Optical probing system with multiple signal modulation and demodulation

Abstract

What is needed is an improved signal transmission system that can preserve the bandwidth, accuracy, and fidelity of all of the high speed differential signals under severe common mode and environmental conditions.SOLUTION: Optical probing systems transmit high fidelity analog signals from a device under test (DUT) to a measurement instrument. The system receives a differential input signal and splits the differential input signal into a high frequency (HF) component and a low frequency (LF) component. Each component is independently modulated using a different analog modulation technique and transmitted over a separate optical fiber. The architecture maintains galvanic isolation between the input and output devices and allows for independent transmission of signal portions optimized for bandwidth and accuracy. The signals are demodulated, delay-matched, and recombined in the analog domain to produce a reconstructed full-bandwidth output.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. provisional patent application Ser. No. 63 / 674,276, filed July 23, 2024, entitled "Optical Probing System with Modulation of Multiple Signals," the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to the field of test and measurement probes, and more particularly to an optical analog optical probing system with modulation and demodulation of multiple analog signals. [Background technology]

[0003] The adoption of wide-bandgap semiconductor technologies, such as gallium nitride (GaN) and silicon carbide (SiC), has brought about significant improvements in power conversion efficiency and switching performance. However, these advantages come at the cost of dramatically increased switching speeds and higher voltage slew rates, which impose stringent demands on signal bandwidth, dynamic range, and measurement accuracy. Fast switching events, especially under high common-mode voltage conditions, can compromise signal integrity and challenge even high-performance measurement systems.

[0004] Reliable in-situ measurement of such signals is essential not only for design verification but also for the continuous refinement of topologies, gate drive circuits, and protection mechanisms. Oscilloscopes, combined with properly designed probes, remain the primary instrument for capturing and analyzing high-speed electrical waveforms in these environments.

[0005] Traditional oscilloscope probes transmit analog signals through a direct electrical path to the oscilloscope input. 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 cause signal distortion, especially in high-side measurements where the reference potential can drift significantly.

[0006] To address these challenges, galvanically isolated probes have been developed. These systems typically incorporate a probe head for capturing differential signals, an intermediate isolation mechanism such as optical transmission, and an electrical output interface compatible with an oscilloscope. By eliminating the direct conductive path between the probe and the measurement instrument, such solutions suppress ground currents and improve common-mode rejection, thereby enabling cleaner signal acquisition even in noisy environments or under high-voltage conditions.

[0007] Despite these advantages, optical signal transmission systems introduce a new set of engineering tradeoffs. Signal modulation techniques used to convert electrical waveforms into optical signals, particularly in analog optical links, can suffer from bandwidth limitations, distortion due to offset mismatch, and nonlinear attenuation behavior due to temperature or mechanical stress. These degradations typically cause amplitude compression, phase shifts, or transient mismatches between different parts of the signal spectrum.

[0008] Thus, there remains a need for improved signal transmission systems that can preserve the full bandwidth, accuracy, and fidelity of high-speed differential signals under harsh common-mode and environmental conditions. Ideally, such systems can provide stable isolation, precise offset handling, and simultaneous delay management without compromising modulation linearity or signal fidelity. Summary of the Invention

[0009] What is needed is a signal transmission system that enables accurate, high-fidelity acquisition of differential electrical signals, especially in environments characterized by fast switching, high common-mode voltages, and electrical noise. The system supports wide bandwidth, low distortion, and robust common-mode rejection while maintaining galvanic isolation between the probe head and the measurement instrument.

[0010] In one embodiment, a signal transmission architecture receives and transmits analog input signals from a device under test (DUT). The signals are processed along multiple frequency-optimized paths, such as a primary path for full-bandwidth signal transmission and a secondary path optimized for precision low-frequency components. These signals are modulated using frequency modulation (FM), amplitude modulation (AM), or other suitable schemes and transmitted over galvanically isolated links, such as optical fibers.

[0011] The system includes circuitry for applying and removing analog DC offsets to ensure modulation compatibility and prevent signal clipping. The system has delay equalization elements to align the timing of signals processed along separate paths. Recombination of these signals at the receiving end provides a full-band, high-integrity analog representation of the original signal suitable for oscilloscope-based visualization and analysis.

[0012] In some embodiments, the system supports multiple signal paths, allowing modular expansion and optimization across multiple frequency bands or functional purposes. Communication and control signals are exchanged over isolated communication channels. In some embodiments, the entire system is housed in a mechanically integrated unit with electrically isolated power domains.

[0013] The disclosed architecture offers significant improvements in measurement accuracy, noise immunity, and design flexibility, making it particularly well suited for characterizing high-speed power electronics, wide bandgap semiconductors, and other advanced switching systems operating in electrically harsh environments. [Brief explanation of the drawings]

[0014] The accompanying drawings illustrate several embodiments of the present disclosure and, together with the detailed description, serve to explain the principles of the present disclosure. [Figure 1] FIG. 1 is a schematic diagram of an exemplary system illustrating signal transmission, modulation, demodulation, and reception. [Figure 2] FIG. 2 is a schematic diagram of the exemplary system of FIG. 1 having multiple analog signal offset stages. [Figure 3] FIG. 3 is a schematic diagram of an optical probing system having separate main and auxiliary analog optical signal modulation and demodulation devices. [Figure 4] FIG. 4 is a schematic diagram of an optical probing system having separate main and auxiliary analog optical signal transmission devices and additional communication links. [Figure 5] FIG. 5 is a schematic diagram of an optical probing system having one main analog optical signal transmission device and two auxiliary analog optical signal transmission devices and a communication link. [Figure 6] FIG. 6 is a schematic diagram of an optical probing system having one housing with a dedicated isolation unit. [Figure 7] FIG. 7 is a diagram of an optical probing system. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present disclosure generally provides an optical probing system having a galvanically isolated probe head that converts an electrical analog signal to an optical analog signal, an optical analog-to-analog optical signal transmission device, and an electrical analog signal output that is removably connectable to an oscilloscope. An exemplary probe head is generally a differential optical probe head suitable for measuring high frequency differential signals with a given DC offset voltage, such as those observed on the high side of a power module. Typically, such a probe head has a probe tip with appropriate DUT connections.

[0016] In the following sections, detailed descriptions of examples of the disclosure are provided. It is understood that the descriptions of preferred and alternative examples are exemplary only, and that variations, modifications, and variations will be apparent to those skilled in the art. As such, the examples should not be understood as limiting the scope of aspects of the present disclosure, which is defined by the claims.

[0017] "High frequency (HF)" and "low frequency (LF)" should be understood broadly. Specifically, these terms can be understood as "primary frequency" and "secondary / auxiliary frequency." Instead of using a "uniform" modulation for different frequencies, modulation of multiple distinct frequencies at hand is used to fit into frequency bands.

[0018] An analog electrical input signal is detected at the DUT by the optical probing system analog electrical signal input device. The analog electrical signal can be amplified. The initially measured overall 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 using the input device circuitry of the present disclosure. The analog electrical signals can also be separately amplified and / or conditioned using the input device circuitry. The resulting analog electrical signals are converted to analog optical signals using a transmitting diode and transmitted to the analog electrical signal output device where they are received and converted back to analog electrical signals along with the analog electrical output signal.

[0019] The optical probing system may have 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.

[0020] The analog electrical signal input device may have input device circuitry 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-band signal that may include DC. The auxiliary analog electrical signal may be the low frequency and DC components of the originally measured signal. The analog electrical signal input device may further have a communication signal transmission device interface to facilitate transmission of control and safety signals. The communication signal transmission device is optional.

[0021] A galvanic isolation barrier, which is a connection between an analog electrical signal input device and an analog electrical signal output device, can include multiple fiber optic cables. Each fiber optic cable can represent one analog optical signal transmission device. The galvanic isolation barrier can include a connection for a primary (HF) path, which can be a fiber optic cable, a connection for a secondary (LF) path, which can also be a fiber optic cable, and any optical communication devices for transmission of control and safety signals. The optical communication devices can include analog optical signal transmission devices.

[0022] The analog electrical signal output device may have an output device circuit. The output device circuit may be configured similarly to the input device circuit. For example, the output device circuit may include a main signal receiving diode, an auxiliary signal receiving diode, and a control signal receiving diode.

[0023] The exemplary embodiment in the figures shows system architecture components arranged in a recommended order along a galvanically isolated signal path from a DUT to an analog output signal device, such as an oscilloscope, and optimized for signal reception, filtering, modulation, transmission, recombination, demodulation, and output. Other orders and input / output devices are contemplated. However, the disclosed system is particularly preferred for high-speed, complete DUT signal transmission to an analysis device, such as an oscilloscope. The system provides improved signal integrity and stability compared to conventional single-path optical transmission systems.

[0024] 1, there is shown an embodiment of a signal transmission system 1. The system 1 receives a differential input signal from a device under test (DUT) and transmits the signal to an analog signal output device such as an oscilloscope through frequency band separation, optical modulation, recombination, etc., while maintaining high signal fidelity and isolation.

[0025] A differential input signal is first received at an amplifier or attenuator section 3 which is able to amplify or attenuate the incoming signal depending on its amplitude. The conditioned signal is then passed through a bandsplitting filter 5.

[0026] The bandsplit filter 5 can be configured to separate the differential input signal into an auxiliary signal component 8, which may be a low-frequency component, and a main signal component 10, which may be a high-frequency component, based on a specified cutoff frequency. In one embodiment, the cutoff frequency is approximately 20 kHz, although other values ​​may be selected depending on the intended application or system bandwidth. The filter can be configured to implement 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 preserve phase and amplitude fidelity across the signal spectrum while ensuring effective separation of the frequency components for their respective modulation and transmission.

[0027] The LF component is directed to LF modulator 7, which modulates the LF signal for optical transmission. The modulated signal is then transmitted via LF analog signal transmit diode 11, which has an AC-coupled light source (e.g., a laser diode or LED) that converts the modulated electrical signal to an optical signal. This optical signal is transmitted over LF fiber optic cable 15 to LF analog signal receive diode 19, which has an AC-coupled photodiode that converts the incoming optical signal back to an electrical signal. The electrical signal is then demodulated by LF demodulator 23 to recover the low frequency signal components.

[0028] Analog modulation techniques used in the auxiliary signal path can include, but are not limited to, frequency modulation (FM), amplitude modulation (AM), phase modulation (PM), pulse width modulation (PWM), pulse frequency modulation (PFM), or pulse density modulation (PDM). These modulation schemes are advantageous for conveying precise amplitude or timing information and can be selected based on the signal's properties and desired fidelity. The auxiliary path can also transmit reference waveforms or other analog content outside the main signal band for calibration or correction purposes. In certain embodiments, the main signal path uses an amplitude-modulated analog signal while the auxiliary path employs a complementary analog modulation format, such as FM, PM, or PWM, to mitigate the effects of gain variations, attenuation drift, or DC offsets that may occur in the main path due to changes in fiber alignment, movement, temperature, or component aging.

[0029] In this configuration, the LF signal path or auxiliary signal path may not support the full bandwidth of the input signal, but it does carry high-precision information used to reconstruct or stabilize the output. For example, the auxiliary signal can be used to correct variations in the main signal path, such as offset drift, gain inaccuracy, or bandwidth nonuniformity. When combined in a mixer or analog recombination circuit 27, the main and auxiliary paths enable higher overall signal fidelity than would be achieved using only a single analog transmission path. The recombination circuit thus combines the high-speed main content and the high-integrity auxiliary content to generate a comprehensive, corrected analog output for oscilloscope-based analysis. Simultaneously, the HF component is sent to HF modulation unit 9, where it is modulated, and then sent to HF analog signal transmitting diode 13, which converts the modulated HF signal to an optical signal. The optical signal is transmitted via HF fiber optic cable 17 to HF analog signal receiving diode 21, which performs optical-to-electrical conversion. The output is processed by HF demodulation unit 25 to recover the high-frequency signal content.

[0030] The modulation can occur via different modulation techniques. Instead of inserting the modulated HF signal and the modulated LF signal into their separate optical fibers, a common optical fiber can be used. The LF signal path can be used to correct for gain, drift, offset, or bandwidth distortion in the HF path.

[0031] The demodulated LF and HF signals are then sent to a mixer or analog recombination circuit 27 which reconstructs the full-band signal in the analog domain. The recombined signal is then passed through an attenuator 29 configured for either a 50 ohm or 1 megaohm termination resistor, depending on the impedance requirements of the connected oscilloscope or measurement equipment.

[0032] Providing the two signal paths separately over single or multiple optical fibers offers the advantage of more efficient and independent tuning. This allows for better DC precision and flatness in the low-frequency domain, as tuning can be done without affecting the high-frequency signals. As a result, the system achieves an expansion of overall bandwidth by optimizing each path individually for each frequency band.

[0033] Referring now to Figure 2, there is shown a variation of the exemplary embodiment of Figure 1. The variation disclosed in Figure 2 includes dedicated analog offset and de-offset stages in both the low frequency (LF) and high frequency (HF) signal paths to accommodate modulation constraints and optimize signal linearity across the optical link.

[0034] In the low frequency domain, the LF signal is directed to an LF analog signal offset stage 31, which applies a predefined offset or level shift to the signal. This ensures compatibility with subsequent modulation stages and prevents clipping during modulation of the laser diode current. The offset-adjusted signal is then sent to an LF modulation section 7 and subsequently to an LF analog signal transmit diode 11, which is AC-coupled and configured to convert the modulated LF electrical signal to an optical signal. The optical signal is transmitted via an LF fiber optic cable 15 to an LF analog signal receive diode 19, which converts the optical signal back to the electrical domain. The resulting signal is demodulated by an LF demodulation section 23 and then passed to an LF analog signal de-offset stage 35, which removes the previously applied offset and restores the signal to its original baseline.

[0035] In the high frequency domain, the HF signal is sent through an HF analog signal offset stage 33, which performs a similar offset operation to prepare the HF signal for high-speed optical modulation. The offset signal is then processed by an HF modulator 9 and converted to an optical signal by an HF analog signal transmit diode 13. The HF optical signal is transmitted via an HF fiber optic cable 17 to an HF analog signal receive diode 21. After optical detection, the electrical signal is demodulated by an HF demodulator 25, followed by an HF analog signal de-offset stage 37, which inverts the applied offset to restore the original signal level.

[0036] Offset or level shifting, and similar offset operations, may be a voltage offset, also called a DC bias shift. This DC bias can be added to the center of the signal (e.g., shifting a -2V to +2V signal to a 0V to 4V window). After demodulation, the bias is subtracted to restore the original signal level.

[0037] The outputs of the LF and HF de-offset stages (35 and 37, respectively) are combined in a mixer or analog recombination circuit 27 to reconstruct the full-band signal. This composite signal is then sent to an attenuator 29, which can be configured for a 50 ohm or 1 megaohm termination resistance to match the impedance of the connected measurement equipment.

[0038] In one embodiment, the system further includes a delay equalization stage located closest to the mixer or analog recombination circuit 27. These include one or more first-order (PT1) or second-order (PT2) analog filter elements configured to compensate for run-time differences between the low-frequency and high-frequency signal paths. Such differences may arise from non-uniform propagation delays caused by variations in photodiode characteristics, fiber length, or modulator response time.

[0039] The delay equalization stage can be implemented before, after, or integrated within the recombination circuit 27 and can comprise passive or active analog filters designed to align signal arrival times and preserve phase coherence between frequency components. In one embodiment, the LF path is slightly delayed using a PT1 filter to match the faster HF optical transmission channel. In another embodiment, the HF path incorporates a PT2 element to simultaneously balance group delay and bandwidth.

[0040] Referring now to Figure 3, there is shown a generalized embodiment of the signal transmission architecture shown in Figures 1 and 2. The system includes a probe head 2 and an interface box connected via an optical transmission path. The probe head receives an input signal from a device under test (DUT) 41 through an input network 43, which may include signal conditioning, amplification, attenuation, and frequency separation functions as described with respect to Figures 1 and 2.

[0041] The input signal is processed in parallel by a main signal transmission section 45 and an auxiliary signal transmission section 47. The main signal transmission section 45 corresponds functionally to a high frequency (HF) signal path including an analog signal offset stage, a high frequency modulation section, and an optical transmission section. The auxiliary signal transmission section 47 corresponds functionally to a low frequency (LF) signal path including a low frequency offset stage, a low frequency modulation section, and an LF optical transmission section.

[0042] The main and auxiliary signals are transmitted over main and auxiliary signal transmission paths 49 and 51, respectively, which may include optical fibers as described above. These signals are received within the interface box by main and auxiliary signal receivers 53 and 55, which correspond respectively to the HF and LF optical detectors, demodulators, and de-offset stages as described with respect to Figures 1 and 2.

[0043] In the main signal path, the input network 43 is designed to interface directly with the device under test (DUT) 41 and condition the received differential input signal for high-fidelity transmission to the receiving circuitry. The input network 43 may include wideband amplifiers, attenuators, or other active or passive circuitry suitable for adapting 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 transient and frequency content, thereby optimizing for linearity and bandwidth rather than filtering or precision scaling.

[0044] The output of the input network 43 is sent through a main signal transmission section 45 that provides for optical or galvanically isolated transmission via a main signal transmission path 49, and finally reaches a main signal receiving section 53. The output stage of the input network can be specifically adapted to interface with a transmission section input or a modulation section input while ensuring signal integrity and impedance matching across the system boundary, allowing the system to send the full bandwidth content of the DUT signal to an oscilloscope or measurement device for high-speed waveform acquisition and analysis.

[0045] The auxiliary signal transmission path 51 can be configured to connect the input network 43 and provide a high precision version of the input signal that is transmitted to the receiving end (interface box side) using an analog modulation technique, such as FM, AM or PM, PWM, PDM, or other analog modulation, that can preserve the precision of the signal but cannot support the full bandwidth of the input signal.

[0046] The split-path amplifier design allows each path to be independently optimized, ensuring optimal performance for the required high-speed and low-frequency signals and reducing the sensitivity to environmental factors. The design can therefore include circuitry for selecting between multiple (n+1) paths based on input signal characteristics or user-defined preferences.

[0047] The recovered signals are combined in an output network 57 which further includes an analog recombination circuit for interfacing with standard test equipment input impedance (e.g., 50 ohms or 1 megaohm), a delay equalization stage (e.g., PT1 / PT2), and an attenuation section.

[0048] In a preferred embodiment, both the main signal transmission path 49 and the auxiliary signal transmission path 51 are implemented using optical fiber, thereby providing galvanic isolation and enabling high fidelity signal transmission over long distances while minimizing electromagnetic interference. The main and auxiliary signals can be transmitted on separate optical fibers, or alternatively, can be multiplexed onto a single optical fiber using wavelength division multiplexing (WDM) or other multiplexing techniques, such as polarization, multiplexed time domain, or mode division separation.

[0049] Although optical fiber is the preferred transmission medium, other galvanically isolated transmission methods can also be employed, including, but not limited to, transformer-coupled links, radio transmission, microwave transmission, or modulation-based techniques such as mixer-based upconversion, quadrature amplitude modulation (QAM), or related analog or digital encoding schemes. These alternatives can be adapted depending on system-level tradeoffs in bandwidth, complexity, cost, or mechanical integration.

[0050] Furthermore, while the embodiments disclosed above primarily describe separate transmission channels for the main signal, auxiliary signal, and communication paths, these three paths (main, auxiliary, and communication) can, in some implementations, be transmitted over a single medium, such as a shared optical fiber or radio frequency link, using appropriate multiplexing or modulation techniques. Conversely, dedicated physical separation, such as three separate optical fibers, or more generally, n+1 isolated transmission paths, is within the scope of this disclosure and may provide advantages in signal integrity, isolation, or system modularity.

[0051] Referring now to Figure 4, a further embodiment of a signal transmission system is shown, which builds on the embodiment described in Figure 3 and incorporates a bidirectional communication channel across the galvanic isolation barrier to support auxiliary control, synchronization and configuration signaling between the probe head and the interface box.

[0052] As in the previous embodiment, a differential signal 58 is received from a device under test (DUT) 41 and sent through an input network 43 located within the probe head. The input network 43 may include impedance matching circuitry, filtering, and signal conditioning components (not shown). The conditioned signal is split and fed in parallel to a main signal transmission section 45 and an auxiliary signal transmission section 47.

[0053] The main signal transmission unit 45 is configured to transmit the high frequency (HF) component of the signal over the main signal transmission path 49 to the main signal receiving unit 53 in the interface box. Similarly, the auxiliary signal transmission unit 47 is configured to transmit the low frequency (LF) component of the signal over the auxiliary signal transmission path 51 to the auxiliary signal receiving unit 55.

[0054] The recovered signals are combined and processed in output network 57 as previously described. In the embodiment of Figure 4, the system further includes a communication path 61 across the galvanic isolation barrier to facilitate the exchange of control, calibration, timing, and / or diagnostic data between the probe head and the interface box.

[0055] At the probe head side, a communication link 63 is provided for transmitting or receiving such data over a communication path 61. At the interface box side, a corresponding communication link 65 is provided. The communication path 61 can be implemented using an optically isolated digital communication channel, a wireless interface, or other galvanically isolated interface.

[0056] The communication system operates independently of the main and auxiliary signal transmission paths to support calibration routines, gain or offset control, run-time diagnostics, synchronization pulses, probe identification, or other system-level functions. This bidirectional communication architecture improves flexibility, deferrability, and reliability in measurement scenarios requiring adaptive control or closed-loop operation.

[0057] Referring now to Figure 5, a generalized embodiment of a signal transmission system is shown. Figure 5 builds on the two-path architecture of Figures 1 and 2 and the modular framework of Figures 3 and 4, introducing the ability to split and process an input signal into n distinct signal transmission paths (where n is an integer equal to or greater than 1). This generalized architecture can improve flexibility, scalability, and signal fidelity in scenarios where two or more frequency bands or signal components must be independently acquired and transmitted. For example, first and second auxiliary signal transmission sections, transmission paths, and receiver sections (87, 89, 91, 93, 95, 97) are shown, along with the main signal and communication path components.

[0058] As in the previous embodiment, a differential signal is received from a device under test (DUT) via an input network 43 located within the probe head. The input network 43 may include impedance matching, filtering, attenuation, and frequency band separation circuitry. The processed signal is then split and provided to a main signal transmission section 45 and multiple auxiliary signal transmission sections, each configured to process and modulate a particular sub-band or component of the overall signal.

[0059] The main signal and each auxiliary signal are transmitted over corresponding optical or galvanically isolated signal transmission paths. In the illustrated embodiment, these include main signal transmission path 49 and auxiliary signal transmission paths. These transmission paths may comprise optical fiber, RF links, or other isolated communication media.

[0060] At the interface box side, the signals are received by a corresponding set of receivers, including a main signal receiver 53 and an auxiliary signal receiver, each of which performs optical-to-electrical conversion, demodulation, and optical signal restoration (e.g., offset removal or delay equalization) as described above in connection with Figures 1 and 2.

[0061] The resulting signal components are fed to an output network 57, which may include summing circuits, delay matching, gain control, and impedance matching. The output network reconstructs the full bandwidth signal in the analog domain as a single analog output signal that is transmitted to an analog signal output device. However, the output network can selectively route the components separately to the analog signal output device.

[0062] A communication path 61 and corresponding communication links 63 and 65 (located in the probe head and interface box, respectively) are also included to facilitate the bidirectional exchange of control, delay, synchronization, and diagnostic information across the galvanic isolation barrier, which can operate independently of the signal transmission path.

[0063] The architecture shown in Figure 5 allows for modular expansion of the transmission system. For example, in some embodiments, the signal can be split into three or more frequency bands using an extended band-splitting filter and routed to corresponding transmission paths. In other embodiments, auxiliary channels can be reserved for specialized monitoring functions, noise analysis, common-mode tracking, or differential signal verification. Some embodiments can include circuitry for selecting between multiple (n+1) paths based on input signal characteristics or user-set preferences.

[0064] Referring now to Figure 6, a further embodiment of a signal transmission system is shown that builds on the system architecture described in Figures 3 to 5 and incorporates a single physical housing 67 that contains both the signal transmission and reception circuitry while maintaining a galvanic isolation barrier 60 between the DUT side and the output side of the system.

[0065] In the embodiment shown, the signal transmission system is enclosed within a single housing that forms part of a compact isolation unit. The isolation unit includes an input interface configured to receive an analog signal from a device under test (DUT). The DUT signal is fed to an input network 43 that can perform impedance matching, attenuation, and band splitting functions as described with respect to the previous embodiments.

[0066] The input signal is then sent to main signal transmission section 45 and auxiliary signal transmission section 47 which process the high frequency and low frequency (or otherwise separated) signal components, respectively. These components are transmitted over respective main and auxiliary signal transmission paths, shown collectively as 49 and 51, which cross a galvanic isolation barrier and connect to corresponding main signal receiving section 53 and auxiliary signal receiving section 55.

[0067] 4, a communication path 61 and associated communication links 63 and 65 are provided to enable bidirectional exchange of control, configuration, and diagnostic data between the isolated probe-side circuitry and the output-side processing circuitry via 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.

[0068] The housing 67 provides mechanical protection and an environmental shield for all components while maintaining different electrical domains on each side of the galvanic isolation barrier. In some embodiments, the housing can be implemented as a bipartite shell or multi-compartment enclosure that physically separates the transmit and receive sections while maintaining an optical or isolated signal path between them.

[0069] The processed and recombined signal is sent through an output network 57 which provides final signal conditioning and impedance matching before sending the signal to an output interface such as a BNC connector. The output interface is electrically isolated from the input of the DUT, making the system well suited for probing high voltage environments and systems with floating ground potentials.

[0070] Referring now to Figure 7, an exemplary implementation of optical probing system 1 is shown. The system is consistent with the architectural embodiments shown and described in Figures 1 through 6 and is shown in an adapted configuration with respect to an optical probe head 39, a fiber optic link 62, an interface box 59, a power supply 71 to the interface box, and an analog signal input device such as an oscilloscope 73. The probe head has a probe tip 81 configured to make contact with a DUT (not shown). The probe head is maintained in position via an adjustable 3D positioner 83 having an electrically isolated socket 83.

[0071] In the embodiment shown, the probe head 39 includes a housing containing analog signal conditioning and transmission circuitry, including a main signal transmission section and one or more auxiliary signal transmission sections, as previously described. The probe head 39 is galvanically isolated from the measurement equipment and the power grid, and in this example is powered by a battery inserted into the probe head battery compartment 75. This local power source allows the probe head 39 to remain electrically isolated while still providing power to internal components such as the analog signal offset stage, modulation section, and optical transmission section. According to an alternative embodiment, a fiber optic power adapter can be inserted into the probe head's battery compartment in place of a battery, thereby allowing continuous operation of the probe head while maintaining galvanic isolation.

[0072] The probe head can be optically coupled to interface box 59 via one or more fiber optic cables provided in fiber optic link 62. These one or more fiber optic cables form main and auxiliary signal transmission paths across a galvanic isolation barrier. These paths correspond to the optical links described in Figures 1-6. Interface box 59 includes main and auxiliary signal receivers, communication links, and output networks, as previously described. In this implementation, the interface box is connected to an oscilloscope using a BNC-type electrical connector 77, so that the recovered and recombined signals can be displayed, analyzed, and recorded.

[0073] The interface box 59 is powered by an external power supply 71 connected to the interface box 59 via a power cord 79. This power supply provides the power necessary to drive the receiver circuitry, demodulator, delay equalization elements, recombination circuitry, and output driver stage. The system architecture therefore supports fully isolated signal acquisition, with the probe head and interface box being independently powered.

[0074] The embodiment shown in Figure 7 serves as an example of how the modular optical probing architecture disclosed in the previous figures can be implemented in a real-world laboratory or test environment. The combination of galvanic isolation, separate power domains, optical signal paths, and standard output interfaces such as BNC allows the system to safely and accurately acquire signals under high-voltage, high-speed test conditions.

[0075] While the present disclosure has been described with reference to exemplary embodiments, the present disclosure is not limited thereto. This description of exemplary embodiments should be understood in connection with the accompanying drawing figures, which are to be considered a part of the entire written description. For example, relative terms such as "lower," "higher," "horizontal," "vertical," "upward," "downward," "up," "downward," "top," "bottom," "back," and "front," as well as their derivatives, such as "horizontally," "downward," and "upward," should be interpreted as referring to directions at the time of description or as shown in the particular view in the description. These relative terms are for convenience of description and do not require the probe head to be configured or operated in a particular orientation. Terms relating to attachment and coupling, such as "connected," refer to a fixed or connected relationship between structures, either directly or indirectly through intermediate structures, and are to be interpreted as including both movable and fixed attachments or relationships, unless expressly stated otherwise.

[0076] While this specification contains many specific implementation details, these details should not be construed as limitations on any of the disclosure or the claims. It should be understood that these exemplary embodiments are susceptible to various modifications and may be represented in alternative forms. All statements herein reciting principles, aspects, and embodiments of the present disclosure are intended to encompass both structural and functional equivalents thereof. Additionally, such equivalents are intended to include both currently known equivalents and any elements developed in the future that perform the same function, regardless of structure. The scope of the claims is not limited to the disclosed embodiments, modifications, and alternatives, but is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure. [Explanation of symbols]

[0077] 1. Optical probing system 3 Amplification or attenuation devices 5 Band division filters with set cutoff frequencies 7 Low Frequency (LF) Modulator 8 Auxiliary Signal Components 9 High Frequency (HF) Modulator 10 Main Signal Components 11 LF analog signal transmission diode (AC coupled) 13 HF analog signal transmission diode (AC coupled) 15 LF fiber optic cable 17 HF fiber optic cable 19 LF analog signal receiving diode (AC coupled) 21 HF analog signal receiving diode (AC coupled) 23 LF demodulator 25 HF demodulator 27 Mixer or analog recombination circuit 29 Attenuation section with 50 ohm or 1 megohm termination resistor 31 LF analog signal offset stage 33 HF analog signal offset stage 35 LF analog signal de-offset stage 37 HF analog signal de-offset stage 39 Analog signal input device 41 DUT 43 Input Network 45 Main signal transmission section 47 Auxiliary signal transmission section 49 Main signal transmission path 51 Auxiliary signal transmission section 53 Main signal receiver 55 Auxiliary signal receiver 57 Output Network 58 Differential Signals 59 Interface Box 60 Galvanic Isolation Barrier 61 Communication Path 62 Fiber Optic Links 63 Communication link (probe head side) 65 Communication link (interface box side) 66 Communication Signal Components 67 Housing 69 BNC output section 71 Interface box power supply 73 Analog signal output device 75 Probe Head Battery Compartment 77 BNC type electrical connection device 79 Power cord 81 Probe Tip 83 3D Positioning Stand 85 Electrically isolated socket 87 First auxiliary signal transmission unit 88 First Auxiliary Signal Component 89 Second auxiliary signal transmission unit 90 Second Auxiliary Signal Component 91 First auxiliary signal receiving unit 93 Second auxiliary signal receiver 95 First auxiliary signal transmission path 97 Second auxiliary signal transmission path 99 single analog output signals

Claims

1. an analog signal input device having an input network, a main signal transmission section, and an auxiliary signal transmission section; an analog signal output device; a galvanic isolation barrier through which an HF main signal transmission path and an LF auxiliary signal transmission path traverse from the analog signal input device to the analog signal output device; an interface box having a main signal receiver, an auxiliary signal receiver, and an output network; An optical probing system comprising:

2. The analog signal input device is receiving a differential signal from the DUT; splitting the differential signal into an auxiliary signal component and a main signal component; transmitting the main signal component via an HF optical fiber cable on the HF main signal transmission path; The system of claim 1 , wherein the LF auxiliary signal transmission path is configured to transmit the auxiliary signal component to the interface box via an LF fiber optic cable.

3. The system of claim 1 , wherein the analog signal input device further comprises an amplifier or attenuator for conditioning a differential signal.

4. 10. The system of claim 1, wherein the LF signal component has a lower bandwidth than the HF signal component and is used to correct gain, offset, or compensate for frequency response variations in the HF signal.

5. 10. The system of claim 1, wherein the analog signal input device further comprises an LF analog offset stage and an HF analog de-offset stage.

6. The system of claim 1 , wherein the interface box further comprises an LF analog offset stage and an HF analog de-offset stage.

7. The system of claim 1 , wherein the interface box further comprises a recombination circuit configured to match and combine LF and HF signal components into analog.

8. 10. The system of claim 1, further comprising a configuration for passing a communication signal on a galvanically isolated communication path from an analog signal input device communication link to an analog signal output communication link.

9. 2. The system of claim 1, wherein the analog signal input device is a probe head and the analog signal output device is an oscilloscope.

10. 10. The system of claim 1, wherein the analog input device further comprises an auxiliary LF signal carrying diode coupled to the LF fiber optic cable and a main HF signal carrying diode coupled to the HF fiber optic cable.

11. 10. The system of claim 1, wherein the output network of the interface box further comprises an auxiliary LF signal receiving diode coupled to the LF fiber optic cable and a main HF signal receiving diode coupled to the HF fiber optic cable.

12. 11. The system of claim 10, wherein the auxiliary LF signal transmitting diode deploys a first analog modulation technique.

13. 11. The system of claim 10, wherein said primary HF signal receiving diode deploys a second analog modulation technique.

14. 12. The system of claim 11, wherein the auxiliary LF signal transmitting diode deploys a first analog modulation technique.

15. 12. The system of claim 11, wherein said primary HF signal receiving diode deploys a second analog modulation technique.

16. 13. The system of claim 12, wherein the first modulation technique is frequency modulation (FM), phase modulation (PM), pulse width modulation (PWM), or pulse density modulation (PDM).

17. 15. The system of claim 14, wherein the first modulation technique is frequency modulation (FM), phase modulation (PM), pulse width modulation (PWM), or pulse density modulation (PDM).

18. 14. The system of claim 13, wherein the second modulation technique is amplitude modulation (AM).

19. 16. The system of claim 15, wherein the second modulation technique is amplitude modulation (AM).

20. 16. The system of claim 15, wherein the output network of the interface box further comprises an analog recombination circuit that combines the main HF signal and the auxiliary LF signal into a single analog output.

21. 20. The system of claim 18, wherein the single analog output is transmitted to an analog signal output device.

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