TE1 mode coupling reflection occurs, and the reflected TE1 mode light is converted to TE0 mode by the second mode multiplexer 22, and comes out from the seventh port 27 and is eliminated by the light absorber 5.

[0062] exist Figure 5 In the figure, after the light enters the CNC grating switch, most of the light passes through the 1x2 CNC grating switch and then goes through the second delay waveguide 4 and comes out from the output port (fifth port 25). Only a small part of the light passes through the 1x2 CNC grating switch and then goes through the first delay waveguide 3. This part of the light is identified as crosstalk. This part of the crosstalk mainly takes the reflection path when passing through the 2x2 CNC grating switch. Therefore, most of the light is eliminated by the light absorber 5 after reaching the seventh port 27. Only a small part of the light takes the direct path and comes out from the output port (fifth port 25), forming crosstalk with the signal light of the output port. Thanks to the low crosstalk performance (-20dB) of the 1x2 CNC grating switch and the 2x2 CNC grating switch themselves and the absorption of crosstalk by the seventh port 27 in the 2x2 CNC grating switch, the crosstalk at the exit end is reduced to an extremely low level. Figure 7 and Figure 8 As shown, the crosstalk signal passing through the first delay waveguide 3 is reduced to below -60dB ( Figure 7 ), while the signal insertion loss after the second delay waveguide 4 is only 0.2dB ( Figure 8 ). Fig. 9 is the crosstalk signal coming out of the seventh port 27, and this part of the crosstalk signal is eliminated by the light absorber 5. Fig. 9 and Figure 2 It can be found that Figure 2 Crosstalk and Fig. 9 The intensities of the crosstalk signals coming out of the seventh port 27 are substantially the same, indicating that most of the crosstalk will be eliminated by the light absorber 5 .

[0063] exist Figure 6In the figure, after the light enters the switch, most of the light passes through the 1x2 CNC grating switch and then goes through the first delay waveguide 3, and then comes out from the output port (fifth port 25). Only a small part of the light passes through the 1x2 CNC grating switch and then goes through the second delay waveguide 4. This part of the light is identified as a crosstalk signal. When passing through the 2x2 CNC grating switch, it mainly takes a direct path. Therefore, most of the light reaches the seventh port 27 and is eliminated by the light absorber 5. Only a small part of the light takes the reflection path and comes out from the output port (fifth port 25), forming crosstalk with the signal light of the output port. Fig.10 and Fig.11 As shown, the crosstalk signal passing through the second delay waveguide 4 is reduced to below -60dB ( Fig.10 ), while the signal insertion loss through the first delay waveguide 3 is only 0.2dB ( Fig.11 ). Fig.12 is the crosstalk signal coming out of the seventh port 27, compared with Fig.12 and Figure 2 It can be found that most of the crosstalk will come out from the seventh port 27 and then be eliminated by the light absorber 5 .

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

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

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

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

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

[0069] In summary, the digitally controlled grating switch proposed in this patent realizes controllable adjustment of delay, and has excellent performances such as small delay error, small insertion loss error, small power consumption fluctuation and small crosstalk.

[0070] Embodiment 2

[0071] See also Fig.13 An embodiment of the present invention further provides an adjustable optical delay line, comprising 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 digitally controlled grating delay switches increases successively along the light transmission direction. 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 digitally controlled grating delay switches of the present invention can be set as required.

[0073] See also Fig.13 An adjustable optical delay line of an embodiment includes three digitally controlled grating delay switches as described in the first embodiment, and the three digitally controlled grating delay switches are connected in series. Connecting three levels of digitally controlled grating delay switches in series can achieve a three-bit delay. Fig.13 As shown, the delay differences of the two delay waveguides in the first, second, and third delay switches are Δt, 2*Δt, and 4*Δt, respectively. Then Fig.13 The delay line in will obtain an adjustable delay of 0-7*Δt, in steps of Δt.

[0074] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but 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 considered to be within the scope of protection of the present invention.

Claims

1. A digitally controlled grating delay switch, characterized in that : It includes a first digitally controlled grating switch with one input and two outputs and a second digitally controlled grating switch with two inputs and two outputs, the first digitally controlled 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 digitally controlled grating delay switch, the second digitally controlled 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 digitally controlled grating delay switch, and the seventh port is connected to a light absorber; the second port of the first digitally controlled grating switch is connected to the sixth port of the second digitally controlled grating switch through a first delay waveguide, and the third port of the first digitally controlled grating switch is connected to the fourth port of the second digitally controlled grating switch through a second delay waveguide; the first digitally controlled grating switch and the second digitally controlled grating switch maintain an abnormal operation.

2. The digital controlled grating delay switch according to claim 1, characterized in that: The first numerically controlled grating switch is in a straight-through state in a normal state and in a reflecting state in a heated state. When the first Bragg grating is in the straight-through state, the 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 reflecting state, the first mode light entering from the first port undergoes mode conversion and reflection under the action of the first Bragg grating, and the reflected second mode light is converted into the first mode light through the first mode multiplexer and is emitted from the second port.

3. The digital controlled grating delay switch according to claim 1, characterized in that: The second digitally controlled grating switch is in a straight-through state in a normal state and in a reflective state in a heated state. When the second Bragg grating is in the straight-through state, the first mode light entering from the sixth port directly passes through the second Bragg grating and is emitted 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, and keeps the second mode and passes through the second Bragg grating and passes through the second mode multiplexer. The second mode multiplexer converts the second mode light into the first mode light and then emits from the seventh port. 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, and 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, and the reflected second mode light is converted into the first mode light through the second mode multiplexer and emitted from the seventh port.

4. The digital controlled grating delay switch according to claim 2 or 3, characterized in that: The first mode light is TE0 mode light; the second mode light is TE1 mode light.

5. The digital controlled grating delay switch according to claim 1, characterized in that: 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, the other end of the first coupling waveguide is connected to the first end of the main waveguide of the first Bragg grating, and one end of the second coupling waveguide is a second port connected to the first end of the first delay waveguide.

6. The digital controlled grating delay switch according to claim 5, characterized in that: The first digitally controlled grating switch also includes a third coupling waveguide, one end of the third coupling waveguide is connected to 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 connected to the first end of the second delay waveguide.

7. The digital controlled grating delay switch according to claim 1, characterized in that: 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 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, and one end of the fifth coupling waveguide is a seventh port connected to the light absorber.

8. The digital controlled grating delay switch according to claim 1, characterized in that: The third mode multiplexer includes 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 to the second end of the main waveguide of the second Bragg grating, and one end of the seventh coupling waveguide is a fourth port connected to the second end of the second delay waveguide.

9. The digital controlled grating delay switch according to claim 1, characterized in that: The first delay waveguide and the second delay waveguide have different lengths.

10. An adjustable light delay line, characterized in that : It comprises at least two digitally controlled grating delay switches as described in any one of claims 1 to 9, and the digitally controlled grating delay switches are connected in series.

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