CN111897173A - 2×2 Optical Switch and N×N Optical Switch Array with Low Loss and Low Random Phase Error - Google Patents

Abstract

The invention discloses a 2×2 optical switch and an N×N optical switch array with low loss and low random phase error. The first and second input waveguides are respectively connected to the first and second front-bending graded waveguides after passing through the first power divider, and the front-bending graded waveguides in the two groups of interference arms pass through the front-end graded waveguide, the phase-shifting waveguide, the rear-end graded waveguide and the rear. The curved graded waveguides are connected in sequence, and the first and second rear curved graded waveguides are connected to the first and second output waveguides through the second power divider. The invention obtains a low-loss ultra-broadband power splitter by adopting adiabatic coupling or bending directional coupling, reduces random phase errors of interference arms by introducing wide waveguides, and further reduces the occurrence of interference arms by adding curved graded waveguides and graded waveguides Finally, a 2×2 optical switch and an N×N optical switch array with low loss and low random phase error are realized, which have the advantages of simple structure, simple process and superior performance.

Description

2×2 Optical Switch and N×N Optical Switch Array with Low Loss and Low Random Phase Error

technical field

The invention belongs to the field of integrated optoelectronic devices, and in particular relates to a 2×2 optical switch and an N×N optical switch array with low loss and low random phase error.

Background technique

With the rapid development of big data, smart Internet of Things and cloud computing, the demand for ultra-large-capacity optical networks is increasing, and higher requirements are also placed on the flexibility and intelligence of the next-generation optical networks. The 2×2 optical switch is the core component of optical interconnection and optical routing. It can freely select the signal transmission channel of the integrated optical chip, which plays an important role in improving the flexibility and scalability of the optical network. Among many integrated platforms, silicon integrated devices have outstanding advantages such as small size, low power consumption, and compatibility with CMOS technology. Therefore, silicon-based optical switching devices have received great attention, among which 2×2 Mach-Zehnder interferometer (MZI) optical switches are the most representative.

At present, MZI-based 2×2 optical switch units have achieved high performance. However, in practical application scenarios such as data centers and programmable logic optical circuits, it is often necessary to integrate a large number of 2×2 optical switches and realize an N×N optical switch array with a large number of ports through the switch topology. At this time, as a single 2×2 optical switch unit device, it must have high performance such as extremely low insertion loss. At the same time, due to the extremely high refractive index difference of silicon optical waveguides, its single-mode waveguides are often only about 450 nm. However, a certain random dimensional deviation will inevitably be introduced in actual manufacturing. Therefore, there is often a large random phase difference between the two phase shifters in the 2×2MZI optical switch, resulting in a random shift of the zero point of its operation. In order to solve this problem, it is often necessary to introduce an additional power monitor and perform very tedious work such as bias voltage calibration for each optical switch unit one by one, which makes the development of N×N optical switch arrays complicated in power consumption, structure and testing. face great challenges.

SUMMARY OF THE INVENTION

In order to solve the problems existing in the background art, the present invention proposes a 2×2 optical switch and an N×N optical switch array with low loss and low random phase error.

The technical scheme adopted in the present invention is:

1. A 2×2 optical switch with low loss and low random phase error:

The structure includes a first input waveguide, a second input waveguide, a first power divider, a first front-bending graded waveguide, a second front-bending graded waveguide, a first front-end graded waveguide, a second front-end graded waveguide, a first phase-shifted waveguide, a second phase-shifted waveguide, a first back-end graded waveguide, a second back-end graded waveguide, a first post-bend graded waveguide, a second post-bend graded waveguide, a second power splitter, a first output waveguide, and a second output waveguide; The first input waveguide and the second input waveguide are respectively connected to the two input ends of the first power splitter, and the two output ends of the first power splitter are respectively connected to one end of the first front bending graded waveguide and the second front bending graded waveguide. connection, the other end of the first front-curved graded waveguide is connected to one end of the first phase-shifted waveguide via the first front-end graded waveguide, and the other end of the first phase-shifted waveguide is connected to one end of the first back-curved graded waveguide via the first rear-end graded waveguide; The other end of the two front-bending graded waveguides is connected to one end of the second phase-shifting waveguide through the second front-end graded waveguide, and the other end of the second phase-shifting waveguide is connected to one end of the second rear-bending graded waveguide through the second rear-end graded waveguide; The other ends of the curved graded waveguide and the second post-curved graded waveguide are connected to the two input ends of the second power divider, and the two output ends of the second power divider are respectively connected to the first output waveguide and the second output waveguide; The first front-bending graded waveguide, the second front-bending graded waveguide, the first rear-bending graded waveguide, and the second rear-bending graded waveguide are all bending graded structures with a graded width. The width of the waveguide at the output end of the power splitter is the same, and the width of the curved graded waveguide at the end close to the phase-shifted waveguide is greater than the width of itself at the end close to the power divider; the phase-shifted waveguide is a wide waveguide, and the width is greater than that of the waveguide at the output end of the power divider width.

The first phase shift region and the second phase shift region are both phase shift structures of wide waveguides equivalent to phase shift waveguides, and adopt phase regulation based on thermo-optic effect or electro-optic effect.

The first power divider and the second power divider adopt but are not limited to an adiabatic gradient structure or a curved directional coupling structure.

The first front-bending graded waveguide, the second front-bending graded waveguide, the first rear-bending graded waveguide, and the second back-bending graded waveguide adopt, but are not limited to, a bend-graded structure based on an Euler curve or an S-shaped arc.

The first front-end tapered waveguide, the second front-end tapered waveguide, the first back-end tapered waveguide and the second back-end tapered waveguide adopt a linear tapered structure or a nonlinear tapered structure.

2. An N×N optical switch array:

The N×N optical switch array includes at least four cascaded 2×2 optical switches according to any one of claims 1 to 5 .

The 2×2 optical switches of adjacent front and rear stages are connected by straight waveguides and crossed waveguides.

A group of two optical switches is used to divide the four optical switches into two groups, and multiple optical switch groups are connected in series in sequence.

A group of two optical switches is used to divide the four optical switches into two groups. One of the output waveguides of the two optical switches in the former group of optical switches and one of the two optical switches in the latter group of optical switches are respectively. The input waveguides are connected, the other output waveguides of the two optical switches in the former group of optical switches are respectively connected to two ends of one side of the crossed waveguide, and the other input waveguides of the two optical switches in the latter group of optical switches are respectively connected to Cross the ends of the other side of the waveguide.

The straight waveguides and the crossed waveguides are single-mode waveguides.

The beneficial effects of the present invention are:

The invention significantly reduces the random phase error in the phase shift region of the 2×2 optical switch by introducing a wide waveguide design in the phase shift region, and connecting the input end or the output end waveguide of the power divider through the curved gradient waveguide and the gradient waveguide, and almost eliminates the Its working zero offset avoids the one-by-one calibration required by traditional 2×2 optical switches. It not only greatly simplifies the N×N optical switch array structure, but also significantly reduces the complexity of N×N optical switch array testing, but also avoids the energy consumption caused by the zero-point calibration of the 2×2 optical switch device.

The invention realizes a power divider with ultra-low loss and ultra-large working bandwidth by adopting a curved directional coupler or adiabatic gradient coupler, thereby greatly reducing the loss of a single 2×2 optical switch device, and also having a large working bandwidth.

Based on the above-mentioned 2×2 optical switch with low loss and low random phase error, the present invention can realize a large number of ports N×N optical switch array by adopting a specific or general topology structure, and it is not necessary to perform complicated work zero point calibration for each switch unit one by one. The additional power monitors typically required for conventional NxN optical switch arrays can also be avoided.

The invention can be fabricated by a standard plane integrated optical waveguide process, and has the advantages of simple process, low cost, low loss, high extinction ratio, compatibility with CMOS process, and large-scale production potential.

To sum up, the present invention realizes a 2×2 optical switch and an N×N optical switch array with low loss and low random phase error by using a phase-shift region waveguide with low random phase error and a low-loss power divider, and has a simple structure. , simple process, superior performance and so on.

Description of drawings

FIG. 1 is an overall schematic diagram of a 2×2 optical switch of the present invention.

Fig. 2 is a schematic structural diagram of a power splitter that can be used in the present invention, wherein Fig. 2(a) is a power splitter based on adiabatic gradient structure, and Fig. 2(b) is a power splitter based on curved waveguide coupling.

FIG. 3 is a schematic diagram of a bend graded waveguide based on an Euler curve that can be used in the present invention.

Fig. 4 is a schematic diagram of a graded waveguide that can be used in the present invention, wherein Fig. 4(a) is a linearly graded waveguide, and Fig. 4(b) is a nonlinear graded waveguide.

FIG. 5 is a schematic diagram of an N×N optical switch array of the present invention.

6 is a graph of simulation results of a power splitter based on a curved directional coupler according to an embodiment.

FIG. 7 is a simulation result diagram of the bending graded waveguide based on the Euler curve according to the embodiment.

In the figure: 11 is the first input waveguide, 12 is the second input waveguide, 2 is the first power divider, 31 is the first front-bending graded waveguide, 32 is the second front-bending graded waveguide, and 41 is the first front-end graded waveguide , 42 is the second front-end graded waveguide, 51 is the first phase-shifted waveguide, 52 is the second phase-shifted waveguide, 61 is the first rear-end graded waveguide, 62 is the second rear-end graded waveguide, and 71 is the first back-bend graded waveguide Waveguide, 72 is the second post-bending graded waveguide, 8 is the second power splitter, 91 is the first output waveguide, and 92 is the second output waveguide.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

As shown in FIG. 1 , the specific implementation includes a first input waveguide 11 , a second input waveguide 12 , a first power divider 2 , a first front-bending graded waveguide 31 , a second front-bending graded waveguide 32 , and a first front-end graded waveguide 41 . , the second front-end graded waveguide 42, the first phase-shifted waveguide 51, the second phase-shifted waveguide 52, the first back-end graded waveguide 61, the second back-end graded waveguide 62, the first back-bending graded waveguide 71, the second back-bending The graded waveguide 72 , the second power divider 8 , the first output waveguide 91 and the second output waveguide 92 ; the first input waveguide 11 and the second input waveguide 12 are respectively connected to the two input ends of the first power divider 2 . The two output ends of a power divider 2 are respectively connected to one end of the first front-bending graded waveguide 31 and the second front-bending graded waveguide 32, and the other end of the first front-bending graded waveguide 31 passes through the first front-end graded waveguide 41 and the first One end of the phase-shifting waveguide 51 is connected, and the other end of the first phase-shifting waveguide 51 is connected through the first rear-end graded waveguide 61 and one end of the first back-bending graded waveguide 71 ; the other end of the second front-bending graded waveguide 32 is connected through the second front-end graded waveguide 42 is connected to one end of the second phase-shift waveguide 52, and the other end of the second phase-shift waveguide 52 is connected to one end of the second rear-end graded waveguide 62 and one end of the second post-bending graded waveguide 72; the first post-bending graded waveguide 71 and the second post-bend graded waveguide 71 The other end of the graded waveguide 72 is connected to the two input ends of the second power divider 8, and the two output ends of the second power divider 8 are respectively connected to the first output waveguide 91 and the second output waveguide 92; the first front bend The graded waveguide 31 , the second front curved graded waveguide 32 , the first rear curved graded waveguide 71 and the second rear curved graded waveguide 72 are all curved graded structures with graded widths, and each curved graded waveguide is located at one end close to 2/8 of the power divider The width of the phase shift waveguide 51/52 is smaller than that of the end of the phase shift waveguide 51/52, and the width of the phase shift waveguide 51/52 is more than twice the width of the curved graded waveguide 31/32/71/72 at the end close to the power divider 2/8.

The first interference arm is mainly composed of the first front-bending graded waveguide 31 , the first front-end graded waveguide 41 , the first phase-shifting waveguide 51 , the first rear-end graded waveguide 61 , and the first back-bending graded waveguide 71 . The two front-bending graded waveguides 32 , the second front-end graded waveguide 42 , the second phase-shifting waveguide 52 , the second rear-end graded waveguide 62 , and the second rear-bending graded waveguide 72 constitute the second interference arm.

In specific implementation, the first power divider 2 and the second power divider 8 may adopt but are not limited to an adiabatic gradient structure or a curved directional coupling structure.

The first front bend graded waveguide 31 , the second front bend graded waveguide 32 , the first back bend graded waveguide 71 and the second back bend graded waveguide 72 adopt but are not limited to a bend graded structure based on an Euler curve type.

The first front-end graded waveguide 41 , the second front-end graded waveguide 42 , the first back-end graded waveguide 61 and the second back-end graded waveguide 62 adopt but are not limited to linearly graded structures or non-linearly graded structures.

Both the first phase-shift waveguide 51 and the second phase-shift waveguide 52 are phase-shift structures of wide waveguides, and adopt, but are not limited to, phase regulation based on thermo-optic effect or electro-optic effect.

The working process of the present invention is as follows: the phase difference of the two interference arms can be controlled by the thermo-optic effect or the electro-optic effect; when the phase difference of the two interference arms is 0, that is, when the 2×2 optical switch is in the “off” state, The light entering from the first input waveguide 11 will be output from the second output waveguide 92, and the light entering from the second input waveguide 12 will be output from the first output waveguide 91; and when the phase difference between the two interference arms is π, that is When the 2×2 optical switch is in the "on" state, the light entering from the first input waveguide 11 will be output from the first output waveguide 91, and the light entering from the second input waveguide 12 will be output from the second output waveguide 92, thereby realizing 2×2 optical switch function.

As shown in FIG. 2 , the first power divider 2 and the second power divider 8 both use adiabatic gradient couplers with large bandwidth and low loss (as shown in FIG. 2( a )) or curved directional couplers (as shown in FIG. 2 ( b) shown).

As shown in Figure 3, the curved gradient waveguide adopts a waveguide structure based on the Euler curve, and sets the width gradient. The Euler curve combines the characteristics of curvature and width gradient to reduce the bending loss of the waveguide, while increasing the waveguide width to further reduce the Random phase errors due to narrow waveguides.

As shown in Figure 4, the graded waveguide can be a linear graded waveguide (as shown in Figure 4(a)) or a nonlinear graded waveguide (as shown in Figure 4(b)), where the nonlinear graded waveguide can use the function y=x ² Optimize the length and loss, x represents the direction of transmission parallel to the waveguide, and y represents the direction of transmission perpendicular to the waveguide.

As shown in Figure 5, it is a 4×4 optical switch array (N=4) composed of the above-mentioned low-loss and low-random phase error 2×2 optical switch units. The figure shows the 4×4 optical switch using the Benes topology. Arrays; for different application scenarios, different topologies are used, and N×N optical switch arrays with more ports can be obtained by cascading more optical switch units.

The 4×4 optical switch array includes six 2×2 optical switches, and the six 2×2 optical switches are divided into two groups in a group of two 2×2 optical switches, and the multiple 2×2 optical switch groups are arranged in sequence. concatenate. One of the respective output waveguides of the two 2×2 optical switches in the former group of 2×2 optical switches is respectively connected with one of the respective input waveguides of the two 2×2 optical switches in the latter group of 2×2 optical switches. The other output waveguides of the two 2×2 optical switches in the group of 2×2 optical switches are respectively connected to two ends of one side of the cross waveguide, and the other output waveguides of the two 2×2 optical switches in the latter group of 2×2 optical switches are respectively connected to An input waveguide is connected to both ends on the other side of the crossed waveguide, respectively.

As shown in Figure 5, specifically, the connection between four adjacent 2×2 optical switches is as follows:

A group of two 2×2 optical switches is used to divide the four 2×2 optical switches into two groups. The first output waveguide 91 of the first 2×2 optical switch of the former group of 2×2 optical switches is guided by a straight It is connected with the first input waveguide 11 of the first 2×2 optical switch of the latter group of 2×2 optical switches, and the second output waveguide 92 of the second 2×2 optical switch of the former group of 2×2 optical switches is The straight waveguide is connected to the second input waveguide 12 of the second 2×2 optical switch of the latter group of 2×2 optical switches, and the second output waveguide of the first 2×2 optical switch of the former group of 2×2 optical switches 92 and the first output waveguide 91 of the second 2×2 optical switch of the former group of 2×2 optical switches are respectively connected to two ends of one side of the cross waveguide, and the first 2×2 optical switch of the latter group of 2×2 optical switches are respectively connected The second input waveguide 12 of the 2 optical switch and the first input waveguide 11 of the second 2×2 optical switch of the latter group of 2×2 optical switches are respectively connected to two ends of the other side of the cross waveguide.

Specific embodiments of the present invention are as follows:

The silicon nanowire optical waveguide based on silicon on insulator (SOI) material is selected: the core layer is silicon material, the thickness is 220nm, and the refractive index is _{3.4744 ;} 2 μm, the upper cladding SiO ₂ thickness is 1 μm, and the refractive index is 1.4404.

For the curved waveguide directional coupler shown in Figure 2(b), the relevant parameters are: the width of the two curved waveguides on the inner side and the outer side are both 450nm, the spacing between the two waveguides is 200nm, and the bending radius of the inner waveguide is 58μm, The coupling angle of the bend is 21°.

For the Euler curved graded waveguide as shown in Figure 3, the relevant parameters are: the narrowest and widest waveguide widths are 450 nm and 850 nm, respectively, the maximum bending radius of the Euler curve-based curved waveguide is 25 μm, and the minimum bending radius is 20μm.

The device's curved waveguide directional coupler and Euler curved graded waveguide are simulated and verified by three-dimensional finite-difference time-domain method. Figure 6(a) is the spectral response of the light input at the left end at the right cross end and the straight end. It can be seen that in the range of 1500-1600 nm, the splitting ratio of the curved waveguide directional coupler is about 50%:50%. At the same time, the coupler loss is only about 0.0005, as shown in Figure 6(b). Therefore, the power divider used in the present invention has the characteristics of low insertion loss and large bandwidth. Fig. 7 is the spectral response of light input on the left side and output on the right side for the Euler bending graded waveguide shown in Fig. 3 . It can be seen that the curved graded waveguide based on the Euler curve can ensure that the width gradient can be achieved in the case of low loss, and high-order modes are not excited.

Therefore, the present invention obtains a low-loss ultra-broadband power divider in the form of adiabatic coupling or bending directional coupling, reduces the random phase error of the interference arm by introducing a wide multi-mode waveguide, and adds a curved graded waveguide and a graded waveguide to further The random phase error of the interference arm is reduced, and the 2×2 optical switch N×N optical switch array 2×2 optical switch and the N×N optical switch array with low loss and low random phase error are finally realized, which has the advantages of simple structure and simple process. , superior performance and so on.

The above-mentioned embodiments are used to explain the present invention, rather than limit the present invention. Within the spirit of the present invention and the protection scope of the claims, any modifications and changes made to the present invention all fall into the protection scope of the present invention.

Claims (9)

1. A 2×2 optical switch with low loss and low random phase error, characterized in that it comprises a first input waveguide (11), a second input waveguide (12), a first power divider (2), a first front A curved graded waveguide (31), a second front curved graded waveguide (32), a first front-end graded waveguide (41), a second front-end graded waveguide (42), a first phase-shifted waveguide (51), a second phase-shifted waveguide ( 52), a first rear-end graded waveguide (61), a second rear-end graded waveguide (62), a first post-curved graded waveguide (71), a second post-curved graded waveguide (72), and a second power divider (8) ), a first output waveguide (91) and a second output waveguide (92); the first input waveguide (11) and the second input waveguide (12) are respectively connected to the two input ends of the first power divider (2), The two output ends of the first power divider (2) are respectively connected to one end of the first front bending graded waveguide (31) and the second front bending graded waveguide (32), and the other end of the first front bending graded waveguide (31) is One end of the first front-end graded waveguide (41) is connected to the first phase-shifted waveguide (51), and the other end of the first phase-shifted waveguide (51) passes through the first rear-end graded waveguide (61) and the first back-bending graded waveguide (71) One end is connected; the other end of the second front-curved graded waveguide (32) is connected to one end of the second phase-shifted waveguide (52) through the second front-end graded waveguide (42), and the other end of the second phase-shifted waveguide (52) is connected through the second rear One end of the end graded waveguide (62) and the second post-curved graded waveguide (72) are connected at one end; the other ends of the first post-curved graded waveguide (71) and the second post-curved graded waveguide (72) are connected to the second power divider (8) ), and the two output ends of the second power divider (8) are respectively connected to the first output waveguide (91) and the second output waveguide (92); the first forward bending graded waveguide (31) ), the second front bending graded waveguide (32), the first back bending graded waveguide (71) and the second back bending graded waveguide (72) are all bending graded structures with a graded width, and the bending graded waveguide is close to the power divider (2). , 8) The width of one end is the same as the width of the waveguide at the output end of the power divider (2, 8), and the width of the curved graded waveguide at one end near the phase-shift waveguide (51, 52) is greater than that at the end near the power divider (2, 8) The width of one end; the phase-shift waveguides (51, 52) are wide waveguides, and the width is greater than the width of the waveguide at the output end of the power divider (2, 8). 2 . The 2×2 optical switch with low loss and low random phase error according to claim 1 , wherein the first phase shift region ( 51 ) and the second phase shift region ( 52 ) are both The phase-shift structure of the broad waveguide adopts the phase control based on the thermo-optic effect or the electro-optic effect. 3. A 2×2 optical switch with low loss and low random phase error according to claim 1, characterized in that: the first power divider (2) and the second power divider (8) adopt but Not limited to adiabatic gradient structures or curved directional coupling structures. 4. The 2×2 optical switch with low loss and low random phase error according to claim 1, characterized in that: the first front bending graded waveguide (31) and the second front bending graded waveguide (32) , The first post-bending graded waveguide (71) and the second post-bending graded waveguide (72) adopt, but are not limited to, a bending graded structure based on an Euler curve or an S-shaped arc. 5. The 2×2 optical switch with low loss and low random phase error according to claim 1, characterized in that: the first front-end tapered waveguide (41), the second front-end tapered waveguide (42), the first front-end tapered waveguide (42), the A back-end graded waveguide (61) and a second back-end graded waveguide (62) adopt a linear gradient structure or a non-linear gradient structure. 6. An N×N optical switch array, characterized in that: The N×N optical switch array includes at least four cascaded 2×2 optical switches according to any one of claims 1 to 5 . 7. An N×N optical switch array according to claim 6, wherein: The 2×2 optical switches of adjacent front and rear stages are connected by straight waveguides and crossed waveguides. 8. An N×N optical switch array according to claim 6, characterized in that: A group of two optical switches is used to divide the four optical switches into two groups, and multiple optical switch groups are connected in series in sequence. 9 . The optical switch array according to claim 6 , wherein the four optical switches are divided into two groups by using a group of two optical switches, and each of the two optical switches in the former group of optical switches is among the two groups. 10 . An output waveguide is respectively connected with one of the input waveguides of the two optical switches in the latter group of optical switches, and the other output waveguides of the two optical switches in the former group of optical switches are respectively connected to two ends of one side of the cross waveguide, The other input waveguides of the two optical switches in the latter group of optical switches are respectively connected to two ends of the other side of the crossed waveguides.

Images