Optical inspection system with multi-signal modulation and demodulation

Abstract

Optical inspection system for transmitting signals with high accuracy from a device under test (DUT) to a measuring instrument. The system receives a differential input signal and separates it into a high-frequency (HF) and a low-frequency (LF) component. Each component is independently modulated using different analog modulation techniques and transmitted via separate optical fibers. The architecture provides galvanic isolation between the input and output devices and enables independent transmission of signal components optimized for bandwidth and accuracy. The signals are demodulated, delayed, and recombined in the analog domain to generate a reconstructed output signal across the entire bandwidth.

Description

CROSS-REFERENCE TO A RELATED REGISTRATION

[0001] This application claims priority over the preliminary US application No. 63 / 674,276, entitled Optical Probing System with Multi-Signal Modulation, filed on July 23, 2024, the entire contents of which are incorporated herein by reference. DISCLOSURE AREA

[0002] The present invention relates to the field of test and measurement probes, in particular to an optical-analog optical testing system with multiple analog signal modulation and demodulation. BACKGROUND TO THE DISCLOSURE

[0003] The advent of wide-bandgap semiconductor technologies—such as gallium nitride (GaN) and silicon carbide (SiC)—has enabled significant improvements in power conversion efficiency and switching performance. However, these advantages are offset by drastically increased switching speeds and voltage rise rates, which place high demands on signal bandwidth, dynamic range, and measurement accuracy. Rapid switching operations, especially at high common-mode voltages, can compromise signal integrity and pose challenges even for high-end measurement systems.

[0004] Reliable in-situ measurement of such signals is essential not only for design validation but also for the ongoing refinement of topologies, gate driver circuits, and protection mechanisms. Oscilloscopes, in conjunction with appropriately designed sensors, remain the most important instruments for capturing and analyzing high-speed electrical waveforms in these environments.

[0005] Conventional oscilloscope probes transmit analog signals to an oscilloscope input via a direct electrical path. These signals are then digitized and visualized for analysis. While electrical probes offer convenience and familiarity, their susceptibility to ground loop interference and common-mode transients can lead to signal distortion, especially in high-side measurements where reference potentials can fluctuate significantly.

[0006] To address these challenges, galvanically isolated probes have been developed. These systems typically include a probe for acquiring differential signals, an intermediate isolation mechanism—such as an optical transmission device—and an electrical output interface compatible with oscilloscopes. By eliminating the direct conductive path between the probe and the measurement equipment, such solutions suppress ground currents and improve common-mode rejection, resulting in cleaner signal acquisition under noisy or high-potential conditions.

[0007] Despite these advantages, optical signal transmission systems introduce a number of new technical compromises. Signal modulation techniques used to convert electrical waveforms into optical signals—particularly in analog optical links—can suffer from limited bandwidth, distortion due to offset mismatches, and nonlinear attenuation under temperature or mechanical stress. These impairments typically result in amplitude compression, phase shifting, or transient mismatches between different parts of the signal spectrum.

[0008] Accordingly, there remains a need for improved signal transmission systems capable of maintaining the full bandwidth, accuracy, and integrity of high-speed differential signals under demanding common-mode and environmental conditions. Ideally, such systems offer robust isolation, precise offset handling, and coordinated delay management without compromising modulation linearity or signal fidelity. SUMMARY OF THE DISCLOSURE

[0009] A signal transmission system is required that enables accurate and reliable acquisition of electrical differential signals, particularly in environments characterized by rapid switching, high common-mode voltages, and electrical noise. The system ensures galvanic isolation between the probe and the measuring instrument while offering a wide bandwidth, low distortion, and robust common-mode rejection.

[0010] In certain embodiments, a signal transmission architecture receives and transmits an analog input signal from a device under test (DUT). The signal is processed along several frequency-optimized paths, such as a main path for full-bandwidth signal transmission and an auxiliary path optimized for high-precision, low-frequency components. These signals are modulated using analog techniques such as frequency modulation (FM), amplitude modulation (AM), or other suitable methods and transmitted over galvanically isolated connections such as optical fibers.

[0011] The system includes circuitry for applying and removing analog DC offsets to ensure compatibility with modulators and prevent signal limiting. It features delay compensation elements to equalize the propagation delays of signals processed along separate paths. Recombination of these signals at the receiver results in a full-bandwidth, high-integrity analog representation of the original signal, suitable for oscilloscope-based visualization and analysis.

[0012] In some embodiments, the system supports a variety of signal paths, enabling modular expansion and optimization across multiple frequency bands or functional purposes. Communication and control signals are exchanged via an isolated communication channel. In some embodiments, the entire system is housed in a mechanically integrated unit with electrically isolated power sections.

[0013] The revealed architecture offers significant improvements in terms of measurement accuracy, noise immunity and design flexibility, and is therefore particularly well suited for the characterization of high-speed power electronics, wide-bandgap semiconductors and other advanced switching systems operating in electrically demanding environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings illustrate several embodiments of the disclosure. Together with the description, the drawings serve to explain the principles of the disclosure.

[0015] Fig. Figure 1 is a schematic representation of an exemplary system showing signal transmission, modulation, demodulation and reception.

[0016] Fig. Figure 2 is a schematic representation of the exemplary system from Fig. 1 with a multitude of analog signal offset stages.

[0017] Fig. Figure 3 is a schematic representation of an optical inspection system with separate analog-optical main and auxiliary signal modulation and demodulation devices.

[0018] Fig. Figure 4 is a schematic representation of an optical inspection system with separate analog-optical main and auxiliary signal transmission devices and an additional communication link.

[0019] Fig. Figure 5 is a schematic representation of an optical inspection system with one main and two auxiliary signal transmission devices and a communication link.

[0020] Fig. Figure 6 is a schematic representation of an optical inspection system with a housing and a special insulating unit.

[0021] Fig. Figure 7 is an illustration of an optical inspection system. REFERENCE NUMBERS OF THE DRAWINGS 1 Optical inspection system 3 Amplifier or attenuator 5 Band-splitting filter with defined cutoff frequency 7 Low-frequency (LF) demodulation device 8 Auxiliary signal component 9 High-frequency (HF) demodulation device 10 Main signal component 11 NF analog signal transmitting diode (AC-coupled) 13 RF analog signal transmitting diode (AC-coupled) 15 LF fiber optic cable 17 RF optical fibers 19 NF analog signal receiver diode (AC-coupled) 21 RF analog signal receiver diode (AC-coupled) 23 LF demodulation device 25 RF demodulation device 27 Mixing or analog recombination circuit 29 Attenuator with 50-ohm or 1-megaohm termination 31 LF analog signal offset stage 33 HF analog signal offset stage 35 NF analog signal de-offset stage 37 HF analog signal offset stage 39 Analog signal input device 41 DUT 43 Input network 45 Main signal transmission device 47 Auxiliary signal transmission device 49 Main signal transmission path 51 Auxiliary signal transmission path 53 Main signal receiving device 55 Auxiliary signal receiving device 57 Output network 58 Differential Signal 59 Interface Box 60 Galvanic isolation barrier 61 Communication path 62 Fiber optic connection 63 Communication link (probe side) 65 Communication connection (interface box side) 66 Component Communication Signal 67 cases 69 BNC output 71 Power supply of the interface box 73 Analog signal output device 75 Battery compartment of the probe 77 BNC type electrical connection device 79 power cables 81 Probe tip 83 3D Positioner Stands 85 Electrically insulated connection socket 87 First Auxiliary Signal Transmission Device 88 First auxiliary signal component 89 Second auxiliary signal transmission device 90 Second auxiliary signal component 91 First auxiliary signal receiving device 93 Second auxiliary signal receiving device 95 First Auxiliary Signal Transmission Path 97 Second auxiliary signal transmission path 99 Single analog output signal DETAILED DESCRIPTION

[0022] The present disclosure generally provides optical testing systems comprising a galvanically isolated probe that converts an electrically analog signal into an optically analog signal, an optically analog signal transmission device, and an electrically analog signal output that can be detachably connected to an oscilloscope. Exemplary probes are typically differential optical probes suitable for measuring high-frequency differential signals at a specific DC offset voltage, such as that observed on the high-side of power modules. Such probes generally include a probe tip with a suitable interface for connecting to the device under test.

[0023] The following sections provide detailed descriptions of examples from the disclosure. The description of the preferred and alternative examples is merely illustrative, and it is understood that variations, modifications, and adaptations may be obvious to the person skilled in the art. It is therefore self-evident that the examples do not limit the scope of aspects of the underlying disclosure as defined in the claims.

[0024] The terms "high frequency (HF)" and "low frequency (LF)" are to be understood in a broad sense. More specifically, these terms can be understood as "primary frequency" and "secondary / auxiliary frequency." Instead of using a single "unified modulation" for different frequencies, several separate frequency modulations are used, each tailored to the respective frequency band.

[0025] The analog-electrical input signal is detected on the test object by the optical inspection system using its analog-electrical signal input device. The analog-electrical signal can be amplified. The originally measured total analog-electrical signal is then split into analog-electrical signal components, such as a main analog-electrical signal and an auxiliary analog-electrical signal. This can be achieved by the input device circuit of this disclosure. The analog-electrical signals can also be amplified and / or processed separately via the input device circuit. The resulting analog-electrical signals are converted into analog-optical signals using transmitting diodes, transmitted to the analog-electrical signal output device, received there, and converted back into analog-electrical signals together with the analog-electrical output signal.

[0026] The optical inspection system can include an analog-electrical signal input device, an analog-electrical signal output device, and a connection between the analog-electrical signal input device and the analog-electrical signal output device.

[0027] The analog-electrical signal input device may include an input circuit configured to split the analog-electrical signal into two signals: a primary analog-electrical signal and an auxiliary analog-electrical signal. The primary analog-electrical signal may be a full-bandwidth signal, which may also contain direct current. The auxiliary analog-electrical signal may be the low-frequency and direct current component of the originally measured signal. The analog-electrical signal input device may also include an interface for transmitting communication signals, enabling the transmission of control and safety signals. The communication signal transmission device is optional.

[0028] The galvanic isolation barrier, the connection between the analog-electrical signal input device and the analog-electrical signal output device, can comprise multiple fiber optic cables. Each fiber optic cable can represent an analog-optical signal transmission device. The galvanic isolation barrier can include a main path (HF) connector, which can be a fiber optic cable, an auxiliary path (LF) connector, which can be a fiber optic cable, and an optional optical communication device for transmitting control and safety signals. The optical communication device comprises an analog-optical signal transmission device.

[0029] The analog-electrical signal output device may include an output device circuit. The output device circuit may be configured analogously to the input device circuit. For example, the output device circuit may connect a main signal receiving diode, an auxiliary signal receiving diode, and a control signal receiving diode.

[0030] The exemplary embodiments shown in the figures depict the components of the system architecture in a recommended sequence along a galvanically isolated signal path from a device under test to an analog output signaling device such as an oscilloscope, and are optimized for signal reception, filtering, modulation, transmission, recombination, demodulation, and output. Other sequences and other input / output devices may be provided. However, the system disclosed is preferably used for the fast and complete transmission of the device under test signal to an analysis device, in particular an oscilloscope. The system improves signal integrity and robustness compared to conventional single-path optical transmission systems. Detailed descriptions of the drawings

[0031] Fig. Figure 1 shows an embodiment of a signal transmission system 1. The system 1 is configured to receive a differential input signal from a device under test (DUT) and to transmit this signal via frequency band separation, optical modulation and recombination to an analog signal output device, such as an oscilloscope, while maintaining high signal fidelity and isolation.

[0032] The differential input signal is first received by an amplifier or attenuator 3, which can amplify or attenuate the input signal depending on its amplitude. The processed signal is then passed on to a band-splitting filter 5.

[0033] The band-splitting filter 5 can be configured to split the differential input signal into an auxiliary signal component 8, which can also be a low-frequency component, and a main signal component 10, which can be a high-frequency component, based on a specific cutoff frequency. In one embodiment, the cutoff frequency is approximately 20 kHz, although other values ​​can be chosen depending on the intended application or system bandwidth. The filter can have a transition band or two corner frequencies to ensure minimal insertion loss and signal degradation at the interface between the low-frequency and high-frequency signal paths. The filter characteristics are selected to maintain phase and amplitude fidelity across the entire signal spectrum while simultaneously ensuring effective separation of the frequency components for the respective modulation and transmission.

[0034] The audio frequency (AF) component is routed to an AF modulator 7, which modulates the AF signal for optical transmission. The modulated signal is then transmitted via an AF analog signal transmitter diode 11, which includes an AC-coupled light source (e.g., a laser diode or LED) that converts the modulated electrical signal into an optical signal. This optical signal is transmitted via an AF fiber optic cable 15 to an analog AF signal receiver diode 19, which includes an AC-coupled photodiode that converts the incoming optical signal back into an electrical signal.

[0035] The electrical signal is then demodulated by an AF demodulator 23 to recover the low-frequency signal component. The analog modulation technique used in the auxiliary signal path can include, among others, frequency modulation (FM), amplitude modulation (AM), phase modulation (PM), pulse width modulation (PWM), pulse frequency modulation (PFM), or pulse density modulation (PDM). These modulation methods are advantageous for transmitting precise amplitude or timing information and can be selected depending on the type of signal and the desired fidelity. The auxiliary path can also transmit reference waveforms or other analog content outside the primary signal bandwidth for calibration or correction purposes.

[0036] In certain embodiments, the primary signal path uses an amplitude-modulated analog signal, while the auxiliary path uses a complementary analog modulation format such as FM, PM, or PWM to mitigate the effects of attenuation drift, DC offset, or gain variations that may occur in the primary path due to changes in fiber orientation, movement, temperature, or component aging. In this configuration, the audio frequency (AF) or auxiliary signal path may not support the full bandwidth of the input signal, but it carries highly accurate information used to reconstruct or stabilize the output. For example, the auxiliary signal can be used to correct deviations in the primary signal path, such as offset drift, gain inaccuracies, or bandwidth irregularities.When combined in the mixing or analog recombination circuit 27, the main and auxiliary paths enable higher overall signal fidelity than could be achieved with a single analog transmission path alone. The recombination circuit thus integrates both the high-speed main content and the highly integrated auxiliary content to generate a comprehensive and corrected analog output signal for oscilloscope-based analysis. Simultaneously, the RF component is routed to an RF modulator 9, modulated, and passed to an RF analog signal transmitting diode 13, which converts the modulated RF signal into an optical signal. The optical signal is transmitted via an RF fiber optic cable 17 to an analog RF signal receiving diode 21, which performs an opto-electrical conversion. The output signal is processed by an RF demodulator 25 to restore the high-frequency signal content.

[0037] Modulation can be achieved using various modulation techniques. Instead of feeding the modulated RF signal and the modulated AF signal into their respective optical fibers, a common optical fiber can be used. An AF signal path can be used to correct gain, drift, offset, or bandwidth distortions in the RF path.

[0038] The demodulated AF and RF signals are then passed to a mixer or analog recombination circuit 27, which reconstructs the signal across the entire bandwidth in the analog domain. The recombined signal is then passed through an attenuator 29, which is configured for either a 50-ohm or a 1-megaohm termination, depending on the impedance requirements of the connected oscilloscope or measuring instrument.

[0039] The separate provision of the two signal paths—either via one or more optical fibers—offers the advantage of more efficient and independent tuning. This enables higher DC accuracy and improved flatness in the low-frequency range, as adjustments can be made without affecting the high-frequency signal. As a result, the system achieves an extended overall bandwidth, since each path can be independently optimized for its respective frequency range.

[0040] Fig. Figure 2 shows a variant of the exemplary embodiment of Fig. 1. The in Fig. Variant 2 shown includes dedicated analog offset and de-offset stages in both the low frequency (LF) and high frequency (HF) signal paths to accommodate modulation limitations and optimize signal linearity across the optical link.

[0041] In the low-frequency range, the AF signal is passed to an analog AF signal offset stage 31, which applies a predefined offset or level shift to the signal. This ensures compatibility with the subsequent modulation stage and prevents clipping during modulation of the laser diode current. The offset-adjusted signal is then passed to the AF modulator 7 and subsequently to the AF analog signal transmitting diode 11, which is AC-coupled and configured to convert the modulated electrical AF signal into an optical signal. The optical signal is transmitted via an AF fiber optic cable 15 to an AF analog signal receiver diode 19, which converts the optical signal back into the electrical range.The resulting signal is demodulated by an AF demodulator 23 and then passed through an AF analog signal decompensation stage 35, which removes the previously applied offset and resets the signal to its original baseline.

[0042] In the high-frequency range, the RF signal is passed through an analog RF signal offset stage 33, which performs an analog offset operation to prepare the RF signal for high-speed optical modulation. The offset signal is then processed by the RF modulator 9 and converted into an optical signal by the RF analog signal transmitting diode 13. The optical RF signal is transmitted via an RF fiber optic cable 17 to an analog RF signal receiving diode 21. After photodetection, the electrical signal is demodulated by an RF demodulator 25, followed by an RF analog signal removal stage 37, which reverses the applied offset and restores the original signal level.

[0043] The offset, or level shift, as well as the analog offset operation, can be a voltage offset, also known as a DC bias shift. This DC bias voltage can be added to center the signal (e.g., shifting -2V to +2V signals into a 0-4V window). After demodulation, the bias voltage is subtracted to restore the original signal levels.

[0044] The outputs of the AF and HF de-offset stages (35 and 37, respectively) are combined in the mixer or analog recombination circuit 27 to reconstruct the signal across the entire bandwidth. This composite signal is then passed to an attenuator 29, which can be configured for a 50-ohm or 1-megaohm termination to match the impedance of the connected measuring instrument.

[0045] In certain embodiments, the system also includes delay compensation stages located near the mixer or analog recombination circuit 27. These may contain one or more first-order (PT1) or second-order (PT2) analog filter elements configured to compensate for propagation delay differences between the low-frequency and high-frequency signal paths. Such differences can arise from unequal propagation delays caused by variations in the properties of the optical diodes, the fiber length, or the response time of the modulator.

[0046] The delay compensation stages can be integrated before, after, or within the recombination circuit 27 and can include passive or active analog filters that serve to equalize the signal arrival times and maintain phase coherence between the frequency components. In one embodiment, the AF path is slightly delayed with a PT1 filter to match it to the faster optical RF transmission channel. In another embodiment, the RF path includes a PT2 element for simultaneous compensation of group delay and bandwidth.

[0047] In Fig. 3 is a generalized embodiment of the in Fig. 1 and Fig. The signal transmission architecture shown in Figure 2 is shown. The system comprises a probe 2 and an interface box connected via optical transmission paths. The probe receives an input signal from a device under test (DUT) 41 via an input network 43, which can include signal conditioning, amplification, attenuation, and frequency separation, as shown in Figure 2. Fig. 1 and Fig. 2 described.

[0048] The input signal is processed in parallel by a main signal transmission device 45 and an auxiliary signal transmission device 47. The main signal transmission device 45 corresponds functionally to the high-frequency (HF) signal path and comprises an analog signal offset stage, a high-frequency modulator, and an optical transmission device. The auxiliary signal transmission device 47 corresponds functionally to the low-frequency (LF) signal path, which comprises a low-frequency offset stage, a low-frequency modulator, and an optical LF transmitter.

[0049] The main signal and the auxiliary signal are transmitted via a main signal transmission path 49 and an auxiliary signal transmission path 51, respectively, which, as already described, may contain optical fibers. These signals are received in the interface box by a main signal receiving device 53 and an auxiliary signal receiving device 55, each of which receives the signal described in the Fig. 1 and Fig. 2 described RF and LF photodetectors, demodulators and de-offset stages correspond to.

[0050] In the main signal path, the input network 43 is designed to be directly connected to the device under test (DUT) 41 and to condition the received differential input signal for high-precision transmission to the receiver circuit. The input network 43 may include a broadband amplifier, an attenuator, or other active or passive circuits suitable for matching the signal level and impedance to the transmission system. Importantly, the main path is configured to preserve the full bandwidth of the incoming signal, including high-speed transients and the frequency component, and is therefore optimized for linearity and bandwidth rather than filtering or precision scaling.

[0051] The output of the input network 43 is routed through the main signal transmission device 45, which prepares the signal for optical or galvanically isolated transmission via the main signal transmission path 49 and finally reaches the main signal receiving device 53. The output stage of the input network can be specifically adapted to the interface with the transmitter or modulator input to ensure signal integrity and impedance matching across the system boundary. This allows the system to deliver the full bandwidth of the signal under test to the oscilloscope or measuring device for high-speed waveform acquisition and analysis.

[0052] The auxiliary signal transmission path 51 can be configured to connect to the input network 43 and provide a high-accuracy version of the input signal. This version of the signal is transmitted to the receiving end (interface box-side end) using an analog modulation technique such as FM, AM or PM, PWM, PFM, PDM, or another analog modulation technique that can preserve the accuracy of the signal but may not support the full bandwidth of the input signal.

[0053] The split amplifier design allows for independent optimization of each path, ensuring optimal performance for the required high-speed and low-frequency signals and reducing the influence of environmental factors. Accordingly, the design can include circuitry for selecting between the (n+1) paths based on input signal characteristics or user preferences.

[0054] The recovered signals are combined in an output network 57, which may also include analog recombination circuits, delay compensation stages (e.g. PT1 / PT2) and an attenuator for connection to standard input impedances of test equipment (e.g. 50 ohms or 1 megaohm).

[0055] In a preferred embodiment, both the main signal transmission path 49 and the auxiliary signal transmission path 51 are implemented using optical fibers, thereby achieving galvanic isolation and enabling high-quality signal transmission over long distances with minimal electromagnetic interference. The main and auxiliary signals can be transmitted via separate optical fibers or, alternatively, multiplexed over a single optical fiber using wavelength division multiplexing (WDM) or other multiplexing techniques such as polarization, time-domain, or mode-division multiplexing.

[0056] Although optical fibers are the preferred transmission medium, other galvanically isolated transmission methods can also be used, including, but not limited to: transformer-coupled links, wireless transmission, microwave transmission, or modulation-based techniques such as mixer-based upconversion, quadrature amplitude modulation (QAM), or related analog or digital coding methods. These alternatives may be suitable depending on the system-level trade-offs regarding bandwidth, complexity, cost, or mechanical integration.

[0057] Furthermore, although the embodiments described above primarily describe separate transmission channels for the main signal, the auxiliary signal, and the communication path, in some embodiments these three paths (main, auxiliary, and communication path) can be transmitted over a single medium, such as a shared fiber optic or RF link, using suitable multiplexing or modulation techniques. Conversely, dedicated physical separation, such as three individual optical fibers or, more generally, n+1 isolated transmission paths, remains within the scope of this disclosure and may offer advantages in signal integrity, isolation, or system modularity.

[0058] In Fig. Figure 4 shows another embodiment of the signal transmission system. Fig. 4 builds on the in Fig. 3 described embodiment by incorporating a bidirectional communication channel across the galvanic isolation barrier to support additional control, synchronization and configuration signals between the probe and the interface box.

[0059] As in the previous embodiment, a differential signal 58 is received from a device under test (DUT) 41 and passed through an input network 43 located in a probe. The input network 43 may include impedance matching circuits, filtering, and signal conditioning components (not shown).

[0060] The processed signal is split and forwarded in parallel to a main signal transmission device 45 and an auxiliary signal transmission device 47. The main signal transmission device 45 is configured to transmit the high-frequency (HF) component of the signal via a main signal transmission path 49 to a main signal receiving device 53 within the interface box. Similarly, the auxiliary signal transmission device 47 transmits the low-frequency (LF) component of the signal via an auxiliary signal transmission path 51 to an auxiliary signal receiving device 55.

[0061] The recovered signals are combined and processed in output network 57, as described previously. In the implementation according to Fig. 4 The system also includes a communication path 61 that spans the galvanic isolation barrier and facilitates the exchange of control, calibration, timing and / or diagnostic data between the probe and the interface box.

[0062] A communication connection 63 is provided on the probe side to send or receive such data via the communication path 61. A corresponding communication connection 65 is provided on the interface box side. The communication path 61 can be implemented via an optically isolated digital communication channel, a wireless interface, or another galvanically isolated interface.

[0063] The communication system can operate independently of the main and auxiliary signal transmission paths to support calibration routines, gain or offset control, propagation delay diagnostics, synchronization pulses, probe identification, or other system-level functions. This bidirectional communication architecture increases flexibility, configurability, and reliability in measurement scenarios requiring adaptive control or closed-loop behavior.

[0064] In Fig. Figure 5 shows a generalized representation of the signal transmission system. Fig. 5 builds on the two-path architecture of the Fig. 1 and Fig. 2 and the modular framework of Fig. 3 and Fig. Section 4 introduces the possibility of splitting and processing the input signal into n different signal transmission paths, where n is an integer greater than or equal to one. This generalized architecture enables improved flexibility, scalability, and signal fidelity in scenarios where more than two frequency bands or signal components need to be independently acquired and transmitted. For example, the transmission, transmission path, and receiver of a first and a second auxiliary signal (87, 89, 91, 93, 95, 97) are shown, along with the components of the main signal and the communication path.

[0065] As in previous embodiments, a differential signal is received from a device under test (DUT) via an input network 43 located in a probe. The input network 43 may include circuits for impedance matching, filtering, attenuation, and frequency band separation. The processed signal is then split and routed to a main signal transmission device 45 and a plurality of auxiliary signal transmission devices. Each transmission device is configured to process and modulate a specific subband or component of the overall signal.

[0066] The main signal and each auxiliary signal are transmitted via appropriate optical or galvanically isolated signal transmission paths. In the illustrated embodiment, these comprise a main signal transmission path 49 and auxiliary signal transmission paths. These transmission paths can include optical fibers, RF links, or other isolated communication media.

[0067] On the interface box side, the signals are received by a corresponding set of receivers, including a main signal receiving device 53 and auxiliary signal receiving devices. Each receiver performs opto-electrical conversion, demodulation, and optional signal recovery (e.g., offset removal or delay compensation), as previously described in conjunction with the Fig. 1 and Fig. 2 described.

[0068] The resulting signal components are fed to an output network 57, which may include summing circuits, delay adjustment, gain control, and impedance matching. The output network reconstructs the full-bandwidth signal in the analog domain as a single analog output signal, which is sent to an analog signal output device. However, the output network can also supply the components separately to an analog signal output device.

[0069] A communication path 61 and corresponding communication connections 63 and 65 (located in the probe head and the interface box, respectively) are also included to facilitate the bidirectional exchange of control, configuration, synchronization, and diagnostic information across the galvanic isolation barrier. These can operate independently of the signal transmission paths.

[0070] The in Fig. The architecture shown in Figure 5 allows for modular expansion of the transmission system. In one embodiment, for example, the signal can be split into three or more frequency bands using an extended band-splitting filter and routed to the corresponding transmission paths. In other embodiments, auxiliary channels can be reserved for special monitoring functions, noise analysis, common-mode tracking, or differential signal validation. One embodiment can include circuitry for selecting between the paths (n+1) based on the input signal characteristics or user-defined preferences.

[0071] In Fig. Figure 6 shows another embodiment of the signal transmission system. Fig. 6 builds on the one in the Fig. 3, Fig. 4 to Fig. 5 described system architecture by containing a single physical enclosure 67 that includes both the signal transmission and reception circuitry, maintaining the galvanic isolation barrier 60 between the device under test side and the output side of the system.

[0072] In the illustrated embodiment, the signal transmission system is housed in a single enclosure that forms part of a compact isolation unit. The isolation unit includes an input interface configured to receive analog signals from a device under test (DUT). The DUT signal is routed to an input network 43, which can perform impedance matching, attenuation, and band-sharing functions as described in previous embodiments.

[0073] The input signal is then routed to a main signal transmission device 45 and an auxiliary signal transmission device 47, which each process the high-frequency and low-frequency (or otherwise separated) signal components. These components are transmitted via the respective main and auxiliary signal transmission paths (49 and 51), which cross the galvanic isolation barrier and are connected to the corresponding main and auxiliary signal receiving devices 53 and 55.

[0074] As in Fig. A communication path 61 and associated communication links 63 and 65 are provided to enable the bidirectional exchange of control, configuration, and diagnostic data between the isolated probe-side circuitry and the output-side processing circuitry via a transmitted communication signal component 66. This communication path is galvanically isolated from the main and auxiliary signal domains and can be implemented optically, capacitively, or wirelessly.

[0075] The housing 67 provides mechanical protection and shielding against environmental influences for all components, while maintaining separate electrical areas on both sides of the galvanic isolation barrier.

[0076] In some embodiments, the housing can be designed as a two-part shell or multi-chamber housing that physically separates the transmission and receiver sections while maintaining optical or isolated signal paths between them. The processed and recombined signal is routed through an output network 57, which provides final signal conditioning and impedance matching before the signal is passed to an output interface, such as a BNC connector. The output interface is electrically isolated from the device under test (DUT) input, making the system well-suited for investigating high-voltage environments or systems with floating ground potentials.

[0077] In Fig. Figure 7 shows an exemplary implementation of an optical test system 1. The system corresponds to the one described in the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 to Fig. Figure 6 shows and describes the architectural embodiments and is illustrated in an applied configuration comprising an analog signal input device such as an optical probe 39, a fiber optic link 62, an interface box 59, a power supply for the interface box 71, and an oscilloscope 73. The probe includes a probe tip 81 configured to make contact with a device under test (not shown). The probe is held in position by an adjustable 3D positioner 83, which includes an electrically isolated socket 83.

[0078] In the illustrated embodiment, a probe 39 comprises a housing containing the analog signal conditioning and transmission circuitry, including a main signal transmission device and one or more auxiliary signal transmission devices, as previously described. The probe 39 is configured to be galvanically isolated from the measuring equipment and the power supply and, in this example, is powered by a battery inserted into the probe's battery compartment 75. This local power source allows the probe 39 to remain electrically isolated while still powering internal components such as analog signal shifting stages, modulators, and optical transmitters. In an alternative embodiment, a power-over-fiber adapter can be inserted into the probe's battery compartment instead of a battery, enabling continuous operation of the probe while maintaining galvanic isolation.

[0079] The probe is optically connected to the interface box 59 via one or more fiber optic cables located in the fiber optic connection 62. These one or more fiber optic cables form the main and auxiliary signal transmission paths that bridge the galvanic isolation barrier. These paths correspond to those described in the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 to Fig. The interface box 59 comprises main and auxiliary signal receiving devices, a communication link, and an output network, as previously described. In this implementation, the interface box is connected to an oscilloscope via a BNC connector 77, allowing the recovered and recombined signal to be displayed, analyzed, or recorded.

[0080] The interface box 59 is powered by an external power supply 71, which is connected to the interface box 59 via a power cable 79. This power supply provides the necessary electrical power for the operation of the receiver circuits, demodulators, delay compensation elements, recombination circuits, and output driver stages. The system architecture thus supports fully isolated signal acquisition with independent power supplies for the probe and the interface box.

[0081] The in Fig.The embodiment shown in Figure 7 serves as an illustrative example of how the modular optical scanning architecture disclosed in previous figures can be implemented in a real laboratory or test environment. The combination of galvanic isolation, independent power sections, optical signal paths, and standard output interfaces such as BNC enables the system to reliably and accurately acquire signals under high-voltage and high-speed test conditions. conclusion

[0082] Although the disclosure has been described in the form of exemplary embodiments, it is not limited thereto. This description of exemplary embodiments is to be understood in conjunction with the figures of the accompanying drawings, which are to be considered as part of the entire written description. Relative terms such as "lower," "upper," "horizontal," "vertical," "above," "below," "high," "down," "top," "bottom," "rear," and "front," as well as derivatives such as "horizontal," "downward," and "upward," are to be understood as referring to the orientation as described or shown in the respective figure. These relative designations serve for the sake of simplicity and do not require that the probe be constructed or operated in a particular orientation. Terms relating to fastenings and couplings, such as...“connected” refers to a relationship in which structures are either directly or indirectly attached or joined to one another by means of intervening structures, and to movable or rigid attachments or relationships, unless expressly described otherwise.

[0083] Although this description contains many specific implementation details, these details should not be understood as limiting the scope of the disclosures or the claimed achievements. It is understood that these exemplary embodiments are subject to various modifications and may also exist in other forms. All statements contained herein describing principles, aspects, and embodiments of the disclosure are intended to include both their structural and functional equivalents. Furthermore, these equivalents are intended to include both currently known equivalents and any elements developed in the future that perform the same function, regardless of their structure.The claims should not be limited to the disclosed embodiments, modifications and alternative forms, but should cover all modifications, equivalents and alternatives that fall within the spirit and scope of the disclosure. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 674,276

[0001]

Claims

[1] Optical inspection system, comprising: an analog signal input device comprising an input network, a main signal transmission device and an auxiliary signal transmission device; an analog signal output device; a galvanic isolation barrier through which an RF main signal transmission path and an LF auxiliary signal transmission path pass from the analog signal input device to the analog signal output device; and an interface box with a main signal receiving device, an auxiliary signal receiving device and an output network. [2] System according to claim 1, wherein the analog signal input device is configured to: Receiving a difference signal from a DUT, Splitting the differential signal into an auxiliary signal component and a main signal component, Transmitting the main signal component via an RF fiber optic cable on the RF main signal transmission path, and The auxiliary signal component is transmitted via an AF fiber optic cable along the AF auxiliary signal transmission path to the interface box. [3] System according to claim 1 or 2, wherein the analog signal input device further comprises: an amplifier or an attenuator that conditions a differential signal. [4] System according to one of claims 1, 2, or 3, wherein the LF signal component has a smaller bandwidth than the HF signal component and is used to correct, amplify, shift or supplement frequency response variations in the HF signal. [5] System according to any one of claims 1 to 4, wherein the analog signal input device further comprises an analog AF offset stage and an analog RF de-offset stage. [6] System according to any one of claims 1 to 5, wherein the interface box further comprises an analog AF offset stage and an analog RF de-offset stage. [7] System according to any one of claims 1 to 6, wherein the interface box further comprises a recombination circuit configured to match and mix the LF and HF signal components to analog. [8] System according to any one of claims 1 to 7, further comprising a communication signal which is configured to travel on a galvanically isolated communication path of a communication link of an analog signal input device to a communication link of an analog signal output device. [9] System according to any one of claims 1 to 8, wherein the analog signal input device is a probe and the analog signal output device is an oscilloscope. [10] System according to any one of claims 1 to 9, wherein the analog signal input device further comprises an AF auxiliary signal transmitting diode coupled to the AF optical waveguide, and an HF main signal transmitting diode coupled to the HF optical waveguide. [11] System according to any one of claims 1 to 10, wherein the output network of the interface box further comprises an auxiliary AF signal receiver diode coupled to the AF optical waveguide, and a main RF signal receiver diode coupled to the RF optical waveguide. [12] System according to claim 10 or 11, wherein the LF auxiliary signal transmitting diode uses a first analog modulation method. [13] System according to claim 10 or 11, wherein the main RF signal receiver diode uses a second analog modulation method. [14] System according to claim 12 or 13, wherein the first modulation technique is frequency modulation (FM), phase modulation (PM), pulse width modulation (PWM) or pulse density modulation (PDM). [15] System according to claim 13 or 14, wherein the second modulation technique is amplitude modulation (AM). [16] System according to claim 15, wherein the output network of the interface box further comprises an analog recombination circuit configured to combine the RF main signal and the AF auxiliary signal into a single analog output. [17] System according to claim 16, wherein the single analog output signal is transmitted to the analog output signal device.

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