Fiber-Based Processing Systems

Abstract

An optical processing unit is presented that is used as a basic block of an optical processor system, configured to perform a predetermined processing task on an input optical signal and comprising: an input fiber unit through which the input optical signal and a weighted optical beam propagate, an output fiber unit, and a nonlinear all-optical modulator arranged upstream of the output fiber unit and exposed to an interaction of the input optical signal and the weighted optical beam, the nonlinear all-optical modulator configured to apply, via said interaction, a spatial modulation of the weighted optical beam to an optical field of the input optical signal, thereby generating a spatially modulated optical field corresponding to the input optical signal, and enabling the spatially modulated optical field to propagate through the output fiber unit to a detection plane.

Description

[Technical Field]

[0001] The present disclosure is in the field of optical fibers and relates to optical fiber-based photonic processors, which are particularly useful in optical data communications and optical computing devices, and may also be useful in optically integrated artificial neural networks (ANNs). [Background technology]

[0002] Photonic computing utilizes the manipulation of light (photons) to perform computational processes, in contrast to traditional electronic-based computing. Generally, the fundamental building block of a modern electronic computer is the transistor. In a photonic computer, the electronic component is replaced with an equivalent optical transistor, which is an optical component; that is, a photonic computer system uses optical pulses rather than electrical transistors to form the basis of logic gates.

[0003] Conventional optical processing systems typically utilize hybrid electro-optical processing, commonly referred to as optoelectronic processing. In these systems, optical signals are used for data transmission and certain processing tasks, and can then be converted to electronic signals for other specific processing tasks. Such optoelectronic devices can lose approximately 30% of their energy when converting electronic energy to photons and vice versa. Furthermore, converting optical signals to electronic signals and vice versa slows data transmission and processing. Significant research effort is being focused on all-optical computing, which eliminates the need for optical-electrical-optical (OEO) conversion, thus requiring less power and increasing processing speed.

[0004] Optical computing allows for faster computational speeds compared to electronic systems, as the manipulation of light pulses can be faster, enabling the transmission of higher bandwidth information. Summary of the Invention

[0005] There is a need in the art for new approaches to performing a variety of all-optical signal processing tasks using optical fibers, particularly suitable for use in neural networks.

[0006] The present disclosure provides novel fiber-based all-optical photonic processors configured and operable to perform a variety of processing tasks performed by optical operations involving linear and nonlinear effects (such as plasma dispersion effects). Some examples of computational tasks that can be performed by the photonic processors of the present disclosure include convolution, matrix multiplication, spatial filtering of optical fields, etc.

[0007] The photonic processor of the present disclosure includes a number N (N≧1) of basic blocks, each configured as a processing unit. The processing unit includes such functional components as a multimode optical fiber defining an input fiber unit and an output fiber unit (with respect to the general direction of light propagation through the processing unit) and a nonlinear optical modulator. The nonlinear optical modulator is located upstream of the output fiber unit, but may be located outside the input fiber unit (e.g., one of the input fibers) downstream of the output fiber unit and / or may be integrated within the input fiber unit.

[0008] Nonlinear optical modulators may be constructed using any known suitable technique to implement nonlinear all-optical effects, such as optical absorption, electro-optic effect (based on the Kerr effect induced by the interaction of two optical fields), photorefractive effect (change in the refractive index of a material due to optically induced redistribution of electrons and holes), etc. Optical modulators may be constructed as thin semiconductor elements, for example as Si or Ge core fibers, or may be doped into the glass of the fiber.

[0009] The input fiber unit is configured and operable to propagate the input optical signal and the weighting optical beam, allowing interaction of the input optical signal and the weighting optical beam with the nonlinear optical modulator. In some embodiments, such interaction occurs at the output of the input fiber unit where the optical modulator is located, while in other embodiments, such interaction occurs while the optical signal and the weighting beam are propagating along the same input fiber that includes the optical modulator integrated into said fiber, or during a combination of both of these implementations. The latter is a so-called "hybrid" configuration, where in one axis the nonlinear medium is integrated into the fiber and in a second axis the nonlinear medium is an external material.

[0010] It should be understood that the optical signal and the weighted optical beam differ from each other in at least one optical property to avoid interference therebetween. In some embodiments, this can be achieved by using a weighted optical beam with a wavelength different from that of the optical signal. In this case, the interaction between them is generated by optical nonlinearity. For example, the nonlinear optical modulator may be configured to perform a plasma dispersion effect, a photorefractive effect, etc. In other embodiments, the weighted optical beam may have substantially the same wavelength as the optical signal. In this case, the nonlinear optical modulator may be configured to perform a cross-phase modulation effect, a soliton effect, a Kerr effect, etc.

[0011] The optical properties (wavelength and intensity) of the weighted light beam are selected so that the weighted light beam excites the optical modulator and induces a nonlinear all-optical effect (a change in the optical properties of the modulator) that appropriately modulates an input light beam that interacts with (e.g., passes through) it. More specifically, in one non-limiting example, the weighted light beam generates charge carriers (electron-hole pairs) while interacting with the optical modulator and is efficiently absorbed. The charge carriers thus generated affect a corresponding modulation of an input optical signal that interacts with the optical modulator, allowing the modulated optical signal to be transmitted through the optical modulator.

[0012] Thus, the processing task, which is a predetermined function applied to the input optical signal, involves the effect of the optical modulation applied to the input optical signal by the weighted optical beam through the interaction of both the input optical signal and the weighted optical beam with the optical modulator.

[0013] Various functions related to a particular processing task (e.g., Fourier transform and / or imaging) utilize input optical signals and weighted beams having the same or different domains (frequency domain and / or spatial domain). In general, the input optical signals and weighted beams may propagate through the same fiber or different fibers of the input fiber unit. In fact, this is possible regardless of whether the input optical signals and weighted beams emerge from the input fiber unit in the same domain or different domains. The input optical signals and weighted beams have different optical properties (e.g., wavelength, polarization, phase, etc.).

[0014] The input optical signal and the weighted optical beam may be configured so that their principal Fourier planes are at different locations. The length of the input fiber (and its refractive index profile) may be determined so that, at the output of the input fiber, one of the input signal and the weighted beam is Fourier transformed and the other is not, or both are Fourier transformed (they have undergone different numbers of Fourier transformations during propagation through the input fiber unit).

[0015] As will be further described below, when the input optical signal and the weighted optical beam are in the same region, their interaction with the optical modulator results in the input optical signal being multiplied by the weighted beam; and when the input optical signal arrives at the interaction region in the frequency domain, its interaction with the optical modulator excited / spatially modulated by the weighted optical beam results in frequency filtering of the input optical signal. For this reason, the input fiber unit and the output fiber unit are configured according to a predetermined function / processing task to be applied.

[0016] In an embodiment, the input fiber unit comprises at least one graded index (GRIN) light guide unit, which may be a GRIN fiber or a rod or a planar waveguide. The structure and operation of such a GRIN light guide unit is known per se and therefore does not need to be described in detail, but it should be noted that such a light guide unit has a decreasing refractive index from its peripheral region to its central region, so that light passing through the GRIN light guide unit is continuously refocused (i.e., lens effect).

[0017] In the following description, such a GRIN light guide unit will be referred to as a GRIN fiber, but it should be noted that this term should be interpreted in a broader sense to also cover GRIN rods and planar waveguides.

[0018] The length and temperature of the input fiber unit and the length and temperature of the output fiber unit utilizing GRIN fiber are selected according to the optical processing to be performed, i.e., whether the plane at which light exits the fiber unit is a Fourier plane or not.

[0019] For example, in one embodiment, the predetermined task / function is the convolution of an input optical signal. In this case, the input fiber unit may be configured to perform a Fourier transform of both the input optical signal Fx and the weighted optical beam Fw, and to enable modulation of the input optical signal by the weighted optical beam through both interactions with an optical modulator to generate Fx·Fw (x denotes the signal and w denotes the weight). The output fiber unit is configured to perform an inverse Fourier transform of the modulated input optical signal while directing the modulated input optical signal to a detection surface, F -1 This results in the overall operation of (Fx·Fw).

[0020] As described below, in some embodiments, the input optical signal and the weighted beam may propagate through different fibers of the input fiber unit, with the optical modulators located at the outputs of these fibers. In such embodiments, both fibers of the input fiber unit may be configured to perform a Fourier transform of the respective optical fields; or both fibers may be configured as imaging fibers; or one of these fibers may be configured to perform a Fourier transform of the input optical signal, and the other fiber through which the weighted optical beam propagates is the imaging fiber.

[0021] In some other embodiments, the input optical signal and the weighted beam propagate through the same fiber of the input fiber unit. In this case, in some embodiments, the optical modulator may be located at the output of the fiber. The fiber through which the input optical signal and the weighted beam propagate may be configured to perform a Fourier transform of both the input optical signal and the weighted beam, or may be configured as an imaging fiber for both of them, or may be configured to perform a Fourier transform on one of them and perform imaging on the other. This depends on the wavelength of the beams and the fiber length.

[0022] In certain other examples, with this configuration of a common input fiber propagating both the input optical signal and the weighted optical beam, an optical modulator may be integrated into the fiber extending therethrough. This may be accomplished by configuring the optical modulator as the material constituting the core through which both signals propagate, or by doping the glass of the input fiber with such a nonlinear optical material. Such a configuration provides that the input optical signal and the weighted optical beam undergo multiple interactions with the optical modulator while propagating along the fiber, resulting in a matrix multiplication at the output of the input fiber unit. In certain examples, this input fiber performs a Fourier transform of the light passing therethrough, and the output fiber unit is then configured to perform an inverse Fourier transform, thus providing a convolution of the input optical signal with a weighting function.

[0023] Thus, according to one broad aspect of the present disclosure, the present disclosure provides an optical processor system comprising at least one optical processing unit configured to perform a predetermined processing task on an input optical signal and comprising an array of optical fibers, the optical fiber array defining: an input fiber unit configured to propagate an input optical signal and a weighted optical beam having at least one optical property different from the input optical signal toward an output face arranged according to the predetermined function to be performed; an output fiber unit spaced from the input fiber unit generally along the direction of light propagation through the optical processing unit and configured to propagate light to a detection face; and a nonlinear all-optical modulator upstream of the output fiber unit, the nonlinear all-optical modulator being exposed to interaction with an optical field corresponding to the input optical signal and the weighted optical beam and being switchable to a spatially modulated state by interaction with the optical field corresponding to the weighted optical beam, applying spatial modulation of the weighted optical beam to the optical field corresponding to the input optical signal, thereby generating a spatially modulated optical field corresponding to said input optical signal and enabling said input optical signal to propagate through the output fiber unit to the detection face.

[0024] In one embodiment, the nonlinear all-optical modulator of the optical processing unit is housed at the output surface and is exposed to interaction with the input optical signal and the optical field corresponding to the weighted optical beam, thereby applying said spatial modulation of the weighted optical beam to the optical field corresponding to the input optical signal and generating a spatially modulated optical field corresponding to said input optical signal.

[0025] The input fiber unit of the optical processing unit may include a common input fiber configured to propagate both the input optical signal and the weighted optical beam, or alternatively, the input fiber unit of the optical processing unit may include a first input fiber and a second input fiber configured to propagate the input optical signal and the weighted optical beam, respectively.

[0026] In one embodiment, when the input fiber unit of the optical processing unit includes a common input fiber configured to propagate both the input optical signal and the weighted optical beam, the nonlinear all-optical modulator comprises a nonlinear medium integrated into this common input fiber, thereby applying spatial modulation of the weighted optical beam to an optical field corresponding to the input optical signal while the input optical signal and the weighted optical beam propagate through the common input fiber, thereby generating a spatially modulated optical field corresponding to said input optical signal.

[0027] In one embodiment, the nonlinear all-optical modulator has a first nonlinear medium integrated into the input fiber and a second nonlinear medium at the output of the input fiber.

[0028] In one embodiment, the light processing unit has the following configuration: the input fiber unit includes at least one graded index (GRIN) fiber configured to apply a Fourier transform function to at least one of the input optical signal and the weighted light beam, and the output plane is a Fourier plane for the optical input of the input fiber unit for the wavelength of at least one of the input optical signal and the weighted light beam; the output fiber unit includes a GRIN fiber configured to apply a continuous Fourier transform function to the spatially modulated light field passing therethrough, and the detection plane is a Fourier plane for the optical input of the GRIN fiber of the output fiber unit for the spatially modulated light field (i.e., the wavelength of the input optical signal).

[0029] In one example, the input optical signal and the weighted optical beam propagate through first and second GRIN fibers of the input fiber unit configured to apply Fourier transforms to the input optical signal and the weighted optical beam, respectively, where a nonlinear all-optical modulator of the optical processing unit is housed at the output face and exposed to interaction with optical fields corresponding to the input optical signal and the weighted optical beam.

[0030] In certain other examples, the input optical signal and the weighted optical beam propagate through the same GRIN fiber, and the GRIN fiber is configured to apply a Fourier transform to both the input optical signal and the weighted optical beam, or to apply a Fourier transform only to the input optical signal. In this case, the nonlinear all-optical modulator may be housed at the output facet, or the nonlinear all-optical modulator may be integrated into the GRIN fiber (e.g., the core of the GRIN fiber may be configured as a nonlinear all-optical modulator), whereby spatial modulation of the weighted optical beam is applied to the input optical signal while propagating through the GRIN fiber.

[0031] In one embodiment, the predetermined processing task performed by the processing unit is a convolution between an input optical signal and a weighted optical beam, the convolution resulting from the interaction of a Fourier transform of the input optical signal and the weighted optical beam with a nonlinear all-optical modulator that generates a spatially modulated optical field, and a continuous Fourier transform of the spatially modulated optical field corresponding to the input optical signal.

[0032] In these embodiments, the input optical signal and the weighted optical beam may propagate through respective first and second GRIN fibers of the input fiber unit configured to apply a Fourier transform thereto, and the nonlinear all-optical modulator is therefore housed within the output face of the input fiber unit. Alternatively, the input optical signal and the weighted optical beam may propagate through the same GRIN fiber configured to apply a Fourier transform thereto, in which case the nonlinear all-optical modulator is a separate element housed within the output face of the input fiber unit or is integrated into the GRIN fiber, whereby spatial modulation of the weighted optical beam is applied to the input optical signal while it is propagating through the GRIN fiber.

[0033] In one embodiment, the predetermined processing task performed by the processing unit is filtering of selected spatial frequencies of the input optical signal resulting from the interaction of the Fourier transform of the input optical signal and the weighted light beam by the nonlinear all-optical modulator with the continuous Fourier transform of the spatially modulated light field corresponding to said input optical signal.

[0034] In some examples of these embodiments, the input optical signal and the weighted optical beam may propagate through a first fiber and a second fiber, respectively, where at least the first fiber is a GRIN fiber configured to perform a Fourier transform of the input optical signal and the second fiber is configured as an imaging fiber for the weighted optical beam. In this case, the nonlinear all-optical modulator is a separate element housed at the output face. In some other examples, the input optical signal and the weighted optical beam propagate through the same GRIN fiber of an input fiber unit configured to apply a Fourier transform to the input optical signal and configured as an imaging fiber for the weighted optical beam. In this case, the nonlinear all-optical modulator may be a separate element located at the output face or may be integrated into the GRIN fiber (i.e., comprised of an appropriately configured GRIN fiber), which applies spatial modulation of the weighted optical beam to the Fourier transform of the input optical signal while propagating through the GRIN fiber.

[0035] In yet other embodiments, the predetermined processing task performed by the processing unit may be signal multiplication between the input optical signal and the weighted optical beam resulting from the interaction of the optical fields corresponding to said input optical signal and the weighted optical beam with the nonlinear all-optical modulator, and successive imaging of the spatially modulated optical field corresponding to said input optical signal on a detection plane. In such embodiments, the input fiber unit may be configured such that the output plane is an image plane of the optical input of the input fiber unit for both the input optical signal and the weighted optical beam, and the output fiber unit may be configured such that the detection plane is an image plane for the optical input of the output fiber unit for the input optical signal.

[0036] According to another broad aspect, the present invention provides an optical processing unit configured to perform a predetermined processing task on an input optical signal, the optical processing unit comprising: an input fiber unit for propagating the input optical signal and a weighted optical beam therethrough; an output fiber unit; and a nonlinear all-optical modulator arranged upstream of the output fiber unit so as to be exposed to an interaction of the input optical signal and the weighted optical beam, the nonlinear all-optical modulator applying spatial modulation of the weighted optical beam to an optical field of the input optical signal through said interaction, thereby generating a spatially modulated optical field corresponding to the input optical signal and enabling the spatially modulated optical field to propagate through the output fiber unit to a detection plane.

[0037] In some embodiments, the input fiber unit includes a common input fiber for propagating both the input optical signal and the combined optical beam. The nonlinear all-optical modulator may be disposed between the input fiber unit and the output fiber unit at an output face of the input fiber unit. In some other embodiments, the nonlinear all-optical modulator is fully integrated into the common input fiber; or has a hybrid configuration by including a first nonlinear medium integrated into the common input fiber, such that the input optical signal and the combined optical beam undergo the interaction with the nonlinear all-optical modulator while propagating through the common input fiber.

[0038] In yet another embodiment, the nonlinear all-optical modulator comprises at least a first nonlinear medium integrated into the common input fiber so that the input optical signal and the weighted optical beam undergo the interaction with the first nonlinear medium while propagating through the common input fiber, thereby applying spatial modulation of the weighted optical beam in a first axis to the input optical signal and generating a first axis modulated optical field of the input optical signal and a second nonlinear medium at the output face of the input fiber unit.

[0039] In one embodiment, the input fiber unit comprises a first input fiber and a second input fiber for propagating the input optical signal and the weighted optical beam, respectively, and the nonlinear all-optical modulator is disposed between the input fiber unit and an output fiber unit in an output face of the input fiber unit.

[0040] The input fiber unit may include at least one input fiber configured as a GRIN fiber, and the output fiber unit may include at least one output fiber configured as a GRIN fiber. [Brief explanation of the drawings]

[0041] For a better understanding of the subject matter disclosed herein, and to illustrate how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0042] [Figure 1A] FIG. 1A is a schematic diagram of an optical processor system of the present disclosure, showing an optical processor system that utilizes a nonlinear all-optical modulator housed outside the input fiber unit. [Figure 1B] FIG. 1B is a schematic diagram of an optical processor system of the present disclosure, showing an optical processor system utilizing an input fiber unit that includes a nonlinear all-optical modulator integrated within the input fiber unit. [Figure 2A] FIG. 2A illustrates different configurations of optical processor units suitable for use in the optical processing systems of FIGS. 1A and 1B, showing an optical processor unit having an input fiber unit including a common fiber for input optical signals and weighted optical beam propagation, and a nonlinear all-optical modulator located at and / or within the output of the input fiber unit. [Figure 2B]FIG. 2B illustrates a different configuration of an optical processor unit suitable for use in the optical processing systems of FIGS. 1A and 1B, showing an optical processor unit having an input fiber unit including a common fiber for input optical signals and weighted optical beam propagation, and a nonlinear all-optical modulator located at and / or within the output of the input fiber unit. [Figure 2C] FIG. 2C illustrates a different configuration of an optical processor unit suitable for use in the optical processing systems of FIGS. 1A and 1B, showing an optical processor unit having an input fiber unit with different fibers for input optical signal and weighted optical beam propagation, and a nonlinear all-optical modulator disposed at the output of the input fiber unit. DETAILED DESCRIPTION OF THE INVENTION

[0043] 1A and 1B, there are shown two schematic examples of optical processor systems 10 of the present disclosure configured and operable to perform various data processing / computational tasks / functions. System 10 is a fiber-based photonic processing system that may be used as an optical communication system or an optical computing system.

[0044] The optical processor system 10 includes at least one optical / photonic processing / computing unit 12 configured to perform a predetermined processing task on an input optical signal IS. The processing unit 12 includes an array of optical fibers (in one embodiment, multimode fibers) including an input fiber unit 12A including one or more input light propagation fibers for propagating the input optical signal IS and the weighted light beam WB therethrough, and an output fiber unit 12C spaced from the input fiber unit generally along the direction of light propagation through the processing unit 12 toward a detection plane DP. The processing unit 12 also includes a nonlinear all-optical modulator 12B.

[0045] The nonlinear all-optical modulator 12B may be a separate element located between the output of the input fiber unit 12A and the input of the output fiber unit 12C. In another example, the nonlinear all-optical modulator 12B may be implemented as an integral part of the input fiber unit. According to yet another example, the nonlinear all-optical modulator 12B may be configured as a hybrid structure including a first nonlinear medium integrated into the input fiber unit (a common input fiber through which the input optical signal and the combined optical beam propagate) and a second nonlinear medium located at the output facet of the input fiber unit.

[0046] As mentioned above, nonlinear all-optical modulators may be constructed using any known suitable technique for implementing nonlinear all-optical effects, non-limiting examples of which include optical absorbers (e.g., based on the plasma dispersion effect), electro-optic modulators (based on the Kerr effect), photorefractive modulators (which respond to interaction with light by changing the refractive index due to a light-induced redistribution of electrons and holes), cross-phase modulation effects (where the optical intensity of one beam affects the phase change of another beam), and soliton effects (which balance diffraction or dispersion with nonlinear effects).

[0047] For simplicity in the following description, the nonlinear all-optical modulator will be referred to as an optical absorber, although it should be understood that the principles of the disclosed technology are not limited to this specific example and that the term "optical absorber" should be interpreted broadly to cover any known suitable type of nonlinear all-optical modulator.

[0048] 1A, the optical absorber 12B is disposed at the output face OP of the input fiber unit 12A and is implemented as a separate element disposed in the propagation path of the light output from the input fiber unit. The optical absorber 12B may have the form of a semiconductor thin film (silicon, germanium) or a Si-core fiber.

[0049] 1B, the optical absorber 12B is integrated into the input fiber unit 12A. The optical absorber 12B may be implemented, for example, as a material constituting a core, i.e., a Si core, through which both the input optical signal IS and the weighted optical beam WB can propagate. Thus, the input fiber unit 12A operates to propagate both the input optical signal IS and the weighted optical beam WB and enable their interaction with the optical absorber 12B.

[0050] The optical absorber 12B is switchable / excitable from its passive state to an active state in which it operates as a spatial light modulator, as will be explained in more detail below.

[0051] The input fiber unit 12A is configured to receive an input optical signal IS having a predetermined wavelength λ1 and a weighted optical beam WB having at least one optical property different from each of the properties (e.g., wavelength, polarization, phase) of the input optical signal IS. In this non-limiting example, the weighted optical beam WB has a predetermined wavelength λ2 different from the wavelength λ1 (λ1 ≠ λ2) of the input optical signal IS. For example, λ1 = 1500 nm and λ2 = 1000 nm.

[0052] The input optical signal IS and the weighted light beam WB propagate (generally in the direction of propagation) through the input fiber unit 12A towards an output face OP.

[0053] The optical absorber 12B is exposed to interactions with both the input optical signal IS and the weighted optical beam WB. In the example of Figure 1A, such interactions occur when the optical absorber element 12B is located at the output face OP, and thus both the input optical signal IS and the weighted optical beam WB are incident on the optical absorber element 12B while exiting the input fiber unit. In the example of Figure 1B, the input optical signal IS and the weighted optical beam WB undergo multiple interactions with the optical absorber 12B while propagating through the input fiber unit 12A.

[0054] The optical absorbers 12B are excitable / switchable by interaction with the weighted light beam WB, apply spatial modulation to the input optical signal IS interacting with them, and thus generate a spatially modulated light field MLF corresponding to the input optical signal IS.

[0055] More specifically, interaction of the weighted light beam WB with the optical absorber 12B (which may be a separate element at the output face OP or integrated into or extending along the input fiber through which both the input optical signal IS and the weighted light beam WB propagate) excites the optical absorber by inducing the generation of free charge carriers (electron-hole pairs) that are efficiently absorbed by the optical absorber 12B, resulting in a spatial modulation pattern within the optical absorber 12B. As the input optical signal IS interacts with the so-excited optical absorber 12B, this affects a corresponding spatial modulation of the input optical signal IS, resulting in a modulated optical signal / modulated light field MLF. The modulated optical signal / modulated light field MLF may be transmitted through the optical absorber 12B.

[0056] It should be appreciated that the optical properties (eg, wavelength and intensity) of the weighted light beam WB may be selected such that the weighted light beam WB appropriately excites the optical absorber 12B.

[0057] In the example of Figure 1A, the optical absorber 12B is disposed in the propagation path of the light output from the input fiber unit 12A at the output face OP, and is therefore exposed to interactions with the input optical signal IS and the weighted light beam WB output from the input fiber unit 12A. In the example of Figure 1B, the core of the input fiber 12A is formed from a light-absorbing material and therefore acts as the optical absorber 12B, and the input optical signal IS and the weighted light beam WB are subjected to multiple interactions with the optical absorber 12B while propagating through the input fiber unit 12A.

[0058] The output fiber unit 12C is configured to receive and propagate the spatially modulated light field SML and direct a light field indicative thereof onto a detection plane DP housed at a predefined position in accordance with a predefined function / processing task to be performed by the processing unit 12. The input fiber unit 12A and the output fiber unit 12C are configured according to the desired processing function / task to be performed, as will be further explained below.

[0059] Therefore, the processing task to be performed by the optical processing unit 12, which may be a predetermined function applied to the input optical signal IS, involves the effect of spatial modulation applied to the input optical signal IS by the weighted light beam WB through the interaction of both the input optical signal IS and the weighted light beam WB with the optical absorber 12B.

[0060] Such a predetermined function may be, for example, a convolution, a matrix multiplication, a spatial filtering of the light field, etc. The structure and length of the input fiber unit 12A and the structure and length of the output fiber unit 12B are appropriately selected to perform the desired optical processing of the light passing therethrough, as will be further explained below.

[0061] 2A-2C, which illustrate different configurations of the optical processor unit 12 of the present invention for performing various processing / computational tasks / functions on the input optical signal IS. For ease of understanding, the same reference numbers are used to identify similar components in all examples described herein.

[0062] 2A and 2B, the input fiber unit 12A includes a common input optical fiber 14A configured to receive and propagate both the input optical signal IS and the weighted optical beam WB. As described above, the input optical signal and the weighted optical beam differ from each other in at least one optical characteristic. In this non-limiting example, the input optical signal and the weighted optical beam have specific, distinct wavelengths λ1 and λ2 (λ1 ≠ λ2). The output fiber unit 12C includes an output fiber 14C.

[0063] In the example of FIG. 2A, the optical absorber 12B is integrated into the fiber 14A (i.e., the core of the fiber 14A is formed from an optically absorbing material), while in the example of FIG. 2B, the optical absorber 12B is a separate element located at the output face OP of the output of the fiber 14A.

[0064] 2C illustrates an optical processor unit 12, in which an input fiber unit 12A includes a first input fiber 14A and a second input fiber 14B configured to receive and propagate, respectively, an input optical signal IS and a weighted optical beam WB toward an output plane OP housed at a predetermined position according to a predetermined function to be performed, in this example an optical absorber 12B being a separate element located in said plane OP.

[0065] As mentioned above, it should be understood that the input optical signal IS and the weighted optical beam WB may propagate within the same fiber or within different fibers of the input fiber unit, regardless of whether the predetermined function / task to be performed involves input optical signals IS and weighted optical beams WB of the same or different domains (frequency and / or spatial domain) at the output of the input fiber unit.

[0066] Since the input optical signal IS and the weighted light beam WB have different wavelengths, their principal Fourier planes are not at the same location, and therefore propagation of both through the same fiber of an appropriately selected length (and an adaptable refractive index profile, e.g., via heating) makes it possible to determine whether they exit the fiber in the same domain or in different domains.

[0067] In either case (i.e., a common fiber or different fibers of the input fiber unit 12A for the propagation of the input optical signal IS and the weighted optical beam WB), the optical absorber 12B may be inside said input fiber or fibers. Also, in the same domain operation mode, the input optical signal IS and the weighted optical beam WB interact with the optical absorber 12B, resulting in the input optical signal being multiplied by the weighted beam.

[0068] As mentioned above, in some embodiments, a hybrid configuration may be used, according to which the nonlinear all-optical modulator 12B comprises a linear all-optical modulator including a first nonlinear medium and a second nonlinear medium, one of which is integrated into the input fiber unit, and the other of which is at the output facet of the input fiber unit. This may be implemented using the input fiber unit configuration of Figure 2A or 2B, i.e., a configuration utilizing a common input fiber for the propagation of both the input optical signal IS and the weighted optical beam WB.

[0069] Thus, although not specifically shown, in the example of Fig. 2A, modulator 12B, shown as being disposed within common input fiber 14A, constitutes a first nonlinear medium, and a second nonlinear medium is disposed at the output plane OP. Similarly, in the example of Fig. 2B, modulator 12B, shown as being disposed at the output plane OP, represents a second nonlinear medium, while the first nonlinear medium is disposed within fiber 14A. As input optical signal IS and weighted optical beam WB subsequently propagate through common input fiber 14A, their interaction with the first nonlinear medium (12B in Fig. 2A) integrated into common input fiber 14A applies a spatial modulation of the weighted optical beam WB along a first axis to the optical field corresponding to the input optical signal, and interaction of the modulated input optical signal and weighted optical beam with a second nonlinear medium (12B in Fig. 2B) disposed at the output of common input fiber 14A applies a spatial modulation of the weighted optical beam along a second axis to the input optical signal.

[0070] As mentioned above, the input fiber unit 12A and the output fiber unit 12C are configured according to a predetermined function / processing task to be performed.

[0071] In some embodiments, the light processing unit 12 is configured to perform a convolution function, in which case the processing unit 12 may have an overall configuration like any of the examples above of Figures 2A-2C, where the fibers of the input fiber unit 12A and the output fiber unit 12B are graded index (GRIN) fibers configured to apply a Fourier transform function to light passing therethrough.

[0072] 2A and 2B, or each of fibers 14A and 14B in the system configuration of FIG. 2C, is a GRIN fiber sized to perform a Fourier transform of the input optical signal IS and the weighted optical beam WB, i.e., the output plane OP is the Fourier plane for the optical input of the input GRIN fiber. As a result, given the use of optical absorber 12B located outside input fiber unit 12A, the input optical signal IS and the weighted optical beam WB are in a frequency / spectral domain as they exit input fiber unit 12A.

[0073] As shown in FIG. 2B, the optical absorber 12B is accommodated at the output plane OP and is exposed to interaction with the Fourier transform light field of the input optical signal IS and the weighted optical beam WB. As described above, the weighted optical beam WB (e.g., having a predetermined wavelength λ2) interacts with and excites the optical absorber 12B while being efficiently absorbed by the optical absorber, thereby applying a corresponding spatial modulation to the input optical signal IS interacting with the optical absorber 12B to generate a spatially modulated light field MLF. The spatially modulated light field MLF thus generated is a multiplication of the input optical signal IS and the weighted optical beam WB in the frequency / spectral domain, which then undergoes an inverse Fourier transform as it passes through the GRIN fiber 14C of the output fiber unit 12B, resulting in the desired convolution function, i.e., the convolution of the optical signal IS with the weighted optical beam WB. The detection plane DP is the Fourier plane for the optical input of the fiber 14C.

[0074] 2A, optical absorber 12B is integrated into input fiber unit 12A as described above. In this case, input optical signal IS and weighted optical beam WB propagate along a common input GRIN fiber 14A and undergo multiple interactions with optical absorber 12B. The resulting modulated light field MLF at the output face OP of input fiber unit 12A may correspond to the Fourier transform of multiple matrix multiplications of input optical signal IS and weighted optical beam WB.

[0075] This modulated light field MLF then undergoes an inverse Fourier transform while passing through the GRIN fiber 14C of the output fiber unit 12B to obtain the desired convolution function. The detection plane DP is the Fourier plane for the optical input of the fiber 14C.

[0076] Thus, in these examples, a convolution function is implemented by the GRIN fiber and the optical absorber to provide a continuous Fourier transform of the Fourier transform of the input optical signal IS and the weighted optical beam WB and the interaction with the optical absorber 12B, and a spatially modulated optical field MLF corresponding to the weighted input optical signal IS.

[0077] In another embodiment, the processing function / task is signal multiplication of the input optical signal IS by the weighted light beam WB, which is performed via an imaging process. Both the input optical signal and the weighted light beam have the same spatial domain. In such an embodiment, a GRIN fiber or a standard fiber may be used. Considering the use of a standard fiber, any of the above configurations of the processing unit illustrated in FIGS. 2A-2C may be used, with the fibers of the input fiber unit 12A and the output fiber unit 12C configured as imaging fibers, i.e., the output plane OP is the image plane for the light input to the input fiber unit 12A, and the detection plane DP is the image plane for the light input to the output fiber unit 12C. When a GRIN fiber is used as a common input fiber for the propagation of both the input signal and the weighted light beam, the GRIN fiber is appropriately adjusted so that both beams exit the image plane.

[0078] 2B and 2C, the optical absorber 12B is positioned at a plane OP outside the fiber unit 12A, and both the input optical signal IS and the weighted light beam WB are guided by the input fiber unit 12A toward the optical absorber 12B and interact with it. The interaction of the optical absorber 12B with the weighted light beam WB excites / switches the optical absorber, generating a spatial pattern therein corresponding to the spatial pattern of the weighted light beam WB while effectively absorbing this beam. A corresponding spatial modulation is applied to the input optical signal IS transmitted through the optical absorber 12B, generating a modulated light field MLF that propagates through the imaging fiber of the output fiber unit 12C to the detection plane DP. The resulting image has a spatial intensity profile corresponding to the product of the matrix multiplication of the input optical signal IS and the weighted light beam WB.

[0079] Therefore, in this case, the predetermined processing task performed by the processing unit 10 may be a signal multiplication between the input optical signal IS and the weighted light beam WB, which is obtained by imaging the input optical signal and the weighted light beam WB onto an optical absorber, which, through interaction with both of these optical fields, generates a modulated light field MLF that is successively imaged onto the detection plane DP.

[0080] In another embodiment, a predetermined processing task performed by the processing unit 10 includes filtering selected spatial frequencies of the input optical signal IS. This may be implemented using a processing unit configuration substantially similar to that of FIG. 2C, i.e., the input fiber unit 12A includes a first fiber 14A and a second fiber 14B for propagating the input optical signal IS and the weighted light beam WB, respectively, toward an optical absorber 12B outside the input fiber unit 12A at an output plane OP. However, for purposes of this embodiment, the first input fiber 14A is a GRIN fiber sized to perform a Fourier transform of the input optical signal IS, while the second input fiber 14B is an imaging fiber. The output plane OP is the Fourier plane for the light input to the first input fiber 14A and the image plane for the light input to the second input fiber 14B. The output fiber 14C is also a GRIN fiber that performs a Fourier transform of the light passing therethrough.

[0081] The optical absorber 12B housed in the output face OP is subjected to interaction with optical fields of different domains, namely, the Fourier transform of the input optical signal IS and the spatial pattern of the weighted light beam WB. The weighted light beam WB interacts with the optical absorber 12B to excite / switch the optical absorber 12B to its modulated state and thus creates a spatial modulation pattern therein while being efficiently absorbed by the optical absorber 12B. Thus, the interaction of the input optical signal IS with the optical absorber 12B affects the amplification of selected spatial frequencies of the input optical signal IS and allows the transmission of these frequencies, while attenuating and absorbing other spatial frequencies of the input optical signal, forming a modulating / filtering optical field MLF.

[0082] This modulated light field MLF propagates through output GRIN fiber 14C, directing the modulated light field MLF to a detection plane DP while performing an inverse Fourier transform of the modulated light field MLF. The detection plane DP is the Fourier plane for the optical input of GRIN fiber 14C. More specifically, the modulated light field MLF is in the frequency domain as it enters output GRIN fiber 14C. Output GRIN fiber 14C performs a Fourier transform on the modulated light field MLF, and the modulated light field MLF is then inverted / shifted to the time / space domain to include only the selected spatial frequencies.

[0083] Thus, the present disclosure provides fiber-based all-optical photonic / optical processing units capable of performing a variety of processing tasks, such as, for example, convolution, matrix multiplication, spatial filtering of optical fields, etc. Such processing units may form components of optical processor systems.

Claims

1. 1. An optical processor system comprising at least one optical processing unit configured to perform a predetermined processing task on an input optical signal, said optical processing unit comprising an array of optical fibers, said array of optical fibers comprising: an input fiber unit configured to propagate the input optical signal and a weighted light beam having at least one optical characteristic different from the optical characteristic of the input optical signal toward an output face of the input fiber unit arranged according to the predetermined function to be performed; an output fiber unit spaced from the output face of the input fiber unit generally along the direction of light propagation through the light processing unit and configured to propagate light to a detection face; a nonlinear all-optical modulator positioned upstream of the output fiber unit so as to be exposed to interaction with the input optical signal and an optical field corresponding to the weighted optical beam, the nonlinear all-optical modulator being switchable to a spatial modulation state by interaction with the optical field corresponding to the weighted optical beam, thereby applying spatial modulation of the weighted optical beam to the optical field corresponding to the input optical signal, thereby generating a spatially modulated optical field corresponding to the input optical signal, and enabling the spatially modulated optical field to propagate through the output fiber unit to the detection surface.

2. 2. The optical processor system of claim 1, wherein the nonlinear all-optical modulator of the optical processing unit is housed at the output surface and is exposed to the interaction with the input optical signal and the optical field corresponding to the weighted optical beam, thereby applying the spatial modulation of the weighted optical beam to the optical field corresponding to the input optical signal and generating the spatially modulated optical field corresponding to the input optical signal.

3. The optical processor system of claim 2 , wherein the input fiber unit of the optical processing unit comprises a common input fiber configured to propagate both the input optical signal and the weighted optical beam.

4. 3. The optical processor system of claim 2, wherein the input fiber unit of the optical processing unit comprises a first input fiber and a second input fiber configured to propagate the input optical signal and the weighted optical beam, respectively.

5. 2. The optical processor system of claim 1, wherein the input fiber unit of the optical processing unit comprises a common input fiber configured to propagate both the input optical signal and the weighted optical beam, and the nonlinear all-optical modulator is integrated into the common input fiber, thereby applying the spatial modulation of the weighted optical beam to the optical field corresponding to the input optical signal while the input optical signal and the weighted optical beam propagate through the common input fiber, and thereby generating the spatially modulated optical field corresponding to the input optical signal.

6. 6. The optical processor system of claim 5, wherein a core of said common input fiber is configured as said nonlinear all-optical modulator.

7. 2. The optical processor system of claim 1, wherein the input fiber unit of the optical processing unit comprises a common input fiber configured to propagate both the input optical signal and the weighted optical beam, and the nonlinear all-optical modulator comprises: a first nonlinear medium integrated into the common input fiber, thereby applying spatial modulation in a first axis of the weighted optical beam to the optical field corresponding to the input optical signal while the input optical signal and the weighted optical beam propagate through the common input fiber; and a second nonlinear medium positioned at an output of the common input fiber, thereby applying spatial modulation in a second axis of the weighted optical beam to the input optical signal, thereby generating the spatially modulated optical field corresponding to the input optical signal.

8. the input fiber unit comprises at least one graded index (GRIN) fiber configured to apply a Fourier transform function to at least one of the input optical signal and the weighted optical beam, the output plane being a Fourier plane for an optical input of the input fiber unit for at least one of the input optical signal and the weighted optical beam; 2. The optical processor system of claim 1, wherein the output fiber unit comprises a GRIN fiber configured to apply a continuous Fourier transform function to the spatially modulated light field passing through the GRIN fiber, and the detection plane is a Fourier plane for an optical input of the GRIN fiber of the output fiber unit for the spatially modulated light field.

9. 9. The optical processor system of claim 8, wherein the input optical signal and the weighted optical beam propagate through first and second GRIN fibers of the input fiber unit configured to apply a Fourier transform to the input optical signal and the weighted optical beam, respectively.

10. 9. The optical processor system of claim 8, wherein the nonlinear all-optical modulator of the optical processing unit is contained within the output surface and is exposed to interaction with the input optical signal and the optical field corresponding to the weighted optical beam, thereby applying the spatial modulation of the weighted optical beam to the optical field corresponding to the input optical signal and generating the spatially modulated optical field corresponding to the input optical signal.

11. 10. The optical processor system of claim 8, wherein the input optical signal and the weighted optical beam propagate through the same GRIN fiber configured to apply a Fourier transform to both the input optical signal and the weighted optical beam.

12. 10. The optical processor system of claim 8, wherein the input optical signal and the weighted optical beam propagate through the same GRIN fiber configured to apply a Fourier transform only to the input optical signal.

13. 12. The optical processor system of claim 11, wherein the nonlinear all-optical modulator is integrated into the GRIN fiber, thereby applying the spatial modulation of the weighted optical beam to the input optical signal while the input optical signal and the weighted optical beam propagate through the GRIN fiber, and generating the spatially modulated optical field corresponding to the input optical signal.

14. 13. The optical processor system of claim 12, wherein the nonlinear all-optical modulator is integrated into the GRIN fiber, thereby applying the spatial modulation of the weighted optical beam to the input optical signal while the input optical signal and the weighted optical beam propagate through the GRIN fiber, and generating the spatially modulated optical field corresponding to the input optical signal.

15. 13. The optical processor system of claim 12, wherein the nonlinear all-optical modulator comprises: a first nonlinear medium integrated into the same GRIN fiber of the input fiber unit, thereby applying spatial modulation of the weighted optical beam in a first axis to the optical field corresponding to the input optical signal while the input optical signal and the weighted optical beam propagate through the common input fiber; and a second nonlinear medium disposed at an output of the same GRIN fiber of the input fiber unit, thereby applying spatial modulation of the weighted optical beam in a second axis to the input optical signal, thereby generating the spatially modulated optical field corresponding to the input optical signal.

16. 14. The optical processor system of claim 13, wherein the nonlinear all-optical modulator comprises: a first nonlinear medium integrated into the same GRIN fiber of the input fiber unit, thereby applying spatial modulation of the weighted optical beam in a first axis to the optical field corresponding to the input optical signal while the input optical signal and the weighted optical beam propagate through the common input fiber; and a second nonlinear medium disposed at an output of the same GRIN fiber of the input fiber unit, thereby applying spatial modulation of the weighted optical beam in a second axis to the input optical signal, thereby generating the spatially modulated optical field corresponding to the input optical signal.

17. 9. The optical processor system of claim 8, wherein the predetermined processing task performed by the processing unit is a convolution between the input optical signal and the weighted optical beam resulting from the interaction of the Fourier transforms of the input optical signal and the weighted optical beam on the nonlinear all-optical modulator that generates the spatially modulated optical field and successively the Fourier transform of the spatially modulated optical field corresponding to the input optical signal.

18. 20. The optical processor system of claim 17, wherein the input optical signal and the weighted optical beam propagate through first and second GRIN fibers of the input fiber unit configured to apply a Fourier transform to the input optical signal and the weighted optical beam, respectively.

19. 20. The optical processor system of claim 18, wherein the nonlinear all-optical modulator of the optical processing unit is contained within the output face and is exposed to the interaction with the input optical signal and the optical field corresponding to the weighted optical beam, thereby applying the spatial modulation of the weighted optical beam to the optical field corresponding to the input optical signal and generating the spatially modulated optical field corresponding to the input optical signal.

20. 20. The optical processor system of claim 17, wherein the input optical signal and the weighted optical beam propagate through the same GRIN fiber configured to apply a Fourier transform to both the input optical signal and the weighted optical beam.

21. 21. The optical processor system of claim 20, wherein the nonlinear all-optical modulator is integrated within the GRIN fiber, thereby applying spatial modulation of the weighted optical beam to the input optical signal while the input optical signal and the weighted optical beam propagate through the GRIN fiber, and generating the spatially modulated optical field corresponding to the input optical signal.

22. 9. The optical processor system of claim 8, wherein the predetermined processing task performed by the processing unit is filtering of selected spatial frequencies of the input optical signal resulting from the interaction of a Fourier transform of the input optical signal and the weighted light beam to the nonlinear all-optical modulator with a continuous Fourier transform of the spatially modulated light field corresponding to the input optical signal.

23. 23. The optical processor system of claim 22, wherein the input optical signal and the weighted optical beam propagate through a first fiber and a second fiber, respectively, and at least the first fiber is the GRIN fiber configured to perform a Fourier transform of the input optical signal, and the second fiber is configured as an imaging fiber for the weighted optical beam.

24. 24. The optical processor system of claim 23, wherein the nonlinear all-optical modulator of the optical processing unit is contained within the output face and is exposed to interaction with the optical field corresponding to the input optical signal and the weighted optical beam.

25. 23. The optical processor system of claim 22, wherein the input optical signal and the weighted optical beam propagate through the same GRIN fiber of the input fiber unit configured to apply a Fourier transform to the input optical signal and configured as an imaging fiber with respect to the weighted optical beam.

26. 26. The optical processor system of claim 25, wherein the nonlinear all-optical modulator is integrated within the GRIN fiber, thereby applying the spatial light modulator of the weighted optical beam to a Fourier transform of the input optical signal while the input optical signal and the weighted optical beam propagate through the GRIN fiber.

27. 2. The optical processor system of claim 1, wherein the predetermined processing task performed by the processing unit is signal multiplication between the input optical signal and the weighted optical beam resulting from the interaction of the optical fields corresponding to the input optical signal and the weighted optical beam with the nonlinear all-optical modulator, and successive imaging of the spatially modulated optical field corresponding to the input optical signal onto the detection plane, wherein the input fiber unit is configured such that the output plane is an image plane of the optical input of the input fiber unit for both the input optical signal and the weighted optical beam, and the output fiber unit is configured such that the detection plane is an imaging plane of the optical input of the output fiber unit for the input optical signal.

28. 10. The optical processor system of claim 1, wherein the nonlinear optical modulator is configured and operable based on one of the following effects: plasma dispersion effect, photorefractive effect, cross-phase modulation effect, soliton effect, and Kerr effect.

29. An optical processing unit configured to perform a predetermined processing task on an input optical signal, the optical processing unit comprising: an input fiber unit through which the input optical signal and a weighted light beam propagate; an output fiber unit; and a nonlinear all-optical modulator arranged upstream of the output fiber unit so as to be exposed to an interaction of the input optical signal and the weighted light beam, the nonlinear all-optical modulator being configured to apply spatial modulation of the weighted light beam to an optical field of the input optical signal through the interaction, thereby generating a spatially modulated light field corresponding to the input optical signal, and to enable the spatially modulated light field to propagate through the output fiber unit to a detection surface.

30. 30. The optical processing unit of claim 29, wherein the input fiber unit comprises a common input fiber for propagating both the input optical signal and the weighted optical beam.

31. 31. The optical processing unit of claim 30, wherein the nonlinear all-optical modulator is disposed between the input fiber unit and the output fiber unit in an output face of the input fiber unit.

32. 31. The optical processing unit of claim 30, wherein the nonlinear all-optical modulator is integrated into the common input fiber such that the input optical signal and the weighted optical beam undergo the interaction with the nonlinear all-optical modulator while propagating through the common input fiber.

33. 31. The optical processing unit of claim 30, wherein the nonlinear all-optical modulator comprises at least a first nonlinear medium integrated into the common input fiber such that the input optical signal and the weighted optical beam undergo the interaction with the first nonlinear medium while propagating through the common input fiber, thereby applying spatial modulation of the weighted optical beam in a first axis to the input optical signal and generating a first axis modulated optical field of the input optical signal.

34. 32. The optical processing unit of claim 31 , wherein the nonlinear all-optical modulator further comprises a second nonlinear medium at the output face of the input fiber unit, such that the first axis modulated optical field and the weighted optical beam undergo an additional interaction with the second nonlinear medium at the output face, the additional interaction applying spatial modulation of the weighted optical beam in a second axis to the first axis modulated optical field of the input optical signal.

35. 30. The optical processing unit of claim 29, wherein the input fiber unit comprises a first input fiber and a second input fiber for propagating the input optical signal and the weighted optical beam, respectively, and the nonlinear all-optical modulator is disposed between the input fiber unit and the output fiber unit at an output face of the input fiber unit.

36. 30. The light processing unit of claim 29, wherein the input fiber unit comprises at least one input fiber configured as a GRIN fiber.

37. 37. The light processing unit of claim 36, wherein the output fiber unit comprises at least one output fiber configured as a GRIN fiber.

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