Optical fiber brain-machine interface array system based on mpo connection technology

Abstract

The application provides an optical fiber brain-computer interface array system based on an MPO linking technology.The system is characterized in that it is composed of a transmitting assembly formed by transmitting light sources 1-1 and 1-2, a single-mode optical fiber wavelength division multiplexer 2 and an optical fiber beam splitter 3, an MPO optical fiber jumper 4, an MPO optical fiber probe 5, an optical fiber combiner 6 and a single photon detector (SPAD) 7.The application can be used to acquire diffuse reflection light information of blood oxygen changes in brain tissues, to monitor a cognitive activity of the brain in real time, to acquire brain activity signals related to brain functions, and can be widely used in the fields of new non-invasive optical brain-computer interface monitoring equipment and the like.

Description

Technical Field

[0001] This invention relates to a fiber optic brain-computer interface array system based on MPO connection technology. This invention can be used to acquire diffuse reflection light information of blood oxygenation changes in brain tissue, monitor the brain's cognitive activities in real time, and obtain brain activity signals related to brain function. The device is convenient to connect and disconnect, has low optical signal loss, and high coupling efficiency. It can be widely used in new non-invasive optical brain-computer interface monitoring equipment and belongs to the field of fiber optic sensing technology. Background Technology

[0002] The biological brain relies on blood metabolism to provide the oxygen needed for neuronal activity. Oxygen consumption stimulates the dilation of local blood vessels in the brain, leading to an increase in local cerebral blood volume and flow, manifested as a rapid increase in cerebral blood oxygen levels. Therefore, when the brain engages in a cognitive activity, the local blood oxygen content in the active brain region will far exceed the required blood oxygen content in unstimulated areas. Oxygen is transported through hemoglobin in the blood; therefore, during cognitive activities, the concentration of oxyhemoglobin in the active brain region will significantly increase, while the concentration of deoxyhemoglobin will significantly decrease. Currently, many brain imaging techniques obtain brain activity signals related to brain function by detecting optical or magnetic changes caused by changes in local hemoglobin concentration during activity.

[0003] Currently, the most widely used mainstream brain imaging techniques include electroencephalography (EEG), magnetoencephalography (MEG), transcranial magnetic stimulation (TMS), electrocorticography (ECoG), local field potential array (LFP), positron emission tomography (PET), magnetic resonance imaging (MRI), functional magnetic resonance imaging (fMRI), and functional near-infrared spectroscopy (fNIRS) [Irani F, Platek SM, Bunce S, Ruocco AC, et al. Functional near infrared spectroscopy (fNIRS): an emerging neuroimaging technology with important applications for the study of brain disorders[J]. Clin Neuropsychol, 21(1):9-37, (2007).]. Invasive devices require craniotomy to implant sensors into brain tissue. This procedure is prone to triggering an immune response, posing a high risk, and the scab formed during wound healing can also affect signal transmission. In contrast, non-invasive devices do not require entry into the brain; signals can be detected simply by looking at the outer side of the skull. The experience, similar to wearing a hat, is more readily accepted, and they offer advantages such as ease of use, portability, and relatively lower cost. While non-invasive methods avoid the risks of surgery, the skull significantly attenuates reflected signals, causing the received signal to become scattered and blurred, affecting both signal strength and resolution. To delve deeper into brain function and elucidate the psychological processes and mechanisms of human cognition, early research into non-invasive neurofunctional detection technologies began. In 1831, London physician Richard Bright and others first applied this technology to clinical medicine, using candlelight to illuminate the back of the head, making the skull translucent.In 1977, Jobsis et al. first applied functional near-infrared spectroscopy (fNIRS) to observe changes in blood oxygen content in animal brains, and published their research results on the absorption characteristics of hemoglobin and cytochrome in the near-infrared spectral range in Science. Oxyhemoglobin (HbO2) and deoxyhemoglobin (HbR) had two absorption peaks at 735 nm and 905 nm, respectively, and proposed that the changes in absorption spectra were directly related to the oxygen carrying capacity of hemoglobin. FF, Noninvasive. Infrared monitoring of cerebral and myocardial oxygen sufficiency and circulatory parameters [J]. Science, 198 (4323): 1264-1267, (1977).].

[0004] This report has attracted widespread attention in the biomedical field. Since then, researchers from different fields have conducted more in-depth research on brain function activities in neuroscience through multidisciplinary collaboration and various non-invasive detection technologies. This has made fNIRS technology play a crucial role in promoting the development and application of cognitive neuroscience [Pinti P, Tachtsidis I, Hamilton A, et al. The present and future use of functional near-infrared spectroscopy (fNIRS) for cognitive neuroscience. Annals of the New York Academy of Sciences, 2020, 1464(1):5-29.]. Near-infrared brain functional imaging technology is a relatively novel non-invasive optical detection technology for brain function in recent years [Quaresima, V.; Ferrari, MA. Mini-Review on Functional Near-Infrared Spectroscopy (fNIRS): Where Do We Stand, and Where Should We Go?]. Photonics, 2019, 6(3): 87.], has been fully affirmed in clinical medical applications in many fields. For example, fNIRS has been applied in the fields of mental illness, pediatrics, stroke rehabilitation, neurodegenerative diseases, anesthesia depth monitoring, and brain oxygen monitoring in neurosurgical patients. With the development of fNIRS technology, near-infrared brain imaging equipment has appeared more and more frequently in clinical applications [LI Mengqi, GONG Anmin, NAN Wenya, XU Bojun, DINGPeng, FU Yunfa. Neurofeedback technology based on functional near infrared spectroscopy imaging and its applications. Journal of Biomedical Engineering, 2022, 39(5): 1041-1049.].

[0005] fNIRS technology generally consists of a light source, a light source detector, and a data acquisition unit. The light source emits near-infrared light into a certain area of ​​the brain through a light-emitting diode or fiber optic bundle. The light is scattered in a "banana-shaped" path, and the detector receives the light signal scattered back by the brain tissue. At present, the effective monitoring distance of the light source and detector of near-infrared brain imaging equipment is generally within the range of 2-7 cm, and the monitoring depth is within 3 cm [Wigal SB, Polzonetti CM, Stehli AA. Phase synchronization of oxygenation waves in the frontal areas of children with attention-deficit hyperactivity disorder detected by optical diffusion spectroscopy correlates with medication[J]. Biomed Opt,17(12):127002,(2012).]. Effective detection signals from the brain tissue within the cerebral cortex must penetrate superficial tissues such as the skull and scalp to be received by the detector. Therefore, the received light signal comprises both superficial and deep cortical components. Current techniques typically compensate for this by increasing the source-detector distance (SDS). As the distance between the light source and detector increases, the "banana-shaped" optical path also becomes longer, meaning the optical path becomes deeper, thus increasing the detection depth. However, according to diffusion theory, this method of compensating for detection depth by increasing SDS reduces the intensity of the received detection signal, and the signal intensity decreases exponentially with increasing SDS.

[0006] To facilitate subsequent signal processing, researchers hope to shorten the SDS to improve spatial resolution [Tamborini D, et al. Portable system for time-domain diffuse correlation spectroscopy[J]. Biomed.Eng.66,3014–3025,(2019).], while also reducing signal interference in the superficial brain and lowering measurement errors in blood flow and blood oxygenation. In 2005, Alessandro Torricelli et al. theoretically proposed a new method to improve the spatial resolution of fNIRS technology. This method improves spatial resolution while reducing the distance between the light source and detector. Compared with traditional methods, this method can better locate diffuse photons. Although at that time it was only derived from theoretical models and no feasible experimental scheme had been found [Alessandro Torricelli, Antonio Pifferi, Lorenzo Spinelli, et al. Time-Resolved Reflectance at Null Source-Detector Separation: Improving Contrast and Resolution in Diffuse Optical Imaging[J]. Physical Review Letters, 95, 078101, (2005).]. To this end, invention patents with application numbers CN202310171813.6 and CN202310170049.0 proposed a solution based on a bidirectional functional device using multi-clad optical fiber and constructed a novel fiber diffuse time-resolved probe system for brain-computer interfaces.

[0007] Based on the above-mentioned technology, this invention overcomes the technical difficulties in the implementation of prior art and proposes a new method that is simple and easy to prepare. This solution not only reduces the difficulty of technical implementation, but also makes it easy to mass-produce, which can greatly reduce costs.

[0008] This invention discloses a fiber optic brain-computer interface array system based on MPO (Mechanical, Power, and Optical) connection technology. It can be used to acquire diffuse reflectance light information of blood oxygenation changes within brain tissue, enabling real-time monitoring of cognitive activities and obtaining brain activity signals related to brain function. The system utilizes an MPO fiber optic probe manufactured using MPO technology to unify the input and received signal optical paths. The light source emitting component and detector convert and amplify the optical signals into electrical signals for processing. Compared to prior art, the integration of the MPO fiber optic patch cord and fiber optic probe improves signal coupling efficiency and enhances the stability of both emitted and received light. Each probe can both emit and receive optical signals, further improving the device's integration. Summary of the Invention

[0009] The purpose of this invention is to provide a fiber optic brain-computer interface array system based on MPO connection technology that has a simple and compact structure, high coupling efficiency, and can integrate multiple optical paths into a single channel.

[0010] The objective of this invention is achieved as follows:

[0011] A fiber optic brain-computer interface array system based on MPO connection technology is characterized by comprising: emission light sources 1-1 and 1-2, a single-mode fiber wavelength division multiplexer 2, a fiber beam splitter 3 forming an emission assembly, an MPO fiber jumper 4, an MPO fiber probe 5, a fiber combiner 6, and a single-photon detector (SPAD) 7. In this system, two near-infrared wavelength light sources 1-1 and 1-2 emit light alternately. The optical signal passes through the wavelength division multiplexer 2, then through the fiber beam splitter 3, and via the MPO fiber jumper 4 to the self-focusing collimating lens 5-2 within the MPO fiber probe 5-1. After passing through the 45° reflecting surface of the prism reflector 5-3, it is focused by the beam adjustment lens 5-4 and injected into the cerebral cortex. The backscattered light signal from the cerebral cortex passes through the same adjustment lens 5-4, then through the prism reflector 5-3, and is sent back to the fiber combiner 6, where it is received by the single-photon detector (SPAD) 7, converted, and amplified into an electrical signal for processing. Based on MPO connection technology, this fiber optic brain-computer interface array system uses MPO fiber optic jumpers and fiber optic probes to connect the signal transmitting component, the signal receiving component, and the brain region to be probed. Each fiber optic probe can both transmit and receive optical signals. The convenient installation and arbitrary position replacement of the fiber optic probes can realize a head-mounted device with multiple independent fiber optic probe systems.

[0012] The MPO fiber optic probe in a fiber optic brain-computer interface array system based on MPO connection technology consists of a brain-computer interface housing, a self-focusing collimating lens, a prism reflector, and a beam adjustment lens. One end of the probe is connected to a fiber optic beam splitter and a fiber optic beam combiner for system input and output, while the other end is connected to the brain-computer interface probe. Each probe structure is connected to two fiber optic pigtails: one for transmitting emitted light signals into the brain, and the other for receiving backscattered light signals from the cerebral cortex. The two fibers at the probe end are coupled to the same self-focusing collimating lens. The coupling connection between the two fiber optic pigtails and the self-focusing collimator is prepared according to the following steps: Step 1. Strip the coating layer from the spare multimode fiber, cut it, and clean it; Step 2. Insert the two fibers into a hollow capillary tube, and melt and collapse them at high temperature to make them fit tightly together; Step 3. Cut the end of the capillary tube to obtain a flat end face where the two fibers are close together, and finally align them with the self-focusing collimating lens and seal them with a protective sleeve.

[0013] The transmitted light signal is emitted via a transmitting pigtail, passes through a self-focusing collimating lens, and is reflected at a 45° angle by a prism reflector. It is then focused by an adjustment lens and injected into the cerebral cortex. Simultaneously, the probe can also provide a bidirectional optical path. Backscattered light signals from the cerebral cortex are received by the adjustment lens, reflected by the same prism reflector, and then pass through a self-focusing collimating lens to the receiving pigtail. Finally, through an MPO connector, they are received by a single-photon detector (SPAD), converted, amplified, and processed into an electrical signal.

[0014] In the process of non-invasively detecting changes in brain blood flow using optical signals, the light needs to penetrate multiple layers of material, including the scalp and skull, to reach the target brain region. However, the signal transmitted to the detector after diffusion is very weak. To improve the efficiency of the optical signal, it is necessary to ensure good collimation of the emitted light, minimizing light diffusion as it passes through the scalp, skull, and multiple layers of meningeal tissue. Simultaneously, the receiving device for collecting diffused light signals must have a large area and a high signal-to-noise ratio to increase signal stability. Therefore, an adjustment lens is placed at the contact point between the interface device and the head before the light signal enters the brain tissue to achieve these goals. Furthermore, the adjustment lens also fulfills the device's bidirectional function: on the one hand, it ensures that light diffusion is suppressed during beam injection as it passes through the scalp, skull, and multiple layers of meningeal tissue via the prism reflector, increasing the penetration depth of the light source; on the other hand, it can converge more scattered light signals into the prism reflector, while simultaneously expanding the effective receiving area for collecting diffused light signals.

[0015] By comparing the light signal transmission with and without the adjustment lens through simulation calculations, the divergence angle θ of the emitted light beam and the solid angle Ω of the diffused light received can be calculated to determine its necessity. Without the adjustment lens, the light from the source begins to diffuse after traveling approximately a few millimeters after exiting the prism reflector; however, the light signal transmitted through the adjustment lens maintains good directivity even at approximately 1 centimeter. This not only effectively suppresses severe beam diffusion of the fiber optic probe output light in the cerebral cortex, skull layer, and superficial brain tissue, improving spatial resolution, but also enhances the penetration depth into brain tissue. Moreover, when receiving diffused light signals, this adjustment lens effectively expands the signal reception solid angle, improving the overall light collection efficiency and enabling the reception of more light signals. In this sense, it further enhances the detection capability of deep brain regions.

[0016] The MPO fiber optic patch cord's connection ports are available in 8-core, 12-core, 24-core, and 48-core designs. The number of multi-transmit / receive fiber optic MPO connection ports is determined by the number of fiber optic probes. The male MPO connector in each port connects to the corresponding female MPO connector via an MPO adapter. The fiber optic probes can be inserted into a head-mounted probe cap and fixed to the brain-computer interface device. According to brain region divisions, detachable and fixed base interface devices are set at the determined head test points. Each probe point can be arbitrarily combined and reconfigured using triangular or square basic units. The convenient installation and arbitrary repositioning of the fiber optic probes enable head-mounted devices with multiple independent fiber optic probes arranged in an array. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a fiber optic brain-computer interface array system based on MPO connection technology.

[0018] Figure 2 This is a schematic diagram of the MPO fiber optic probe structure.

[0019] Figure 3 This is a schematic diagram of a fiber optic probe device used in fiber optic brain-computer interfaces, in which two fiber optic pigtails are coupled to a self-focusing collimating lens.

[0020] Figure 4 This is a schematic diagram of the structure of an MPO fiber optic probe with four probes.

[0021] Figure 5 It is an array of head-mounted detection caps and their brain-computer interface fiber optic probes, which can be arranged and combined using triangular or square basic units. Detailed Implementation

[0022] The present invention will be further illustrated below with reference to specific embodiments.

[0023] Example:

[0024] It is well known that the activity level of brain nerves is closely related to the degree of change in cerebral blood oxygen content. This allows us to infer the activity of brain nerves by measuring changes in local cerebral blood oxygen levels, thereby analyzing the neural activity of the brain and accurately locating specific brain regions of interest (e.g., the epileptogenic zone leading to epilepsy, the memory impairment zone corresponding to Alzheimer's disease, etc.). The fiber optic brain-computer interface array system based on MPO connection technology disclosed in this invention features bidirectional operation. It constructs an integrated multi-channel fiber optic brain-computer interface system that can be arrayed and distributed using MPO fiber optic jumpers and fiber optic probes. By acquiring diffuse reflected light information of blood oxygen changes within brain tissue, it monitors the amount of blood oxygen change and blood flow in the brain in real time, improving the spatial resolution of the detection. By testing the dynamic changes of HbO2 and HbR in the brain region under test, it provides information reflecting changes in cerebral hemodynamics, and then determines the location of brain regions with abnormal blood flow changes, providing a basis for establishing a convenient correspondence between brain functional activity and anatomical location.

[0025] Figure 1 A structural diagram of a fiber optic brain-computer interface array system based on MPO connection technology is presented. The system consists of a transmitting assembly formed by light sources 1-1 and 1-2, a single-mode fiber wavelength division multiplexer 2, and a fiber beam splitter 3; an MPO fiber jumper 4; an MPO fiber probe 5; a fiber combiner 6; and a single-photon detector (SPAD) 7. In the system, the two near-infrared wavelength light sources 1-1 and 1-2 emit light alternately. The optical signal passes through the wavelength division multiplexer 2, then through the fiber beam splitter 3, and via the MPO fiber jumper 4 to the self-focusing collimating lens 5-2 inside the MPO fiber probe 5-1. After passing through the 45° reflection surface of the prism reflector 5-3, it is focused by the beam adjustment lens 5-4 and injected into the cerebral cortex. The backscattered light signal from the cerebral cortex passes through the same adjustment lens 5-4, then through the prism reflector 5-3, and is sent back to the fiber combiner 6. It is received by the single-photon detector (SPAD) 7, converted, and amplified into an electrical signal for processing. In the fiber optic brain-computer interface array system based on MPO connection technology, two near-infrared wavelength light sources emit light at 735nm and 905nm respectively. The optical signal is transmitted to the MPO fiber optic patch cord via a wavelength division multiplexer and then a fiber optic beam splitter. Figure 4As shown, if four fiber optic probes are used, eight fiber optic pigtails are required. The male MPO connector in the eight-core MPO connection port is connected to the corresponding female MPO connector via an MPO adapter. Each fiber optic probe structure is connected to two fiber optic pigtails: one for transmitting the emitted light signal into the brain, and the other for receiving the backscattered light signal scattered from the cerebral cortex. The two fibers at the probe end are coupled to the same self-focusing collimating lens. The emitted light signal reaches the 45° reflecting surface of the prism reflector via the transmitting pigtail, and is then focused by the adjusting lens before being injected into the cerebral cortex. Simultaneously, this probe can also satisfy bidirectional optical path requirements. The backscattered light signal scattered from the cerebral cortex is received by the adjusting lens, reflected by the same prism reflector, and then enters the receiving pigtail through the self-focusing collimating lens. Finally, it is received by the single-photon detector (SPAD) via the MPO connector, converted, and amplified into an electrical signal for processing.

[0026] Four fiber optic probes can be inserted into a head-mounted detection cap and fixed to the brain-computer interface device. According to brain region divisions, detachable and fixed base interface devices are set at the determined head test points. Each detection point can be arbitrarily combined using triangular or square basic units. The convenient installation and arbitrary repositioning of the fiber optic probes enable a head-mounted device with multiple independent fiber optic probes arranged in an array, allowing for multi-point detection experiments on different brain regions. Figure 5 As shown in the figure. In the experiment, the required light signals can be measured at multiple locations in the cerebral cortex using a fiber optic brain-computer interface head-mounted testing device. These light signals can reflect changes in blood flow and blood oxygenation in the brain regions during brain activity.

Claims

1. A fiber optic brain-computer interface array system based on MPO connectivity technology, characterized in that: It consists of two near-infrared wavelength light sources 1-1 and 1-2, a single-mode fiber wavelength division multiplexer 2, a fiber beam splitter 3 forming the transmitting assembly, an MPO fiber optic patch cord 4, an MPO fiber optic probe 5, a fiber optic combiner 6, and a single-photon detector (SPAD) 7. In this system, the two near-infrared wavelength light sources 1-1 and 1-2 emit light alternately. The optical signal passes through the wavelength division multiplexer 2, then through the fiber beam splitter 3, and via the MPO fiber optic patch cord 4 to the self-focusing collimating lens 5-2 within the MPO fiber optic probe 5-1. After passing through the 45° reflecting surface of the prism reflector 5-3, it is focused by the beam adjustment lens 5-4 and injected into the cerebral cortex. The backscattered light signal from the cerebral cortex passes through the same adjustment lens 5-4, then through the prism reflector 5-3, and is sent back to the fiber beam combiner 6. The single-photon detector (SPAD) 7 receives, converts, and amplifies the signal into an electrical signal for processing.

2. The MPO fiber optic patch cord and fiber optic probe used in the fiber optic brain-computer interface array system based on MPO connection technology according to claim 1, characterized in that: The MPO fiber optic port is a fiber optic probe, and its connector part is made according to the MPO fiber optic patch cord connection technology. It has designs with 8 cores, 12 cores, 24 cores, 48 ​​cores, etc., and can be connected to the corresponding number of MPO fiber optic patch cords according to the number of fiber optic probes and application requirements.

3. The MPO fiber optic patch cord and fiber optic probe used in the fiber optic brain-computer interface array system based on MPO connection technology according to claim 1, characterized in that: The MPO fiber optic patch cord is connected at one end to a fiber optic splitter and a fiber optic combiner for system signal input and output, and at the other end to a brain-computer interface fiber optic probe. Each probe has two fiber optic pigtails, both coupled to the same self-focusing collimating lens. One pigtail is used to transmit emitted light signals into the brain, and the other is used to receive backscattered light signals from the cerebral cortex. The fiber optic probe consists of a brain-computer interface housing 5-1, a self-focusing collimating lens 5-2, a prism reflector 5-3, and a beam adjustment lens 5-4.

4. According to claim 1, a fiber optic brain-computer interface array system based on MPO connection technology is characterized by the array arrangement of the head-mounted probe cap and its brain-computer interface fiber optic probe embedding device as follows: according to the division of brain regions, a detachable fixed base interface device is set at the determined head test point; each probe point can be arbitrarily combined and reconstructed according to triangular or square basic units; the convenient installation and arbitrary position replacement function of the fiber optic probe can realize a head-mounted device with multiple independent fiber optic probes with array arrangement characteristics.

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