Photonic Network

Abstract

A photonic system is provided that includes a first array of N input light guiding units disposed in a first plane and spaced apart along a first axis in a substantially parallel relationship, and a second array of M output light guiding units disposed in a second plane and spaced apart along a second axis that intersects the first axis in a substantially parallel relationship, thus defining a matrix of N×M nodes, and a matrix of N×M optical couplers housed in each node. The optical couplers are configured to couple a portion of the input optical signals from the input light guiding units to the output light guiding units of each node, and are configured as a tunable modulation structure that can be controllably switched between various operating states by the application of a tuning electric field that is an electric field or an optoelectronic field configured as a weighting signal to provide an intensity modulation corresponding to a portion of the optical signals coupled from the input light guiding units to the output light guiding units by the optical couplers.

Description

Technical Field

[0001] The technology of the present disclosure relates to photonic networks and is particularly useful in photonic artificial intelligence neural network applications.

[0002] In a general-purpose processor with high computational flexibility, matrix operations are performed serially one by one, so continuous access to the cache memory is required, resulting in the so-called "von Neumann bottleneck". Various architectures of neural networks (NNs), such as graphics processing units (GPUs) and tensor processing units (TPUs), are designed to mitigate the impact of the von Neumann bottleneck and realize state-of-the-art machine learning models. The paradigms of these architectures, unlike CPUs, provide domain-specificity, for example, being optimized for the execution of convolution and matrix-vector multiplication (MVM) operations through parallel expansion via systolic algorithms.

[0003] In recent years, due to the revolutionary impact of machine learning (ML), especially neural networks (NNs), the development of various emerging photonic technologies aimed at improving the computational efficiency of specific tasks performed by ML / NN has been promoted, from free-space diffractive optical systems to nanofabricated photonic processors. This is because photonic chips utilize the interaction between light and matter, such as phase shifters, to essentially perform dot products, enable signal accumulation (addition) either through electromagnetic coherent interference or incoherent accumulation via detectors, and further enable parallel processing strategies and high throughput using multiplexing schemes such as wavelength division multiplexing and polarization division multiplexing.

[0004] For example, the paper "Parallel convolutional processing using an integrated photonic tensor core", J. Feldmann et al., Nature, vol. 589, January 7, 2021, describes an integrated photonic hardware accelerator (tensor core) specialized for computing. The tensor core can be considered as an optical analog of an application-specific integrated circuit (ASIC). It provides parallel photonic in-memory computing using a phase change material memory array and a photonic chip-based optical frequency comb (soliton microcomb). SUMMARY OF THE INVENTION

[0005] In this technical field, there is a need for a novel photonic processing device that can execute computationally parallelized tasks / operations (e.g., matrix-vector multiplication (MVM)) at an optical data rate that enables high computational throughput and low latency with a single physical processing unit. Examples of computational tasks that a photonic processing device can execute include convolution, matrix multiplication, Fourier transform, and the like.

[0006] Considering the technology of J. Feldmann et al. described above, it should be noted that the speed of signal modulation implemented by a phase change material (PCM) is related to the transition phase of the material in response to a temperature change of the material, and thus is not sufficiently high. As a result, when implemented in a photonic processor (e.g., due to optical attenuation), these PCMs may significantly slow down the overall computing time of the processor.

[0007] The present disclosure provides a novel photonic processor device including a network (e.g., a mesh) of fully connected light guiding units (e.g., waveguides or optical fibers), and realizes a complete and flexible connection by integrating controllable optical couplers at each optical intersection (node) between the light guiding units. The controllable optical coupler includes a light guiding element for optically coupling a part of light from one light guiding unit to another intersecting light guiding unit, and is configured as a tunable modulation structure that can be tuned electrically or optically.

[0008] Each of the controllable optical couplers can be independently controlled by the application of a control electric field (voltage) or an opto-electric field (light), changing the operating state of the coupler from a passive state to an active state and between various active states, where the coupler applies an intensity modulation to the passing light in any of its operating states. In this regard, it should be understood that the change in the operating state of the coupler can be continuous using an analog voltage value.

[0009] As described above, the controllable optical coupler configured according to the technology of the present disclosure may also be referred to herein as the following "coupler", "optical coupler", "controller" or "control unit".

[0010] To integrate the above-described electrically or optically tunable modulation function into the optical coupler, the light guiding element of the coupler is configured as an electrically or optically tunable modulation structure, or an electrically or optically tunable modulator is integrated into the light guiding element of the coupler.

[0011] The coupler (electrically or optically tunable modulation structure) is configured such that its optical properties change in response to the applied electric field or opto-electric field. That is, the coupler directly affects the intensity of the passing light or affects it through the phase change of the components of the passing light in response to the applied electric field due to changes in optical properties such as absorption / transmission characteristics and / or refractive index and / or amplification characteristics.

[0012] Such a change in optical properties in response to an applied electric or optoelectric field can be carried out relatively quickly and provides modulation of the optical signal passing through the coupler. Thus, the application of a time-varying modulation of the optical signal (through switching between various different modulation / operating states of the coupler) can be carried out fast enough.

[0013] The photonic mesh of the present disclosure includes a first array of input light guiding units arranged in a substantially parallel relationship spaced along a first axis in a first plane, and a second axis intersecting the first axis (e.g., the second axis is substantially perpendicular to the first axis) A second array of output light guiding units arranged in a substantially parallel relationship spaced along the second axis in a second plane. This configuration forms a matrix of alignment regions of input light guiding units and output light guiding units representing network nodes.

[0014] It should be understood that the first plane and the second plane may substantially coincide or may be spaced apart from each other as long as appropriate coupling between the light guiding units at the nodes is included.

[0015] The photonic mesh also provides a matrix of optical couplers each housed in a network node, each optical coupler being configured and operable to provide optical coupling of light from an input light guiding unit to an output light guiding unit at each node (i.e., in the alignment region of the input light guiding unit and the output light guiding unit, to provide an "intersection" between these units). Also, each optical coupler is configured as an electrically or optically tunable modulation structure.

[0016] Thus, each input light guiding unit can be optically coupled to each output light guiding unit in the region of the network node via its respective coupler, and the coupler redirects ( "drops") a portion of the input optical signal propagating within the input light guiding unit (depending on the coupling degree) to the intersecting output light guiding unit, while the remaining portion of the input optical signal continues to propagate within the input light guiding unit towards the next node, where each coupler performs such a redirect to its respective output light guiding unit.

[0017] As described above, the optical coupler is configured as an electrically or optically tunable modulation structure and can be controllably switched between various operating states by applying a tuning electric field (electric field (voltage) or optical field) independently for each. When in the active state, the coupler affects the intensity modulation of the optical portion that is dropped (coupled) to the output light guiding unit. The applied tuning electric field is selected (controlled) according to a predetermined weighting applied to the optical portion coupled / dropped to the output light guiding unit. Accordingly, all couplers are connected to a control system including a weighting signal controller.

[0018] It should be noted that substantial non-interference can be obtained between these due to the optical characteristics of the input optical signal. This is achieved by using a substantially non-coherent optical signal or optical signals of different wavelengths. For this reason, the optical input device associated with the input port of the input light guiding unit may include a wavelength division multiplexer.

[0019] The light guiding unit can be manufactured using various techniques including, in particular, 3D femtosecond laser scribing, 3D printing, and silicon photonics technology.

[0020] In some embodiments, the tunable modulation structure of the coupler can be realized by incorporating a tunable modulator within the light guiding element of the coupler. Such a tunable modulator can be an electro-absorption modulator (EAM), a semiconductor optical amplifier (SOA), or a liquid crystal modulator. The tunable modulator is accommodated in the optical path of the optical portion that is dropped from the input light guiding unit by the coupler and propagates toward each output light guiding unit within the light guiding element of the coupler.

[0021] As described above, in some other embodiments, the tunable modulation structure of the coupler is implemented by configuring the light guiding element of the coupler as a tunable modulator. This can be implemented, for example, by fabricating the core of the light guiding element of the coupler from an electro-absorption material (typically a semiconductor material composition), such as Si or Ge-Si, InGaAlAs or InP. In such embodiments, the light guiding unit and the coupler (light guiding element) can be fabricated using similar CMOS-compatible technologies.

[0022] In a further embodiment, the light guiding element of the coupler is configured as, or includes, an electro-optic modulator such as a Mach-Zehnder interferometer incorporating a phase shift unit such as one made of LiNbO3.

[0023] Thus, according to a broad aspect of the present invention, a photonic system comprising a first array of N input light guiding units arranged in a first plane and spaced along a first axis in a substantially parallel relationship, and a second array of M output light guiding units arranged in a second plane and spaced along a second axis intersecting the first axis in a substantially parallel relationship, thereby defining a matrix of N×M nodes, a photonic mesh, and a matrix of N×M optical couplers respectively housed in the nodes, wherein each of the optical couplers is configured to optically couple a portion of an optical signal from an input light guiding unit to an output light guiding unit of each node, and each of the optical couplers is configured as a tuning electric field that is an electric field or an opto-electric field that provides an intensity modulation corresponding to a portion of the optical signal coupled from the input light guiding unit to the output light guiding unit by the optical coupler, and is configured as a tunable modulation structure that can be controllably switched between various operating states by applying the tuning electric field. A photonic system is provided.

[0024] The number N of the input light guiding units may be the same as or different from the number M of the output light guiding units.

[0025] The optical coupler is a light guiding element disposed at the node, which couples a portion of the optical signal propagated by the input light guiding unit to an output light guiding unit passing through the node, and configures the remaining portion of the input optical signal to be propagated through the input light guiding unit towards the next node. It includes a light guiding element configured as such.

[0026] In some embodiments, the optical coupler is composed of a light guiding element configured as an electrically tunable modulator / modulation structure, which responds to an excitation / tuning electric field due to a change in the optical characteristics of the light guiding element, thereby causing intensity modulation of the optical signal passing through the coupler corresponding to the excitation electric field.

[0027] For example, such a light guiding element configured as a tunable modulation structure / modulator may include Er-doped glass whose received intensity of electrically controlled pump light changes.

[0028] In some examples, the core of the light guiding element is composed of an electro-absorption material composition, typically a semiconductor material composition, such as Si, Si-Ge, InGaAlAs, or InP.

[0029] In some other embodiments, the optical coupler includes a light guiding element having an internal tunable modulator. Such a tunable modulator is configured to be switchable between various operating states characterized by various optical characteristics of the modulator by an excitation / tuning electric field (electric field or optoelectronic field), and when the optical signal interacts with the modulator, intensity modulation of the optical signal is brought about corresponding to the excitation electric field.

[0030] The tunable modulator in the light guiding element of the coupler can be configured to include any one of an electro-absorption modulator, a semiconductor optical amplifier, a liquid crystal modulator, and a Mach-Zehnder interferometer. In the latter case, at least one arm of the interferometer has a region including a tunable modulator (e.g., a LiNbO3 unit), and when an excitation / tuning electric field is applied thereto, it affects the phase change of the optical component passing therethrough, affects the phase difference between the optical components passing through the arms of the interferometer, and results in intensity modulation of the light output from the interferometer.

Brief Description of the Drawings

[0031] To better understand the subject matter disclosed herein and to illustrate how it can be actually implemented, embodiments will be described as non-limiting examples only with reference to the accompanying drawings.

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0032] Referring to FIG. 1, a photonic system 10 of the present disclosure is schematically shown. The photonic system 10 includes a fully connected photonic mesh / network 12 associated with a control system 16. The photonic mesh 12 is interconnected between an optical input device 14 and an optical output device (optical detection system) 20.

[0033] The photonic mesh 10 includes N (N≧2) substantially parallel input light guiding units IW1…IW arranged at intervals along a first axis A1 n (waveguide or optical fiber) input array IL, and M (M≧2) substantially parallel output light guiding units OW1…OW arranged at intervals along a second axis A2 intersecting the input light guiding units m output array OL. The number M of the output light guiding units OW1…OW m may or may not be equal to the number N of the input light guiding units IW1…IW n . For example, the input light guiding units may be substantially orthogonal to the output light guiding units. The input ports IP1…IP n for the input light guiding units IW1…IW n are connected to the input device 14, and the output ports OP1…OP m for the output light guiding units OW1…OW m are connected to the photodetection device 20.

[0034] In the exemplary system 10 shown in the figure, three input light guiding units IW1, IW2, IW3 and three output light guiding units OW1, OW2, OW3 are shown. The input light guiding units IW1, IW2, IW3 are connected to the input device 14 by the input ports IP1, IP2, IP3, and the output light guiding units OW1, OW2, OW3 are connected to the photodetection device 20 by the output ports OP1, OP2, OP3.

[0035] The input light guiding units and the output light guiding units are arranged in a first and a second plane that substantially coincide or are spaced apart from each other, whereby an intersection region between the input light guiding units and the output light guiding units (when the first and second planes substantially coincide), or the regions of the input light guiding units and the output light guiding units (when the first and second planes are spaced apart) form an N×M array of nodes / junctions J of the mesh / network n,m . In the figure, the nodes J 11 , J 12 , J 13 , J 21 , J22 、J 23 、J 31 、J 32 、J 33 is shown.

[0036] Each ij-th node is associated with respective optical couplers C ij (coupler C 11 、C 12 、C 13 、C 21 、C 22 、C 23 、C 31 、C 32 and C 33 ) and is illustrated in association with respective nodes J 11 、J 12 、J 13 、J 21 、J 22 、J 23 、J 31 、J 32 and J 33 . Thus, each i-th input light guiding unit IW i from the N input light guiding units is optically coupled to each of the M output light guiding units OW1...OW i1 ...C im through respective optical couplers C m .

[0037] Each optical coupler C i,j (i = 1,..,N; j = 1,…M) is configured as a tunable modulation structure that optically couples between the i-th input light guiding unit and the j-th output light guiding unit and can selectively apply intensity modulation to the light passing therethrough at each node where the coupler C ij is disposed.

[0038] The operation of each coupler is illustrated in the figure with respect to coupler C 11 . As shown, the coupler drops / couples a part (IS1) d of the input optical signal IS1 propagating in the input light guiding unit IW1 to the output light guiding unit OW1 at the node J 11 and the remaining part (IS1)t propagates through the input light guiding unit IS1 towards the next node J 12 and propagates towards the next node J 12 where, at the coupler C 12 a part of this signal IS1 is continuously coupled to the next output light guiding unit OW2 and is intensity - modulated by an electrically or optically tunable modulation function (by controllable switching of the coupler between different operating states characterized by different modulation functions).

[0039] The optical portion (IS1) dropped by the coupler d can be intensity - modulated by the tunable modulation structure of the coupler. The dropped optical portion (IS1) d (e.g., with intensity modulation) continues to propagate along each output light guiding unit OW1 towards each output port OP1.

[0040] Note that the optical signals input to the mesh are signals that do not substantially interfere. This can be achieved by using wavelength - division multiplexers 15 in the optical input device 14, for example, or by using optical input signals that are substantially non - coherent, that is, by using optical signals of different wavelengths.

[0041] The amount of light in the drop / combine portion is defined by a predetermined coupling ratio at each node. Note that the coupling ratios can be the same or different at different nodes. Generally, the coupling ratio depends mainly on the material used for the coupler and the distance between the light guiding units (waveguides) and the light guiding elements of each coupler.

[0042] The tunable modulation structure (coupler) is connected to the control system 16. The latter includes a controllable tuning electric field source (such as a voltage supply system or a light source system) that functions as a weighted signal controller 18. The coupler can be switched from a passive state / condition where the optical characteristics of the coupler do not change and do not affect the light passing through it, to a selective active state / condition by applying a tuning electric field that causes a change in the modulation structure of the coupler or the optical characteristics within the coupler (as described above). Similarly, the coupler can be switched between various different active states characterized by different optical characteristics, and different effects are exerted on the light passing through it. While in the active operating state, the coupler affects the intensity modulation (attenuation / gain) of the light (passing through it) that interacts with such a coupler according to the weighted signal corresponding to the applied electric field.

[0043] Generally, the tunable modulation structure can be implemented as a light guiding element (such as a waveguide or an optical fiber) with a core made of a tunable material composition, or as a light guiding element (such as a waveguide or an optical fiber) with a tunable modulator disposed therein. As shown in the non-limiting example of FIG. 1, each coupler is a light guiding element that generally includes a tunable modulator indicated by 22.

[0044] The tunable modulator 22 can be configured, for example, as an electro-absorption modulator (EAM) in which the applied electric field causes a change in the absorption spectrum via the Franz-Keldysh effect in a bulk semiconductor or the quantum-confined Stark effect (QCSE) in a quantum well. Although electro-absorption modulators are generally known and will not be specifically described, the following points should be noted. In the Franz-Keldysh effect, the electric field changes the bandgap energy by changing the overlap of the wavefunctions of excitons (electrons and holes), thereby affecting the optical absorption / transmission of the optical signal that interacts with the electrically tunable modulator 20 (the greater the overlap, the stronger the absorption). In the quantum-confined Stark effect (QCSE), the applied electric field distorts the potential well (quantum well), thereby shifting the energy levels of holes and electrons, reducing the gap between these levels, and changing the optical absorption.

[0045] Alternatively, the tunable modulator 20 may be an optical amplifier in which electrons are excited in response to an applied tuning electric field, such as a semiconductor optical amplifier (SOA). When photons pass through the active region, these electrons lose some of their extra energy in the form of more photons that match the wavelength of the first photon. Thus, the optical signal passing through the active region is amplified. Since SOAs are also generally known, they will not be specifically described.

[0046] In some embodiments, the tunable modulation structure C or the tunable modulator 22 within the light guiding element of the coupler C can be implemented as an electro-optic modulator, such as a Mach-Zehnder modulator (MZM) in which at least one of the arms is made of a material (such as LiNbO3, InGaAs, InP) having a strong electro-optic effect. When an electric field is applied to the at least one arm of the MZM, the optical path length within the arm changes, affecting the phase modulation of the optical components passing through each arm of the MZM, and as a result, a phase difference occurs between the optical components propagating through the two arms. By combining optical components having such a phase difference, intensity modulation can be obtained.

[0047] Note that other types of modulators that are electrically or optically tunable, such as a liquid crystal (LC) modulator, can also be used.

[0048] Each tunable modulation structure (e.g., the tunable modulator 22 in the light guiding element of the coupler, or the light guiding element configured as a modulator) is connected to a weighting controller 18 that selectively supplies a weighting signal (voltage or light) according to the weighting applied to the optical signal passing through each coupler.

[0049] The optical signal (including the intensity-modulated optical signal) is output from the M output guide units through their respective output ports and directed to the photodetector system 20.

[0050] Referring to FIGS. 2A and 2B, an exemplary configuration of a coupler C configured and operable as a tunable modulation structure is schematically shown. The coupler C includes a light guiding element LGE having a first coupling portion 24 that defines a coupling region with the input light guiding unit IW, a second coupling portion 26 that defines a coupling region with the intersecting / aligned output light guiding unit OW, and an intermediate segment 25 therebetween. The dimensions and material compositions of the coupling regions 24 and 26 are selected to provide the desired degree of coupling with their respective light guiding units. The first and second coupling regions 24 and 26 may have the same or different degrees of coupling.

[0051] It should be noted that the coupling regions may be formed of or include any one or more light guiding materials such as, but not limited to, silica, silicon, InGaAs, Ge, etc., depending on the operating wavelength. The coupling coefficient depends not on the material but on the structure of the coupler (distance from the waveguide, width, NA, etc.).

[0052] As described above, the entire light guiding element of the coupler or at least a part of the intermediate segment 25 is configured to have a tunable modulation function / characteristic, thereby forming a tunable modulation structure of the coupler.

[0053] Referring to the example of FIG. 2A, the intermediate segment 25 is made of a material such as SiO2 or SiN, and electrodes for applying an electric field in a direction orthogonal to the optical signal propagating therein may be accommodated within and along the segment 25, or the entire light guiding element of the coupler C may be made of an electrically tunable material such as Si, Ge-Si, InGaAlAs, InP, etc.

[0054] Alternatively, as illustrated in FIG. 2B, the intermediate segment 25 includes a tunable modulator 22. As described above, such a tunable modulator can be an EAM or an SOA.

[0055] As described above, the light guiding element LGE of the coupler C can be configured as a Mach-Zehnder modulator or can include such a Mach-Zehnder modulator 22. This is illustrated in an obvious form in FIG. 2C. The Mach-Zehnder modulator includes a lithium niobate (LiNbO3) coating / film within a part / segment of one arm, which exhibits a change in refractive index when excited by the applied tuning electric field, and thus affects the phase of the optical signal passing through the segment. For example, the input and output parts of the Mach-Zehnder modulator can represent the input part 24 and the output part 26 of the coupler.

[0056] Referring to FIGS. 3A to 3C, a three-dimensional configuration of the fully connected photonic mesh 12 of the present disclosure is schematically shown. FIGS. 3A and 3B show a perspective view and a side view of the mesh 12 respectively, and FIG. 3C shows a state in which the light guiding element of the coupler C is implemented in a three-dimensional configuration.

[0057] As shown in FIGS. 3A and 3B, the input layer IL (the plane where the input light guiding units are located) and the output layer OL (the plane where the output light guiding units are located) are spaced parallel layers. As shown in the figure, the input light guiding units IW1, IW2, IW3 of the input layer IL are arranged above or below the output light guiding units OW1, IW2, OW3 of the output layer OL. FIG. 3C is a diagram showing the light guiding element LGE of the coupler C connecting between a certain input light guiding unit IW and a certain output light guiding unit OW.

Claims

1. A photonic system, comprising: a first array of N input light guiding units arranged on a first plane and spaced along a first axis in a substantially parallel relationship; and a second array of M output light guiding units arranged on a second plane and spaced along a second axis intersecting the first axis in a substantially parallel relationship, thus defining a matrix of N×M nodes, a photonic mesh; a matrix of N×M optical couplers respectively housed in the nodes; each of the optical couplers is configured to couple a part of an input optical signal from the input light guiding unit to the output light guiding unit of each node, and each of the optical couplers is configured as an electric field or an opto-electric field which is a weighting signal for providing intensity modulation corresponding to a part of the optical signal coupled from the input light guiding unit to the output light guiding unit by the optical coupler, and is configured as a tunable modulation structure that can be controllably switched between various operating states by the application of a tuning electric field. A photonic system characterized by that.

2. The optical coupler is a light guiding element arranged in the node, and includes a light guiding element configured to couple a part of the optical signal passing through the node propagated by the input light guiding unit to the output light guiding unit, and propagate the remaining part of the input optical signal through the input light guiding unit towards the next node. The photonic system according to claim 1.

3. The light guiding element of the optical coupler is configured as a tunable modulation structure responsive to the tuning electric field so as to be switchable between different operating states characterized by different optical characteristics of the tunable modulation structure that have different effects on the intensity modulation of the optical signal passing through the light guiding element according to the applied tuning electric field. The photonic system according to claim 2.

4. The core of the light guiding element is composed of an electroabsorption material composition. The photonic system according to claim 3.

5. The core of the light guiding element is composed of a semiconductor material composition. The photonic system according to claim 3.

6. The core of the light guiding element is composed of a semiconductor material composition. The photonic system according to claim 4.

7. The core of the light guiding element is composed of at least one of Si, Si—Ge, InGaAlAs, and InP, the photonic system according to claim 5.

8. The core of the light guiding element is composed of at least one of Si, Si—Ge, InGaAlAs, and InP, the photonic system according to claim 6.

9. The photonic system according to claim 2, wherein the optical coupler includes Er-doped glass.

10. The light guiding element of the coupler includes a tunable modulator therein, and the tunable modulator is characterized by different optical characteristics of modulators that differently affect the intensity modulation of an optical signal passing through the light guiding element in response to the electric field, and is configured to be switchable by the tuning electric field among various operating states, the photonic system according to claim 2.

11. The photonic system according to claim 10, wherein the tunable modulator is configured as an electro-absorption modulator.

12. The photonic system according to claim 10, wherein the tunable modulator is configured as a semiconductor optical amplifier.

13. The photonic system according to claim 10, wherein the tunable modulator is configured as a liquid crystal modulator.

14. The tunable modulator is configured as a Mach-Zehnder interferometer, and at least one arm of the interferometer includes a region including a tunable unit, and when an electric field for tuning is applied thereto, it affects the phase change of a passing optical component, thereby affecting the phase difference between the optical components passing through the arms of the interferometer, and as a result, causing intensity modulation of the light output from the interferometer, the photonic system according to claim 10.

15. The tunable unit is configured as a LiNbO ３ photonic system according to claim 14, which is configured as a unit.

16. The photonic system according to claim 14, wherein the tunable unit is configured as a semiconductor optical amplifier (SOA).

17. An optical coupler for use in a node of an N×M matrix of nodes of a photonic system formed by an array of N input light guiding units in a first plane and an array of M output light guiding units in a second plane, wherein at the node, a part of an input optical signal from the input light guiding unit is configured to be coupled to the output light guiding unit, and the optical coupler is configured as a tunable modulation structure that can be controllably switched between various operating states by applying a tuning electric field, which is an electric field or an optoelectronic field configured as a weighting signal that brings about an intensity modulation corresponding to the part of the optical signal coupled from the input light guiding unit to the output light guiding unit. **Claim 18** The optical coupler according to claim 17, comprising a light guiding element disposed at the node, the light guiding element configured to couple a part of an optical signal passing through the node propagated by the input light guiding unit to the output light guiding unit and to propagate the remaining part of the input optical signal through the input light guiding unit towards the next node of the photonic system. **Claim 19** The optical coupler according to claim 18, configured as a tunable modulation structure responsive to the tuning electric field such that it can be switched between different operating states characterized by different optical properties of the tunable modulation structure that differently affect the intensity modulation of the optical signal passing through the light guiding element in response to the applied tuning electric field. **Claim 20** The optical coupler according to claim 19, wherein the core of the light guiding element is composed of an electro-absorption material composition. **Claim 21** The optical coupler according to claim 19, wherein the core of the light guiding element is composed of a semiconductor material composition. **Claim 22** The optical coupler according to claim 20, wherein the core of the light guiding element is composed of a semiconductor material composition. **Claim 23** The optical coupler according to claim 21, wherein the core of the light guiding element is composed of at least one of Si, Si-Ge, InGaAlAs, InP. **Claim 24** The photonic system according to claim 6, wherein the core of the light guiding element is composed of at least one of Si, Si-Ge, InGaAlAs, InP. **Claim 25** The optical coupler according to claim 18, comprising Er-doped glass. **Claim 26** The light guiding element includes a tunable modulator therein, and the tunable modulator is characterized by different optical characteristics of the modulator that have different effects on the intensity modulation of an optical signal passing through the light guiding element in response to the electric field, and is configured to be switchable by the tuning electric field among various operating states, the optical coupler according to claim 18.

27. The optical coupler according to claim 26, wherein the tunable modulator is configured as an electro-absorption modulator.

28. The optical coupler according to claim 26, wherein the tunable modulator is configured as a semiconductor optical amplifier.

29. The optical coupler according to claim 26, wherein the tunable modulator is configured as a liquid crystal modulator.

30. The optical coupler according to claim 26, wherein the tunable modulator is configured as a Mach-Zehnder interferometer, and at least one arm of the interferometer includes a region including a tunable unit, and when this is applied with a tuning electric field, it affects the phase change of the optical components passing through, thereby affecting the phase difference between the optical components passing through the arm of the interferometer, and as a result, causing intensity modulation of the light output from the interferometer.

31. The tunable unit is composed of a LiNbO ３ optical coupler according to claim 30, configured as a unit.

32. The optical coupler according to claim 30, wherein the tunable unit is configured as a semiconductor optical amplifier (SOA).

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