Optical data transfer

Abstract

To provide an optical data transfer system.SOLUTION: In a holographic storage system incorporating multi-waveguide networks, an input waveguide network includes a first input light pipe 203 to which a plurality of second input light pipes 204A, 204B are coupled. An input beam 104 from an emitter system 504 is coupled into the first input waveguide 203 through an in-coupling region thereof, and can be guided from there into the second input waveguide 204A or 204B. A reference waveguide network includes a first reference waveguide 205 to which a plurality of second reference waveguides 206A, 206B are coupled. A reference beam 106, 116 from the emitter system 504 is similarly coupled into the first reference waveguide 205, and can be guided into the second reference waveguide 206A or 206B. An output waveguide network includes a first output waveguide 207 to which a plurality of second output waveguides 208A, 208B are coupled.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] Technical Field

[0001] This disclosure generally relates to optical data transfer.

Background Art

[0002] Background

[0002] An optical waveguide is in the form of an optical component that can guide a beam through total internal reflection. The waveguide can be "multimode" in the sense that it has sufficient physical dimensions to support a wide range of "modes" (i.e., spatial paths through the waveguide for a given channel, corresponding to different propagation directions for example). This is in contrast to simple single-mode optical waveguides such as thin optical fibers used in optical fiber systems, whose purpose is to essentially limit the light entering the fiber to a single propagation mode. A single-mode optical waveguide can only carry data using amplitude, phase, or frequency modulation, while a multimode optical waveguide can carry more data (e.g., potentially an entire image of millions of pixels) by means of angular variations within the waveguide. Put another way, a multimode waveguide provides a larger bandwidth by increasing angular and / or spatial diversity by providing multiple optical paths (different paths corresponding to different propagation modes) through the waveguide from an emitter to a detector for any given channel.

[0003]

[0003] Multimode waveguides are more generally used in, for example, head-mounted displays (HMDs) and waveguide-based display systems. In this context, a multimode waveguide typically carries an image from a display or optical engine to the user's eye, and the image is reconstructed by the eye's optical system and thus in a form perceivable by a human user. A diffractive optical system can be used to ensure that the beam entering and exiting the waveguide preserves the original image so that the original image can be reconstructed by the eye and beam expansion is provided. [Overview of the Initiative] [Means for solving the problem]

[0004] overview

[0004] This summary is provided to give a simplified introduction to the selected concepts, which are further described in the following detailed description. This summary is not intended to identify any important or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Nor is the claimed subject matter limited to any implementation that solves any or all of the defects described herein.

[0005]

[0005] A first aspect of this specification provides an optical data transfer system. A beam modulator is configured to embed a set of data into an input beam. A multimode optical waveguide network has an incoupling region for receiving the input beam. The multimode optical waveguide network is configured to guide the input beam into an outcoupling region of the multimode optical waveguide network. A spatial coherent detector is configured to measure the phase and amplitude of the output optical field at multiple locations. The output optical field is at least partially defined by the input beam and therefore exhibits distortion effects resulting from the beam passing through the multimode waveguide network. At least one processor is coupled to the spatial coherent detector and configured to apply signal processing to the output of the spatial coherent detector to compensate for the distortion effects, thereby recovering the set of data embedded in the input beam from the output of the spatial coherent detector.

[0006]

[0006] This has the advantage of significantly increasing optical data transfer capacity due to its ability to transfer potentially large amounts of data in parallel (e.g., images of millions of pixels) and using potentially complex waveguide networks (e.g., to provide spatial multiplexing). The use of coherent detection allows for more effective distortion compensation to be applied to the measured phase and amplitude of the output optical field, which is made possible by providing adequate resilience to waveguide distortion. One example of the application of this waveguide network is in holographic data storage / retrieval systems, where beams are carried to and from holographic recording media. In this context, the multimode capability of the waveguide can be used, for example, to read / write entire images simultaneously, and the capacity and robustness of the system are increased by its ability to effectively compensate for waveguide distortion at the output of the spatial coherent detector.

[0007]

[0007] Other examples include optical communications or optical computing and any other optical data transfer situations using multimode waveguides in which data is embedded in a beam and then recovered.

[0008] Simple explanation of the diagram

[0008] For a better understanding of the present disclosure and to illustrate how embodiments of the present disclosure may be carried out, the following figures are merely examples. [Brief explanation of the drawing]

[0009] [Figure 1A]

[0009] A schematic perspective view of the holographic recording medium is shown. [Figure 1B]

[0009] A schematic perspective view of the holographic recording medium is shown. [Figure 2A]

[0010] A schematic perspective view of a holographic memory system is shown, which includes a set of waveguides that can be used to guide beams to / from different subvolumes of a holographic recording medium in order to provide spatial multiplexing across the medium. [Figure 2B]

[0010] A plan view of the system during the writing period is shown. [Figure 2C]

[0010] A side view of one side of the system during the writing period is shown. [Figure 2D]

[0010] A side view of one side of the system during the writing period is shown. [Figure 2E]

[0010] The plan view during the reading period is shown. [Figure 2F]

[0010] A side view of one side during the reading period is shown. [Figure 2G]

[0010] A side view of one side during the reading period is shown. [Figure 3A]

[0011] A schematic side view of an active light pipe in a certain configuration is shown. [Figure 3B]

[0011] A schematic side view of an active light pipe with a certain configuration is shown. [Figure 3C]

[0011] A schematic side view of an active light pipe with a certain configuration is shown. [Figure 3D]

[0011] A schematic side view of an active light pipe with a certain configuration is shown. [Figure 3E]

[0011] A plan (cross-sectional) view of the active light pipe is shown. [Figure 3F]

[0011] A plan (cross-sectional) view of the active light pipe is shown. [Figure 4A]

[0012] This shows a side view of one side of an optical waveguide network (or a portion thereof). [Figure 4B]

[0012] A side view of one side of the optical waveguide network (part thereof) is shown. [Figure 5]

[0013] A schematic diagram of an example of a multiplexed waveguide network used for multiplexing across multiple pieces of a holographic storage medium is shown. [Figure 6A]

[0014] An example of an emitter system for providing input and reference beams in a holographic memory system is shown. [Figure 6B]

[0014] Shows a modified form of an emitter system with a simplified optical system. [Figure 7]

[0015] An example of a data recovery system is shown that uses spatial coherent detection to measure the optical field of an output beam and signal processing to reduce waveguide distortion in the measured optical field. [Figure 8]

[0016] A functional block diagram showing the functions performed within a holographic memory system is shown. [Figure 9]

[0017] An alternative holographic memory system is shown that uses at least one waveguide network to spatially multiplex two-dimensionally across a slab of a holographic recording medium. [Figure 10A]

[0018] Shows how spatial multiplexing can be achieved using passive guiding elements, where spatial multiplexing is achieved by modulating beam characteristics. [Figure 10B]

[0018] Shows how spatial multiplexing can be achieved using passive guiding elements, where spatial multiplexing is achieved by modulating beam characteristics. [Figure 11A]

[0019] A light pipe with a passive optical filter having different frequency responses is shown. [Figure 11B]

[0019] A light pipe with a passive optical filter having different frequency responses is shown. <T [Figure 12]

[0020] An example of a waveguide network having three hierarchical levels is shown.

Mode for Carrying Out the Invention

[0010] Detailed Description of Examples of Embodiments

[0021] One application example of waveguide networks taught herein is a holographic memory device. A holographic memory device is a form of computer memory in which information is recorded on a photosensitive holographic recording medium by exposing the medium to an optical pattern. For example, a region (subvolume) of the medium can be exposed to an optical interference pattern resulting from the interference of an input beam and a reference beam in which a set of data is embedded. The beam can be, for example, a laser beam generated using a single laser and a beam splitter. Spatial light modulation (SLM) can be used to embed the set of data in the input beam (for example, an image encoding the set of data can be spatially modulated and embedded in the input beam). To avoid misunderstanding, in this specification, “light,” “optics,” and similar terms are not limited to visible light. Holographic memory devices can be implemented using, for example, infrared or ultraviolet beams in the non-visible portion of the electromagnetic spectrum.

[0011]

[0022] With sufficient beam power and exposure time, the optical interference pattern results in a sustained state change within the subvolume (at this point, the interference pattern is referred to herein as sustainably recorded or written to the subvolume). The state change of the subvolume is such that, at a later point, as soon as the subvolume is exposed to a substantially matched reference beam, the interaction between the matched reference beam and the subvolume allows the set of data originally embedded in the input beam to be recovered from the output beam (this may be referred herein as reading the recorded pattern), thus generating an output beam that is essentially matched to the original input beam.

[0012]

[0023] Rather than storing individual bits as discrete units, a single interference pattern can encode many (e.g., millions) bits. For example, a set of data could be a megapixel image embedded in an input beam. Furthermore, by utilizing the sensitivity of certain forms of holographic recording media to small changes in the angle of the reference beam, it is possible to record many (e.g., hundreds or thousands) such patterns in the same subvolume. In the case of such media, once an interference pattern is generated with a reference beam at a given angle, the recorded pattern can only be read by using a reference beam that is precisely matched to the reference beam originally used to generate it. This effect can be used to record multiple patterns (encode different sets of data) in the same subvolume at different reference beam angles. Theoretically, data storage capacity is limited only by the wavelength of the beam, potentially hundreds of megabytes per cubic millimeter for red light and tens of gigabytes for ultraviolet light. In practice, other limiting factors may exist, but nevertheless, there is great potential for high-density data storage.

[0013]

[0024] To achieve spatial multiplexing across one or more holographic storage media in a manner that reduces or eliminates the need for mechanical movement, “active” light pipes, “passive” light pipes, or combinations of active and passive light pipes may be used. Note that the terms “waveguide” and “light pipe” are used interchangeably herein.

[0014]

[0025] An "active light pipe" refers to a waveguide having one or more active switching elements or other inductive elements mounted on the surface of the waveguide or within the bulk of the waveguide, and is therefore configurable to cause "one-to-many" light transmission (i.e., light is guided from a first surface region to one of several possible second surface regions (in which case the first surface region becomes an incoupling region and the second region becomes an outcoupling region)) or "many-to-one" light transmission (i.e., light is guided from any one of the second surface regions (in this case, an incoupling region) to the same first surface region (in this case, an outcoupling region)) (i.e., has modifiable optical properties). The term "passive light pipe" refers to a light pipe with inductive elements having different light sensitivities (e.g., different wavelengths and / or polarization sensitivities), and a similar effect can be achieved instead by changing the optical properties or beam (e.g., using a tunable laser and changing its wavelength, polarization, etc., so that it is guided along different routes by inductive elements having different wavelength / polarization responses, etc.). The term "passive light induction" is merely a convenient label and, in this case, coincides with the fact that the induction element does not need to be active; however, in relation to this, active or passive induction elements with different light sensitivities (e.g., different wavelengths and / or polarization sensitivities, etc.) can be used (i.e., the induction element may be active and have different light sensitivities).

[0015]

[0026] A digital image (or data encoded as a digital image) can propagate as a beam along an active or passive light pipe. The guide elements of the active light pipe can be individually controlled to transmit or reflect the incident light beam.

[0016]

[0027] Many such light pipes (active, passive, or a combination of both types) can be combined in various geometries to create switching networks that can be used to manipulate beams and images to one of many addressable locations in one or more spatial dimensions. The input to the light pipe can be generated using a spatial light modulator (SLM), and the output is read, for example, in a CCD (charge-coupled device). Phase interference and noise can be corrected using a combination of optical and computational techniques (including machine learning techniques), which would involve learning one or more signal processing parameters from training data. In some embodiments, coherent detection is used in combination with such techniques to provide more effective waveguide distortion reduction.

[0017]

[0028] In contrast to the types of optical switches and fibers conventionally used in optical data communications, the embodiments described utilize a light pipe capable of transmitting an entire image at once. This leverages currently available high-resolution optical devices such as SLMs and digital cameras, which have millions of pixels and enable the encoding and decoding of megabytes of data. This allows for high-bandwidth transmission even with modest switching rates of the SLM, camera, and active light pipe elements (in the case of an active light pipe) or beam optical properties (in the case of a passive light pipe). In addition, applications such as holographic storage devices require interference between multiple beams, and at least one of the beams is modulated in an image. In holographic storage devices, an active light pipe can be used to efficiently manipulate beams and images to interfere at any desired location in the holographic storage medium. A simpler advantage, as described, can be achieved with a passive light pipe, in which switching is instead applied at the emitter stage.

[0018]

[0029] The light pipes described below are "multimode" waveguides in the sense that they have sufficient physical dimensions to support a wide range of "modes" (i.e., spatial paths through the waveguide for a given channel, corresponding to different propagation directions, for example). This is in contrast to simple single-mode optical waveguides, such as the thin optical fibers used in optical fiber systems, whose purpose is to restrict the light entering the fiber to essentially a single propagation mode. While single-mode optical waveguides can only carry data using amplitude, phase, or frequency modulation, multimode optical waveguides can carry much more data (e.g., an entire image of several million pixels) through angular variations within the waveguide. In other words, multimode waveguides provide greater bandwidth through increased angular and / or spatial diversity by providing multiple optical paths through the waveguide from emitter to detector for any given channel (different paths corresponding to different propagation modes).

[0019]

[0030] Another aspect disclosed herein is a holographic data storage system that spatially multiplexes across a holographic recording medium (i.e., reads from / writes to different subvolumes of the medium) using one or more waveguide networks without requiring any relative mechanical movement between the medium and the waveguide network. Examples of such systems are described below and utilize active and / or passive light pipes. In the examples described, multimode waveguides can be used to carry an entire digital image simultaneously into / from the holographic recording medium or to carry a reference beam at one of several possible angles.

[0020]

[0031] However, the optical waveguide networks taught herein are not limited to holographic storage devices in their applications. Other applications include, for example, optical communications and optical computing.

[0021] Active light pipe:

[0032] Figures 3A–D show schematic side views of examples of configurations of the active light pipe 300 having a specific physical structure. As should be understood, this is merely one example of a suitable physical structure that can provide the desired optical configurability. Further examples will be considered below.

[0022]

[0033] The active light pipe 300 is shown to have at least a first surface region 300-0 and a plurality of active switches in the form of switchable Bragg gratings (SBGs) that may be on the surface or volume-embedded. In this example, two such SBGs 300-1, 300-2 are shown on the first surface 300-S1 of the waveguide 300, but it will be understood that more SBGs can be placed in appropriate locations on the surface 300-S1 of the waveguide 300 and / or embedded within the bulk of the waveguide 300. Each SBG 300-1, 300-2 can be individually controlled so that its reflectance / transmission properties change in order to transmit or reflect an incident beam. The SBGs 300-1, 300-2 form the respective surface regions of the active light pipe 300, in which light can enter (incoupled) or exit (outcoupled) the waveguide 300, depending on how the waveguide 300 is used.

[0023]

[0034] The first surface region 300-0 is the end region of the waveguide 300, from which the first side surface 300-S1 of the waveguide extends along the axis 301 of the waveguide 300.

[0024]

[0035] Figures 3E and 3F show cross-sectional views of the waveguide 300, respectively, which in this example have a rectangular cross-section and can be seen that four sides 300-S1, 300-S2, 300-S3, and 300-S4 extend along the axis 301 of the waveguide 300. In this example, as depicted in the figures, SBGs 300-1 and 300-2 are all located along the first side 300-S1, but generally, such SBGs can be mounted on multiple surfaces of the waveguide 300, depending on the application.

[0025]

[0036] SBGs 300-1 and 300-2 are positioned along the first side 300-S1 of the waveguide, with increasing distance from the first region 300-0, and the first SBG 300-1 is located closest to the first region 300-0.

[0026]

[0037] Figures 3A, 3B, and 3E illustrate a "one-to-many" use case, where the first surface region 300-0 is the incoupling region, and the second surface regions 300-1 and 300-2 of the SBG are the outcoupling regions. As an example, Figure 3 shows a first ray 304 being taken into the waveguide 300 via the incoupling region 300-0. In this example, the first surface region 300-0 is angled with respect to sides 300-S1, ..., 300-S4, so that the first ray 304 passes through the first surface region 300-0 and enters the bulk of the waveguide 300 at an angle sufficient to achieve total internal reflection at each of the sides 300-S1, ..., 300-S4 within the waveguide 300.

[0027]

[0038] Each of the SBGs 300-1 and 300-2 can be configured to switch between a reflective state and a transmitted state. Figure 3A shows a configuration in which the first SBG 300-1 is in the reflective state, and the incident light ray 304 is reflected by the first SBG 300-1 and returned into the waveguide 300, and guided along the waveguide 300 until it reaches the second SBG 300-2. SBG 300-2 is shown in the transmitted state, and the light ray 304 is diffracted out of the waveguide 300 through the second SBG 300-2, thereby being extracted from the waveguide 300 through the surface region of the second SBG 300-2. This configuration of SBGs 300-1 and 300-2 creates a "channel" through the waveguide 300 between the surface region of the first SBG 300-0 and the surface region of the second SBG 300-2.

[0028]

[0039] In contrast, Figure 3B shows that the first SBG 300-1 is in a transmitted state. Therefore, as soon as the first ray 304 reaches the first SBG 300-1, it is instead diffracted out of the waveguide 300 through the first SBG 300-1, and thus is extracted from the waveguide 300 instead through the surface region of the first SBG 300-1. This configuration creates a channel through the waveguide 300 between the first surface region 300-0 and the surface region of the first SBG 300-1.

[0029]

[0040] This method allows the first ray 304 to be guided through the waveguide 300 from the first region 300-0 to the surface region of SBG 300-1 or 300-2, until it exits the waveguide 300. For simplicity, only SBGs 300-1 and 300-2 are discussed in relation to each other, but it will be understood that the same principle can be applied to more SBGs.

[0030]

[0041] Figure 3E shows, in cross-sectional view, how the first ray 304 can propagate through TIR from some or all of the sides 300-S1, ..., 300-S4, depending on the angle of the first ray 304.

[0031]

[0042] As depicted in Figures 3C, 3D, and 3F, it is equally possible to use the depicted active light pipe 300 for many-to-one optical transfer.

[0032]

[0043] Figure 3C shows the same SBG configuration as in Figure 3A. The only difference is the use of waveguide 300, where a second ray 308 is shown incident on the second SBG 300-2 from an external source (not shown). With the second SBG in a transmitted state, the second ray 308 diffracts into waveguide 300 through the second SBG (which here provides incoupling in its surface region) and is then guided through waveguide 300 to the first surface region 300-0 (here, the outcoupling region). This includes reflection from the first SBG 300-1, which here is in a reflective state. The reflective state of the first SBG 300-1 prevents the ray 308 from exiting the waveguide through the first SBG 300-1. Furthermore, any external light rays 309 that might coincidentally be incident on the first SBG 300-1 are essentially reflected away from the first SBG 300-1 and therefore do not enter the waveguide 300.

[0033]

[0044] Figure 3D shows the same configuration as Figure 3B, but here a second ray 308 is incident on the first SBG 300-1 from an external source. As the first SBG 300-1 is in a transmission state, the second ray 308 enters the waveguide 300 at that location by diffraction and is guided to the first surface region 300-0.

[0034]

[0045] Figure 3F shows how the second ray 308 can propagate within the waveguide 300 in cross-section, and the same explanation as in Figure 3E applies, but the direction of the ray is reversed.

[0035]

[0046] The above explanation assumes perfect reflectivity / transmittance of the SBG in the transmitted / reflected state. As should be understood, this is not actually an absolute requirement, and more generally, the system has some tolerance for imperfections in SBG 300-1, 300-2 and waveguide 300. Appropriate signal processing techniques for compensating for distortion introduced into waveguide 300 will be discussed later.

[0036]

[0047] Although SBGs 300-1 and 300-2 are described as separate elements, in effect, a single large SBG with separately and independently controllable regions may extend over all or most of the first aspect 300-S1.

[0037]

[0048] SBG is just one possible form of active switching element. For example, in a polarized beam, the same effect can be achieved using a controllable polarizing filter that is mounted on the surface of the waveguide 300 or embedded within the bulk of the waveguide. SBG and controllable polarizing filters are examples of non-mechanical active switches that can alter the optical properties of the waveguide 300 through non-mechanical effects. Other examples of inductive elements include controllable mirrors such as micromirror devices or other micro-electromechanical systems (MEMs), which are examples of mechanical inductive elements.

[0038]

[0049] When using a polarizing filter as a guide element, the SBG 300-1 and 300-2 can be replaced with a passive diffracting element, and the polarizing filter operates to guide the beam toward or away from the passive diffracting element in a controllable manner as needed, without requiring the diffracting element to be reconfigured.

[0039]

[0050] It should be noted that even if the inductive elements themselves are mechanical, the need for mechanical operation of the waveguide 300 as a whole is still avoided.

[0040] Active Lightpipe Network

[0051] In this specification, a "waveguide network" can take the form of a single waveguide or a network of interconnected waveguides. Waveguide networks with multiple active light pipes have particular advantages in terms of flexible optical data transfer.

[0041]

[0052] Figures 4A and 4B show a side view of one side of a waveguide network (or a portion thereof) including first and second active light pipes 400 and 420. The second light pipe 420 has a first surface region 420-0 positioned to be aligned adjacent to a corresponding surface region of the first light pipe 400 in order to receive a beam from the second waveguide 420 via the first surface region 400-0 or to guide a beam into the second waveguide 420. Purely as an example, a ray 404 is shown propagating through the first waveguide 400 to a corresponding surface region of the first waveguide 400, the corresponding surface region of the first waveguide 400 being adjacent to the first surface region 420-0 of the second waveguide 420. The ray 404 is extracted from the first waveguide 400 via SBG 400-1 attached to an adjacent surface region of the first waveguide 400 and taken into the second waveguide 420 via the first surface region 400-0. From there, the ray 404 can be guided to one of the multiple SBGs 420-1, 420-2 of the second waveguide 420 in a one-to-many configuration. In a many-to-one configuration, the same configuration can be used to reverse the direction of the ray and guide the beam in the other direction from the second waveguide 420 to the first waveguide 400.

[0042]

[0053] This example considers two interconnected waveguides 400 and 420, but the principle can be applied to more interconnected waveguides to enable flexible data routing through the waveguide network.

[0043]

[0054] More generally, a surface region of a medium can be optically coupled to a corresponding surface region of a waveguide in another way, such as via an air interface or one or more other optical components (which themselves may be waveguides and may or may not provide active or passive switching functionality).

[0044] Holographic memory

[0055] This section describes the application of active light pipes to holographic storage devices.

[0045]

[0056] Figures 1A and 1B show schematic perspective views of a holographic recording medium 102, which is a relatively thick volume of photosensitive material capable of persistently storing a light pattern as a “hologram” embodied within the holographic recording medium 102 (which can be simply called medium 102 for brevity). The hologram is generated by exposing the subvolume 110 (region) of medium 102 to a light pattern so that a persistent state change occurs within the subvolume 110. The hologram generated in the subvolume 110 by this state change records the light pattern to medium 102, from which the light pattern can be reproduced at a later point in time. The hologram is persistent in that, at the time of generation, medium 102 does not require power to maintain it. The composition and structure of medium 102 may be such that the hologram cannot be erased once generated (thus providing a “write-once-three-many” (WORM) storage device) or it may be such that the hologram can be erased and replaced (but persists unless erased and until erased).

[0046]

[0057] A single hologram can record a light pattern encoding a very large number of bits (e.g., millions), thereby allowing very large amounts of data to be written to / read from the holographic recording medium 102 in parallel (simultaneously). Another advantage of holographic storage devices is that many holograms can be written to the same sub-volume 110 of the holographic recording medium 102, thereby greatly increasing the data storage capacity per unit volume of the holographic recording medium 102.

[0047]

[0058] More specifically, Figure 1A shows how the input beam 104 and reference beam 106 are directed to the subvolume 110 through the first and second sides 102-4 and 102-6, respectively, of the medium 102 in order to write a set of data to the medium 102. This generates a light pattern in the form of an interference pattern resulting from the interference between the input beam 104 and the reference beam 106. If beams 104 and 106 have sufficient power and the subvolume 110 is exposed for a sufficient duration, the interference pattern generated by the interfering beams 104 and 106 will be persistently recorded in the subvolume 110 as a hologram. As described below, the set of data can be embedded in the input beam 104 and recovered from the resulting hologram. In this way, the encoded set of data is written to the subvolume 110. In the following example, the set of data is encoded as a digital image and then embedded in the input beam 104 via spatial modulation.

[0048]

[0059] As shown in Figure 1B, in order to read data from the subvolume 110, a matched reference beam 116 is directed towards the subvolume 110 via a second side 102-6 of the medium 102, the matched reference beam 116 interacts with the hologram to generate an output beam 108, which is essentially matched with the input beam 104 used to write the hologram to the extent that the embedded data is recoverable from the output beam 108. The output beam 108 propagates out of the subvolume 110 via a third side 102-8 of the medium 102.

[0049]

[0060] The reference beam 116 used to read the data is substantially aligned with the reference beam 106 originally used to write the data, and is directed at an angle (or more generally, direction) that precisely matches the angle of the original reference beam 106. This is because the ability to read the hologram (i.e., generate an output beam 108 that can recover the data) is highly sensitive to angular deviations between the reference beam 106 used to write the hologram and the reference beam 116 used to read the hologram. This sensitivity can be used to record multiple holograms within the same subvolume 110, each hologram being generated using a different reference beam angle, and two completely different holograms can be generated using only a very small difference in the reference beam angles. In this way, many (e.g., hundreds or thousands) of holograms can be written to the same subvolume 110, each encoding many (e.g., millions) of bits.

[0050]

[0061] Figure 2A shows a schematic perspective view of an example of a holographic memory system 200 incorporating a particular principle of the present disclosure. In this particular example, three separate waveguides 204, 206, and 208 are used to carry an input beam 104, reference beams 106, 116, and output beam 108, and the three separate waveguides 204, 206, and 208 can be referred to individually as the input waveguide 204, the reference waveguide 206, and the output waveguide 208. As described herein, the terms “optical waveguide” and “light pipe” are used interchangeably with each other. Each of the waveguides 204, 206, and 208 provides spatial multiplexing in the sense that it can induce a signal to any one of several subvolumes in the holographic recording medium 102 (in the case of input and reference waveguides 204, 206) or from any one of several subvolumes in the holographic recording medium 102 (in the case of output waveguide 208). This provides spatial multiplexing across the volume of the holographic recording medium 102 without requiring any mechanical movement of waveguides 204, 206, and 208 relative to the holographic recording medium 102. To avoid the need for such mechanical movement, inductive elements can be located on or within each waveguide 204, 206, and 208, and configured to change the optical properties of waveguides 204, 206, and 208 to induce signals into or from different subvolumes of the medium 102. That is, to create different channels within waveguides 204, 206, and 208 as needed. In this particular example, the inductive elements take the form of active optical switching elements (switches). The switches can take various forms. In this example, the switches take the form of SBGs located in different surface regions of waveguides 204, 206, and 208 in the same general arrangement as in Figures 3A-F. In other words, each waveguide 204, 206, and 208 takes the form of an active light pipe, and each waveguide 204, 206, and 208 has the same general physical structure as the active light pipe 300 shown in Figures 3A to F.

[0051]

[0062] Each waveguide 204, 206, and 208 is positioned such that its first surface (i.e., the surface on which its SBG is located) is adjacent to a different side of the medium 102, thereby causing its SBG to extend along that side of the medium 102. The first and second SBGs of each waveguide 204, 206, and 208 are indicated by reference numbers 204-1, 204-2, 206-1, 206-2, 208-1, and 208-2, respectively, and they are all configurable in the manner described above. Further SBGs are described without reference numbers, and the number of SBGs can be selected to accommodate any size of holographic recording medium 102. For brevity, the following description refers to the first and second SBGs of each waveguide 204, 206, and 208, but it will be understood that the description also applies to more SBGs.

[0052]

[0063] Figures 2B-2D illustrate how the input and reference waveguides 204 and 206 are used to write data to the medium 102 in a one-to-many manner. Figure 2B is a schematic plan view of the system 200, and Figures 2C and 2D are side views showing the input and reference waveguides 204 and 206, respectively. The input waveguide 204 is used in the manner described above to guide the input beam 104 to one of several subvolumes of the medium 102 via either SBG 204-1 or 204-2 of the input waveguide 204. The reference waveguide 206 is configured to guide the reference beam 106 to the same subvolume simultaneously, generating the desired interference pattern to be written to that subvolume. In the example described, both the input waveguide 204 and the reference waveguide 206 are configured to guide the input and reference beams 104, 106, respectively, to subvolumes indicated by reference number 110, via the second SBGs 204-2, 206-2 of each waveguide 204, 206.

[0053]

[0064] Figures 2E to 2G show how the reference and output waveguides 206 and 208 can be used to read data from the medium 102. Figure 2E is a plan view, and Figures 2F and 2G show a side view of one side where the reference and output waveguides 206 and 208 are visible. The reference waveguide 206 is used in exactly the same way as depicted in Figures 2B to 2D, but here the reference beam 116 is guided to the subvolume (subvolume 110 in this case) from which the hologram is read. The output waveguide 208 is used in a one-to-many manner to guide the resulting output beam 108 from subvolume 110 through waveguide 208 for subsequent detection.

[0054]

[0065] Each subvolume 110 may have a height and width of several millimeters, for example, measured along any side, which would generally be sufficient to store several million pixels per data "page" (e.g., multiplexing angle). In this example, the volume of the subvolumes is sufficient to store (several million pixels) * (number of multiplexing angles).

[0055]

[0066] The inductive elements (SBGs in this example) of the input waveguide 204 and the reference waveguide 206 are configured to provide channels for the input beam 104 and the reference beams 106, 116 from the beam source (emitter system) to the subvolume 110 being read. The SBGs are set to a transmitted or reflected state as needed to create the channels. Similarly, the inductive elements (SBGs in this example) of the output waveguide 208 are similarly configured to provide channels from the subvolume 110 being read to the detector. For additional context, this will be discussed in more detail below with reference to the multiple waveguide network depicted in Figure 5. However, the principles described in relation to the specific example in Figure 5 are more generally applicable to other waveguide network topologies, including both simpler networks (e.g., single waveguides) and more complex waveguide networks.

[0056]

[0067] As described above, this enables spatial multiplexing across medium 102 without mechanical movement of medium 102 relative to waveguides 204, 206, and 208. This is true regardless of the form the inducting elements take (as described above, these inducting elements themselves can be mechanical or non-mechanical).

[0057] Holographic storage device using a multiple waveguide network

[0068] Figure 5 shows an example of a holographic memory system incorporating the type of multiple waveguide network shown in Figure 4.

[0058]

[0069] The input waveguide network is shown to include a first input light pipe 203 ("parent" waveguide) into which multiple second input light pipes 204A, 204B ("child" waveguides) are coupled. The input beam 104 from the emitter system 504 is taken into the first input waveguide 203 through its incoupling region and can be guided from there to the second input waveguides 204A or 204B.

[0059]

[0070] The reference waveguide network is shown to include a first reference waveguide 205 into which multiple second reference waveguides 206A, 206B are coupled. Reference beams 106, 116 from the emitter system 504 can similarly be taken up by the first reference waveguide 205 and guided to the second reference waveguides 206A or 206B.

[0060]

[0071] The output waveguide network is shown to include a first output waveguide 207 into which multiple second output waveguides 208A, 208B are coupled.

[0061]

[0072] Depending on the depicted arrangement, beams can be directed to / from different subvolumes of multiple pieces 102A, 102B of the holographic storage medium.

[0062]

[0073] Figure 5 shows the input beam 104, reference beams 106, 116, and output beam 108, but it will be understood that the subvolumes will typically be written to and read at different times in the manner described above with reference to Figures 2A-G.

[0063]

[0074] The first groups 204A, 206A, and 208A of the second waveguide (one each of input, reference, and output) are located around the first piece 102A (first medium) of the holographic storage medium, and the second groups 204B, 206B, and 208B of the second waveguide are located around the second piece 102B (second medium), each in the same general arrangement as in Figures 2A-G. Thus, the input and reference beams 104, 106, and 116 can be directed to any subvolume of any medium piece 102A, 102B by first directing their beams to the desired second waveguides of the input and reference network, respectively, and then directing them to the desired subvolume of the medium piece adjacent to the desired waveguide.

[0064]

[0075] The output waveguide network can be used to guide the output beam 108 from any subvolume of any medium piece 102A, 102B to the first output waveguide 207 via the applicable second output waveguides 208A, 208B, and then to the detector 508 via the outcoupling region of the first output waveguide 207. To make a read from a particular subvolume, the SBG is configured to provide a channel from that subvolume to the detector; therefore, in this example, SBGs 204A-2 and 207-1 are set to a transmission state, and other SBGs in the output waveguide network are set to a reflection state as needed to provide a channel for the output beam 108 to the detector 508 (for example, in this example, SBG 207-2 of the first output waveguide 207 is set to a reflection state to prevent propagation of the output beam 108 to waveguide 208B). Other SBGs in the output waveguide network can be configured to reflect to the extent necessary to prevent unwanted light transmission (i.e., "leakage") from other areas of the same medium piece 102A or different medium piece 102B (for example, in this example, SBG 204A-1, which is closer to the subvolume being read, is shown to be configured to reflect to prevent unwanted leakage).

[0065]

[0076] In the example above, three separate waveguide networks are used for the input, reference, and output beams 104, 106, 116, and 108, but this is not always necessary. For example, the same waveguide network can be used to carry both the input beam 104 and the reference beams 106 and 116, and / or the same waveguide network can be used to carry the input beam 104 and the output beam 108, and / or the same waveguide network can be used to carry the output beam 108 and the input beam 104. Generally, having three separate networks is expected to provide optimal performance, but nevertheless, there are perfectly viable implementations using only one or two waveguide networks.

[0066]

[0077] Although not depicted in any of the figures, a fourth waveguide network can be used to carry the beam to the remaining sides of the medium pieces 102A and 102B. For example, the fourth network can be used to carry an erase beam to a desired subvolume that is at least suitable for erasing the hologram from there (in the case of an erasable holographic storage device).

[0067]

[0078] Figure 9 shows an alternative physical structure in which a single "slab" of holographic medium 102 is used instead of the individual pieces 102A, 102B in Figure 5. The input waveguide network is depicted, having essentially the same physical configuration, but here the second input waveguides 204A, 204B are configured to guide the input beam 104 to different subvolumes of the same slab 102. In Figure 5, each of the second input waveguides 204A, 204B provides one-dimensional multiplexing along the length of the different single medium pieces 102A, 102B, whereas in Figure 9, the second waveguides 204A, 204B provide two-dimensional spatial multiplexing across the slab of holographic medium 102 (each waveguide individually provides one-dimensional multiplexing, but together there is two-dimensional multiplexing across the slab 102).

[0068]

[0079] The system in Figure 9 is limited to a maximum of two waveguide networks (one on each side of slab 102). As mentioned above, this is still a viable configuration because the same network can be used to carry multiple beams.

[0069] Data encoding

[0080] Figure 6A shows an example of an emitter system 504 that provides both an input beam 104 and a reference beam 106. The input beam is an expanded spatially modulated laser beam. Laser 600 emits a coherent narrow laser beam, which is split using a beam splitter 602.

[0070]

[0081] A portion of the beam from beam splitter 602 is used as reference beam 106. In this example, a controllable reference beam steering element 612 is used to manipulate reference beam 106 so that it enters reference waveguide 206 at a desired angle. By changing the angle of reference beam 106 before it enters reference waveguide 206, different holograms can be written to / read from the same subvolume of the medium in the manner described above.

[0071]

[0082] As an alternative to or in addition to beam angle multiplexing, multiple patterns with different phases (phase multiplexing) of reference beams 106, 116 can be stored in the same subvolume and read from the same subvolume. Thus, logical addresses can correspond to specific reference beam angles and / or phase characteristics. All explanations regarding reference beam angle modulation also apply equally to phase modulation.

[0072]

[0083] The remaining portion of the beam from the beam splitter 602 is expanded using the beam expander 604, and the expanded beam passes through the spatial light modulator (SLM) 606. The encoder 610 receives a set of data to be encoded, encodes that set of data as a digital image, and the digital image is then modulated via the SLM 606 and embedded in the expanded beam. An incoupling optical system (in this case, the Fourier lens 608) positioned such that the plane of the SLM 606 is substantially at the focal plane of the Fourier lens 608 is used to separate the expanded beam into entirely different propagation modes, where in this example, the modes correspond to their own propagation directions, and here, each mode corresponds to a specific point in the plane of the SLM 606. The different propagation modes are taken into the input waveguide 204 and induced from there in the manner described above. With the incoupling optical system 608, the data is “angle-coded” within the input beam in the sense that points in the digital image essentially correspond to their own propagation directions (i.e., their own propagation modes in the input beam 104). This is analogous to a ray of light from a distant object that can be perceived as a point at infinity. The angle-encoded input beam 104 in Figure 6A is an example of multiple propagation modes (i.e., components propagating in different directions) of a “multimode” optical signal, and this arrangement provides a form of angular diversity.

[0073]

[0084] It should be noted that the term "multimode" does not necessarily imply the use of such an incoupling optical system 608, nor does it necessarily mean that all image points must uniquely correspond to a given propagation direction. In other words, multimode does not necessarily imply a one-to-one correspondence between propagation modes and image points / data points. For example, Figure 6B shows an alternative viable emitter system in which the spatially modulated beam is directly taken into the input waveguide 204. In this example, there are still multiple modes (i.e., multiple spatial paths through the waveguide for any given channel), but there is no one-to-one correspondence between propagation direction and image points, and in some cases, no one-to-one correspondence between image / data points and modes. This provides a form of spatial diversity based on the MIMO (Multiple Input Multiple Output) transfer configuration through the multiple pixels of the SLM 606 and the detector array of the spatially coherent detector 508.

[0074] Data Decryption

[0085] Figure 7 shows a spatial coherent detector 508 used to measure the optical field of the output beam 108. In contrast to conventional "direct detection," the spatial coherent detector 508 comprises an array of pixels (or more generally, detector elements), each configured to measure both the amplitude and phase (not just the intensity) of the optical field at the location of that pixel. These can be measured, for example, using the local oscillator 712 of the spatial coherent detector 508. Thus, the array of pixels can measure variations in the phase and amplitude of the optical field in both time and space, and can therefore provide an analog or digital representation of the measured optical field. In this example, the optical field to be measured is the optical field of the output beam 108 induced in the spatial coherent detector 508 via the output waveguide 208.

[0075]

[0086] Although only a single array is depicted, multiple physical arrays can effectively work together as a single "logical array." For example, this logical array can be divided across two physical cameras.

[0076]

[0087] A physical detector array can take the form of a single camera (where each detector element is a pixel or set of pixels in the camera) or multiple cameras. In an extreme case, each detector element could be a separate camera, in which case the logical detector array could potentially be divided across a very large number of physical detectors.

[0077]

[0088] As described, the route from a specific incoupling region in which a beam enters a waveguide network to a specific outcoupling region in which the beam exits the waveguide network (these regions may be in the same or different waveguides) can be referred to herein as a “channel.” As described, in a multimode waveguide network, a single channel encompasses multiple spatial paths. The output beam 108 will be induced through a specific channel in the output waveguide network (i.e., from that specific incoupling region to the outcoupling region of the output waveguide 208). Furthermore, the output beam 108 will be generated from a hologram produced using an input beam induced from the incoupling region of the input waveguide network to that specific outcoupling region. The hologram will be generated and read using a reference beam similarly induced through a specific channel in the reference waveguide network. All of the input beam 104, reference beams 106, 116, and output beam 108 are susceptible to distortion within the associated waveguide network specific to the channel through which they are induced. To compensate for such distortions, the signal processing component 700 applies analog and / or digital signal processing to the measured field representation. The signal processing component 700 does this using a channel model associated with the subvolume currently being read (i.e., the subvolume from which the output beam 108 was generated). The channel model associated with a particular subvolume models not only the channel through which the output beam 108 is guided to the detector 508, but also the channel through which the input beam 104 used for writing the hologram is guided to that subvolume, and the channel through which the reference beams 106, 116 used for writing to / reading the hologram are guided to that subvolume.

[0078]

[0089] Each channel model can take the form of, for example, a transfer function (which directly models the channel) or an inverse transfer function (which models the channel with its approximate inverse function). It should be noted that the transfer function is applied to the measured representation of the light field (i.e., both its measured phase and amplitude at different spatial points) and not merely to the intensity of light. Spatial coherent detection provides a wider range for eliminating or reducing such channel distortion, with the aim of recovering the original digital image with sufficient accuracy, and allowing the decoder 704 to easily decode the encoded data from the recovered image.

[0079]

[0090] The signal processing 700 can correct for phase interference and noise, for example, by using a combination of optical and computational techniques (which may include, for example, machine learning techniques).

[0080]

[0091] Using a learning method, the path from the emitter system 504 to the spatial coherent detector 508 is treated as a channel to be modeled. The channel can be modeled by a learned function (such as an inverse transfer function) that inverts the channel distortion effect. The input to such a function is the distorted field (phase and amplitude) of the output beam measured through the spatial coherent detector, and the output of such a function is the undistorted field (phase and amplitude) of the input beam. Given a sufficient number of training examples (i.e., pairs of distorted output fields and clean input fields), the model can be trained to approximate this inverse function (i.e., given a distorted output field (phase and amplitude) as input, the trained model will nearly recover the original input field). This is true even if the model does not encounter its exact form of the distorted output field during training, because such a model can be generalized from a sufficient set of training examples. For example, the output and input fields can be represented as input and output tensors of a convolutional neural network (CNN), and the CNN can be trained for each training example based on a loss function that penalizes the difference between the output tensor of that training example (such as that generated by applying the CNN to the input tensor of that training example) and a known corresponding input field. As can be seen, this method can be applied not only in holographic memory but also in any situation where the output field exhibits waveguide distortion, provided that such training examples can be collected.

[0081]

[0092] Although described in relation to holographic memory devices, the use of such signal processing 700 in combination with spatial coherent detection is not limited thereto and can be applied in other contexts such as optical communications or optical computing, or in any other context in which the received output beam is susceptible to distortion introduced in one or more waveguide networks.

[0082]

[0093] Figure 7 shows an outcoupling optical system 715 arranged to essentially reverse the effect of the incoupling optical system 608 in Figure 6B (i.e., essentially resolve each propagation mode to a single point in the plane of the spatially coherent detector 508). Again, this is not essential, and the outcoupling optical system 715 can be omitted by using the alternative emitter system in Figure 6B.

[0083]

[0094] Although not depicted in Figure 6A or Figure 6B, a certain level of preprocessing can be applied to the digital image before modulation and embedding it in the input beam 104. This allows for a reduction in the compensation level required on the detector side. Even with such preprocessing, some detector-side processing may still be applied to account for different distortion effects between different channels.

[0084] Dynamic scheduling

[0095] Figure 8 shows a controller in the form of a scheduler 800 that can schedule read and write operations within the holographic storage system of the type described above. To facilitate effective scheduling, subvolumes within the medium 102 or within each medium piece 102A, 102B are assigned unique addresses. This provides a form of addressable holographic storage device that is more similar to a more conventional form of addressable electronic storage device. However, it has many features that surpass conventional addressing.

[0085]

[0096] Firstly, as described above, a single subvolume can store multiple holograms at different reference beam angles. To accommodate this, each address uniquely corresponds to a specific subvolume in combination with a specific reference beam direction (i.e., each available tuple is assigned a unique address), indicating a specific subvolume within medium 102 or within one of medium pieces 102A, 102B, and indicating a specific reference beam direction (e.g., an angle or a set of angles defining the beam direction; the term “angle” can be used as a concise expression to refer to the direction of the reference beam, although it will be understood that the direction can, in effect, be defined by multiple angles depending on the system configuration). Thus, a subvolume can be associated with potentially many addresses corresponding to different reference beam angles. Tuples define logical storage locations, and the same subvolume at different reference beam angles provides multiple logical storage locations at the physical level. Each logical storage location has a unique address (ADDR). This notation is used as a concise expression to mean the address corresponding to the subvolume and reference beam angle, but it will be understood that this does not imply a representation of a specific address. Any address space and addressing mechanism that uniquely identifies a logical memory location of this nature can be used.

[0086]

[0097] Secondly, in contrast to conventional memory devices, each logical memory location can store an entire image, and therefore, a single logical memory location can potentially store a very large number of bits (e.g., thousands or millions).

[0087]

[0098] The scheduler 800 operates at the logical memory level and schedules incoming read and write operations for different addresses within appropriate time intervals.

[0088]

[0099] Reference numerals 804, 806, and 808 are used to indicate input, reference, and output optical waveguide networks, respectively. As described above, each may be a single waveguide network or a multiple waveguide network (e.g., similar to Figure 5) and may have one or more configurable inductive elements (e.g., SBGs or other active switching elements) that can be used to create channels to different subvolumes of one (or more) pieces of a holographic storage medium.

[0089]

[0100] During the period in which a write operation for a specific address is scheduled (the write period), the inductive elements in the input and reference waveguide networks 804 and 806 are configured to create channels for the input beam 104 and the reference beam 106 from the emitter system 504 through the input and reference networks 804 and 806 to the corresponding subvolumes, respectively. In addition, the reference beam steering element 612 is configured to direct the reference beam 106 toward the reference network 806 in the corresponding direction. This generates a desired interference pattern at the reference beam angle within the subvolume, and therefore, if the subvolume is exposed to the interference pattern for a sufficiently long duration, the interference pattern is persistently stored as a hologram.

[0090]

[0101] During the period in which a read operation for a specific address is scheduled (read period), the guide elements in the reference and output networks 806 and 808 are configured to similarly create a channel for the reference beam 116 through the reference network 806 to the subvolume, and a channel for the output beam 108 from the subvolume through the output network 808 to the detector 508. The reference beam steering element 612 is similarly configured to direct the reference beam 116 toward the reference network 806 in the corresponding direction in order to read the intended hologram in the subvolume at the reference beam angle.

[0091] Alternative waveguide networks:

[0102] Figures 10A and 10B show an alternative system in which spatial multiplexing is achieved by modulating one or more optical properties of the input and reference beams 104, 106, and 116. In such a system, passive (non-switchable) inductive elements can be used instead of the active (switchable) inductive elements shown in the previous figures.

[0092]

[0103] The example in Figure 10A considers frequency (or uniformly wavelength) modulation. In this example, the light pipes themselves are passive and have static wavelength-dependent outcoupling (such as a continuous Longer-path dichroic interference filter or a variable center-wavelength bandpass filter).

[0093]

[0104] Figure 11A shows a light pipe 1100 having an outer surface 1100-S, with multiple passive filters 1100-1, 1100-2 along the outer surface 1100-S. The configuration of the light pipe 1100 is the same as in Figures 3A-D, except that filters 1100-1, 1100-2 replace SBGs 300-1, 300-2. Filters 1100-1, 1100-2 have different frequency responses (i.e., they act as frequency filters). More specifically, each filter 1100-1, 1100-2 essentially transmits a relatively narrow range of optical frequencies and essentially reflects frequencies outside that range. Figure 11A shows an incoupling beam 1104, whose frequency is within the range of the second filter 1100-2 but outside the range of the first filter 1100-1. Therefore, beam 1104 is reflected by the first filter 1100-1 but is transmitted through the second filter 1100-2 (and thus exits the light pipe 1100 at that point). Figure 11B shows beam 1104' of a different frequency, where its frequency is within the range of the first filter 1100-1 and therefore is transmitted through the first filter 1100-1.

[0094]

[0105] Such a light pipe 1100 can be used in place of the active light pipe described above, and the above description also applies to the following system modifications.

[0095]

[0106] Figure 10A shows a scheduler 800 communicatively coupled to a laser 600 in the emitter system for varying the frequencies (or equally wavelengths) of the input and reference beams 104, 106, and 116. In this example, each beam can be directed to a desired holographic memory area by setting its frequency accordingly. Here, different beam frequencies correspond to different routes through the waveguide network (defined by the different frequency characteristics of the passive filters), and the frequencies can be set to correspond to any desired route.

[0096]

[0107] In this example, wavelength is used as the switching dimension. Laser 600 is a high-speed, tunable laser that acts as the active element.

[0097]

[0108] In such a view, the switching may be in only one spatial dimension (i.e., along a single pipe). However, using a laser with a sufficient range and narrow linewidth, the first light pipe can filter coarsely (i.e., over a relatively wide wavelength range), and subsequent light pipes can sample more finely (i.e., over a narrower wavelength range). Another factor limiting the linewidth is the requirement for a relatively long coherence length, and therefore, in any event, the linewidth can be sufficiently narrow. In relation to holographic memory devices, to achieve replication of the input field to addressable locations across a two-dimensional output space, this implementation can be combined with a second implementation using, for example, different switchable parameters (e.g., polarization).

[0098]

[0109] In relation to the reading operation, the frequency of the output beam 108 is matched to the frequency of the reference beam 116 used to read a specific subvolume, and the same principle can be applied to return it to the detector using an appropriate filter in the output waveguide network 808.

[0099]

[0110] Figure 10B shows an example of such an implementation comprising a controllable polarizing element 601 that can be used to change the polarization of the input and reference beams 104, 106, and 116. This can be combined with a passive polarizing filter on or within the light pipe. This can be implemented as an alternative to or in addition to the passive frequency filter in the example of Figure 10A. Such polarization modulation provides two independent routes and can be used in combination with, for example, passive wavelength filtering and / or an active light pipe. Beam polarization modulation can also be combined with an active polarizing filter.

[0100]

[0111] It should be noted that all of the various "passive" and "active" implementation forms described above can be implemented separately or in combination (for example, a combination of active and passive inductive elements can be used). That is, a waveguide can have both passive and active elements, and / or active and passive waveguides can be combined within the same network.

[0101] Additional hierarchy levels:

[0112] The above example considers a waveguide network with two hierarchical "levels": a parent waveguide and child waveguides. However, a multiple waveguide network can have three (parent, child, grandchild) or more levels. Note that the terms "child," "parent," and "grandchild" do not necessarily imply a direct hierarchical relationship. That is, the terms child or grandchild can refer to any waveguide at any hierarchical level below each of the parent or child waveguides. In other words, a child / grandchild waveguide can be optically coupled to a parent / child waveguide not only via an air interface (direct descendant), for example, but also via one or more other child / grandchild waveguides (indirect descendants).

[0102]

[0113] Figure 12 shows an example of a waveguide network with three hierarchical levels. The parent waveguide 1200 has two direct child waveguide networks 1202A and 1202B that are optically coupled to the parent waveguide 1200 in the manner described above, and each of these child waveguides 1202A / 1202B has two grandchild networks 1204A-A, 1204A-B / 1204B-A, and 1204B-B that are optically coupled to the child waveguides 1202A / 1202B in the same manner.

[0103]

[0114] An extreme example is a "binary tree" architecture where every waveguide has exactly two direct children, potentially having more than three levels of waveguides. However, in practice, there may be situations where increasing the number of direct children is preferable to reduce the number of required hierarchical levels.

[0104]

[0115] The scheduler 800 shown in Figures 8, 10A and 10B is a functional component of the system. Similarly, the encoder 610, decoder 704, and signal processing component 700 are also functional components. Such components can be implemented in software (i.e., as program code executed on one or more programmable hardware processors such as a CPU, accelerator, e.g., a GPU) or using other forms of processor hardware such as field-programmable gate arrays and / or application-specific integrated circuits. The signal processing performed by the signal processing component 700 may be analog or digital signal processing or any combination thereof. Such program code and other data (e.g., channel model 702) can be encoded in a computer-readable storage device. Examples of computer-readable storage devices include optical, magnetic, and / or solid-state storage devices that can store code, data, and similar in a non-temporary form. This is in contrast to temporary media such as temporary signal carriers.

[0105]

[0116] A first aspect of this specification provides an optical data transfer system comprising: a beam modulator configured to embed a set of data in an input beam; an input waveguide network formed from one or more multimode optical waveguides, having an incoupling region for receiving an input beam and configured to guide the input beam into an outcoupling region of the input waveguide network; a spatial coherent detector configured to measure the phase and amplitude of an output optical field at a plurality of locations, wherein the output optical field is at least partially defined by the input beam and therefore exhibits a distortion effect at least partially resulting from the input beam passing through the input waveguide network; and at least one processor coupled to the spatial coherent detector, configured to apply signal processing to the output of the spatial coherent detector to compensate for the distortion effect, thereby recovering the set of data embedded in the input beam from the output of the spatial coherent detector.

[0106]

[0117] In the embodiment, the optical data transfer system may include at least one holographic recording region, and the input waveguide network is configured to guide the input beam to the holographic recording region to store embedded data in a pattern recorded within that region via interference between the input beam and a reference beam, and the output optical field is generated at a later point in time via interaction between the recorded pattern and the reference beam to read the embedded data from the holographic recording region.

[0107]

[0118] The optical data transfer system may be configured to guide a reference beam into the holographic recording area via an input waveguide network and a reference waveguide network formed from one or more further multimode optical waveguides, and the passage of the reference beam through the input or reference waveguide network may also contribute to the distortion effect compensated by signal processing.

[0108]

[0119] The optical data transfer system may be configured to guide an output beam, at least partially defined by the input beam, to a spatially coherent detector via one of an input waveguide network, the aforementioned reference waveguide network, and an output waveguide network formed from one or more further multimode optical waveguides, and the output beam passing through the input, reference, or output waveguide network may also contribute to the distortion effect compensated by signal processing.

[0109]

[0120] At least one of the input waveguide network, the reference waveguide network described above, and the output waveguide network described above may include at least one configurable and / or responsive inductive element, thereby enabling different channel choices for the at least one waveguide network by reconfiguring the at least one inductive element and / or modulating the at least one beam characteristic, and at least one processor may be configured to apply the signal processing in accordance with the channel selection associated with the output optical field.

[0110]

[0121] At least one processor may be configured to select a channel model corresponding to an associated channel selection from a plurality of channel models corresponding to different channel selections, and to apply the signal processing according to the selected channel model.

[0111]

[0122] Each channel model may include a set of signal processing parameters learned for the corresponding channel selection.

[0112]

[0123] A second aspect of this specification provides an optical data transfer system comprising: a beam modulator configured to embed a set of data in an input beam; a spatial coherent detector configured to measure the phase and amplitude of the optical field of an output beam at a plurality of locations, wherein the output beam is at least partially defined by the input beam; an output waveguide network formed from one or more multimode optical waveguides, having an incoupling region for receiving the output beam and configured to guide the output beam into an outcoupling region of the output waveguide network for reception by the spatial coherent detector; and at least one processor coupled to the spatial coherent detector, configured to apply signal processing to the output of the spatial coherent detector to at least partially compensate for distortion effects caused by the output beam passing through the output waveguide network, thereby recovering the set of data embedded in the input beam from the output of the spatial coherent detector.

[0113]

[0124] The optical data transfer system may include a plurality of holographic recording regions, and the output optical waveguide network has at least one configurable and / or responsive to at least one beam characteristic, thereby allowing any region of the plurality of holographic recording regions to be selected for reading using the same spatially coherent detector, and guiding the output beam from the selected holographic recording region to the spatially coherent detector, by reconfiguring the at least one guiding element and / or modulating the at least one beam characteristic, and at least one processor is configured to apply the signal processing according to the holographic recording region being read.

[0114]

[0125] Each holographic recording area may be associated with at least one channel model, and at least one processor may be configured to apply the signal processing using the channel model associated with the holographic recording area being read.

[0115]

[0126] Each holographic recording area may have at least one logical address, and the channel model may be selected based on a logical address associated with the current read operation, which identifies the holographic recording area being read.

[0116]

[0127] The optical data transfer system may be configured to guide a reference beam to a selected holographic recording area via an output waveguide network and a reference waveguide network formed from one or more further multimode optical waveguides, and the passage of the reference beam through the output or reference waveguide network may also contribute to the distortion effect, which is compensated for by signal processing.

[0117]

[0128] The optical data transfer system may be configured to direct an input beam to a selected holographic recording area via an output waveguide network and an input waveguide network formed from one or more additional multimode optical waveguides, wherein the input beam passing through the output or input waveguide network may contribute to the distortion effect, which is compensated for by signal processing.

[0118]

[0129] A third aspect of this specification provides an optical data transfer system comprising: a beam modulator configured to embed a set of data in an input beam; a spatial coherent detector configured to measure the phase and amplitude of an output optical field at a plurality of locations, wherein the output optical field is at least partially defined by an input beam and a reference beam; a reference waveguide network formed from one or more multimode optical waveguides, having an incoupling region for receiving a reference beam and configured to guide the reference beam into an outcoupling region of the reference waveguide network to define an output optical field; and at least one processor coupled to the spatial coherent detector, configured to apply signal processing to the output of the spatial coherent detector to at least partially compensate for distortion effects caused by the reference beam passing through the reference waveguide network, thereby recovering the set of data embedded in the input beam from the output of the spatial coherent detector.

[0119]

[0130] An optical communication system or optical computing system may include at least one such optical data transfer system.

[0120]

[0131] In one of the embodiments described above, a waveguide network as described below can be used.

[0121]

[0132] A multimode optical waveguide network may include a parent waveguide and a plurality of child waveguides, each of which is a multimode optical waveguide having a first surface region, a plurality of second surface regions, and at least one inductive element attached to the surface of the waveguide or embedded within the waveguide, each of which the second surface regions of the parent waveguide is optically coupled to the first surface region of the corresponding child waveguide, and at least one inductive element of the parent waveguide is arranged to guide a beam from or to its first surface region to or from a selected second surface region of its plurality of second surface regions, the beam corresponding to the second surface region of the parent waveguide A first surface region of a sub-waveguide is incorporated into or received from a corresponding sub-waveguide, which is optically coupled to a second surface region of a parent waveguide, via a first surface region of the sub-waveguide, and at least one inducting element of each sub-waveguide is arranged to guide a beam from or to its first surface region to a selected second surface region of a plurality of second surface regions, or from a selected second surface region, and at least one inducting element of each waveguide can be configured to select a second surface region of its waveguide, and / or to select a second surface region of its waveguide via modulation of at least one beam characteristic in response to at least one beam characteristic.

[0122]

[0133] A multimode optical waveguide network may include a plurality of sub-waveguides, each of which is a multimode optical waveguide having a first surface region, a plurality of second surface regions, and at least one inductive element attached to the surface of the sub-waveguide or embedded within the sub-waveguide, wherein each of the second surface regions of each sub-waveguide is optically coupled to the first surface region of the corresponding sub-waveguide, and at least one inductive element of each sub-waveguide is connected to or from its first surface region to a selected second surface of its plurality of second surface regions. A beam can be positioned to guide a beam into or from a selected second surface region, and the beam is taken into or taken out of the grandchild waveguide via its first surface region and via a second surface region of a child waveguide optically coupled thereto, and at least one guiding element of each grandchild waveguide can be configured to select a second surface region of the grandchild waveguide and / or to select a second surface region of the grandchild waveguide via modulation of at least one beam characteristic in response to at least one beam characteristic.

[0123]

[0134] Each waveguide may have at least one active inductive element that can be configured to select a second surface region of the waveguide.

[0124]

[0135] Each waveguide may have at least one inductive element that selects a second surface region of the waveguide via modulation of at least one beam characteristic in response to at least one beam characteristic.

[0125]

[0136] At least one waveguide may have at least one active inductive element that can be configured to select a second surface region of the waveguide, and at least another waveguide may have at least one inductive element that, in response to at least one beam characteristic, selects a second surface region of the other waveguide via modulation of at least one beam characteristic.

[0126]

[0137] One of the parent waveguides and one of the child waveguides may have at least one wavelength response inducting element, thereby a beam in the first wavelength range is induced from or to its first surface region by the first child or grandchild waveguide or by the first child or grandchild waveguide; a beam in the second wavelength range is induced from or to its first surface region by the second child or grandchild waveguide or by the second child or grandchild waveguide; the first child or grandchild waveguide may have at least one wavelength response inducting element, thereby a beam in the first sub-range of the first wavelength range is induced from or to its first surface region by one of its second surface regions or by its second A beam guided from one of the two surface regions, within a second sub-range of the first wavelength range, is guided from or to the first surface region, to another of the second surface regions, or from another of the second surface regions, and the second child or grandchild waveguide may have at least one wavelength-response-guiding element, thereby a beam within a first sub-range of the second wavelength range is guided from or to the first surface region, to one of the second surface regions, or from one of the second surface regions, and a beam within a second sub-range of the second wavelength range is guided from or to the first surface region, to another of the second surface regions, or from another of the second surface regions.

[0127]

[0138] Each active induction element may have at least one of a configurable transmittance and reflectance and a configurable refractive index.

[0128]

[0139] Each active induction element may be a switchable grating or grating region.

[0129]

[0140] At least one of the inductive elements may be a wavelength and / or polarization filter having a fixed or configurable wavelength response and / or a fixed or configurable polarization axis.

[0130]

[0141] At least one waveguide may have two or more inductive elements and three or more second surface regions, any of which can be selected by constituting one or both of the two or more inductive elements and / or modulating at least one beam characteristic.

[0131]

[0142] An optical system incorporating such a waveguide network may include a first optical system component, a plurality of second optical system components, at least one multimode optical waveguide network according to any of the above-described aspects or embodiments, the multimode optical waveguide network being arranged to guide a beam from or to the first optical system component to or from a selected second optical system component of the plurality of second optical system components, and a controller configured to select one second optical system component of the plurality of second optical system components, the controller causing a beam to be guided from or to the first optical system component to or from a selected second optical system component by configuring at least one of the guiding elements of the multimode optical waveguide network and / or modulating at least one beam characteristic.

[0132]

[0143] The first system component may include an emitter system for emitting a beam and guiding it to a selected second system component, or a detector array from which the beam is guided from the selected second system component.

[0133]

[0144] The optical system may include one or more holographic recording media, and at least some of the second system optical components may be subvolumes of each of the one or more holographic recording media.

[0134]

[0145] The optical system may include a second multimode optical waveguide network according to any of the above-described aspects or embodiments, and the controller may be configured to induce a second beam from or to the first optical system component, to the same selected second optical system component, or from the same selected second optical system component by configuring at least one of the inductive elements of the second multimode optical waveguide network and / or modulating the beam characteristics of at least one of them.

[0135]

[0146] The optical system may include a third multimode optical waveguide network according to any of the above-described aspects or embodiments, and the controller may be configured to induce a third beam from or to a first optical system component, to the same selected second optical system component, or from the same selected second optical system component by constituting at least one of the inductive elements of the third multimode optical waveguide network and / or modulating at least one beam characteristic.

[0136]

[0147] For example, in relation to optical communication or optical computing, at least one of the first and / or second optical system components may include a signal converter or optical processor configured to convert a beam into an electrical signal (or vice versa).

[0137]

[0148] In one of the embodiments described above, a waveguide network as described below can be used.

[0138]

[0149] A multimode optical waveguide network may include a parent waveguide and a plurality of child waveguides, each of which is a multimode optical waveguide having a first surface region, a plurality of second surface regions, and at least one inductive element attached to the surface of the waveguide or embedded within the waveguide, each of which the second surface regions of the parent waveguide is optically coupled to the first surface region of the corresponding child waveguide, and at least one inductive element of the parent waveguide is arranged to guide a beam from or to its first surface region, to or from a selected second surface region of its plurality of second surface regions, and the beam is transmitted through its second surface region of the parent waveguide and A beam is taken into or received from a corresponding sub-waveguide via its first surface region, which is optically coupled to a second surface region of a parent waveguide, and at least one inducting element of each sub-waveguide is arranged to guide a beam from or to its first surface region to or from a selected second surface region of a plurality of second surface regions, and at least one inducting element of each waveguide can be configured to select a second surface region of its waveguide and / or select a second surface region of its waveguide via modulation of at least one beam characteristic in response to at least one beam characteristic.

[0139]

[0150] A multimode optical waveguide network may include a plurality of sub-waveguides, each of which is a multimode optical waveguide having a first surface region, a plurality of second surface regions, and at least one inductive element attached to the surface of the sub-waveguide or embedded within the sub-waveguide, wherein each of the second surface regions of each sub-waveguide is optically coupled to the first surface region of the corresponding sub-waveguide, and at least one inductive element of each sub-waveguide is connected to or from its first surface region to a selected second surface region of its plurality of second surface regions The beam can be positioned to guide a beam into a surface region or from a selected second surface region, and the beam is taken into or taken out of the grandchild waveguide via its first surface region and via a second surface region of a child waveguide optically coupled thereto, and at least one guiding element of each grandchild waveguide can be configured to select a second surface region of the grandchild waveguide and / or select a second surface region of the grandchild waveguide via modulation of at least one beam characteristic in response to at least one beam characteristic.

[0140]

[0151] Each waveguide may have at least one active inductive element that can be configured to select a second surface region of the waveguide.

[0141]

[0152] Each waveguide may have at least one inductive element that selects a second surface region of the waveguide via modulation of at least one beam characteristic in response to at least one beam characteristic.

[0142]

[0153] At least one waveguide may have at least one active inductive element that can be configured to select a second surface region of the waveguide, and at least another waveguide may have at least one inductive element that, in response to at least one beam characteristic, selects a second surface region of the other waveguide via modulation of at least one beam characteristic.

[0143]

[0154] One of the parent waveguides and one of the child waveguides may have at least one wavelength response inducting element, thereby a beam in the first wavelength range is induced from or to its first surface region by the first child or grandchild waveguide or by the first child or grandchild waveguide; a beam in the second wavelength range is induced from or to its first surface region by the second child or grandchild waveguide or by the second child or grandchild waveguide; the first child or grandchild waveguide may have at least one wavelength response inducting element, thereby a beam in the first sub-range of the first wavelength range is induced from or to its first surface region by one of its second surface regions or by its second A beam guided from one of the two surface regions, within a second sub-range of the first wavelength range, is guided from or to the first surface region, to another of the second surface regions, or from another of the second surface regions, and the second child or grandchild waveguide may have at least one wavelength-response-guiding element, thereby a beam within a first sub-range of the second wavelength range is guided from or to the first surface region, to one of the second surface regions, or from one of the second surface regions, and a beam within a second sub-range of the second wavelength range is guided from or to the first surface region, to another of the second surface regions, or from another of the second surface regions.

[0144]

[0155] Each active induction element may have at least one of a configurable transmittance and reflectance and a configurable refractive index.

[0145]

[0156] Each active induction element may be a switchable grating or grating region.

[0146]

[0157] At least one of the inductive elements may be a wavelength and / or polarization filter having a fixed or configurable wavelength response and / or a fixed or configurable polarization axis.

[0147]

[0158] At least one waveguide may have two or more inductive elements and three or more second surface regions, any of which can be selected by constituting one or both of the two or more inductive elements and / or modulating at least one beam characteristic.

[0148]

[0159] An optical system incorporating such a waveguide network may include a first optical system component, a plurality of second optical system components, at least one multimode optical waveguide network according to any of the above-described aspects or embodiments, the multimode optical waveguide network being arranged to guide a beam from or to the first optical system component to or from a selected second optical system component of the plurality of second optical system components, and a controller configured to select one second optical system component of the plurality of second optical system components, the controller causing a beam to be guided from or to the first optical system component to or from a selected second optical system component by configuring at least one of the guiding elements of the multimode optical waveguide network and / or modulating at least one beam characteristic.

[0149]

[0160] The first system component may include an emitter system for emitting a beam and guiding it to a selected second system component, or a detector array from which the beam is guided from the selected second system component.

[0150]

[0161] The optical system may include one or more holographic recording media, and at least some of the second system optical components may be subvolumes of each of the one or more holographic recording media.

[0151]

[0162] The optical system may include a second multimode optical waveguide network according to any of the above-described aspects or embodiments, and the controller may be configured to induce a second beam from or to the first optical system component, to the same selected second optical system component, or from the same selected second optical system component by configuring at least one of the inductive elements of the second multimode optical waveguide network and / or modulating the beam characteristics of at least one of them.

[0152]

[0163] The optical system may include a third multimode optical waveguide network according to any of the above-described aspects or embodiments, and the controller may be configured to induce a third beam from or to a first optical system component, to the same selected second optical system component, or from the same selected second optical system component by constituting at least one of the inductive elements of the third multimode optical waveguide network and / or modulating at least one beam characteristic.

[0153]

[0164] For example, in relation to optical communication or optical computing, at least one of the first and / or second optical system components may include a signal converter or optical processor configured to convert a beam into an electrical signal (or vice versa).

[0154]

[0165] It will be understood that the embodiments described above are merely illustrative. Other variations or uses of the techniques disclosed will be apparent to those skilled in the art at the time the disclosure of this specification is given. The scope of this disclosure is not limited by the embodiments described, but only by the appended claims.

Claims

1. An optical data transfer system, A beam modulator configured to embed data into the input beam, A spatial coherent detector configured to measure the phase and amplitude of the optical field of an output beam at multiple locations, wherein the output beam is at least partially defined by the input beam, An output waveguide network formed from a multimode optical waveguide, having an incoupling region and configured to guide the output beam into the outcoupling region of the output waveguide network for reception by the spatial coherent detector, A processor coupled to the spatial coherent detector, configured to use signal processing applied to the output of the spatial coherent detector to compensate, at least in part, for distortion effects caused by the output beam passing through the output waveguide network, thereby recovering the data embedded in the input beam from the output of the spatial coherent detector. Optical data transfer systems including

2. An optical data transmission system including a holographic recording region, wherein the output waveguide network has a guide element that responds to beam characteristics, and each of the holographic recording regions can be selected to be read using the same spatially coherent detector by at least one of reconfiguring the guide element or modulating the beam characteristics, and an output beam can be guided from the selected holographic recording region to the spatially coherent detector, and the processor is configured to apply the signal processing in accordance with the holographic recording region being read, as described in claim 1.

3. The optical data transfer system according to claim 2, wherein each holographic recording area is associated with a channel model, and the processor is configured to apply the signal processing using the channel model associated with the holographic recording area being read.

4. The optical data transfer system according to claim 3, wherein each holographic recording area has a logical address, and the channel model is selected based on a logical address associated with the current read operation, which identifies the holographic recording area being read.

5. The optical data transfer system according to any one of claims 2 to 4, configured to guide a reference beam to a selected holographic recording area via one of the output waveguide network and a reference waveguide network formed from further multimode optical waveguides, wherein the passage of the reference beam through the output or reference waveguide network contributes to the distortion effect compensated by the signal processing.

6. An optical data transfer system according to any one of claims 2 to 5, configured to direct the input beam to a selected holographic recording area via one of the output waveguide network and an input waveguide network formed from further multimode optical waveguides, wherein the input beam passing through the output or input waveguide network contributes to the distortion effect compensated by the signal processing.

7. An optical data transfer system, A beam modulator configured to embed data into the input beam, A spatial coherent detector configured to measure the phase and amplitude of an output light field at multiple locations, wherein the output light field is at least partially defined by the input beam and the reference beam, A reference waveguide network formed from multimode optical waveguides, having an incoupling region and configured to guide the reference beam into the outcoupling region of the reference waveguide network in order to define the output optical field, A processor coupled to the spatial coherent detector, configured to use signal processing applied to the output of the spatial coherent detector to compensate at least in part for distortion effects caused by the reference beam passing through the reference waveguide network, thereby recovering the data embedded in the input beam from the output of the spatial coherent detector. Optical data transfer systems including

8. An optical data transfer system including a holographic recording region, the optical data transfer system comprising an output waveguide network having a guide element that responds to beam characteristics, wherein each of the holographic recording regions can be selected to be read using the same spatially coherent detector by at least one of reconfiguring the guide element or modulating the beam characteristics, and an output beam can be guided from the selected holographic recording region to the spatially coherent detector, and the processor is configured to apply the signal processing in accordance with the holographic recording region being read, according to claim 7.

9. The optical data transfer system according to claim 8, wherein each holographic recording area is associated with a channel model, and the processor is configured to apply the signal processing using the channel model associated with the holographic recording area being read.

10. The optical data transfer system according to claim 9, wherein each holographic recording area has a logical address, and the channel model is selected based on a logical address associated with the current read operation, which identifies the holographic recording area being read.

11. The optical data transfer system according to claim 7, configured to guide an output beam, at least partially defined by the input beam, to the spatial coherent detector via one of the input waveguide network, the reference waveguide network, and an output waveguide network formed from further multimode optical waveguides, wherein the output beam passing through the input, reference, or output waveguide network also contributes to the distortion effect compensated by the signal processing.

12. Input waveguide network, The aforementioned reference waveguide network, and Output waveguide network The optical data transfer system according to claim 7, wherein at least one of the elements includes a guide element that responds to beam characteristics, and the processor is configured to apply the signal processing in accordance with channel selection associated with the output optical field.

13. The optical data transfer system according to claim 12, wherein the processor is configured to select a channel model corresponding to the associated channel selection from a plurality of channel models corresponding to different channel selections, and to apply the signal processing according to the selected channel model, each channel model including signal processing parameters learned for the corresponding channel selection.

Images