Method and apparatus for selecting optical path through photonic circuit, and evaluation method and apparatus

Abstract

The invention relates to a method and device for selecting an optical path through a photonic circuit and an evaluation method and device. A method of selecting an optical path through a photonic circuit between an input port and an output port, in which there are a plurality of different optical paths connecting the input port and the output port, and each optical path is configured to include a plurality of constituent elements, the method comprising: establishing at least one characteristic of each of the constituent elements; and selecting an optical path based on the established at least one characteristic.

Description

Technical Field

[0001] The present technology relates to an apparatus, a computer program, and a method. Background Art

[0002] The "Background Art" provided herein is for the purpose of generally presenting the background of the present disclosure. The achievements of the currently named inventors to the extent described in the Background Art section and aspects of the description that could not, as of the time of filing, be regarded as prior art are not admitted, either explicitly or implicitly, as prior art against the present technology.

[0003] In recent years, programmable photonic circuits have been developed. These programmable photonic circuits consist of a large waveguide mesh of tunable couplers that connect multiple optical inputs to multiple optical outputs. This allows for optical connections without the need to convert optical light to an electrical signal for routing and then convert the electrical signal back to optical light for transmission over a fiber optic connection. For example, this allows for very high bandwidth, low latency communication over a wireless telecommunications infrastructure.

[0004] However, waveguides have optical losses. In other words, some light leaks from the waveguide as the light passes through it. This is not desirable because the signal-to-noise ratio decreases with optical losses. Additionally, leakage from one waveguide can cause crosstalk with another waveguide.

[0005] An object of the present disclosure is to solve at least one of these problems. Summary of the Invention

[0006] According to an embodiment of the present disclosure, there is provided a method of selecting an optical path through a photonic circuit between an input port and an output port, wherein there are multiple different optical paths connecting the input port and the output port, and each optical path is configured to include a plurality of constituent elements, the method comprising: establishing at least one characteristic of each of the constituent elements; and selecting an optical path based on the established at least one characteristic.

[0007] The above paragraphs have been provided by way of general introduction and are not intended to limit the scope of the appended claims. The described embodiments, as well as additional advantages, will be best understood by reference to the following detailed description in conjunction with the accompanying drawings. Brief Description of the Drawings

[0008] The present disclosure is better understood when considered in conjunction with the accompanying drawings, and thus a more complete understanding of the present disclosure and many of its attendant advantages will be readily obtained, wherein:

[0009] Figure 1 A photonic circuit is shown;

[0010] Figure 2Shows a configurable photonic circuit 100 according to an embodiment of the present disclosure;

[0011] Figure 3 Shows a detector 105 according to an embodiment;

[0012] Figure 4 Shows a controller according to an embodiment;

[0013] Figure 5 Shows data associated with each component;

[0014] Figure 6A And Figure 6B Shows a user interface according to an embodiment; and

[0015] Figure 7 Shows a process according to an embodiment executed by the controller. Detailed Description

[0016] Now referring to the drawings, wherein like reference numerals represent like or corresponding components throughout the several views.

[0017] In view of the above teachings, many modifications and variations of the present disclosure are possible. Accordingly, it is to be understood that within the scope of the appended claims, the present disclosure may be practiced differently than specifically described herein.

[0018] Figure 1 Generally shows a photonic circuit. The photonic circuit has a grid of optical paths formed by components. These components are formed by waveguides on a semiconductor substrate. For example, the waveguides are formed on a silicon substrate. Specifically, in the case where the semiconductor substrate is silicon, an SiO2 layer is deposited on the silicon, and components of the optical paths formed of silicon or silicon nitride (SiN) are formed within the SiO2 to act as segments of the optical paths. Of course, the present disclosure is not limited thereto and may include barium titanate (BTO) or lithium niobate (LiNbO3), etc. Now, configurable photonic chips can be formed, for example, as part of the EU Horizon 2020 Superpixels project, those developed at the Politecnico di Milano in cooperation with the Scuola Superiore Sant'Anna in Pisa, the University of Glasgow, and Stanford University.

[0019] Back to Figure 1, in this example, the photonic circuit has one input ("input" IN) and two outputs ("output 1" OUT1 and "output 2" OUT2). With a configurable photonic chip, the optical path can be routed between the input IN and one or both of the outputs OUT1 and OUT2. For example, in the case where an optical path between IN and OUT1 is required, the components A6, B1, B6, B5, B4, D5, D4, F5, and F4 can be used. Alternatively, the optical path can be formed from the components A1, A2, A3, D2, D3, F5, F4. In fact, there are many possible alternative components that can form the optical path between the input IN and the output OUT1.

[0020] A similar situation occurs in the case where an optical path between the input IN and the output OUT2 is required. Specifically, the optical light can follow a path along the components A6, A5, B3, B4, E6, E5 or the components A1, A2, A3, A4, B3, B4, E6, E5. Additionally, there are many components that can form the optical path between the input and the output OUT2.

[0021] As will be appreciated, the appropriate components can be selected to form the optical path by providing phase shifters and tunable couplers that can be configured in the components as a through state or a cross state. These arrangements are known and have been demonstrated by the Polytechnic University of Valencia, where a programmable 7 hexagonal unit circuit was demonstrated.

[0022] In the example, the selection of the components used is arbitrary, and simply, the selection of the optical path is sufficient. This is especially the case when the system switches the optical path between the outputs (i.e., for example, from OUT1 to OUT2). In other words, it is important to select any components that form the optical path between the input and the output, rather than the specific components that form the path.

[0023] The inventors have realized that with a configurable photonic circuit, it is desirable to select the most appropriate route between the input and any one or both of the outputs. In other words, carefully selecting the components that form the optical path can improve the performance of the configurable photonic circuit. In an embodiment, the most appropriate route is selected based on at least one characteristic of the components that form the optical path. In an embodiment, the at least one characteristic is the optical loss along the corresponding component. However, it should be understood that the present disclosure is not limited to this, and other criteria can be used when determining the most appropriate route. For example, the length of the component can be used, as this will not only affect the optical loss but also the delay within the configurable photonic circuit, since the further the light needs to travel, the higher the delay.

[0024] Figure 2Shows a configurable photonic circuit 100 according to an embodiment of the present disclosure.

[0025] In the configurable photonic circuit 100 according to an embodiment, the detector 105 is positioned on the constituent member A6. Reference will be made to Figure 3 describe the structure of the detector 105 according to an embodiment. However, the purpose of the detector 105 is to detect the optical light emitted from the constituent member A6. This emitted optical light will create optical losses in the constituent member A6, which reduces the signal-to-noise ratio and increases crosstalk between the constituent members. The detector 105 is thus positioned along at least a portion of the constituent member A6 to measure the optical losses.

[0026] In an embodiment, the detector 105 can be positioned anywhere along the constituent member. However, in an embodiment, the detector 105 can be positioned near the junction between different constituent members. This is because the optical losses tend to be worse near the junction, and thus placing the detector 105 such that the optical losses are measured at the junction improves the determined optical path.

[0027] It should be noted that while Figure 2 a single detector 105 is shown, it is contemplated that there will be multiple detectors 105 in an embodiment, and in an example, there is one or more detectors 105 along each constituent member.

[0028] Figure 3 Shows a detector 105 according to an embodiment. Although any detector 105 capable of detecting and measuring the optical light emitted from the constituent member A6 is contemplated, the inventors have found a particular type of detector 105 to be particularly useful.

[0029] Specifically, it is contemplated that the detector 105 will be formed by one or more graphene patches in an embodiment. For a variety of reasons, the detector 105 formed by one or more graphene patches is particularly advantageous. First, graphene readily absorbs light in the range of 1 µm - 3 µm. This wavelength of light is typically used to form photonic circuits on silicon substrates. Additionally, the graphene detector is unbiased, meaning it has zero power consumption in the idle state. Furthermore, graphene detects high data rate signals due to its high electron mobility.

[0030] Reference Figure 3, detector 105 is shown. Detector 105 is located above the waveguide forming part of the compositional member A6 shown. Detector 105 has a source, a drain, and two gates (gate 1 and gate 2). The graphene patch 110 is positioned between the two gates and above the waveguide. The graphene patch 110 can be deposited directly on the SiO2 layer or can be encapsulated to avoid contamination. In an embodiment, the graphene patch can be encapsulated with Al2O3 to preserve the graphene layer and avoid contamination. Although a single patch of graphene is shown, the present disclosure is not limited thereto, and a multi-patch structure that can be used to cover more complex circuits is envisioned.

[0031] An example of detector 105 is described in [1], the content of which is incorporated herein by reference. Specifically but not restrictively, the content of [1] describing the fabrication and operation of graphene detectors is incorporated by reference.

[0032] Referring again to Figure 2 , the output from detector 105 is fed to controller 200. In addition, controller 200 is connected to configurable photonic circuit 100. Controller 200 is configured to control the operation of configurable photonic circuit 100 by selecting optical paths and the compositional members forming the optical paths based at least on the output of detector 105 or each detector 105. In other words, controller 200 controls the tunable couplers and phase shifters within the compositional members of the optical paths in configurable photonic circuit 100 to control the flow of light through the compositional members.

[0033] Referring to Figure 4 , controller 200 according to an embodiment is shown. Controller 200 includes connections to each of the detectors 105 within configurable photonic circuit 100. This allows the output from each detector 105 to be provided to controller 200, as will be described subsequently. In addition, controller 200 includes connections to each of the compositional members to control the phase shifters and / or tunable couplers within the compositional members. It should be understood that although Figure 4 direct connections between controller 200 and each detector 105 and the tunable couplers and phase shifters are shown, the present disclosure is not limited thereto, and controller 200 can be connected via any kind of arrangement without the need for a direct connection.

[0034] In an embodiment, the control component 210 is disposed in the controller 200. In an embodiment, the control component 210 is a solid-state circuit system such as an application-specific integrated circuit, or in an embodiment, is a circuit system whose operation is controlled using computer software. Further, a memory 215 is provided. In an embodiment, the memory 215 is a solid-state circuit system configured to store data and computer-readable code associated with each constituent component, and when loaded onto the control component 210, the computer-readable code configures the control component 210 to perform steps in accordance with embodiments of the present disclosure.

[0035] The data associated with each component stored within the memory 215 is shown in Figure 5 Specifically, Figure 5 a table showing the association of at least one characteristic of the constituent component with the constituent component is shown. In an embodiment, the at least one characteristic includes optical loss along the constituent component and / or the length of the constituent component. It should be noted that the present disclosure is not limited to any one characteristic of the constituent component, and any one or more characteristics may be selected, as will be understood. Further, one or more characteristics of one or more constituent components can be used to determine an optical path. For example, the optical loss across a number of constituent components can be used to determine an optical path.

[0036] It will be understood that the characteristics of the constituent component are updated periodically. In an embodiment, the update will occur regularly (which can be twice per second) or can occur when the difference between the stored value and the current value is above a threshold. For example, if the optical loss along the constituent component changes by more than a threshold amount (e.g., 0.05 dB / km), the characteristic is updated. The optical loss value will be provided by the detector 105 connected to the controller 200, and the controller 200 will update the stored optical loss value. In an embodiment, the output from the detector 105 can be amplified before being provided to the controller 200.

[0037] It should also be understood that since it is defined by the length of the waveguide, the length of the constituent component is not likely to change.

[0038] Further, although the constituent component has been described as part of a waveguide, the present disclosure is not limited thereto. In fact, the constituent component can include any part of the optical path, such as an optical switch or a coupler, etc. In other words, the term "constituent component" can include any element that forms part of the optical path, such as a waveguide (or a part thereof), a coupler, an optical switch, etc. In an embodiment, a graphene detector is used to measure the optical loss at the element. However, the present disclosure is not limited thereto, and any suitable mechanism can be used to determine the optical loss (or other characteristics) at the constituent component.

[0039] Figure 6A and Figure 6BShows a user interface according to various embodiments. In an embodiment, the user interface shows a schematic diagram of a photonic circuit having an input ("Input" IN) and outputs ("Output 1" OUT1 and "Output 2" OUT2). Of course, the present disclosure is not limited thereto, and the user interface can be any configuration that allows a user to control the controller 200. In an embodiment, the user interface is displayed on a display 600 having a touch screen, which allows the user to use the touch screen to control the operation of the controller 200. Of course, the present disclosure is not limited thereto, and any type of display and user control element (such as a mouse, etc.) is contemplated.

[0040] In any case, in an embodiment, the user touches the input (at Figure 6A ), and then touches one of the outputs. In this example, the user touches "Output 1" (OUT1). This user control instructs the controller 200 to create an optical path between the "Input" and "Output 1". Of course, any equivalent control is contemplated, and any number of inputs and / or outputs is contemplated.

[0041] Then, the controller 200 selects an optical path based on one or more characteristics of the components stored in the Figure 5 table shown in. The selection process will be described with reference to Figure 7 this.

[0042] Figure 7 Shows a process 700 according to an embodiment performed by the controller 200. The process starts at step 705. The process then moves to step 710, in which an input port and an output port are selected. In an embodiment, this is performed by the user, but in an embodiment, this is performed by an external controller that selects the input and output ports based on one or more other criteria (such as routing an input fiber optic port to a different fiber optic output port).

[0043] Then, the process moves to step 715, in which each path between the selected input port and output port is processed such that an optical path is determined. In an embodiment, this can be performed using Dijkstra's algorithm, whereby one or more characteristics of interest are used as the cost of a vector. In other words, in an embodiment, using Dijkstra's algorithm, the optical loss characteristic will provide the cost of each vector, and in an embodiment, the length of each component will also provide the cost of each vector. Of course, the present disclosure is not limited thereto, and any one or more characteristics can provide the cost of each vector. In addition, the present disclosure is not limited to using Dijkstra's algorithm, and any suitable routing algorithm is contemplated.

[0044] After determining the optical path between the input port and the output port, the process moves to step 720, where the controller 200 controls the photonic circuit to route light via the path with the lowest cost. In other words, in an embodiment, the controller will control the photonic circuit to route light according to the characteristics used in Dijkstra's algorithm. As will be understood, such control will be performed by controlling phase shifters and / or tunable couplers (not shown) disposed within the photonic circuit. This control of the phase shifters and tunable couplers uses known techniques.

[0045] Then, the process moves to step 725, where process 700 ends.

[0046] In addition to establishing the optical path between the input and the output (or between multiple inputs and outputs), in an embodiment, the controller 200 also controls the output power of the input transmitter. Such control can be via direct control of the input transmitter or by issuing commands to the input transmitter. In an embodiment, the term "input transmitter" refers to the provider of optical light at the input port, which is a laser in an embodiment.

[0047] Specifically, for any given desired optical power at the output port, when the controller 200 has determined the optical loss along the optical path, the controller 200 notifies the input transmitter of the optical power required to achieve the given output optical power at the input port. This allows the input transmitter to dynamically change the input optical power to achieve a specific output laser power. This improves the energy efficiency of the system while ensuring that the output port has sufficient optical power. Of course, although the optical loss is described above as a characteristic, the present disclosure is not limited thereto, and any characteristic is contemplated.

[0048] Other embodiments

[0049] The above describes a dynamic routing technique for determining the optical path between the input port and the output port based on at least one characteristic of the photonic circuit. However, in other embodiments, a similar principle is used to evaluate the manufacturing associated with the production of the photonic circuit.

[0050] Specifically, for a given photonic circuit, the detector 105 is positioned on each of the constituent components. The optical loss is measured for each constituent component and stored in the memory 215. However, instead of using the optical loss to determine the optical path between the input and the output as described above, in an embodiment, this optical loss information for each constituent component is used to evaluate the manufacturing of the photonic circuit.

[0051] In an embodiment, the optical losses of each constituent component are stored and compared with previous iterations of the manufacturing process. For example, in a previous iteration of a fabricated photonic circuit, the level of SiN doping used in the constituent components of an optical path may be different from the level of SiN doping in the current iteration. Thus, it can be evaluated whether, for example, the previous level of doping is better or the current level of doping is better.

[0052] This allows the manufacturer to determine the most appropriate manufacturing techniques and processes to reduce optical losses. In other words, for each new iteration of a photonic circuit under development, the graphene detector 105 is used to establish the optical losses along at least one constituent component or the Dijkstra constituent components, and the manufacturer can iterate their manufacturing techniques to reduce the optical losses in one or more constituent components to a specific level.

[0053] Insofar as embodiments of the present disclosure have been described as being implemented at least in part by a software-controlled data processing device, it should be understood that a non-transitory machine-readable medium carrying such software, such as an optical disc, a magnetic disk, a semiconductor memory, etc., is also considered to embody embodiments of the present disclosure.

[0054] It should be understood that, for the sake of clarity, the above description has described embodiments with reference to different functional units, circuitry, and / or processors. However, it is obvious that any suitable distribution of functions between different functional units, circuitry, and / or processors can be used without departing from the embodiments.

[0055] The described embodiments can be implemented in any suitable form, including hardware, software, firmware, or any combination thereof. The described embodiments can optionally be at least partially implemented as computer software running on one or more data processors and / or digital signal processors. The elements and components of any embodiment can be physically, functionally, and logically implemented in any suitable manner. In fact, the functions can be implemented in a single unit, in multiple units, or as part of other functional units. Thus, the disclosed embodiments can be implemented in a single unit, or can be physically and functionally distributed between different units, circuitry, and / or processors.

[0056] Although the present disclosure has been described in connection with some embodiments, the present disclosure is not limited to the specific forms set forth herein. Additionally, although the features may seem to be described in connection with specific embodiments, those skilled in the art will recognize that the various features of the described embodiments can be combined in any manner suitable for implementing the technology.

[0057] References

[0058] [1] Photo thermal effect graphene detector featuring 105 Gbit s -1 NRZand 120 Gbit s -1 PAM 4 direct detection – S. Marconi, A. Giambra et al.NatureCommunications https: / / doi.org / 10.1038 / s41467-021-21137-z

[0059] Embodiments of the present technology can generally be described by the following numbered clauses:

[0060] 1. A method of selecting an optical path through a photonic circuit between an input port and an output port, wherein there are multiple different optical paths connecting the input port and the output port, and each optical path is configured to include a plurality of constituent elements, the method comprising:

[0061] Establishing at least one characteristic of each of the constituent elements; and

[0062] Selecting the optical path based on the established at least one characteristic.

[0063] 2. The method according to clause 1, wherein the at least one characteristic is the optical loss along the constituent element, and the method further comprises: using a graphene photodetector to establish the optical loss.

[0064] 3. The method according to clause 1 or 2, wherein the at least one characteristic is the length of each constituent element.

[0065] 4. The method according to any one of the preceding clauses, further comprising:

[0066] Controlling the output power of a transmitter of light received at the input port based on at least one characteristic.

[0067] 5. The method according to any one of the preceding clauses, wherein Dijkstra's algorithm is used to select the optical path.

[0068] 6. A method of evaluating the manufacture of a photonic circuit having multiple different optical paths, each optical path including a plurality of constituent elements, the method comprising:

[0069] Using a detector made of graphene placed on at least one of the constituent elements to establish an optical loss along at least one of the plurality of constituent elements; and

[0070] Evaluating the photonic circuit based on the established optical loss.

[0071] 7. An apparatus for selecting an optical path through a photonic circuit between an input port and an output port, wherein there are multiple different optical paths connecting the input port and the output port, and each optical path is configured to include a plurality of constituent elements, the apparatus comprising circuitry configured to:

[0072] Establish at least one characteristic of each of the constituent elements; and

[0073] Select an optical path based on the at least one established characteristic.

[0074] 8. The apparatus according to clause 7, wherein the at least one characteristic is the optical loss along the constituent element, and the circuitry is configured to: establish the optical loss using a graphene photodetector.

[0075] 9. The apparatus according to clause 7 or 8, wherein the at least one characteristic is the length of each constituent element.

[0076] 10. The apparatus according to any one of clauses 7 to 9, wherein the circuitry is further configured to:

[0077] Control the output power of a transmitter of light received at the input port based on the at least one characteristic.

[0078] 11. The apparatus according to any one of clauses 7 to 10, wherein Dijkstra's algorithm is used to select the optical path.

[0079] 12. An apparatus for evaluating the fabrication of a photonic circuit having multiple different optical paths, each optical path including a plurality of constituent elements, the apparatus comprising circuitry configured to:

[0080] Use a detector made of graphene placed on at least one of the constituent elements to establish an optical loss along at least one of the plurality of constituent elements; and

[0081] Evaluate the photonic circuit based on the established optical loss.

[0082] 13. A computer program comprising computer-readable code which, when loaded onto a computer, configures the computer to perform the method according to any one of clauses 1 to 6.

[0083] 14. A computer program product comprising the computer program according to clause 13 stored in or on the computer program product.

Claims

1. A method for selecting a light path through a photonic circuit between an input port and an output port, wherein: There are a plurality of different optical paths connecting the input port and the output port, and each optical path is configured to include a plurality of component elements, and the method comprises: establishing at least one characteristic of each of said constituent elements; and The light path is selected based on the established at least one characteristic.

2. The method according to claim 1, wherein: The at least one characteristic is light loss along the component element, and the method further comprises establishing the light loss using a graphene photodetector.

3. The method according to claim 1, wherein: The at least one characteristic is the length of each constituent element.

4. The method according to claim 1, further comprising: An output power of a transmitter of light received at the input port is controlled based on the at least one characteristic.

5. The method according to claim 1, wherein: The light path is selected using the Dijkstra algorithm.

6. A method for evaluating the manufacture of a photonic circuit, the photonic circuit having a plurality of different optical pathways, each optical pathway comprising a plurality of component elements, the method comprising: establishing a light loss along at least one of the plurality of component elements using a detector made of graphene placed on at least one of the component elements; as well as The photonic circuit is evaluated based on the established optical losses.

7. A device for selecting a light path through a photonic circuit between an input port and an output port, wherein: There are a plurality of different optical paths connecting the input port and the output port, and each optical path is configured to include a plurality of component elements, and the apparatus includes a circuit system, the circuit system being configured to: establishing at least one characteristic of each of said constituent elements; and The light path is selected based on the established at least one characteristic.

8. The device according to claim 7, wherein: The at least one characteristic is light loss along the component element, and the circuit system is configured to establish the light loss using a graphene photodetector.

9. The device according to claim 7, wherein: The at least one characteristic is the length of each constituent element.

10. The device according to claim 7, wherein: The circuit system is also configured to: An output power of a transmitter of light received at the input port is controlled based on the at least one characteristic.

11. The device according to claim 7, wherein: The light path is selected using the Dijkstra algorithm.

12. An apparatus for evaluating the manufacture of a photonic circuit having a plurality of different optical pathways, each optical pathway comprising a plurality of component elements, the apparatus comprising a circuit system configured to: establishing light loss along at least one of the plurality of component elements using a detector made of graphene placed on at least one of the component elements; and The photonic circuit is evaluated based on the established optical losses.

13. A computer program product comprising a computer program stored in or on the computer program product, which, when loaded onto a computer, configures the computer to perform the method according to claim 1.

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