System and method for testing an optical layer of an optical printed circuit board

Abstract

There is provided a method of testing an optical layer of an optical printed circuit board, OPCB, the optical layer comprising one or more input ports, one or more respective output ports, and one or more optical waveguides coupling the one or more input ports to the one or more respective output ports, the method comprising aiming one or more light sources to provide light, over a source air interface, towards the one or more input ports; detecting by a detector, over a detector air interface, the presence or absence of the light output from the one or more output ports of the optical layer to determine one or more test parameters associated with the presence or absence of the light; and verifying, based on the detection, the transmission of the light passing between the one or more input ports and the respective one or more output ports.

Description

[0001] SYSTEM AND METHOD FOR TESTING AN OPTICAL LAYER OF AN OPTICAL PRINTED CIRCUIT BOARD

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to testing an optical layer of optical printed circuit boards. In particular, the disclosure relates to methods and apparatuses for testing an optical layer of an optical printed circuit board.

[0004] BACKGROUND

[0005] Co-packaged optics (CPO) and near-packaged optics (NPO) technologies aim to improve data transmission efficiency and reduce power consumption in high-capacity Application-Specific Integrated Circuits (ASICs), for example, in data centres.

[0006] Conventional architectures utilising pluggable transceivers face limitations, including high power consumption and strict design constraints to manage electrical signal processing at high speeds. CPO and NPO technologies represent a shift from traditional pluggable optical transceivers towards integrated optical modules directly mounted onto printed circuit boards (PCBs). By eliminating the need for separate pluggable modules, CPO and NPO technologies enhance performance, simplify system architectures, and reduce the energy demands of data centres. CPO and NPO technologies also enable efficient transmission of optical signals over short distances using low-loss substrates, eliminating the need for electrical signal regeneration, which is both power-intensive and complex. Issues such as electromagnetic interference (EMI) and signal integrity degradation are also mitigated. Optical PCBs (OPCB) enable both CPO and NPO technologies. The optical layer in a CPO OPCB enables high-speed optical communication between co-packaged ASICs and external systems while minimizing power consumption and signal degradation. In NPO architectures, OPCBs bridge the gap between electrical and optical layers by combining optical waveguides (for high-speed data transmission) and electrical traces (for control and power delivery) into a single hybrid board.

[0007] Despite their advantages, CPO and NPO implementation presents significant challenges. The co-integration of optical and electrical wiring on a single PCB requires precise alignment of optical couplers to ASICs, thus driving up manufacturing costs. Moreover, design changes, reconfigurations, and suspected defects may demand a full PCB redesign, leading to high development costs and extended timelines. The optical fibre connections required for interconnection, in particular, complicate design and implementation.A particular issue associated with OPCB technology is the high cost and complexity of testing, which requires specialized equipment with low tolerance, along with different coupling methods than conventional electrical PCB testing. Accessing optical I / O ports during testing presents a greater challenge than accessing electrical test pads, as conventional optical probes are typically designed for silicon photonic chips which use aligned grating couplers, and might not account for the varied (often bespoke) positions of optical I / O ports on OPCBs.

[0008] SUMMARY

[0009] In an aspect, there is provided a method of testing an optical layer of an optical printed circuit board, OPCB. The optical layer comprises one or more input ports, one or more respective output ports, and one or more optical waveguides coupling the one or more input ports to the one or more respective output ports. The method comprises aiming one or more light sources to provide light, over a source air interface, towards the one or more input ports. The method further comprises detecting by a detector, over a detector air interface, the presence or absence of the light output from the one or more output ports of the optical layer to determine one or more test parameters associated with the presence or absence of the light. The method further comprises verifying, based on the detection, the transmission of the light passing between the one or more input ports and the respective one or more output ports.

[0010] The method provides a quick and convenient means of testing the optical layer, without the need for physical connections, thereby reducing complexity and cost during testing at various stages of the OPCB fabrication pipeline.

[0011] The verifying based on the detection may comprise using the one or more test parameters and one or more respective reference parameters.

[0012] The verifying the transmission of light passing between the one or more input ports and the respective one or more output ports may be performed based on a comparison of the one or more test parameters against the respective one or more reference parameters. Comparison with readily-accessible reference values, such as those predefined in standards, improves accuracy and provide reliable verification of optical transmission. The method may further comprise determining the one or more test parameters associated with the presence or absence of the telecommunications wavelength light.

[0013] The one or more test parameters associated with the absence or presence of light may comprise a spatial property. The respective one or more reference parameters may comprise a reference spatial property. The verifying may comprise using the spatial property and the reference spatial property to determine an indication of the extent towhich each optical waveguide of the respective one or more optical waveguides is optically coupling the one or more input ports to the respective one or more output ports.

[0014] Consideration of spatial properties allows for rapid, quickly iterable determination of optical performance (e.g., determining binary indications of "dark" or "bright" spots), without the need for complex calculations or optical reference parameters, providing a convenient and flexible option for testing.

[0015] The one or more test parameters may be associated with the presence of light, and the spatial property may comprise a spatial position associated with the detected light. The reference spatial property may comprise one or more of: an expected spatial position of the one or more input ports; an expected spatial position of the one or more output ports; an expected spatial position of one or more locations at the detector, at which one or more locations light is detected; and an expected spatial position or configuration of one or more optical paths defined between the one or more input ports and the respective one or more output ports.

[0016] Considering both detected light positions with corresponding expected positions / configurations provides an effective and convenient method for reliably identifying defects in the optical layer, and / or identifying misalignments of the system which may prompt recalibration / realignment.

[0017] The spatial property may comprise a spatial position associated with the absence of light. The reference spatial property may comprise one or both of: an expected spatial position of the one or more input ports; an expected spatial position of the one or more output ports; an expected spatial position of one or more locations at the detector, at which one or more locations light is detected; and an expected spatial position of one or more further locations at the detector, at which one or more locations light is absent.

[0018] Identification of a spatial position at which light is not detected (a "dark" spot) where a reference spatial position indicates that light is expected to be detected there (a "light" spot is expected instead) provides an effective means to pinpoint defects in the optical layer.

[0019] The one or more test parameters may comprise an optical property. The respective one or more reference parameters may comprise a reference optical property. The verifying may comprise using the optical property and the reference optical property to determine an indication of the extent to which each optical waveguide of the respective one or more optical waveguides is optically coupling the one or more input ports to the respective one or more output ports.Consideration of optical properties allows a comprehensive and / or qualitative assessment of optical performance, enabling robust verification of light transmission.

[0020] The verifying the transmission of the light may comprise determining an indication of an optical loss associated with the passage of light between the one or more input ports and the respective one or more output ports.

[0021] The verifying the transmission of the light may comprise determining whether the optical loss is at or below a reference value.

[0022] Consideration of an optical loss further provides a reliable indication of the extent of light transmission, and allows qualitative / relative assessment of different probed areas of the optical layer.

[0023] The optical property may comprise one or more of: an intensity of the detected or absent light at the detector; an amplitude of the detected or absent light at the detector; a power of the detected or absent light at the detector; a spatial dimension of the detected or absent light at the detector; and an angle of incidence of the detected or absent light at the detector. The reference optical property may comprise one or more of: a reference intensity of light; a reference amplitude of light; a reference power of light; a spatial dimension of light; and an angle of incidence of light.

[0024] Consideration of one or more of these parameters provides a particularly convenient and reliable way to determine the extent of light transmission, enabling more robust verification of light transmission.

[0025] The expected spatial position of the one or more input and / or the expected spatial position of the one or more output ports may be provided via a reference testing map comprising at least one of: a digitally created map or computer-aided design (CAD) model of the optical layer under test; one or more manufacturing specifications associated with the optical layer under test; a digitally created map or CAD model of a further reference optical layer having substantially the same configuration and / or expected optical behaviour as the optical layer under test; and one or more manufacturing specifications associated with the further reference optical layer having substantially the same configuration and / or expected optical behaviour as the optical layer under test.

[0026] Use of a testing map provides a convenient, readily-accessible, and / or standardised reference for comparison, facilitating low-cost and repeatable testing for deviations or defects in the optical layer.

[0027] The one or more reference parameters may include a reference-test parameter determined by a reference test performed prior to the method, the reference test comprising passing light along fibre optic wiring coupled to at least one of: an input port of the optical layeror further reference optical layer; and at least one output port of the optical layer or further reference optical layer. The plurality of input ports may be arranged as a source array of ports in the optical layer and the plurality of output ports may be arranged as a detector array of ports in the optical layer.

[0028] Use of prior, conventional refence test results provides a readily-accessible, and / or standardised reference for comparison, and may improve reliability or robustness of the verification by incorporating historical test data (or, e.g., use-case-specific data) into expected benchmark values.

[0029] The plurality of light beams may be formed by a plurality of lasers. The plurality of input ports may be arranged as a first array of ports in the optical layer and the plurality of output ports may be arranged as a second array of ports in the optical layer.

[0030] This allows for testing of a standard, modular optical layer of an OPCB, by any suitable, readily-available means of forming the light beams.

[0031] The aiming the one or more light sources to provide light, over an air interface, towards the one or more input ports may comprise aiming the one or more light sources at an optical probe shaper configured to receive incident light and output one or more beams of the light.

[0032] Use of an optical probe shaper improves precision and accuracy in aiming light, thereby more reliably probing targeted input ports and improving overall testing efficiency by reducing the required beam-spot intensity and minimising spatial-parameter value discrepancies.

[0033] The optical probe shaper may comprise an array of individually controllable mirrors configured to receive incident light and reflect the incident light towards the one or more input ports. The adjusting the configuration of the optical probe shaper may be performed in response to comparing the one or more test parameters against the respective one or more reference parameters to refine. The adjusting the configuration of the optical probe shaper may thereby adjust a spatial configuration of the plurality of light beams so as to more accurately I more precisely aim the plurality of light beams to provide telecommunications wavelength light, over the air interface, towards the plurality of input ports.

[0034] Dynamic adjustment of the light beams results in improved alignment with input ports and facilitates real-time minimisation of spatial-parameter value discrepancies.

[0035] Adjustment of the configuration of the optical probe shaper may be performed in response to obtaining the reference testing map providing the one or more reference values of the respective one or more reference parameters. Adjustment of the configuration of theoptical probe shaper may be performed in response to comparing the one or more test parameters against the respective one or more reference parameters. Adjustment of the configuration of the optical probe shaper may thereby adjust a spatial configuration of the plurality of light beams.

[0036] Adjustment in response to reference-value comparison, such as that readily obtained by the testing map, allows for easy recalibration of the plurality of light beams to more accurately and precisely probe one or more input ports of the optical layer.

[0037] One or more optical paths in the optical layer between the one or more input ports and the respective one or more output ports may be adjusted by control of one or more interferometers disposed within the optical layer,.

[0038] This facilitates the rapid, robust testing of optical layers used in smart (reconfigurable) OPCBs.

[0039] The verifying based on the detection may comprise verifying a configuration of one or more interferometers which define the one or more optical paths.

[0040] The method may further comprise adjusting one or more optical paths in the optical layer between the one or more input ports and the respective one or more output ports by controlling the one or more interferometers, thereby to alter one or more paths which the light traverses between the one or more input ports and the respective one or more output ports. The method may further comprise subsequently iterating some or all of the above steps of this aspect. The method may further comprise verifying, based on the detection, a functionality or reconfigurability of the one or more interferometers controlled.

[0041] The method may further comprise adjusting one or more optical paths in the optical layer, thereby to optically couple at least one of the one or more input ports to an output port other than the one or more respective output ports. The method may further comprise subsequently iterating some or all of the above steps of this aspect. The method may further comprise verifying, based on the detection, a functionality or reconfigurability of the one or more interferometers controlled.

[0042] This facilitates the rapid testing of the configuration and functionality of the interferometers in smart (reconfigurable) OPCBs.

[0043] The method may further comprise one or both of: focussing, using a source array of lenses positioned between the one or more light sources and the optical layer under test, the light towards the one or more input ports; and focussing, using a detector array of lenses positioned between the optical layer under test and the detector, the light towards the detector.The method may comprise one or both of: focussing, using one or more parabolic mirrors positioned between the one or more light sources and the optical layer under test, the light towards the one or more input ports; and focussing, using one or more parabolic mirrors positioned between the optical layer under test and the detector, the light towards the detector

[0044] The verifying the transmission of the light may comprise performing a free-path calibration to account for one or more of: an attenuation of the detected light; a dispersion of the detected light; and a diffusion of the detected light.

[0045] Calibration allows compensation for intensity-loss due to dispersive and / or free-path attenuation effects, improving efficiency of the system while also improving accuracy of the comparison.

[0046] The source one or more lenses and / or the detector one or more lenses may be controllable to adjust their configurations.

[0047] Control of the optical probe shaper and control of the source one or more lenses may be coupled and / or simultaneous; and / or control of the optical probe shaper and control of the detector one or more lenses may be coupled and / or simultaneous.

[0048] Control in this manner allows for better flexibility in fine-tuning alignment, and further facilitates the iteration of tests to determine a minimum discrepancy between test and reference parameter values. Coordination of the focussing and probe shaping means facilitates smart and / or centralised control of the system.

[0049] The method may further comprise passing the light through a diffusive film or cap disposed between the one or more output ports and the detector.

[0050] The detector may be an infra-red camera and the light detected or absent at the detector may have a wavelength within the infrared spectrum. The detector may be a planar detector. The detector may comprise a plurality of point detectors.

[0051] Use of readily available, high-sensitivity equipment provides a reliable, cost-effective means of verifying the optical transmission of light relevant to use-cases in electronic telecommunications devices.

[0052] In a further aspect, there is provided a system for testing an optical layer of an optical printed circuit board (OPCB). The optical layer comprises one or more input ports, one or more respective output ports, and one or more optical waveguides coupling the one or more input ports to the one or more respective output ports. The system comprises one or more light sources configured to be aimed to provide light, over a source air interface, towards the one or more input ports. The system further comprises a detector configuredto detect, over a detector air interface, the presence or absence of the light output from the one or more output ports of the optical layer to determine one or more test parameters associated with the presence or absence of the light. The system further comprises a processor configured to verify, based on the detection, the transmission of the light passing between the one or more input ports and the respective one or more output ports. The processor may be configured to verify the presence or absence of the light output using the one or more test parameters and one or more respective reference parameters. The processor may be further configured to determine the one or more test parameters associated with the detected presence or absence of light.

[0053] The optical layer may be separated from any optical module of the OPCB, and the method may be performed prior to assembly of any optical modules on the OPCB.

[0054] The OPCB may be the optical board of an electro-optical PCB. The optical layer may be separated from any electrical layer or electrical module of the electro-optical PCB. The method may be performed prior to assembly of any electrical layers or electrical modules on the electro-optical PCB.

[0055] The processor may be configured to verify the presence or absence of the light output using the one or more test parameters and one or more respective reference parameters. The processor may be further configured to determine the one or more test parameters associated with the detected presence or absence of light.

[0056] One or more optical paths in the optical layer between the one or more input ports and the respective one or more output ports may be adjusted by control of one or more interferometers disposed within the optical layer. The one or more light sources, the detector, and the processor may be respectively configured to iteratively perform the aiming, detecting, and verifying.

[0057] The processor may be configured to verify, based on the iterated detection following adjustment of the one or more optical paths by control of the one or more interferometers, a configuration of the one or more interferometers.

[0058] The processor may be configured to verify, based on the iterated detection following adjustment of the one or more optical paths by control of the one or more interferometers, a functionality or reconfigurability of the one or more interferometers.

[0059] In a yet further aspect, there is provided a computer-implemented method for testing an optical layer of an optical printed circuit board (OPCB). The optical layer comprises one or more input ports, one or more respective output ports, and one or more optical waveguides coupling the one or more input ports to the one or more respective output ports. Themethod comprises detecting the presence or absence of the light received, over a detector air interface, from the respective one or more output ports of the optical layer to determine a respective one or more test parameters associated with the presence or absence of light. The method further comprises verifying, based on the detection, the transmission of the light passing between respective input and output ports.

[0060] The method may further comprise verifying the transmission of the light using the one or more test parameters and one or more respective reference parameters.

[0061] The method may further comprise aiming one or more light sources to provide the light, over a source air interface, towards the one or more input ports.

[0062] In a yet further aspect, there is provided a computer-readable medium having stored thereon computer-executable instructions which, when executed by a computer, cause the computer to carry out a method in accordance with a preceding aspect. The method may be carried out by an apparatus in accordance with the preceding aspect.

[0063] Provision of computer-executable instructions enables widespread and automated execution of methods disclosed herein.

[0064] The present disclosure includes one or more aspects, examples, or features, in isolation or in various combinations, whether or not specifically stated (including claimed) in that combination or in isolation. Corresponding means and corresponding functional units for performing one or more of the discussed functions are also within the present disclosure. Corresponding computer programs for implementing one or more of the methods disclosed are also within the present disclosure and encompassed by one or more of the described examples.

[0065] The above summary is intended to be merely exemplary and non-limiting.

[0066] BRIEF DESCRIPTION OF THE FIGURES

[0067] Embodiments are described below with reference to the accompanying drawings, in which:

[0068] Figure 1 is a schematic illustration depicting an exemplary apparatus comprising electronic components, including a memory and a processor, the apparatus being suitable for being implemented in certain embodiments;

[0069] Figure 2 is a schematic illustration depicting an optical layer of an OPCB, under test by a system;

[0070] Figure 3 is a schematic illustration of the optical layer of an OPCB, shown in schematic cross-section, under test by the system;

[0071] Figure 4 is a schematic illustration of an exemplary test case in which the system is used to test the optical layer;Figure 5 is a schematic illustration of a further exemplary test case in which the system for testing the optical layer;

[0072] Figure 6 is a schematic illustration of a yet further exemplary test case in which the system is used to test the optical layer;

[0073] Figure 7 is a schematic illustration of a yet further exemplary test case in which the system is used to test the optical layer;

[0074] Figure 8 is a schematic illustration of an exemplary test case in which a further system is used to test the optical layer;

[0075] Figure 9 is a schematic illustration of a further exemplary test case in which the further system is used to test the optical layer of an OPCB;

[0076] Figure 10 is a schematic illustration of a test case in which a yet further system is used to test the optical layer of an OPCB;

[0077] Figure 11 is a schematic illustration of a further test case in which the yet further system is used to test the optical layer of an OPCB;

[0078] Figure 12 is a schematic illustration of an exemplary test case in which the optical layer, shown in schematic cross-section, is under test by the system, further system, or yet further system;

[0079] Figure 13 is a schematic illustration of an exemplary test case in which a further optical layer, shown in schematic cross-section, is under test by the system, further system, or yet further system;

[0080] Figure 14 is a schematic illustration of a further exemplary test case in which the further optical layer, shown in schematic cross-section, is under test by the system, further system, or yet further system;

[0081] Figure 15 is a schematic illustration of a yet further exemplary test case in which the further optical layer, shown in schematic cross-section, is under test by the system, further system, or yet further system;

[0082] Figure 16 is a schematic illustration of a perspective view of the optical layer or further optical layer, under test by the system, further system, or yet further system;

[0083] Figure 17 is a schematic illustration of components of the yet further system, indicating their functional relationship with each other and with the optical layer or further optical layer;

[0084] Figure 18 is a process flow chart illustrating steps of a method for testing the optical layer or further optical layer;

[0085] Figure 19 is a process flow chart illustrating steps of a further method for testing the optical layer or further optical layer;

[0086] Figure 20 is a process flow chart illustrating steps of a yet further method for testing the optical layer or further optical layer;Figure 21 is a flow diagram depicting an exemplary test flow for testing one or more layers of an OPCB;

[0087] Figure 22 is a flow diagram depicting a further exemplary test flow for testing one or more layers of an OPCB;

[0088] Figure 23 is a flow diagram depicting a yet further exemplary test flow for testing one or more layers of an OPCB; and

[0089] Figure 24 is a flow diagram depicting a yet further exemplary test flow for testing one or more layers of an OPCB.

[0090] DETAILED DESCRIPTION

[0091] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

[0092] The present disclosure relates to the field of testing / probing optical layers of OPCBs (including those associated with co-packaged optics (CPO) and near-packaged optics (NPO) technologies), and associated systems, apparatuses, and computer programs for the implementation thereof. The OPCBs may be used as components in telecommunication network equipment (including network servers) or end user electronic devices (including include computers, laptops, tablet PCs, smartphones, cameras, and other smart devices). Figure 1 depicts an exemplary embodiment of an electronic device 100, such as a personal computer, a portable electronic device, a portable telecommunications device, telecommunication network equipment, or a server or a module for such a device. As mentioned above, the OPCB may be a component of such a device, or such a device may be modified to control one or more aspects of the presently disclosed methods for use in testing an optical layer of an OPCB.

[0093] Optionally, the electronic device 100 may comprise a display device 102 such as, for example, a liquid crystal display (LCD), e-Ink or touch-screen user interface. The device 100 is configured such that it may receive, include, and / or otherwise access data. To this end, the device 100 comprises a communications unit 104, such as a receiver, transmitter, and / or transceiver, in communication with an antenna (not shown) for connecting to a wireless network and / or with a port (not shown) for accepting a physical connection to a network, such that data may be received via one or more types of networks. The device 100 comprises a memory 106 that stores data, possibly after being received via the antenna or the port or after being generated at a user interface 108. A processor 110 may receive data from the user interface 108, from the memory 106, and / or from the communication unit 104. It will be appreciated that, in certain example embodiments, the display device 102 may incorporate the user interface 108. Regardless of the origin of thedata, these data may be outputted to a user of device 100 via the display device 102, and / or any other output devices provided with apparatus. The processor 110 may also store the data for later use in the memory 106. The memory 106 may store computer program code and / or applications which may be used to instruct / enable the processor 110 to perform functions (e.g. read, write, delete, edit or process data).

[0094] The memory 106 is a storage medium which may be configured to store computer code configured to perform, control or enable the operation of the device 100, and / or operation of an external apparatus. The storage medium 106 may be configured to store settings for the other device components within the device 100. The processor 110 may access the storage medium 106 to retrieve the component settings in order to manage the operation of the other device components. The storage medium 106 may be a temporary storage medium such as a volatile random access memory. The storage medium 106 may also be a permanent storage medium such as a hard disk drive, a flash memory, a remote server (such as cloud storage) or a non-volatile random access memory. The storage medium 106 could be composed of different combinations of the same or different memory types. In the following description of embodiments and examples, like reference numerals are used to denote like or analogous features, eliminating the need for repetitive description of like features amongst different embodiments or exemplary cases.

[0095] System for testing an optical layer

[0096] The optical layer of an OPCB has a number of characteristics which may be leveraged in systems and methods of testing set out in the present disclosure. One such characteristic, for example, is the larger alignment tolerance enjoyed by OPCB I / O ports compared with lines in photonic chips. For example, for PCBs comprising electrical circuits, electrical contacts are required for I / O testing. For optical circuitry within OPCBs, electrical probes (e.g., flying wires) may be used to control and test I / O functionality in the electrical layer circuitry.

[0097] Figure 2 depicts a system 200 for testing an optical layer 202 of an OPCB. The optical layer 202 comprises a plurality of optical I / O ports connected by respective optical paths formed of respective optical waveguides. In particular, in this embodiment, the optical layer 202 comprises a plurality of input ports 204 connected to a plurality of respective output ports 206 via waveguides 208.

[0098] In a conventional test procedure for optical circuitry, light would typically be supplied via optical fibre into one or more of the plurality of input ports 204, and conveyed by optical fibre out of a corresponding one or more of the plurality of output ports 206.In an embodiment according to the present disclosure, however, the system 200 for testing the optical layer 202 comprises one or more light sources for providing light to the plurality of inputs via the air interface, i.e., without the need for optical wiring. In this embodiment, the one or more light sources is a laser 210 configured to provide light, for example, monochromatic light. For example, the monochromatic light is telecommunications wavelength light of a wavelength suitable for end use in an OPCB, e.g., in a CPO or NPO architecture. In particular, in this embodiment, the light has a wavelength in the infra-red spectrum, e.g., 1260 nm - 1625 nm. In other embodiments, the laser 210 (or other suitable light source) is configured to provide light of a different wavelength (e.g., visible light). For example, the laser 210 (or other suitable light source) may be configured to provide light of a wavelength within, e.g., the 100 nm - 2000 nm range, e.g., the 800 nm - 1600 nm range, or e.g., the 100 nm - 800 nm range. In some embodiments, the light is not monochromatic, but is instead light comprising a spectrum of wavelengths, e.g., within the telecommunications wavelength light range, e.g., the 1260 nm - 1625 nm range. In other embodiments, the light comprises a spectrum of wavelengths in another wavelength range, e.g., the 100 nm - 2000 nm range, e.g., the 800 nm - 1600 nm range, or e.g., the 100 nm - 800 nm range. In some examples, the use of a the light source over an air interface may be considered as injecting testing light using one or more time- variant schemes.

[0099] In Figure 2, the laser beam aimed at the plurality of input ports 204 by the laser 210 is denoted by the reference label L. The respective light inputs to the plurality of input ports are indicated diagrammatically with block arrows and denoted by the reference label LI. The system 200 further comprises a detector 212 configured to detect light output from the plurality of output ports 206. In this embodiment, the detector 212 comprises a camera for receiving and detecting the light output from the plurality of output ports 206. As will be described below, the detector 212 may be any means suitable for detecting the absence and / or presence of light output from the optical layer 202. The detector may be a planar detector or a point detector, or may comprise a plurality of point detectors. In some examples, the detector comprises one or more photodiode.

[0100] In Figure 2, the light output by the plurality of output ports 206 is indicated diagrammatically with block arrows, and denoted by the reference label LO.

[0101] In some embodiments, the detector 212 is, in addition to or instead of being configured to detect a presence of light, configured to detect an absence of light output separately from the plurality of output ports 206. Such an absence is indicative of an ineffective or failed transmission of light between one or more of the plurality of light output ports 206 and a corresponding one or more of the plurality of input ports 204.In this and other embodiments, a processor (not shown) within the system 200 is configured to determine, from the light (or absence thereof) detected by the detector 212, a value of one or more test parameters associated with the detected light (or absence thereof). A further processor, which may be the same processor or a different processor as the processor which determines the one or more test parameters, is included in the system 200. The further processor is configured to verify, based on the one or more test parameters, the transmission of light passing between the probed one or more input ports and a corresponding one or more output ports.

[0102] It will be understood that, herein, the term "verifying" encompasses a positive finding (i.e., successfully verifying or determining a "pass") or a negative finding (i.e., failing to verify or determining a "fail").

[0103] In this and other embodiments, the further processor is configured to obtain a value of one or more reference parameters against which said further processor is configured to compare the value of the one or more test parameters, thereby to make an assessment as to the extent of transmission of light passing between the probed one or more input ports and a corresponding one or more output ports.

[0104] In some aspects, the light source (e.g. laser) used for testing is configured to provide a light beam over the air interface which is movable over the optical layer under test. In some examples, the light beam can move over two-dimensions on the optical layer under test. In some aspects, the movement of the light beam allows light to be directed to a selected input port of the optical layer under test.

[0105] In some aspects, the detector used for testing is configured to detect a light beam over the air interface which allows identification of the emitted light origin location from the optical layer under test. In some examples, the detector can detect the emission location in two-dimensions on the optical layer under test. In some aspects, the detector allows light to be detected as from a particular output port of the optical layer under test.

[0106] Suitable test and reference parameters, and the nature of the verification and / or comparison performed by the system, will be described in more detail below with reference to the embodiments depicted in Figures 3-15.

[0107] Figure 3 depicts the optical layer 202 under test by the system 200, the optical layer 202 being shown in schematic cross-section. The light input LI to the one or more input ports 204 (only one being visible in cross-section) is directed, via vertical couplers 300, along respective waveguides 208 (only one being visible in schematic cross-section) and out of a corresponding one or more output ports 206 (only one being visible in cross-section). In some examples, the vertical couplers 300 are mirrors 300, e.g. parabolic mirrors, orgrating couplers. The light output LO leaving the one or more output ports 206 is detected by the detector 212, and the system 200 subsequently determines a value (or values) of one or more test parameters. As will be described in more detail below, the system 200 is configured to use the determined value (or values) to verify the transmission of light passing between the probed one or more input ports 204 and the corresponding one or more output ports 206.

[0108] While in Figure 3 the waveguide 208 is shown in schematic cross-section and depicted for clarity as transparent, it will be understood that the waveguide may, in some embodiments, not be hollow, i.e. may be filled with an optical material other than air. The optical material may be a solid optical material comprising, e.g., glass and / or polymer. As can be seen from Figure 3, the system 200 does not interact with, and hence does not require, any physical (e.g., wired) interface nor electrical components; the light LI used to probe the optical path(s) between one or more input ports 204 and one or more output ports 206 is delivered, and subsequently detected, over respective air interfaces. It will be understood that, while the term "air interface" is used herein to describe a wireless interface over which the probing light LI is delivered or the output light LO is detected, said interface may in fact be any un-wired / non-contact interface with varying compositions and conditions, e.g., a vacuum, or another interface comprising an atmospheric or non-atmospheric gas or gaseous mixture, or comprising a fluid. The light input LI from the laser light source 210 to the one or more input ports 204 can be considered to travel over a source air interface, whereas the light output LO output from the one or more output ports 206 can be considered to travel over a detector air interface. They are shown to be different parts of a continuous and same air interface in the embodiment of Figure 3, but in other embodiments (not shown), they may be one or more of separated and have differing compositions / conditions (e.g. different gases and / or pressures / temperatures). Figure 4 depicts an exemplary test case in which the system 200 is used to test the optical layer 202.

[0109] In this embodiment, the system 200 is configured to irradiate a plurality of input ports 204 by a plurality of beams formed by the laser 210. In particular, the light input LI to the probed plurality of input ports 204 is formed of a plurality of beams whose respective beam spots are each aimed at a respective input port 204. In this embodiment, the plurality of beams is formed at a plurality of outputs of the laser 210 (or other suitable light source), as indicated in Figure 4 by dashed lines and denoted by the reference numeral 404. In other embodiments, as will be described in detail below, a plurality of beams of the light input LI may be formed by, e.g., splitting one or more outputs of thelaser 210 (or other suitable light source), or may be formed by a respective plurality of lasers (or other suitable light sources).

[0110] In this embodiment, the system 200 is configured to detect the light output LO by the plurality of output ports 206 at a respective plurality of locations at the detector 212, as indicated in Figure 4 by dashed lines and denoted by the reference numeral 406.

[0111] In this embodiment, the optical layer 202 under test comprises a plurality of input ports 204 and plurality of output ports 206 which are respectively offset arrays of ports in a surface of the optical layer 202, connected / coupled, as depicted in Figure 3, by respective waveguides 208. The waveguides 208 form respective optical paths through which, and from which, vertical couplers, e.g. mirrors 300, direct the light received at a respective input port 204. In some suitable optical layers 202, the plurality of input ports 204 may be formed of an array having a different size or shape, and / or having a different number of constituent ports, to the array forming the plurality of output ports 204. In some suitable optical layers 202, the plurality of input ports 204 may instead be only one input port 204, and / or the plurality of output ports 206 may instead be only one output port 206 (i.e., the optical layer 202 under test may comprise only one input port 204 and / or may comprise only one output port 206). Although Figure 3 shows a single continuous optical layer 202, the optical layer 202 may be formed from multiple discrete layers which would be considered functionally equivalent to the single continuous layer, e.g. in that the multiple discrete layers comprise one or more optical waveguides 208 which connect respective I / O ports 204, 206 across one or more of the discrete formed layers.

[0112] As will be described in detail below, where the optical layer 202 comprises a plurality of input ports 204 and a plurality of output ports 206, methods of testing disclosed herein may be used to test or probe only a subset of said input ports 204, e.g., a subset of one input port 204, or a subset of two input ports 204, or a subset of three input ports 204, or a subset of a greater number of input ports 204. In some examples, only a subset of input ports, e.g. one input port, is tested at any one time. One or more further input port is tested separately, at a later time.

[0113] It will thus be understood that embodiments of the systems and methods disclosed herein provide an automated means for optical testing.

[0114] The term "optical path" as used herein will be understood to mean a path optically coupling an input port 204 of the optical layer 202 to an output port 206 of the optical layer 202. An optical path may comprise one or more waveguides 208, and may connect adjacent or non-adjacent I / O ports 204, 206. In some examples, an optical path may be defined at least in part by configuration of one or more waveguides 208 and / or one or more optical components, e.g. an interferometer or mirror. Configuration of the one or more mirrorsmay be achieved by any suitable means, including fixed setting of optical components (e.g., during manufacture) or dynamic control (in situ) of the optical paths, e.g., by interferometry (such as by adjustment of one or more cascading interferometers, which may be, e.g., Mach-Zehnder interferometers), or, e.g., by adjustment of one or more of the mirrors.

[0115] As will be described in detail, where the optical layer 202 comprises a plurality of optical paths, the methods of testing disclosed herein may be used to test or probe only a subset of said optical paths, e.g., a subset of one optical path, or a subset of two paths, or a subset of three optical paths, or a subset of a greater number of optical paths.

[0116] In this embodiment, the processor (which may be integral with or separate from the (camera) detector 212, and as mentioned above, may be the processor 110 of Figure 1) and, whether distinct or otherwise, further processor, are configured to, respectively, determine a value of one or more test parameters associated with the detected light (or absence thereof), and verify, based on the one or more test parameters, the transmission of light passing between the probed one or more input ports and a corresponding one or more output ports. Said processor and, whether distinct or otherwise, further processor together constitute a controller 408 of the system 200. The controller 408 is coupled to the detector 212. In this embodiment, the controller 408 is also coupled to the laser 210, thereby to form a feedback loop by which the laser 210 may be controlled, e.g., in response to the determination and verification (described in more detail below). The controller 408 may be an integrated entity within the system 200, or may be distributed over one or more entities within the system (e.g., within the detector 212 and / or the laser 210), and / or partially or wholly distributed over one or more entities external to the system, e.g., via a network connection.

[0117] As will be understood with reference to embodiments described below, the feedback loop formed by the detector 212, controller 408, and laser 210 is particularly advantageous for cases in which multiple (different) subsets of input ports 204 are to be probed.

[0118] In the case depicted in Figure 4, each of the plurality of output ports 206 expected to contribute to the light output LO forms a corresponding "bright spot" at the plurality of locations 406 on the detector 212.

[0119] In this and other embodiments, the one or more test parameters determined by the system 200 may comprise, e.g., a spatial position (or spatial positions) of one or more of the locations 406 at the detector 212. Said spatial position(s) may be used to verify the transmission of light passing between the probed one or more input ports and a corresponding one or more output ports. For example, the verification may include comparing the spatial position(s) against respective reference position(s) (generally, oneor more reference parameters) associated with expected spatial position(s) of the probed one or more input ports 204, and / or of the probed one or more output ports 206. For example, the one or more reference parameters may comprise: an expected spatial position of one or more of the probed input ports 204; and / or an expected spatial position of one or more output ports 206; and / or an expected spatial position of one or more of the locations 406 at the detector. The spatial position(s) of one or more of the locations 406 detected may be considered a spatial property of the one or more test parameters. The expected spatial position(s) associated with expected spatial position(s) of the probed one or more input ports 204 and / or of the probed one or more output ports 206 may be considered a reference spatial property of the one or more reference parameters.

[0120] Having determined a value of the one or more test parameters, a comparison of said value against a value of the one or more reference parameters is advantageous. An assessment may thus be made as to the extent of transmission of light passing between the probed one or more input ports 204 and a corresponding one or more output ports 206.

[0121] In the case depicted in Figure 4, described above, only a spatial distribution of the light output LO explicitly considered. However, as described in more detail below, in this and other embodiments, the one or more test parameters may comprise a non-spatial (e.g., optical) property. The one or more test parameters may be compared against one or more reference parameters comprising a reference non-spatial (e.g., optical) property. In such embodiments, a characteristic other than (or in addition to) a spatial distribution of the light at the detector 212 is used to verify the transmission of light passing between the probed one or more input ports 204 and a corresponding one or more output ports 206. In some embodiments, the system 200 is configured to determine the optical property of the one or more test parameters based on the spatial property, the determined optical property being compared against the reference optical property in the verification of transmission of light.

[0122] Figure 5 depicts the system 200 again being used to probe a plurality of input ports 204. In the case depicted in Figure 4, each of the plurality of output ports 206 expected to contribute to the light output LO forms a respective spot at the plurality of locations 406 on the detector 212 (showing ten output locations 406). In contrast, Figure 5 depicts a converse test result in which not every expected location on the detector 212 is provided with a respective spot by the light output LO from the plurality of output ports 206 (only nine output locations 406). This may be indicative that one of the output ports 204 has failed to transmit, or ineffectively transmitted, light. Such a negative indication at the verification stage may be caused, for example, by one or more defects of the optical layer 202, including, for example, misalignment or defect of one or more of the input ports 204,misalignment or defect of one or more waveguides 208, leakage of light within one or more optical paths within the optical layer 202, or the defective operation of one or more optical components (e.g., one or more mirrors 300). Alternatively, a negative indication could also be due to misalignment of one or more of the plurality of beams of the light input LI with one or more input ports 204. The feedback loop mentioned above is particularly advantageous in embodiments of the system 200 which are configured for iterative realignment or recalibration of the laser 210 and / or splitting means, as will be described in more detail. Such iteration may allow a determination as to whether misalignment or misdirection of the laser 210 is the root cause for discrepancies between expected and actual distributions of light at the detector 212 (i.e., between the value(s) of the spatial property of the one or more test parameters and the value(s) of the reference spatial property of the one or more reference parameters).

[0123] It will be understood that, while the spatial position(s) of one or more of the locations 406 (i.e., "bright spots") at the detector 410 can be used as one or more test parameters for the verification, in some embodiments of the system 200 the spatial position(s) of absences of light (i.e., a "hole" or "dark spot") at the detector 212 may be used at the verification stage. In a manner analogous with that described above with respect to the bright-spot locations 406, the one or more test parameters may comprise, e.g., a spatial position (or spatial positions) of an absence of one or more of the bright-spot locations 406 at the detector 212. Said spatial position(s) of the absence(s) may be used to determine a failed or ineffective transmission of light passing between the probed one or more input ports 204 and a corresponding one or more output ports 206. For example, the system 200 may be configured to compare a value (or values) of said spatial position(s) against a value (or values) of respective reference position(s). The respective reference position(s), which are non-limiting examples of the one or more test parameters, may comprise one or more of: an expected spatial position(s) of the probed one or more input ports 204; an expected spatial position(s) of one or more output ports 206; an expected spatial position(s) of one or more of the locations 406 at the detector 212; and an expected spatial position(s) of one or more "holes" or "dark spots" at the detector 212. Having determined a value of the spatial position(s), a comparison of the value (or values) of the one or more test parameters against a value (or values) of the one or more reference parameters. An assessment may thereby be made as to the extent of transmission of light passing between the probed one or more input ports 204 and a corresponding one or more output ports 206.

[0124] Figure 6 depicts the system 200 being used to probe a subset 600 of input ports 204.In this embodiment, the subset 600 is probed by a corresponding subset (not shown) of the plurality of beams of the light input LI to the optical layer 202. The subset of beams is formed by a corresponding subset 602 of outputs 404 of the laser 210, although it will be understood with reference to embodiments described below that the subset of beams may be formed, e.g., by splitting of one or more beams from the laser 210 (or other suitable light source). As in the case depicted in Figure 4, each output port 206 expected to contribute to the light output LO (i.e., those output ports 206 expected to be in optical communication with the probed / irradiated subset 600 of input ports 404) indeed forms a respective bright spot at the plurality of locations 406 on the detector 212. In some examples, further one or more input ports are verified in a separate step.

[0125] Figure 7 depicts the system 200 again being used to probe the same subset 600 of input ports 204.

[0126] Unlike the case depicted in Figure 6 with four light output location 406, Figure 7 depicts a case in which (as in Figure 5) not every location on the detector 212 expected to be provided with a respective bright spot of the light output LO is so-provided (as only three light output locations 406 are shown). This may be indicative that one of the output ports 204 has failed to transmit, or ineffectively transmitted, light.

[0127] In the embodiments described above with reference to Figures 3-6, a feedback loop formed by the detector 212, controller 408, and laser 210 may be implemented in the system 200. In this embodiment, the feedback loop may sequentially probe differing subsets 600 of input ports 404, thereby to quickly test a large number of I / O combinations (or, put differently, a large number of distinct optical paths). For example, the controller 408 may, in response to a positive verification of the transmission of light passing between the probed one or more input ports 204 and a corresponding one or more output ports 206 (e.g., as depicted in Figure 6), control the laser 210, or otherwise instruct the laser 210, to irradiate a (partly or wholly) different subset 600 of input ports 204.

[0128] Additionally or alternatively, the feedback loop formed by the detector 212, controller 408, and laser 210 may be implemented to iteratively probe the same subset 600 of input ports 404, via reconfiguration or recalibration of one or more components of the system 200, thereby to quickly obtain a minimised discrepancy (or, put differently, a maximised chance of a positive verification). For example, the controller 408 may, in response to a negative finding, control the laser 210, or otherwise control the laser 210, to attempt to irradiate the same subset 600 of input ports 204 with a spatially reconfigured plurality of beams. Such operation of the system 200 is appropriate where, e.g., it is suspected (e.g., by a user or automatically by the controller 408) that a negative finding is the result ofmisalignment of the light input LI with the plurality of input ports 204 (e.g., rather than the result of a defect in the optical layer 202).

[0129] In embodiments in which a light-splitting and / or light-directing means is used to form the light input LI from the light L output from the laser 210, the controller 408 may reconfigure, or otherwise instruct reconfiguration of, the light-splitting and / or lightdirecting means. In this manner, a spatial configuration or distribution of the plurality of beams may be adjusted, thereby to more accurately irradiate the subset 600 of input ports 204.

[0130] In embodiments in which a plurality of outputs of the laser 210 is used to form the light input LI, or where a plurality of light sources is used to form the light input LI, the controller 408 may reconfigure, or otherwise instruct the reconfiguration of, the laser 210 (or plurality of light sources). In this manner, a spatial configuration or distribution of the plurality of beams, may be adjusted, thereby to more accurately irradiate the subset 600 of inputs.

[0131] Figure 8 depicts an embodiment of the system 200 being used to probe a plurality of input ports 204.

[0132] In this embodiment, the system 200 comprises an optical probe shaper 800 through which the light L output by the laser 210 passes to form the plurality of beams of the light input LI to the probed plurality of input ports 204. In this embodiment, the optical probe shaper 800 comprises a plurality / array of mirrors arranged to deflect light L received from the laser 210 towards the probed plurality of input ports 204. The test light may be considered as directed towards the optical PCB under test by implementing the contactless probes as laser sources with a reconfigurable deflector mirror array.

[0133] Figure 9 depicts the system 200 being used to probe a subset 600 of input ports 204. In embodiments (e.g., those described above) in which the feedback loop formed by the detector 212, controller 408, and laser 210 is implemented to reconfigure the plurality of beams of the light input LI to either probe differing subsets 600 of input ports 204 or more accurately probe the same subset 600 of input ports 204, the optical probe shaper 800 may form a part of said feedback loop. For example, the optical probe shaper 800 may be communicatively coupled to the controller 408 such that reconfiguration of the plurality of beams of the light input LI may be done at least in part by spatially reconfiguring or recalibrating the optical probe shaper 800. This may be done by spatially reconfiguring or reorienting the plurality of mirrors of the optical probe shaper 800, thereby to aim the plurality of beams of the light input LI towards a different subset 600 of input ports 204, or alternatively more accurately towards the same subset 600 of input ports 204.Figure 10 depicts an embodiment of the system 200 comprising the optical probe shaper 800, in which the light L is output by the laser 210 via a single output 404. The optical probe shaper 800 is, in this embodiment, further configured to split the light L into the plurality of beams forming the light input LI to the plurality of input ports 204. In this embodiment, the splitting of the light L is done by a plurality / array of mirrors of the optical probe shaper 800.

[0134] Figure 11 depicts the system 200 being used to probe a subset 600 of input ports 204. In this embodiment, the optical probe shaper 800 is configured to split the light L into a plurality of beams forming the light input LI to the subset 600 of input ports 204.

[0135] Figure 12 depicts the optical layer 202 under test by the system 200, the optical layer 202 again being shown in schematic cross-section.

[0136] As can be seen in Figure 12, the optical components disposed within the optical layer may include, in addition to vertical couplers (e.g. mirrors) 300 and waveguides 208, collimating lenses 1200 disposed at or proximate to one or more I / O port 204, 206 of the optical layer 202. The collimating lenses 1200 may compensate for the more relaxed alignment tolerances associated with air-interface transmission of light at the I / O ports 204, 206, compared with the stricter alignment tolerances associated with wired interfaces (e.g., optical fibre interfaces). For example, one or more of the plurality of beams forming the light input LI to the probed input ports 204 may be non-normal to the optical layer surface (i.e., incident to the optical layer 202 at an oblique angle to its surface plane), such that the light input LI must be collimated at the probed input port 204 prior to transmission along a respective optical path to a respective output port 206. In some examples, the lenses 1200 are micro-lenses.

[0137] It will thus be understood that embodiments of the systems and methods disclosed herein facilitate, by virtue of larger alignment tolerances and / or the implementation of collimating lenses, the use of larger (i.e., less precise) beam spots forming the light input to the one or more input ports. The need for complex beam alignment procedures, or specialised testing equipment, is thereby obviated.

[0138] Figure 12 again depicts a case in which not every expected bright-spot location receives a respective bright-spot of the plurality at the detector 410 by the light output LO from the output ports 206. This may be indicative that one or more of the I / O ports 204, 206 or other component being probed has failed to transmit, or ineffectively transmitted, light as expected. In the case in which said failing I / O port is one of the ports 204, 206 shown in the schematic cross-section of Figure 12 (which may be determined, as is described in more detail below, based on, e.g., a test map or other reference data) it may be inferredthat a defect 1202 exists within the optical path expected to couple the probed input port 204 to the output port 206 (or else that the probed input port 204 has not been accurately irradiated by the light input LI). The defect 1202 may, as depicted in Figure 12 for illustrative purposes, be a physical defect associated with (e.g., formed in) the optical waveguide 208 or the optical material which it contains. For example, the defect may include a defect in the lamination or deposition of the optical waveguide 208 in the optical layer 202, and / or a defect or impurity in the (e.g., solid) optical material contained therewithin, which include glass, and / or polymer, and / or another optically guiding material. In some cases, the defect could include, in addition to or instead of the defects described previously, a defect in one or more collimating lenses 1200 for collimating light at the I / O ports 204, 206 of the optical layer 202.

[0139] Alternatively, rather than inferring a defect 1202 within an optical path of the layer 202, it may be inferred that the actual position of the input port 204 corresponding to (i.e., optically coupled to) the failing one of the output ports 206 differs from an expected position of said input port 204 such that the plurality of beams, though "accurately" aligned with the expected position, is failing to properly irradiate the actual area of the dislocated input port 204.

[0140] Figure 13 depicts a further example optical layer 202 under test by the system 200. The further optical layer 202 comprises a further waveguide 208 extending through the optical layer 202, thereby to optically couple to another I / O port (not shown) of the optical layer 202. The waveguide and further waveguide (and other waveguides of the plurality of waveguides 208, which are not shown) provide respective pathways to optically connect different I / O ports 204, 206 of the optical layer 202, the pathways forming optical paths whose arrangement depends on a configuration of one or more reconfigurable components, in this embodiment, interferometers 1300a, 1300b (e.g., cascading interferometers, which may be Mach-Zehnder interferometers). The one or more reconfigurable components are arranged to which control the direction or attenuation of light in the optical layer 202, e.g. control the transmission direction towards one or more of the mirrors 300. in one example, the respective states of the interferometers 1300a, 1300b (which may be electrically controlled via respective electrical contacts - not shown) control the configuration of the one or more optical paths within the further optical layer 202. In other embodiments, the configuration of one or more of the optical paths may be set by other suitable means, e.g., by adjustment of one or more optical components within the optical layer 202 (e.g., one or more of the mirrors 300). It will be understood that although only two interferometers 1300a, 1300b are graphically depicted in Figures 13-15, in some embodiments the further optical layer 202 may comprise more (e.g., more than two, or more than five, or more than ten, or more than a hundred) interferometers,thereby to define a plurality (e.g., more than two, or more than five, or more than ten, or more than a hundred, or more than a thousand) of possible optical paths within the further optical layer 202.

[0141] Examples of the testing method comprise performing testing of the optical layer at different configurations of the one or more reconfigurable components. As such, the method comprises controlling the configuration of one or more reconfigurable components to iterate through the different configurations, performing verification of the output at each iteration, i.e. at each configuration to be tested of the one or more reconfigurable components.

[0142] It will be understood that in cases where the optical layer under test is in accordance with the further optical layer 202, the OPCB for which the further optical layer 202 is configured or in which the further optical layer 202 is disposed may be considered a "smart", or "reconfigurable", OPCB. As such, the further layer 202 itself may analogously be referred to as a "smart", or "reconfigurable", optical layer, irrespective of whether it is yet disposed in an OPCB (and thus fully functional). In end-use of such a smart optical layer (as opposed to test-use in the system 200), the optical paths are configured to be dynamically controlled in situ by interferometry (e.g., by adjustment of one or more cascading interferometers, which may be Mach-Zehnder interferometers) provided electrical means for such control is provided (e.g., via electrical contacts). In embodiments of the system 200 suitable for testing such an optical layer, multiple different optical paths (and, correspondingly, multiple different output ports 206) may be verified for any given probed input port 204, or for any given probed plurality / subset of input ports 204, according to the different configurations possible.

[0143] Since the need to reconfigure wired optical connections between testing iterations is obviated by the omission of optical wiring, the system 200 allows quick and convenient testing of a large number of I / O combinations (or, put differently, a large number of different optical paths). This advantage is particularly exploited when the system 200 implements the feedback loop disclosed herein.

[0144] Figure 13 depicts a case in which every expected location at the detector 212 is provided with a respective bright spot by the light output LO from the plurality of output ports 206. This is indicative (at least, as far as a consideration of spatial distribution of the light output LO is concerned) that light has been effectively transmitted between the probed plurality / subset of input ports 204 and the corresponding plurality of output ports 206. Figure 14 depicts the further optical layer 202 under test by the system 200.In this embodiment, the laser 210 is configured to probe (i.e., irradiate) a different plurality of input ports 204 (e.g., a different subset 600 of input ports 204), to that depicted as probed in Figure 13. The probe configuration depicted in Figure 14 may be adopted subsequently to the probe configuration depicted in Figure 13, e.g., in response to the verification (whether positive or negative) of transmission of light in the case shown in Figure 13, or in response to instruction by the feedback loop to change the plurality / subset of input ports 204 to be probed. It will be understood that in some embodiments (as described above) the system 200 may reconfigure the plurality of beams, e.g., by reconfiguring or activating a plurality of outputs 404 of the laser 210, or by selecting a plurality of lasers (or other suitable light sources), or by reconfiguring the optical probe shaper 800 (not shown in Figures 13 or 14) to redirect and / or split the light L in a different spatial configuration.

[0145] As depicted in Figure 14, the respective states of the interferometers 1300a, 1300b (which may, as shown, be a physical / spatial state such as a relative position in the further optical layer 202) are the same in this case as that depicted in Figure 13. As a result, the one or more optical paths within the further optical layer 202 should be identical in the cases of Figures 13 and 14, meaning that any detected discrepancies in light transmission should not be indicative of the (correct) functioning or reconfigurability of the interferometer 1300a, 1300b, and are more likely to indicate one or more other irregularities discussed above. However, it will be appreciated that discrepancies between probing iterations where no optical path reconfiguration has been (deliberately) carried out may still be reflective of incorrect interferometer function (e.g., accidental reconfiguration or unstable alignment).

[0146] In contrast to Figure 13, Figure 14 depicts a case in which not every location for which light is expected to be received at the detector 410. This may be indicative of one of the input ports 204being probed being associated with a light path which is failing to transmit effectively as expected. In the case in which said failing I / O port is one of the ports 204, 206 indicated in the schematic cross-section of Figure 14 (which may be determined, as is described in more detail below, based on, e.g., a test map or other reference data) it could be inferred that a defect exists within the optical path expected to be formed between the input port 204 and output port 206, or else that the input port 204 has not been accurately irradiated by the light input LI from the laser 210.

[0147] Figure 15 depicts a further example optical layer 202 under test by the system 200, the system 200 being used to probe (i.e., irradiate) the same plurality / subset of input ports 204 to that probed in the case depicted in Figure 13.However, in this case, the optical paths of the further optical layer 202 coupling the probed input ports 204 to corresponding output ports 206 are differently configured than in the case depicted in Figures 13 and 14.

[0148] More specifically, in the case depicted in Figure 15, the respective states of the interferometers 1300a, 1300b (represented in the Figures as a position) are not the same as in the cases depicted in Figures 13 and 14. Consequently, the configuration / position of one or more optical paths within the further optical layer 202 differ between cases, and the plurality of bright-spot locations 406 adopts a different configuration (e.g., spatial distribution) than in the case depicted in Figure 13.

[0149] It will be understood that, in the case depicted in Figure 15, while the same plurality / subset of input ports 204 are being probed as in the case of Figure 14, a (partially or wholly) reconfigured set of optical paths is being tested (wherein one or more new / different physical paths is traversed in space by the light during its passage through the further optical layer 202).

[0150] In transitioning from the optical path configuration of Figure 14 to that depicted in Figure 15, one or more of the plurality / subset of input ports 204 is newly optically coupled, by operation (e.g., state change) of one or more of the reconfigurable components. For example, interferometers (or, in other embodiments, other suitable means, e.g., dynamic control of one or more of the mirrors 300) to one or more output ports 206, results in a plurality of bright-spot locations 406 at the detector 212 having a new spatial configuration. In this embodiment, interferometer 1300b is graphically depicted as having changed state, though it will be understood that a change in optical path configuration may be brought about by the other interferometer 1300a changing state, or both interferometers 1300a, 1300b changing respective states. In other embodiments in which the further optical layer 202 under test comprises more interferometers, reconfigurations of one or more optical paths may be brought about by some or all of the interferometers within the further optical layer 202 changing respective states.

[0151] In embodiments such as those depicted in Figures 12-15, in which testing is to be done on the further layer 202 having optical paths which are dynamically reconfigurable in situ (e.g., reconfigurable between probing / testing iterations), the reference spatial property of the one or more reference parameters used for verification of transmission of light may include, in addition to or instead of the parameters described previously, a spatial configuration of one or more optical paths within the optical layer 202 and / or a configuration of one or more interferometers within the optical layer 202.

[0152] Thus, with reference to the description of embodiments above, it will be understood that the system 200 may be used to verify, based on detection at the detector 202, thetransmission of the light passing between the probed plurality / subset of input ports 204 and the corresponding plurality of output ports 206. The system 200 may also be used to verify, based on detection at the detector 202, the absence of optically significant defects along the one or more optical paths between the probed plurality / subset of input ports 204 and the corresponding plurality of output ports 206. The system 200 may also be used to verify, based on detection at the detector 202, the correct alignment of the light input LI with the probed plurality / subset of input ports 204. The system 200 may also be used to verify, based on detection at the detector 202, the correct location (e.g., to manufacturing specifications) of one or more of the probed plurality / subset of input ports 204. In use to test a smart optical layer specifically, as described with reference to Figures 13-15 above, it will be understood that the system 200 may further be used to verify, e.g., positively in such cases as depicted in Figure 13, a configuration of the one or more interferometers which define the one or more optical paths between the probed plurality / subset of input ports 204 and the corresponding plurality of output ports 206. In such use cases, the system 200 may further be used to verify the reconfigurability (i.e., reconfigurable functionality of) of the one or more interferometers, i.e., by iteratively reconfiguring one or more optical paths before performing the verification of the transmission of the light passing between the probed plurality / subset of input ports 204 and the corresponding plurality of output ports 206.

[0153] It will be understood that, where the system 200 is used to test a smart optical layer specifically, as described with reference to Figures 13-15 above, both optical and electrical testing may be performed in tandem, or sequentially. In such cases, the optical testing of the further optical layer 202 may be carried out according to embodiments disclosed herein, and the electrical control of the interferometers of the reconfigurable interferometer system may be tested by coupling electrical probes (e.g., flying wires) to respective electrical contacts of the interferometers (not shown in Figures 13-15). Alternatively or additionally, the electrical performance of the interferometers may be inferred, rather than tested directly by electrical probes, by the optical performance tested by the optical testing of the layer throughout iterations of reconfiguring the interferometers. This obviates the need for electrical wiring, although electrical testing by wired means may alternatively be used.

[0154] In the above-described embodiments of the system 200, the only parameters explicitly described, with reference to Figures 2-15, are test parameters comprising a spatial property of the detected light received at the detector 212 (or, as the case may be, light absent at the detector 212) and reference parameters comprising a reference spatial property. However, in some embodiments, including those described above, the abovedescribed one or more test parameters may comprise a non-spatial (e.g., optical)property, and / or may be compared against one or more reference parameters which comprise a reference non-spatial (e.g., optical) property. In such embodiments of the system 200, a characteristic other than a spatial distribution of the light output LO to the detector 212 may be used to verify the transmission of light passing between the probed one or more input ports 204 and a corresponding one or more output ports 206.

[0155] For example, in some embodiments of the system 200, the one or more test parameters are associated with the presence of light at the detector 212, in which case the spatial property of the one or more test parameters comprises a spatial position associated with the detected light. In such embodiments, the reference spatial property may comprise one or both of: an expected spatial position of one or more input ports 204; an expected spatial position of one or more output ports 206; and an expected spatial position of one or more bright-spot locations 406 at the detector 212. In such embodiments which are suitable for testing the further (reconfigurable) optical layer 202, the reference spatial property may, in addition to or instead of the reference spatial properties described above, comprise an expected spatial position or configuration of one or more optical paths.

[0156] By way of further example, in some embodiments of the system 200, the one or more test parameters are associated with the absence of light at the detector 212, in which case the spatial property of the one or more test parameters comprises a spatial position associated with the absence of light. In such embodiments, the reference spatial property may comprise one or both of: an expected spatial position of one or more input ports 204; an expected spatial position of one or more output ports 206; an expected spatial position of one or more bright-spot locations 406 at the detector 212; and an expected spatial position of one or more "holes" or "dark spots" at the detector 212. In such embodiments which are also suitable for testing the further (reconfigurable) optical layer 202, the reference spatial property may comprise an expected spatial position or configuration of one or more optical paths.

[0157] By way of further example, in some embodiments of the system 200, the one or more test parameters comprise an optical property associated with the presence of light at the detector 212. The optical property may comprise one or more of: an intensity (e.g., measured in lumens or lux) of the detected light; an amplitude (e.g., measured in V or V / m) of the detected light; a power (e.g., measured in mW or dBm) of the detected light; a spatial dimension (e.g., a diameter) of the light at the detector 212; and an angle of incidence of the light at the detector 212. In such embodiments, the one or more reference parameters comprise a reference optical property comprising one or more of: a reference intensity (e.g., measured in lumens or lux) of light; a reference amplitude (e.g., measured in V or V / m) of light; a reference power (e.g., measured in mW or dBm) of light; areference spatial dimension (e.g., a diameter) of the light of the light at the detector 212; and a reference angle of incidence of the light at the detector 212.

[0158] In some embodiments, the system 200 is configured to use a spatial property of the one or more test parameters to determine said optical property, while in some embodiments the system 200 is configured to determine the optical property without prior determination of a spatial property. Similarly, the system 200 may be configured to use a reference spatial property to determine a reference optical property, or the system 200 may determine or obtain the reference optical property without prior determining or obtaining a reference spatial property.

[0159] In some embodiments of the system 200, the controller 408 is configured to verify the transmission of light using both the optical property and the reference optical property. In some embodiments, the controller 408 is configured to determine an indication of the extent to which each waveguide 208 is optically coupling the probed one or more input ports 204 to the corresponding one or more output ports 206.

[0160] In some embodiments, the controller 408 is configured to determine an indication of an optical loss associated with the passage of light between the probed one or more input ports 204 to the corresponding one or more output ports 206.

[0161] It will thus be understood that embodiments of systems and methods disclosed herein allow for a wide range of measurable / determinable test parameters (including, but not limited to, those described herein) to be compared against a correspondingly wide range of reference parameters. It will be understood that different use-cases will render possible, or convenient, different combinations of test and reference parameters. The present inventors envisage a wide range of parameters which would be understood as suitable for comparison, which is not necessarily limited to those described in embodiments herein. Returning to the one or more reference parameters described above, an expected spatial position(s) of the one or more probed input ports 204 and / or an expected spatial position(s) of a corresponding one or more output ports 206 may be provided to the system 200 (e.g., to the controller 408) via a reference testing map. The reference testing map may include, e.g., a digitally-created map or computer-aided design, CAD, model of a portion or the entirety of the optical layer 202 (or further optical layer 202) under test. Additionally, or alternatively, the reference testing map may include one or more manufacturing specifications associated with a portion or the entirety of the optical layer 202 (or further optical layer 202) under test.

[0162] Alternatively, the reference testing map may include a digitally created map or computer-aided design, CAD, model of a portion or the entirety of a reference optical layer havingsubstantially the same configuration and / or expected optical behaviour as the optical layer 202 (or further optical layer 202) under test. The reference testing map may include one or more manufacturing specifications associated with a portion or the entirety of the reference optical layer having substantially the same configuration and / or expected optical behaviour as the optical layer 202 (or further optical layer 202) under test.

[0163] It will thus be understood that embodiments of the systems and methods disclosed herein provide an automated means for optical testing which exploits readily-obtainable CAD mapping, digitally-image mapping, or manufacturer specifications for benchmarking the determined test parameters, and / or which exploits reference test measurements for benchmarking determined test parameters.

[0164] In some embodiments of the system 200, the one or more reference parameters include a reference-test parameter determined by a reference test performed on a reference-test layer, the reference-test layer being the optical layer 202 (or further optical layer 202) or the reference optical layer. The reference test may comprise passing light along fibre optic wiring coupling at least one input port 204 of the reference layer to a corresponding output port 206 of the reference layer.

[0165] In the above-described embodiments, the system 200 comprises an optical probe shaper 800 (depicted only schematically) configured to direct and / or split light L output from the laser 210. In some embodiments, the optical probe shaper comprises a plurality (e.g., an array) of individually controllable mirrors (e.g. micro-mirrors) configured to receive incident light L and reflect the light LI towards the one or more input ports 204 to be probed. The micro-mirrors can be digital mirror devices (DMD). They can be configured to deflect the light probe to the optical input port of the PCB. In some examples, the locations of the inputs are known from a digital model of the board under test: a processing / control system translates this information into a command to a digital beam shaper.

[0166] In some embodiments, the system 200 further comprises one or more arrays of lenses to focus one or more beams of light within the system 200.

[0167] As depicted in Figure 15 (not shown in Figures 12-14, for clarity), in some embodiments, the optical layer 202 comprises one or more electrical vias 1500. The vias 1500 provide for an electrical connection through a part, or all of, the optical layer 202. In some examples, the vias 1500 are connected to a respective metal pad 1502, to provide for an external electrical connection. For example, the metal pads 1502 provide the electrical contacts necessary for the assembly of electrical and / or optical modules on the optical PCB. for maintaining structural integrity and connecting layers of substrate in an O PCB. The vias 1500 form at least part of the sidewalls of each waveguide 208, thereby to confine light within the optical layer 202 or further optical layer 202. In this embodiment In someexamples, the vias 1500 provide for an electrical connection to a component in the optical layer, e.g. interferometer 1300a, 1300b. The optical waveguide 208 does not cross the vias 1500. The vias 1500 also act to minimise losses and interference with nearby components.

[0168] Figure 15 further depicts electrical probes 1504 (omitted from the preceding Figures) electrically coupling to the optical layer 202 under test, e.g. by connecting to components of the optical layer 202 which are reconfigurable. In some examples, the reconfigurable components are interferometers 1300a, 1300b, connected via electrical contacts on the board. The electrical probes 1504 are arranged to carry a signal to drive the interferometers between states, and so reconfigure one or more of the optical paths of the further optical layer 202. This reconfiguration provides for testing of different configurations of the optical layer. The probes 1504 may be, in some embodiments, flying leads, or nails (e.g., a bed of nails), or any other suitable means of connection for electrically coupling a voltage source to the reconfigurable components e.g. interferometers 1300a, 1300b via respective electrical contacts. The metal contacts may be the metal pads 1502 connected to the interferometers 1300a, 1300b through electrical vias 1500 and the electrical layers of the PCB. In some examples, the testing system comprises multiple electrical probes 1504 configured to control multiple reconfigurable components. The test signal applied by the electrical probes 1504 is controlled by an electrical probe control.

[0169] Figure 16 depicts the system 200 comprising the optical probe shaper 800, a source array of lenses 1600, and a detector array of lenses 1602. The source array of lenses 1600 is positioned downstream, in terms of direction of light travel, of the laser 210 and upstream of the optical layer 202 under test. The detector array of lenses 1602 is positioned downstream of the optical layer 202 under test and upstream of the detector 212. The source array of lenses 1600 is configured to focus the plurality of beams of the light input LI onto the respective plurality / subset of input ports 204 to be probed. The detector array of lenses 1602 is configured to focus the light output LO from the output ports 206 onto the detector 212.

[0170] In some embodiments, the source array of lenses 1600 and / or the detector array of lenses 1602 function in combination with, or are replaced by, one or more mirrors, .eg. a parabolic mirror or micro-mirror in an array.

[0171] In some embodiments of the system 200, the source array of lenses 1600 and / or the detector array of lenses 1602 are controllable (e.g., independently or together) to adjust their configurations. In some embodiments, control of the optical probe shaper 800 and control of the source array of lenses 1600 is coupled and / or simultaneous. In someembodiments, control of the optical probe shaper 800 and control of the detector array of lenses 1602 is coupled and / or simultaneous.

[0172] In some embodiments, control of some or all of the optical probe shaper 800, the source array of lenses 1600, and the detector array of lenses 1602 is effected, or otherwise instructed, by the feedback loop (e.g., by the controller 408) in response to a verification (whether positive or negative) of transmission of light between the probed one or more input ports 204 and a corresponding one or more output ports 206. In some examples, the light source is a plurality of laser modules, for example to provide a sufficient light power at the optical input ports.

[0173] In some embodiments, the system 200 further comprises a diffusive element (e.g., a film or cap), disposed downstream of the optical layer 202 under test and upstream of the detector 212, and configured to diffuse the light output LO over a separation distance between the optical layer 202 and the detector 212.

[0174] Figure 17 schematically depicts the components of embodiments of the system 200, and the relationship of the components with each other and with the optical layer 202 (or further optical layer 202).

[0175] As described above, upstream of the optical layer 202 under test, the laser 210 and, in some embodiments, the optical probe shaper 800 and / or source array of lenses 1600, is configured to direct the light input LI towards the one or more input ports 204 to be probed.

[0176] As described above, a corresponding one or more output ports 206 optically coupled to the probed one or more input ports 204 may direct a light output LO towards downstream system components, namely the detector 212. In some embodiments of the system 200, the detector array 1602 and / or diffusive element (not shown) direct the light output LO towards the detector 212.

[0177] As described above, the detector 212 is communicatively coupled to the controller 408, which may comprise the processor and / or further processor described above, and which may be partly or wholly located within or external to the detector 212.

[0178] As described above, the controller 408 is configured to determine a value (or values) of one or more test parameters 1700, which parameters may comprise a spatial property 1700a and / or an optical property 1700b. The optical property 1700b may be a property which is itself determined based on a determined spatial property 1700a.

[0179] As described above, the controller 408 is further configured to obtain (e.g., receive or be pre-programmed with) a value (or values) of one or more reference test parameters 1702, which may comprise a reference spatial property 1702a and / or a reference optical property1702b. The reference optical property 1702b may be a property which is itself determined based on an obtained reference spatial property 1702a.

[0180] As described above, based on the determined one or more test parameters and obtained one or more reference parameters (e.g., by comparison thereof), the controller 408 is configured to verify the transmission of light between the probed one or more input ports 204 and a corresponding one or more output ports 206.

[0181] As described above, the controller 408 may be controllably coupled to one or more of the system components upstream of the optical layer 202, e.g., the laser 210, and / or the optical probe shaper 800, and / or the source array of lenses 1600. Additionally or alternatively, the controller 408 may be controllably coupled to one or more of the system components downstream of the optical layer 202, e.g., the detector array of lenses 1602 and / or the detector 212.

[0182] Thus, a system for testing an optical layer of an OPCB is provided.

[0183] Method for testing an optical layer

[0184] With reference to embodiments of the system 200 described above, a method for testing an optical layer of an OPCB will now be described.

[0185] It will be understood that embodiments of the methods disclosed herein may be performed by suitable embodiments of the system 200 described above.

[0186] It will be understood that the one or more test parameters 1700 and one or more reference parameters 1702, and the spatial and optical properties 1700a, 1700b and the reference spatial and reference optical properties 1702a, 1702b, referred to in method steps below may be as described in any suitable embodiment of the system 200.

[0187] Figure 18 depicts steps of a method 1800 of testing a single input port 204 of an optical layer in accordance with an optical layer 202 (or further optical layer 202) described above in which at least one input port is optically coupled to at least one output port.

[0188] The method comprises, at step S1802, aiming light from the laser 210 (or other suitable light source) to provide, over a first air interface (i.e., the source air interface), the light input LI towards the input port 204 of the optical layer 202. In some embodiments of the method 1800, the aiming the light at step S1802 may optionally comprise redirecting light L from the laser 210 via the optical beam splitter 800. In some embodiments, the method may comprise focussing the light input LI to the input port 204.

[0189] The method 1800 comprises, at step S1804, detecting by the detector 212, over a second air interface (i.e., the detector interface), the presence or absence of the light output LO from a corresponding output port 206 of the optical layer 202.In some embodiments, the method 1800 may comprise, prior to the detecting at step S1804, focussing the light output LO by a detector array of lenses 1602 onto the detector 212.

[0190] The method 1800 comprises, at step S1806, verifying, based on the detecting at step S1804, the transmission of light passing between the input port 204 and the corresponding output port 206.

[0191] In some embodiments of the method 1800, the verifying at step S1806 comprises determining (e.g., by a processor of the controller 408) from the light (or absence thereof) detected at S1804, a value (or values) of one or more test parameters associated with the detected light (or absence thereof), and verifying (e.g., by the processor or a further processor of the controller 408), based on the value (or values) of the one or more test parameters, the transmission of light passing between the probed input port 204 and the corresponding output port 206.

[0192] In embodiments of the method 1800 in which the probed input port 204 of the optical layer 202 (or further optical layer 202) under test is optically coupled to multiple output ports 206 via respective optical paths, the detecting at S1804 may comprise detecting the presence or absence of the light output LO from each of the corresponding multiple output ports 206. In such embodiments, the verifying at step S1806 comprises determining a value (or values) of one or more test parameters associated with the detected light (or absence thereof), and verifying, based on the value(s) of the one or more test parameters, the transmission of light passing between the probed input port 204 and the corresponding multiple output ports 206.

[0193] In some embodiments of the method 1800, the verifying at step S1806 is done based on, or comprises, comparing the value(s) of the one or more test parameters against the value(s) of the one or more respective reference parameters.

[0194] In some embodiments, the verifying at step S1806 is done based on the value(s) of the one or more test parameters 1700 and on a value (or values) of one or more respective reference parameters 1702.

[0195] In some embodiments, the verifying at step S1806 is done based on, or comprises, using both the spatial property 1700a and the reference spatial property 1702a to determine an indication of the extent to which the waveguide 208 coupling the probed input port 204 to the output port 206 (or each waveguide 208 coupling the probed input port 204 to the corresponding multiple output ports 206).

[0196] In some embodiments, the verifying at step S1806 comprises using both the optical property 1700b and the reference spatial property 1702b to determine an indication of theextent to which the waveguide 208 is coupling the probed input port 204 to the output port 206 (or each waveguide 208 is coupling the probed input port 204 to the corresponding multiple output ports 206). In such embodiments, the verifying at step S1806 may optionally include determining a value (or values) of the optical property 1700b based on a determined or measured value (or values) of the spatial property 1700a. In some embodiments, the method 1800 may further comprise controlling, based on the verifying at step S1806, one or more components of the system 200 upstream of the optical layer 202, e.g., the laser 210, and / or the optical probe shaper 800 (if present), and / or the source array of lenses 1600 (if present). For example, the controller 408 may reconfigure the one or more upstream components in an attempt to more accurately probe (i.e., irradiate) the same input port 204. That is, the feedback loop of the system 200 may attempt, in response to the verifying at step S1806, to minimise a discrepancy identified in the comparison of the value(s) of the one or more test parameters against the value(s) of the one or more reference parameters (or, phrased differently, to maximise the chance of positive verification at subsequently-iterated step S1806).

[0197] In some embodiments, the method 1800 may further comprise controlling, based on the verifying at step S1806, one or more components of the system downstream of the optical layer 202, e.g., the detector 212, and / or the detector array of lenses 1602 (if present), and / or a diffusive element. For example, the controller 408 may reconfigure the one or more downstream components in an attempt to minimise a discrepancy identified in the comparison of the value (or values) of the one or more test parameters against the value (or values) of the one or more reference parameters (or, phrased differently, to maximise the chance of positive verification at subsequently-iterated step S1806).

[0198] Thus, a method of testing a single input port of an optical layer for an OPCB is provided. Figure 19 depicts steps of a method 1900 of testing a plurality of input ports 204 of an optical layer in accordance with an optical layer 202 (or further optical layer 202) described above in which a plurality of input ports is optically coupled to a respective plurality of output ports. The plurality of input ports 204 may consist of all of the input ports 204 of the optical layer 202, or a subset 600 of a greater plurality of input ports 204.

[0199] The method 1900 comprises, at step S1902, aiming light from the laser 210 (or other suitable light source) to provide, over the first air interface (i.e., the source air interface), the light input LI towards the plurality / subset of input ports 204 of the optical layer 202. In some embodiments, the aiming the light at step S1902 may comprise splitting light L from the laser 210 via the optical beam splitter 800, thereby to form a plurality of beams of the light input LI to the plurality of input ports 204. Additionally or alternatively, the aiming the light at step S1902 may optionally comprise redirecting light L from the laser210 via the optical beam splitter 800, thereby to form a plurality of beams of the light input LI to the probed plurality of input ports 204. In some embodiments, the method 1900 may comprise focussing the light input LI (whether formed of a single beam or plurality of beams) to the probed plurality / subset of input ports 204.

[0200] The method 1900 comprises, at step S1904, detecting by the detector 212, over the second air interface (i.e., the detector interface), the presence or absence of the light output LO from a corresponding plurality of output ports 206 of the optical layer 202. In some aspects, the detector 212 acquires one or more planar images of the Optical PCB in response to the testing light.

[0201] It will be understood that, by virtue of steps S1902 and S1904, the method 1900 does not require optical wiring, and implement apparatuses with larger tolerances and lower operation costs.

[0202] More particularly, the optically-wireless nature of embodiments disclosed herein overcomes the expense and inconvenience associated with disassembly or wholesale replacement of OPCBs whose optical layers are suspected to include defects. It also allows the implementation of readily-available, low-cost light-sources (e.g., VCSEL lasers) and detection means (e.g., planar detectors, such as infra-red cameras, or point detectors). The larger alignment tolerances of embodiments disclosed herein provide a faster, simpler, and more cost-effective means to iteratively test a large number of I / O port combinations In some embodiments, the method 1900 may comprise, prior to the detecting at step S1904, focussing the light output LO (whether formed of a single beam or plurality of beams) by the detector array of lenses 1602 onto the detector 212.

[0203] The method 1900 comprises, at step S1906, verifying, based on the detecting at step S1904, the transmission of light passing between the probed plurality / subset of input ports 204 and the corresponding plurality of output ports 206.

[0204] In some embodiments of the method 1900, the verifying at step S1906 may be based on, or comprise, steps analogous to those described in detail above with reference to embodiments of the system 200 and the method 1800.

[0205] In some embodiments, the method 1900 may comprise controlling, e.g., by the feedback loop of the system 200, one or more components upstream of the optical layer 202 and / or one or more entities downstream of the optical layer 202, thereby to minimise a discrepancy identified in the comparison of the value(s) of the one or more test parameters against the value(s) of the one or more reference parameters, in a manner analogous with that described above with reference to the system 200 and the method 1800.By way of example, the verifying at step S1906 may result in the controller 408 reconfiguring the one or more upstream components in an attempt to probe (i.e., irradiate) a new / different plurality (e.g., a different subset 600) of input ports 204. For example, the optical probe shaper 800 may be spatially reconfigured so as to split the light L output from the laser 210 in such a way as to form a plurality of beams of the light input LI which irradiates a (partly or wholly) new / different plurality / subset of input ports 204.

[0206] The method 1900 may then be subsequently iterated, each iteration being performed in respect of a (partly or wholly) different plurality / subset of input ports 204, thereby to verify, at each iterated step S1906, the transmission of light for multiple different pluralities / subsets of input ports 204.

[0207] It will thus be understood that embodiments of systems and methods disclosed herein provide the flexibility to dynamically select a subset of I / O ports for testing, allowing iterations which probe different subsets of ports and / or paths, thereby to quickly and easily narrow down a candidate set of faulty I / O ports or faulty optical paths to a particular offending port(s) or path(s).

[0208] Thus, a method of testing a plurality of input ports of an optical layer for an OPCB, and, in particular, iteratively testing different subsets of input ports of the optical layer, is provided.

[0209] Figure 20 depicts steps of a method 2000 of testing a plurality of optical paths within a reconfigurable optical layer, the reconfigurable optical layer being accordance with the further optical layer 202 described above with reference to Figures 13-15.

[0210] The method 2000 comprises, at step s2002, aiming light from the laser 210 (or other suitable light source) to provide, over the first air interface (i.e., the source air interface), the light input LI towards one or more input ports 204 of the optical layer 202. In some embodiments of the method 2000, the aiming the light at step S1902 may comprise splitting and / or redirecting light L from the laser 210 via the optical beam splitter 800, in a manner analogous with that described above with reference to steps S1802 and S1902. The method comprises, at step s2004, detecting by the detector 212, over the second air interface (i.e., the detector interface), the presence or absence of the light output LO from a corresponding one or more output ports 206 of the optical layer 202.

[0211] In some embodiments, the method may optionally comprise, prior to the detecting at step s2004, focussing the light output LO (whether formed of a single or plurality of beams) by the detector array of lenses 1602 onto the detector 212.The method comprises, at step s2006, verifying, based on the detecting at step s2004, the transmission of light passing between the probed plurality / subset of input ports 204 and the corresponding plurality of output ports 206.

[0212] In various embodiments, the verifying at step s2006 may be based on or comprise steps analogous to those described in detail above with reference to embodiments of system 200 and methods 1800 and 1900.

[0213] The method 2000 comprises, at step s2008, reconfiguring one or more optical pathways of the reconfigurable optical layer, thereby to result in a new one or more optical couplings between one or more input ports 204 and one or more output ports 206 of the optical layer 202. For example, one or more reconfigurable components are reconfigured to test a different optical path connected to a particular input and / or output port. The reconfiguration at step s2008 may be carried out, e.g., in a manner analogous to that described in detail above with respect to Figures 13-15.

[0214] The steps of the method 2000 may then be subsequently iterated, each iteration being performed in respect of a different one or more optical couplings between respective input port(s) 204 and output port(s) 206. At each iterated step s2006, the transmission of light for a (partly or wholly) new / different plurality / subset of optical couplings may be verified. In some embodiments, each iteration of the method 2000 may be performed to probe a set of optical couplings of which only some (e.g., one optical coupling) differ from those probed in the previous iteration(s).

[0215] In various embodiments, the method 2000 may comprise controlling, e.g., by the feedback loop of the system 200, one or more components upstream of the reconfigurable optical layer and / or one or more components downstream of the reconfigurable optical layer, thereby to minimise a discrepancy identified in the comparison of the value(s) of the one or more test parameters against the value (or values) of the one or more reference parameters, in a manner analogous to that described in detail above with reference to embodiments of the system 200 and methods 1800, 1900.

[0216] In some embodiments, each iteration of the method 2000 may, in addition to being carried out to probe different (reconfigured) sets of optical paths within the reconfigurable optical layer, be carried out to probe a (partly or wholly) new / different plurality / subset of input ports 204, thereby to verify, at each iterated step s2006, the transmission of light for multiple different plurality / subset of input ports 204.

[0217] Thus, a method of testing a plurality of optical pathways of a reconfigurable optical layer for an OPCB, and, in particular, iteratively testing different optical pathways and / or different subsets of input ports of the reconfigurable optical layer, is provided.In some embodiments of the methods 1800, 1900, 2000 described above, each of the analogous steps S1806, S1906, s2006 of verifying the transmission of light may comprise, or be based on, performing a free-path calibration to account for one or more of: an attenuation of the detected light; a dispersion of the detected light; and a diffusion of the detected light.

[0218] It will be understood that embodiments of the systems and methods disclosed herein are suitable for implementation at various stages of the PCB manufacturing process. For example, the end-user may implement the above-described systems and methods to assess the functionality of optical lines on a fully-formed OPCB. Alternatively, a manufacturer or vendor may implement the above-described systems and methods on a formed optical PCB before its integration into an electro-optical PCB. Alternatively, a manufacturer or vender may implement the above-described systems and methods on an isolated optical layer prior to formation of an optical PCB (including prior to assembly of optical modules to the OPCB, avoiding the requirement to disassemble an optical module in the case of a defect in the optical line (input-waveguide-output) of the OPCB).

[0219] Figure 21 depicts an exemplary use case of the above-described systems and methods, and more specifically an exemplary test flow 2100.

[0220] In the exemplary test flow 2100, the optical layer 202 or further optical layer 202 is tested (as described above) in isolation from any electrical layer, prior to assembly on an electrical layer.

[0221] An electrical layer of the OPCB, or electrical PCB, is fabricated at 2102. In this example, subsequently, but prior to assembly of the electrical layer onto the OPCB (i.e., prior to combination with the optical layer 202), electrical testing is performed at 2104 (e.g., as described above, or by other suitable means).

[0222] Independently, (that is, before, during, or after) the electrical layer manufacture at 2102, an optical layer 202 or further optical layer 202, in accordance with those described above, is fabricated at 2106. In this example, subsequently to the OPCB fabrication, and prior to assembly of the electrical layer onto the OPCB (i.e., prior to combination with the optical layer 202), optical testing is performed, at 2108 the fabricated OPCB, as described above. Subsequently to the fabrication, at 2102, 2106, of the PCBs, and the respective testing, at 2104, 2108, of the electrical and optical layers, the OPCB is assembled at 2110.

[0223] In this example, subsequently, optical testing may optionally be performed on one or more I / O ports of the optical layer 202 or further optical layer 202 of the assembled OPCB, as described above, but this is not essential since the functionality of both layers has already been verified.Thereafter, further printed board assembly components may be assembled (e.g., soldered) onto the OPCB assembly, at 2112, before any further assembly testing which may be carried out downstream at 2114.

[0224] Thus, a test flow is provided in which a vendor may opt to perform testing of an isolated optical layer (or smart optical layer), in isolation from any electrical layers of OPCB assembly, e.g., thereby to check or guarantee functionality of the optical layer for subsequent use in the OPCB manufacturing pipeline.

[0225] Figure 22 depicts a further exemplary use case of the above-described systems and methods, and more specifically a further exemplary test flow 2200.

[0226] In the further exemplary test flow 2200, the optical layer 202 or further optical layer 202 is tested (as described above) after assembly on an electrical layer.

[0227] An electrical layer of the OPCB is fabricated at 2202. In this example, subsequently to fabrication, but prior to assembly of the electrical layer onto the OPCB (i.e., prior to combination with the optical layer 202) electrical testing is performed at 2204 (e.g., as described above, or by other suitable means).

[0228] Independently (that is, before, during, or after) the electrical layer manufacture at 2202, the optical layer 202 or further optical layer 202, in accordance with those described above, is fabricated at 2206, but is not yet tested.

[0229] Subsequently to the fabrication, at 2202, 2206, of the layers, and the electrical testing, at 2204, of the electrical layer, the OPCB is assembled at 2208.

[0230] In this example, subsequently to assembly of the OPCB, optical testing is performed, at 2210, on the assembled OPCB, using the optical testing of an example as described above. In some examples, this optical testing at the post-assembly stage is performed in combination or in sequence with further / repeat electrical testing (as described above). Thereafter, further printed board assembly components may be assembled (e.g., soldered) onto the OPCB assembly, at 2212, before any further assembly testing which may be carried out downstream at 2214.

[0231] Thus, a test flow is provided in which a vendor may opt to perform testing only after the assembly of the optical layer with the electrical layer.

[0232] In some examples, the optical layer may be produced together with the electrical layer in such a way that it is not possible to separate the tests, and both tests are performed post-OPCB assembly. Figure 23 depicts such an exemplary test flow 2300, in which the OPCB assembly is fabricated, at 2302, in such a way that isolated testing of layers in impractical or undesirable. Thus, optical testing, in combination or in sequence with electrical testing(as described above), is performed subsequently to electro / optical PCB fabrication, at 2304. In smart-OPCB embodiments, one option to perform the optical and electrical testing in tandem, thereby to maximise the diagnostic value of the measurements taken (e.g., by cross-referencing electrical and optical results, and / or by considering the potential testresult factors described in detail above).

[0233] Thereafter, further printed board assembly components may be assembled (e.g., soldered) onto the OPCB assembly, at 2306, before any further assembly testing which may be carried out downstream at 2308.

[0234] Thus, a further test flow is provided in which a vendor may opt to perform combined or sequential testing after assembly of the optical layer with the electrical layer.

[0235] Figure 24 depicts a further exemplary use case, and more specifically a further exemplary test flow 2400.

[0236] In the exemplary test flow 2400, the optical layer 202 or further optical layer 202 is tested (as described above) in isolation from any electrical layer, prior to assembly on an electrical layer.

[0237] The electrical layer of the OPCB is fabricated at 2402. In this example, subsequently to fabrication, but prior to assembly of the electrical layer onto the OPCB (i.e., prior to combination with the optical layer 202), electrical testing is performed at 2404 (e.g., as described above, or by other suitable means).

[0238] Independently (that is, before, during, or after) the electrical layer manufacture at 2402, an optical layer 202 or further optical layer 202, in accordance with those described above, is fabricated at 2406. In this example, subsequently to fabrication, but prior to assembly of the electrical layer onto the OPCB (i.e., prior to combination with the optical layer 202), optical testing is performed, at 2408, on the fabricated OPCB, as described above.

[0239] Subsequently to the fabrication, at 2402, 2406, of the layers, and the respective testing, at 2404, 2408, of the electrical and optical layers, the OPCB is assembled at 2410.

[0240] In this example, subsequently, optical testing is again performed, at 2412, on one or more I / O ports of the optical layer 202 or further optical layer 202 of the assembled OPCB, as described above. In some examples, this optical testing at the post-assembly stage is performed in combination or in sequence with further / repeat electrical testing (as described above).

[0241] Thereafter, further printed board assembly components may be assembled (e.g., soldered) onto the OPCB assembly, at 2414, before any further assembly testing which may be carried out downstream at 2416.Thus, a test flow is provided in which a vendor may opt to perform testing of an isolated optical layer (or smart optical layer), in isolation from any electrical layers of OPCB assembly, and a (same or different) vendor may opt to perform testing of the pre-tested optical layer and / or of the pre-tested electrical layer post-assembly but before further (e.g., bespoke, irreversibly-assembled, or end-use specific) components are added.lt will be understood that embodiments of the systems and methods disclosed herein may use artificial intelligence and machine learning technologies to more quickly or accurately perform the verification (e.g., the determination or comparison of test and reference parameters), and / or to more quickly and accurately control the feedback loop to, e.g., minimise value discrepancies during verification and / or intelligently iterate the methods disclosed herein.

Claims

CLAIMS1. A method of testing an optical layer of an optical printed circuit board, OPCB, the optical layer comprising one or more input ports, one or more respective output ports, and one or more optical waveguides coupling the one or more input ports to the one or more respective output ports, the method comprising:aiming one or more light sources, over an air interface, towards the one or more input ports;detecting, over an air interface, the presence or absence of the light output from the one or more output ports of the optical layer to determine one or more test parameters associated with the presence or absence of the light; andverifying, based on the detection, the transmission of the light passing between the one or more input ports and the respective one or more output ports.

2. The method of claim 1, wherein the verifying based on the detection comprises using the one or more test parameters and one or more respective reference parameters.

3. The method of claim 2, wherein:the one or more test parameters associated with the absence or presence of light comprise a spatial property;the respective one or more reference parameters comprise a reference spatial property; andthe verifying comprises using the spatial property and the reference spatial property to determine an indication of the extent to which each optical waveguide of the respective one or more optical waveguides is optically coupling the one or more input ports to the respective one or more output ports.

4. The method of claim 3, wherein:the one or more test parameters is associated with the presence of light, and the spatial property comprises a spatial position associated with the detected light; andthe reference spatial property comprises one or both of:an expected spatial position of the one or more input ports; andan expected spatial position of the one or more output ports.

5. The method of any preceding claim, wherein one or more of:the one or more light sources are aimed to direct light to a plurality of input ports located in two-dimensions on the optical layer, anddetecting the presence or absence of the light output from the one or more output ports of the optical layer comprises detection a location of the light output in two-dimensions on the optical layer.

6. The method of any preceding claim, wherein:the one or more test parameters comprise an optical property;the respective one or more reference parameters comprise a reference optical property; andthe verifying comprises using the optical property and the reference optical property to determine an indication of the extent to which each optical waveguide of the respective one or more optical waveguides is optically coupling the one or more input ports to the respective one or more output ports.

7. The method of claim 6, wherein the verifying the transmission of the light comprises determining an indication of an optical loss associated with the passage of light between the one or more input ports and the respective one or more output ports.

8. The method of claim 6 or claim 7, wherein:the optical property comprises one or more of:an intensity of the detected light;an amplitude of the detected light;a power of the detected light;a spatial dimension of the detected light; andan angle of incidence of the detected light,the reference optical property comprises one or more of:a reference intensity of light;a reference amplitude of light.a reference power of light.a spatial dimension of light; andan angle of incidence of light.

9. The method of claim 4, wherein the expected spatial position of the one or more input and / or the expected spatial position of the one or more output ports are provided via a reference testing map comprising at least one of:a digitally created map or computer-aided design, CAD, model of the optical layer under test;one or more manufacturing specifications associated with the optical layer under test;a digitally created map or computer-aided design, CAD, model of a reference optical layer having substantially the same configuration and / or expected optical behaviour as the optical layer under test; andone or more manufacturing specifications associated with the reference optical layer having substantially the same configuration and / or expected optical behaviour as the optical layer under test.

10. The method of any preceding claim, wherein the one or more reference parameters include a reference-test parameter determined by a reference test performed prior to the method, the reference test comprising passing light along fibre optic wiring coupled to at least one of:an input port of the optical layer or reference optical layer; andan output port of the optical layer or reference optical layer.11 The method of any preceding claim, wherein:one or more optical paths in the optical layer between the one or more input ports and the respective one or more output ports may be adjusted by control of one or more interferometers disposed within the optical layer; andthe verifying based on the detection comprises verifying a configuration of the one or more interferometers.

12. The method of claim 11, further comprising :adjusting, by control of the one or more interferometers, one or more optical paths in the optical layer between the one or more input ports and the respective one or more output ports, thereby to alter one or more paths which the light traverses between the one or more input ports and the respective one or more output ports;subsequently, iterating the steps of claim 1; andverifying, based on the iterated detection, a functionality or reconfigurability of the one or more interferometers.

13. The method of claim 11, further comprising :adjusting, by control of the one or more interferometers, one or more optical paths in the optical layer, thereby to optically couple at least one of the one or more input ports to an output port other than the one or more respective output ports;subsequently, iterating the steps of claim 1; andverifying, based on the iterated detection, a functionality or reconfigurability of the one or more interferometers controlled.

14. The method of any preceding claim, wherein the aiming the one or more light sources to provide light, over an air interface, towards the one or more input ports comprises aiming the one or more light sources at an optical probe shaper configured to receive incident light and output one or more beams of the light.

15. The method of claim 14, wherein the optical probe shaper comprises an array of individually controllable mirrors configured to receive incident light and reflect the incident light the towards the one or more input ports.

16. The method of any preceding claim, further comprising one or both of:focussing, using a source array of lenses and / or a parabolic source mirror, positioned between the one or more light sources and the optical layer under test, the light towards the one or more input ports; andfocussing, using a detector array of lenses and / or a parabolic detector mirror positioned between the optical layer under test and the detector, the light towards the detector; wherein, optionallythe source array of lenses and / or the parabolic source mirror is controllable to adjust its configuration and / or the detector array of lenses and / or the parabolic detector mirror is controllable to adjust its configuration.

17. The method of claim 16, wherein:control of the optical probe shaper and control of the source array of lenses is coupled and / or simultaneous; and / orcontrol of the optical probe shaper and control of the detector array of lenses is coupled and / or simultaneous.

18. The method of any preceding claim, wherein the detector is an infra-red camera and the light detected or absent at the detector has a wavelength within the infrared spectrum.

19. The method of claim 18, wherein the light has a wavelength in the infrared band defined by the range of wavelengths of 1260 nm - 1625 nm.

20. A system for testing an optical layer of an optical printed circuit board, OPCB, the optical layer comprising one or more input ports, one or more respective output ports, and one or more optical waveguides coupling the one or more input ports to the one or more respective output ports, the system comprising:one or more light sources configured to be aimed to provide light, over a source air interface, towards the one or more input ports;a detector configured to detect, over a detector air interface, the presence or absence of the light output from the one or more output ports of the optical layer to determine one or more test parameters associated with the presence or absence of the light; anda processor configured to verify, based on the detection, the transmission of the light passing between the one or more input ports and the respective one or more output ports.

21. The system of claim 20, wherein:the processor is configured to verify the presence or absence of the light output using the one or more test parameters and one or more respective reference parameters; and / orthe processor is further configured to determine the one or more test parameters associated with the detected presence or absence of light.

22. The system of claim 20 or 21, wherein:one or more optical paths in the optical layer between the one or more input ports and the respective one or more output ports is adjustable by control of one or more interferometers disposed within the optical layer;the one or more light sources, the detector, and the processor are respectively configured to iteratively perform the aiming, detecting, and verifying; andthe processor is configured to verify, based on the iterated detection following adjustment of the one or more optical paths by control of the one or more interferometers,a functionality or reconfigurability of the one or more interferometers, a configuration of the one or more interferometers.

23. The system of claim 20 or 21, wherein:one or more optical paths in the optical layer between the one or more input ports and the respective one or more output ports is adjustable by control of one or more interferometers disposed within the optical layer;the one or more light sources, the detector, and the processor are respectively configured to iteratively perform the aiming, detecting, and verifying; andthe processor is further configured to verify, based on the iterated detection following adjustment of the one or more optical paths by control of the one or more interferometers, a functionality or reconfigurability of the one or more interferometers.

24. The system of any one of claims 20 to 23, wherein one or more of:the one or more light sources are aimed to direct light to a plurality of input ports located in two-dimensions on the optical layer, andthe detector is configured to detect the presence or absence of the light output from the one or more output ports of the optical layer at a location in two-dimensions on the optical layer.

25. A computer-implemented method for testing an optical layer of an optical printed circuit board, OPCB, the optical layer comprising one or more input ports, one or more respective output ports, and one or more optical waveguides coupling the one or more input ports to the one or more respective output ports, the computer implemented method comprising:detecting the presence or absence of the light received, over a detector air interface, from the respective one or more output ports of the optical layer to determine a respective one or more test parameters associated with the presence or absence of light; andverifying, based on the detection, the transmission of the light passing between respective input and output ports.4926. A computer-readable medium having stored thereon computer-executable instructions which, when executed by a computer, cause the computer to carry out the method of any preceding method claim.

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