Gigabit visible light network communication equipment

Abstract

The invention relates to the technical field of communication, in particular to gigabit visible light network communication equipment. The equipment comprises a bidirectional transmitting and receiving system and a shell, the bidirectional transmitting and receiving system comprises a first signal transmission link and a second signal transmission link and is used for realizing bidirectional conversion and transmission of Ethernet signals and visible light signals, and the shell is used for integrating the bidirectional transmitting and receiving system; the first signal transmission link comprises a gigabit Ethernet, a first digital terminal, a first linear power amplifier, a first modulation circuit and a first LED lamp which are connected in sequence; the second signal transmission link comprises a second optical filter, a second avalanche photodiode, a second digital signal recovery circuit and a gigabit Ethernet which are connected in sequence, so that the second signal transmission link is converted into an Ethernet signal and then is output through the gigabit Ethernet; the first signal transmission link and the second signal transmission link are symmetrical in structure and form a transmitting-receiving corresponding relation. The stability of visible light communication can be improved.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a gigabit visible light network communication device. Background Art

[0002] Although VLC technology has numerous advantages, current research on VLC is mostly at the theoretical research and laboratory testing stage, and there are still many shortcomings. Research on existing visible light digital transmission systems often faces problems such as distance limitations, poor stability, and insufficient speed, and it is difficult to simultaneously meet both speed and transmission distance. For example, in the direction of high-speed transmission, the transmission distance of visible light communication systems exceeding 100Mbps is generally not high, and most are still in the laboratory stage. Communication is almost impossible beyond ten meters, making it of limited practicality. Alternatively, systems capable of transmitting over longer distances cannot reach speeds above 10Mbps. This is partly because signals exceeding 10Mbps place higher impedance matching requirements on the circuit, which cannot be met by conventional circuit designs. Furthermore, conventional LEDs do not have such a high response bandwidth.

[0003] In addition, similar patents such as CN201810343439.2 disclose a long-distance wireless laser WIFI communication system and method. The system includes a first digital optical terminal, a first optical amplifier, a first wavelength division multiplexer, a first optical antenna, a second optical antenna, a second wavelength division multiplexer, a second optical amplifier, a second digital optical terminal, and a wireless router. The method uses a wireless laser channel instead of a radio channel to transmit information. This invention solves the problems of the existing technology such as small WIFI signal coverage, insufficient bandwidth, poor transmission security, and unstable signal caused by interference of communication signals. It achieves long-distance WIFI signal coverage, increases the wireless WIFI communication bandwidth, makes the communication signal more stable, more secure, and has a shorter delay. Although it can achieve a balance between distance and transmission rate of communication signals, it has the following disadvantages in terms of laser signals:

[0004] 1. The laser beam divergence angle is extremely small, and the transmitter and receiver need to be aligned with high precision, making it difficult to maintain a connection in dynamic scenarios (such as mobile devices). VLC uses LEDs for wide-angle coverage, which has low requirements for terminal position.

[0005] 2. High-power lasers can damage the retina (especially infrared lasers, which are invisible), and require strict safety standards; VLC uses visible light, which has low power and is safer.

[0006] High-speed signal modulation for LED devices is much more difficult than for laser devices, but it can solve the above-mentioned shortcomings of laser space communication. Summary of the Invention

[0007] In order to solve the above-mentioned technical problems existing in existing gigabit network communication equipment, the present invention provides a research based on visible light audio and video transmission, which adopts OOK (On-OffKeying) modulation technology under gigabit Ethernet to couple 8b10b encoded serial signals to LED lights, realizes the transmission of optical signals in space through light and dark changes that are imperceptible to the naked eye, converts weak visible light signals into analog electrical signals through avalanche photodiodes, and uses a digital signal recovery circuit to restore the OOK modulated analog signals into digital signals, and finally communicates with terminal equipment through Ethernet. The gigabit visible light network communication equipment specifically includes a bidirectional transmitting and receiving system and a housing, wherein the bidirectional transmitting and receiving system includes a first signal transmission link and a second signal transmission link, which are used to realize bidirectional conversion and transmission of Ethernet signals and visible light signals, and the housing is used to integrate the bidirectional transmitting and receiving system;

[0008] The first signal transmission link includes a Gigabit Ethernet, a first digital terminal, a first linear power amplifier, a first modulation circuit, and a first LED lamp connected in sequence. The Gigabit Ethernet is used to access Ethernet signals. The first digital terminal converts the Ethernet signal of the Gigabit Ethernet RG45 interface into a serial differential digital signal, and converts the serial differential digital signal into a single-ended signal through an integrated differential-to-single-ended function. The first linear power amplifier amplifies the single-ended signal and reduces the output impedance. The first modulation circuit modulates the amplified digital signal to the first LED lamp through DC-AC coupling, so that the first LED lamp acts as an optical antenna to transmit a visible light signal.

[0009] The second signal transmission link includes a second optical filter, a second avalanche photodiode, a second digital signal recovery circuit, and a Gigabit Ethernet network connected in sequence; the second optical filter only passes blue light in the visible light band, the second avalanche photodiode converts the weak visible light signal transmitted through the second optical filter into an analog electrical signal, and the second digital signal recovery circuit converts the analog electrical signal into a CMOS-level digital signal, sends the digital signal to the second digital terminal, converts it into an Ethernet signal, and then outputs it via the Gigabit Ethernet network;

[0010] The first signal transmission link and the second signal transmission link are symmetrical in structure, and a corresponding sending and receiving relationship is formed between the first LED lamp and the second filter, and between the first filter and the second LED lamp.

[0011] The bidirectional transmitting and receiving system of the present invention achieves efficient and reliable communication by converting and transmitting Ethernet signals into visible light signals. First, the Gigabit Ethernet and the first digital terminal in the first signal transmission link can convert the Ethernet signal into a serial differential signal, which is then amplified by a first linear power amplifier to ensure that the signal is not affected by attenuation during transmission. The second modulation circuit modulates the enhanced digital signal into an LED light to transmit the visible light signal. This optical transmission method not only avoids interference from traditional radio waves but also provides a higher transmission rate and bandwidth. The second signal transmission link filters out the blue light signal through a second filter. In conjunction with a second avalanche photodiode and a digital signal recovery circuit, it can effectively recover the received weak visible light signal and convert it into a high-quality Ethernet signal output. The communication hardware structure corresponding to the entire Gigabit visible light network communication device adopts a symmetrical design, ensuring the consistency of the receiving and transmitting paths, reducing signal attenuation and distortion, and improving the overall stability and transmission efficiency of the Gigabit visible light network communication device. In addition, the integrated housing design of the gigabit visible light network communication equipment facilitates the combination and installation of components, reduces space occupancy, and helps with the heat dissipation management of the gigabit visible light network communication equipment. Through this optoelectronic bidirectional transmission system, high-speed and low-latency data transmission can be achieved, meeting the requirements of modern communication systems for high efficiency, low power consumption and high bandwidth, and has broad application prospects.

[0012] Preferably, the first digital terminal and the second digital terminal are both self-developed modules with an operating voltage of 3.0V-3.6V, and both include an RG45 interface, a power interface, an RX serial interface and a TX serial interface; the RG45 interface of the first digital terminal is connected to the Gigabit Ethernet to access the Ethernet signal, and the TX serial interface outputs the serial differential digital signal; the RX serial interface of the second digital terminal receives the digital signal output by the second digital signal recovery circuit, and its RG45 interface is connected to the Gigabit Ethernet to output the Ethernet signal.

[0013] The self-developed design of the first digital terminal and the second digital terminal in the present invention has many significant advantages. The self-developed module can be highly customized according to system requirements, ensuring the efficient conversion of the device between Ethernet signals and serial differential signals. It is connected to Gigabit Ethernet through the RG45 interface, ensuring high speed and stability of data transmission. The TX serial interface outputs serial differential digital signals, while the second digital terminal receives and converts digital signals through the RX serial interface, and further outputs Ethernet signals through the RG45 interface. This design effectively supports the conversion and transmission of bidirectional data streams, improves the flexibility and compatibility of the system, and also reduces the interference of external modules on the system stability, making the entire system more reliable and accurate. The voltage range (3.0V-3.6V) of the self-developed module adapts to a variety of power supply requirements, further improving the applicability and versatility of the communication equipment.

[0014] Preferably, the differential-to-single-ended functions integrated in the first digital terminal and the second digital terminal are both implemented by a balun; the left side of the balun is a 90Ω-110Ω differential input interface for receiving the serial differential digital signal output by the corresponding digital terminal, and the right side is a 45Ω-55Ω single-ended output interface for outputting the converted single-ended signal to the corresponding linear power amplifier, thereby realizing impedance conversion from differential signal to single-ended signal and matching the impedance of the front and back ends.

[0015] The differential-to-single-ended function in the present invention is realized by a balun, which has significant impedance matching and signal conversion effects. By using the 90Ω-110Ω differential input interface of the balun to receive serial differential digital signals, and then converting the signals into single-ended signals through the 45Ω-55Ω single-ended output interface, the impedance conversion of differential signals to single-ended signals is effectively realized. This conversion not only optimizes the transmission quality of the signal, but also ensures that the signal is not lost during the transmission process, ensuring the efficient transmission of the system. The impedance matching process makes the signal transmission more stable, avoids the signal reflection and loss problems caused by the impedance mismatch between the front and back ends, and improves the overall performance of the communication equipment. The implementation of this step plays a key role in the stable transmission of high-frequency signals and the overall efficiency improvement of the communication equipment.

[0016] Preferably, the first linear power amplifier and the second linear power amplifier are both wide-bandwidth RF amplifiers, and their input and output impedances are both 48Ω-52Ω; the first linear power amplifier amplifies the single-ended signal output by the first digital terminal to increase the signal power and reduces the output impedance to achieve impedance matching with the first modulation circuit; the second linear power amplifier amplifies the single-ended signal output by the second digital terminal to achieve impedance matching with the second modulation circuit.

[0017] In the present invention, the first linear power amplifier and the second linear power amplifier adopt a wide-bandwidth RF amplifier design, and the input and output impedance are between 48Ω-52Ω, which makes the impedance matching in the signal amplification process more accurate and efficient. By amplifying the single-ended signal and reducing the output impedance, the first linear power amplifier can significantly increase the signal power, thereby providing a strong and stable signal for the subsequent modulation circuit. In addition, the second linear power amplifier can also effectively amplify the signal output by the second digital terminal, ensuring its impedance matching with the modulation circuit, and optimizing the efficiency and stability of the signal transmission process. The wide-bandwidth RF amplifier has a wider frequency response range and can adapt to higher frequency and more complex signal processing requirements, enhancing the adaptability and anti-interference ability of the entire communication equipment in different environments, and laying a solid foundation for high-performance data transmission of the communication equipment.

[0018] Preferably, the first modulation circuit and the second modulation circuit both couple the transmitted AC digital signal and the DC bias voltage together, do not contain any active devices, and have a bandwidth of 1GHz-1.2GHz; the first modulation circuit makes the voltage acting on both ends of the first LED lamp equal to the sum of the DC signal and the AC signal voltage values ​​according to the circuit superposition principle, driving the first LED lamp to produce light and dark changes that are imperceptible to the naked eye, thereby realizing OOK modulation; the second modulation circuit drives the second LED lamp to perform signal modulation using the same principle.

[0019] The first modulation circuit and the second modulation circuit in the present invention couple the AC digital signal with the DC bias voltage without using any active devices, and the bandwidth range reaches 1GHz-1.2GHz. This design has multiple advantages. First, the passive design reduces the power consumption of the circuit and improves the energy efficiency of the system. Through the principle of circuit superposition, the first modulation circuit drives the first LED lamp to produce light and dark changes that are imperceptible to the naked eye, and uses OOK modulation to achieve efficient optical signal transmission. Since the frequency of the modulated signal is high and does not produce obvious visual changes, this not only avoids the flicker perceived by the human eye, but also effectively transmits information, which is suitable for high-speed data communication. The second modulation circuit adopts the same principle to ensure the symmetry and consistency of signal transmission, which helps to improve the overall performance of the system. In addition, the wide bandwidth range (1GHz-1.2GHz) makes the signal transmission more stable and adapts to more application scenarios, providing the communication equipment with a higher signal transmission rate and a wider applicability.

[0020] Preferably, the first filter and the second filter are both band-pass filters for the blue light band, and the passband wavelength range is 400nm-480nm; the first LED lamp and the second LED lamp emit blue light through semiconductors and excite yellow phosphors to produce yellow light mixed into white light, and the first filter and the second filter respectively filter out the yellow light and only pass the blue light, thereby avoiding the corresponding avalanche photodiode from being unable to operate in the linear region due to the DC component generated by the yellow light, thereby improving the signal-to-noise ratio.

[0021] In the present invention, the first filter and the second filter serve as bandpass filters for the blue light band, with a passband wavelength range of 400nm-480nm, which has significant advantages. The filters can accurately and selectively pass the blue light band and filter out yellow light, thereby avoiding the negative impact of yellow light interference on system performance. The first LED lamp and the second LED lamp emit blue light through semiconductors and excite yellow phosphors to produce yellow light mixed into white light. The blue light band is the key frequency band for signal transmission. Only blue light is allowed to pass through the filter, which avoids the avalanche photodiode from generating a DC component after receiving yellow light, thereby preventing it from being unable to operate in the linear region. This design effectively improves the signal-to-noise ratio and enhances the anti-interference ability of communication equipment, making the received optical signal purer. When converted into an electrical signal, the quality of data transmission is significantly improved, ensuring stable operation in various environments.

[0022] Preferably, the first avalanche photodiode and the second avalanche photodiode are both used as spatial light detectors, which output voltage signals of different amplitudes through a transresistance amplifier circuit according to the different received light illumination. The output voltage range is 0.01V-1.5V, and the blue light signals passing through the corresponding filters are converted into analog electrical signals.

[0023] In the present invention, the first and second avalanche photodiodes serve as spatial light detectors, converting received optical signals into voltage signals of varying amplitudes through a transimpedance amplifier circuit, with an output voltage range of 0.01V-1.5V. This design effectively converts blue light signals passing through the filter into analog electrical signals. The high sensitivity of the avalanche photodiodes enables them to capture weak blue light signals and accurately convert them into corresponding voltage outputs, ensuring high-quality acquisition of photoelectric signals. The transimpedance amplifier circuit converts weak current signals into more powerful voltage signals, enhancing signal processing capabilities and providing sufficient dynamic range to adapt to signal changes under varying light intensities. This design enables high-precision signal conversion to be maintained under varying lighting conditions, avoiding distortion caused by optical signal attenuation, improving the overall performance and stability of communication equipment, and laying the foundation for high-quality photoelectric signal conversion and accurate data transmission.

[0024] Preferably, the first digital signal recovery circuit and the second digital signal recovery circuit both include a high-speed decision device with a bandwidth of 1.2GHz-1.8GHz; the high-speed decision device adopts a zero-crossing decision circuit with hysteresis decision, which filters noise and maintains high sensitivity by controlling the comparison level, and converts the analog signals output by the corresponding avalanche photodiode into CMOS-level digital signals.

[0025] The first and second digital signal recovery circuits in the present invention use a high-speed decider with a bandwidth of 1.2GHz-1.8GHz and a zero-crossing decision circuit with hysteresis decision. This design provides multiple advantages. First, the bandwidth range of the high-speed decider ensures that the signal recovery process can process high-frequency signals and meet the needs of modern high-speed data communications. The hysteresis decision circuit filters out noise by controlling the comparison level, effectively improving the accuracy of signal recovery and avoiding misjudgment caused by noise, thereby ensuring high-quality signal recovery. Through this circuit, the analog signal output by the avalanche photodiode can be accurately converted into a digital signal at the CMOS level, ensuring that the subsequent digital processing circuit can accurately receive and process data. This highly sensitive and reliable signal conversion method improves the anti-interference ability of the communication equipment, enabling it to still work stably in complex environments. Overall, the design of the digital signal recovery circuit not only improves the stability and reliability of the communication equipment, but also greatly improves the quality of data transmission and enhances the practical application value of the equipment.

[0026] Preferably, in the PCB design, the characteristic impedance of the transmission line is maintained at 48Ω-52Ω through calculation, SMA RF connectors are used for input and output, and coaxial RF cables are used to connect different modules or PCBs; the first LED lamp and the second LED lamp are both connected in series with a 50R resistor, and the first modulation circuit and the second modulation circuit both use bias ties in a compact package to achieve good insertion loss and isolation performance over a wide frequency band of 400kHz-3GHz, so as to realize impedance matching during signal transmission.

[0027] The PCB design in the present invention maintains the characteristic impedance of the transmission line between 48Ω-52Ω through precise calculation, and uses SMA RF connectors for input and output. This design ensures the stability and reliability of signal transmission. The matching of characteristic impedance enables good attenuation control of the signal during transmission, reduces signal reflection and loss, and ensures high-quality signal transmission. By using coaxial RF cables to connect different modules or PCBs, external interference is effectively avoided and the anti-interference ability of the equipment is improved. The first and second LED lights achieve impedance matching in signal transmission by connecting a 50Ω resistor in series, further optimizing the signal transmission process. The compact packaged bias breaker achieves excellent insertion loss and isolation performance over a wide frequency band of 400kHz-3GHz, ensuring signal integrity and high efficiency of the equipment. The design of this step improves the stability, flexibility and compatibility of the signal transmission process, while reducing power consumption and improving the overall performance of the equipment.

[0028] Preferably, the shell has a size of 10x9x14cm, and is provided with two groups of light emitting lenses and light receiving lenses with a size of 5cm-7cm each; the first LED lamp and the second avalanche photodiode are respectively fixed at the focus of one group of light emitting lenses and light receiving lenses, and the second LED lamp and the first avalanche photodiode are respectively fixed at the focus of another group of light emitting lenses and light receiving lenses; the power management module, the first digital terminal and the second digital terminal are placed at the bottom of the shell, and two gigabit network ports and a power interface are led out on the shell to realize the two-way communication integration and convenient use of the equipment.

[0029] The shell size of the present invention is 10x9x14cm, and it is equipped with two sets of light-emitting lenses and light-receiving lenses, with a size of 5cm-7cm, which optimizes the optical performance of the device. By fixing the first LED lamp and the second avalanche photodiode at the focus of the light-emitting lens and the light-receiving lens respectively, the efficient transmission and reception of the optical signal is guaranteed. This precise optical alignment improves the transmission efficiency of the optical signal, reduces the loss of the optical signal, and ensures that the device can operate stably under different lighting conditions. In addition, the configuration of the second set of light-emitting lenses and receiving lenses further enhances the optical symmetry of the device and optimizes the signal transmission and reception effect. The power management module, the first and second digital terminals placed at the bottom of the shell ensure the integration of the device, enhance the compactness and overall stability of the device, and the two gigabit network ports and power interface led out from the shell make it more convenient to connect the device to other devices, support two-way communication, and improve the operability and scalability of the device. This design not only improves the reliability of the device, but also increases the convenience of use of the device, providing users with a better experience.

[0030] The present invention specifically has the following beneficial effects:

[0031] (1) The first signal transmission link realizes efficient signal conversion and transmission through the integrated Gigabit Ethernet, the first digital terminal, the first linear power amplifier, the first modulation circuit and the first LED lamp. The Gigabit Ethernet access can stably receive network signals, ensuring the efficiency and stability of the communication equipment. The first digital terminal converts the Gigabit Ethernet signal into a serial differential digital signal, and converts it into a single-ended signal through the differential to single-ended function, thereby optimizing the interference and loss during the signal transmission process. The first linear power amplifier amplifies the signal and reduces the output impedance, ensuring that the signal can be stably transmitted and obtains a stronger driving capability, thereby enhancing the anti-interference capability of the equipment. The first modulation circuit modulates the signal and drives the first LED lamp to send a visible light signal, so that the signal can be transmitted over a long distance through the optical antenna, thereby improving the coverage range and transmission speed of the network.

[0032] (2) The design of the second signal transmission link ensures the efficient reception and conversion of visible light signals. The second filter accurately selects blue light in the visible light band and effectively filters out other spectral interference, ensuring the purity and accuracy of signal reception. The second avalanche photodiode can capture the weak visible light signal that passes through the filter with high sensitivity and convert it into an analog electrical signal, providing high-quality input for signal recovery. Then, the second digital signal recovery circuit converts the analog signal into a CMOS-level digital signal, further improving the stability and accuracy of the signal and reducing distortion during signal transmission. Finally, the Ethernet signal processed by the second digital terminal can be output through Gigabit Ethernet, ensuring signal integrity and efficient network connection. The structural design of this link effectively improves the reception and recovery capabilities of visible light network communication and enhances the signal transmission quality of the entire communication equipment.

[0033] (3) The design of the bidirectional transmitting and receiving system enables the device to achieve stable bidirectional Ethernet signal and visible light signal conversion and transmission, optimizes the bandwidth utilization during data transmission, and realizes bidirectional communication function through the symmetrical structure of the first signal transmission link and the second signal transmission link, supports balanced transmission of upload and download data streams, and improves the overall efficiency of the network. At the transmitting end, the LED light acts as an optical antenna to modulate the digital signal into a visible light signal for transmission, ensuring that the signal propagates quickly and stably in the optical field. At the receiving end, precise filters and high-sensitivity photodiodes are used to receive the optical signal, and the digital signal recovery circuit is used to restore it to a high-quality digital signal, ensuring the accuracy and integrity of the information. In addition, the bidirectional structure not only improves the transmission rate of the communication equipment, but also enhances the adaptability of the equipment in a variety of environments. It is suitable for high-density, low-latency network environments and has broad application prospects.

[0034] (4) The receiving end of the present invention uses a spatial light detector to convert the optical signal into an electrical signal. This process is based on the different light illumination received by the detector, and outputs voltage signals of different amplitudes through the transimpedance amplifier circuit. Since light propagates in space, after passing through different distances, media or obstructions, the light intensity reaching the receiving end is not fixed, so the signal quality is not fixed, and the level range of the photodetector output is also not fixed. For example, in a harsh communication environment, the voltage signal output by the receiving end after amplification is only tens of mV, while in the case of strong light at close range, the voltage signal output by the receiving end reaches more than 1V. If the level is not processed, it cannot pass normally. Although there are technologies such as automatic gain control that can achieve level stability, this will cause a decrease in the signal-to-noise ratio. Therefore, it is necessary to use OOK modulation technology in combination with zero-crossing judgment to achieve stable and reliable spatial optical communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments thereof made with reference to the following drawings:

[0036] Figure 1 This is a schematic diagram of the hardware structure of the gigabit visible light network communication device of the present invention;

[0037] Figure 1 The symbols in the figure are: 1. Gigabit Ethernet; 2. First digital terminal; 3. First linear power amplifier; 4. First modulation circuit; 5. First LED lamp; 6. First lens; 7. First optical filter; 8. First avalanche photodiode; 9. First digital signal recovery circuit; 10. Second LED lamp; 11. Second modulation circuit; 12. Second linear power amplifier; 13. Second digital terminal; 14. Gigabit Ethernet; 15. Second lens; 16. Second optical filter; 17. Second avalanche photodiode; 18. Second digital signal recovery circuit.

[0038] Figure 2 Schematic diagram of the working principle of the bidirectional transmitting and receiving system corresponding to the transmitting process of the present invention;

[0039] Figure 3 Schematic diagram of the working principle of the receiving process of the bidirectional transmitting and receiving system of the present invention;

[0040] Figure 4 Schematic diagram of the working principle of the balun of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described below with reference to the accompanying drawings and examples, but they are not intended to limit the present invention.

[0042] To achieve this, please refer to Figures 1 to 4, the embodiment of the present invention provides a gigabit visible light network communication device, such as Figure 1 As shown, it includes a bidirectional transmitting and receiving system and a housing. The bidirectional transmitting and receiving system includes a first signal transmission link and a second signal transmission link, which are used to realize bidirectional conversion and transmission of Ethernet signals and visible light signals. The housing is used to integrate the bidirectional transmitting and receiving system.

[0043] The first signal transmission link includes a Gigabit Ethernet 1, a first digital terminal 2, a first linear power amplifier 3, a first modulation circuit 4, and a first LED lamp 5, which are connected in sequence. The Gigabit Ethernet 1 is used to access Ethernet signals. The first digital terminal 2 converts the Ethernet signal of the RG45 interface of the Gigabit Ethernet 1 into a serial differential digital signal, and converts the serial differential digital signal into a single-ended signal through an integrated differential-to-single-ended function. The first linear power amplifier 3 amplifies the single-ended signal and reduces the output impedance. The first modulation circuit 4 modulates the amplified digital signal to the first LED lamp 5 through DC-AC coupling, so that the first LED lamp 5 acts as an optical antenna to transmit a visible light signal.

[0044] The second signal transmission link includes a second optical filter 16, a second avalanche photodiode 17, a second digital signal recovery circuit 18, and a Gigabit Ethernet 14, which are connected in sequence. The second optical filter 16 only passes blue light in the visible light band. The second avalanche photodiode 17 converts the weak visible light signal transmitted through the second optical filter 16 into an analog electrical signal. The second digital signal recovery circuit 18 converts the analog electrical signal into a CMOS-level digital signal, sends it to the second digital terminal 13, converts it into an Ethernet signal, and then outputs it through the Gigabit Ethernet 14.

[0045] The first signal transmission link and the second signal transmission link are symmetrical in structure, and the first LED lamp 5 and the second filter 16 , as well as the first filter 7 and the second LED lamp 10 form a corresponding sending and receiving relationship.

[0046] In an embodiment of the present invention, the shell of the gigabit visible light network communication device is made of aluminum alloy and is formed by precision CNC processing. The dimensions are strictly controlled to be 10 cm in length, 9 cm in width, and 14 cm in height. The interior of the shell adopts a double-layer structure design, the inner layer is the installation area of ​​the core components of the device, and the outer layer is a heat dissipation channel. Air convection heat dissipation is achieved through fine heat dissipation holes on the surface of the shell. The bidirectional transmitting and receiving system is installed in the inner layer of the shell. Its first signal transmission link and the second signal transmission link are symmetrically arranged to ensure the balance and stability of signal transmission. Two standard RJ45 gigabit network ports and a power interface are set on the front of the shell. The RJ45 network port adopts a metal shielding design with a built-in electromagnetic shielding layer and an isolation transformer to effectively prevent electromagnetic interference from affecting the Ethernet signal; the power interface adopts a DC power socket equipped with an anti-reverse protection circuit to ensure safe power supply for the equipment. The components are fixed inside the shell by insulating brackets and shock-absorbing gaskets to reduce the impact of vibration on signal transmission, thereby realizing the integration and compact structure of the bidirectional transmitting and receiving system. The transmitting process and receiving process corresponding to the bidirectional transmitting and receiving system are as follows: Figure 2 and Figure 3 shown.

[0047] In the first signal transmission link, Gigabit Ethernet 1 is connected to external network equipment via a standard Cat6 network cable. The 8-core RJ45 cable is wired strictly according to the T568B standard to ensure stable Ethernet signal access. The first digital terminal 2 uses an application-specific integrated circuit (ASIC) chip with an operating voltage of 3.3V. Its internal network interface controller parses the Ethernet signal and converts it into a serial differential digital signal. The terminal integrates a balun device to achieve differential-to-single-ended conversion. The balun's differential input interface impedance is 100Ω, and its single-ended output interface impedance is 50Ω. Signal conversion and impedance matching are achieved through electromagnetic coupling. The converted single-ended signal is then transmitted to the first linear power amplifier 3, which utilizes a multi-stage amplification circuit design consisting of an input matching network, an amplification unit, and an output matching network. The input matching network converts the 50Ω input signal to the amplifier's optimal input impedance. The amplification unit then amplifies the signal, and the output matching network adjusts the signal impedance to 48Ω to meet the input requirements of the subsequent first modulation circuit 4. The first modulation circuit 4 is composed of a passive LC coupling network. Through a combination of inductors and capacitors, the amplified digital signal is superimposed with a DC bias voltage, and the first LED lamp 5 is driven by voltage superposition. The LED lamp produces high-frequency brightness changes according to the high and low levels of the digital signal, and converts the electrical signal into a visible light signal and transmits it, realizing the conversion and transmission of Ethernet signals into visible light signals.

[0048] In the second signal transmission link, the second filter 16 uses multi-layer dielectric film interference filter technology. Materials with different refractive indices are alternately deposited on a glass substrate through a vacuum coating process to form a precise film structure, achieving high transmittance (greater than 95%) for the 400nm-480nm blue light band and high rejection rate (OD value greater than 5) for other bands. The second avalanche photodiode 17 is fixed behind the filter, and its photosensitive surface maintains a distance of 1mm from the filter to ensure maximum reception of the transmitted blue light signal. When weak blue light is irradiated on the photosensitive surface of the avalanche photodiode, photons excite electron-hole pairs, which undergo an avalanche multiplication effect under the action of a high reverse bias voltage, converting the light signal into a weak current signal. This current signal is transmitted to the second digital signal recovery circuit 18, which first converts the current signal into a voltage signal through a transimpedance amplifier. The transimpedance amplifier uses a low-noise operational amplifier and a 10kΩ feedback resistor to achieve initial signal amplification. Next, a high-speed decision maker with a bandwidth of 1.2GHz-1.8GHz is used to process the amplified analog voltage signal through the hysteresis comparison principle and convert it into a CMOS-level digital signal. After the second digital terminal 13 receives the digital signal, it converts it into an Ethernet signal format through an internal protocol conversion circuit, and finally outputs it to an external network device through the RJ45 interface of the Gigabit Ethernet 14, completing the conversion of the visible light signal into an Ethernet signal.

[0049] The first signal transmission link and the second signal transmission link are strictly symmetrical in terms of physical structure and signal processing flow. Inside the housing, the first lens 6, the first filter 7 and the first avalanche photodiode 8 are on the same optical axis, ensuring that the visible light signal emitted by the second LED lamp 10 can accurately pass through the first lens 6 and the first filter 7 and be received; similarly, the second lens 15, the second filter 16 and the second avalanche photodiode 17 are also on the same optical axis, forming a corresponding relationship between sending and receiving. This symmetrical layout allows the device to have consistent signal transmission paths and processing methods during bidirectional communication, ensuring stable bidirectional transmission of data. Unlike traditional optical communication equipment, the communication technology corresponding to the first signal transmission link and the second signal transmission link adopts spatial optical communication, which allows a certain angular error between the transmitting and receiving ends to work normally. This is also one of the advantages of the present invention, that is, no precise alignment is required. In terms of circuit design, the component parameters and performance indicators of corresponding functions in the two links are strictly matched. For example, the first digital terminal 2 and the second digital terminal 13 use the same chip architecture and processing logic, the first linear power amplifier 3 and the second linear power amplifier 12 have the same amplification factor and impedance characteristics, and the first modulation circuit 4 and the second modulation circuit 11 have consistent coupling parameters, ensuring the consistency and stability of the signal during bidirectional transmission, thereby realizing efficient and reliable bidirectional gigabit visible light network communication for the equipment.

[0050] Furthermore, the first digital terminal 2 and the second digital terminal 13 are both self-developed modules with an operating voltage of 3.0V-3.6V, and both include an RG45 interface, a power interface, an RX serial interface and a TX serial interface; the RG45 interface of the first digital terminal 2 is connected to the Gigabit Ethernet 1 to access the Ethernet signal, and the TX serial interface outputs the serial differential digital signal; the RX serial interface of the second digital terminal 13 receives the digital signal output by the second digital signal recovery circuit 18, and its RG45 interface is connected to the Gigabit Ethernet 14 to output the Ethernet signal.

[0051] In an embodiment of the present invention, both the first digital terminal 2 and the second digital terminal 13 utilize an ASIC chip solution, with operating voltages strictly controlled within the range of 3.0V-3.6V. Voltage stability is achieved through the corresponding TPS62912 power management IC. Both digital terminals include an RG45 interface, a power interface, an RX serial interface, and a TX serial interface. The RG45 interface utilizes a Molex 50-57-9300 Ethernet connector and supports 10 / 100 / 1000Mbps adaptive transmission. The RG45 interface of the first digital terminal 2 is connected to the Gigabit Ethernet 1 switch via a Cat6 network cable to receive data packets from the network layer. The MAC layer chip within the terminal converts Ethernet frames into serial differential digital signals, which are output via the TX serial interface to ensure signal anti-interference capability during long-distance transmission. The RX serial interface of the second digital terminal 13 receives digital signals from the second digital signal recovery circuit 18. After processing by the internal MAC layer, the signals are output via the RG45 interface to the D-Link DES-3200 switch of the Gigabit Ethernet 14, completing bidirectional transmission of network data.

[0052] Furthermore, the differential-to-single-ended conversion functions integrated in the first digital terminal 2 and the second digital terminal 13 are both implemented by baluns; the left side of the balun is a 90Ω-110Ω differential input interface for receiving the serial differential digital signal output by the corresponding digital terminal, and the right side is a 45Ω-55Ω single-ended output interface for outputting the converted single-ended signal to the corresponding linear power amplifier, thereby realizing impedance conversion from differential signals to single-ended signals and matching the impedance of the front and back ends.

[0053] In the embodiment of the present invention, the differential to single-ended conversion function of the first digital terminal 2 and the second digital terminal 13 are both implemented using baluns (eg Figure 4The impedance of the balun's left differential input interface is designed to be 90Ω-110Ω, strictly matching the output / input impedance of the digital terminal's TX / RX serial interface to ensure reflection-free signal transmission. The impedance of the right single-ended output interface is designed to be 45Ω-55Ω, perfectly matching the input impedance of the subsequent linear power amplifier. In terms of PCB layout, the balun's differential input uses equal-length wiring with a length error controlled within ±5mil to ensure phase consistency of the differential signal. A 50Ω load resistor is connected in series to ground at the single-ended output to form a standard 50Ω impedance environment. During signal transmission, the balun converts the differential signal into a single-ended signal through the principle of electromagnetic coupling, while achieving a 1:2 impedance transformation to ensure maximum signal power transmission efficiency. The converted single-ended signal is transmitted to the linear power amplifier via a low-loss microstrip line. The microstrip line width is accurately calculated to be 20mil based on the characteristics of the PCB material to ensure a characteristic impedance of 50Ω.

[0054] Furthermore, the first linear power amplifier 3 and the second linear power amplifier 12 are both wide-bandwidth RF amplifiers, and their input and output impedances are both 48Ω-52Ω; the first linear power amplifier 3 amplifies the single-ended signal output by the first digital terminal 2 to increase the signal power and reduces the output impedance to achieve impedance matching with the first modulation circuit 4; the second linear power amplifier 12 amplifies the single-ended signal output by the second digital terminal 13 to achieve impedance matching with the second modulation circuit 11.

[0055] In the embodiment of the present invention, the first linear power amplifier 3 and the second linear power amplifier 12 are both selected from corresponding broadband RF amplifiers, whose input and output impedances are designed to be 48Ω-52Ω, and the operating bandwidth covers 100MHz-3GHz, meeting the high-frequency signal amplification requirements of gigabit visible light communication. The single-ended signal output by the first digital terminal 2 is transmitted to the input end of the broadband RF amplifier through a 50Ω microstrip line. The amplifier adopts a multi-stage amplification structure inside. The first stage provides a fixed gain of 10dB, and the second stage realizes adaptive gain control through a feedback network. The total gain can reach 20dB. The signal is transmitted to the first modulation circuit 4 through a 50Ω output matching network. The matching network consists of a π-type LC network. L1 uses a 1.2nH high-frequency inductor in a 0402 package, and C1 and C2 use 2.2pF high-frequency capacitors in a 0402 package to ensure optimal impedance matching at a frequency of 1GHz. The second linear power amplifier 12 uses the same circuit design to amplify the single-ended signal output by the second digital terminal 13. Through optimized PCB layout and grounding design, the noise coefficient of the amplifier is controlled within 2.5dB, ensuring that the signal quality meets the requirements of the subsequent modulation circuit.

[0056] Furthermore, the first modulation circuit 4 and the second modulation circuit 11 both couple the transmitted AC digital signal and the DC bias voltage together, and do not contain any active devices, with a bandwidth of 1GHz-1.2GHz; the first modulation circuit 4, based on the circuit superposition principle, makes the voltage value acting on both ends of the first LED lamp 5 equal to the sum of the DC signal and the AC signal voltage values, driving the first LED lamp 5 to produce light and dark changes that are imperceptible to the naked eye, thereby realizing OOK modulation; the second modulation circuit 11 drives the second LED lamp 10 to perform signal modulation using the same principle.

[0057] In an embodiment of the present invention, both the first modulation circuit 4 and the second modulation circuit 11 utilize a passive LC network to couple the AC digital signal with the DC bias voltage. The circuit comprises a 10μH high-frequency choke inductor and a 0.1μF DC-blocking capacitor, forming a π-type network. The bandwidth is controlled within the 1GHz-1.2GHz range by precisely calculating the inductor and capacitor values. When a digital signal passes through, the inductor blocks the AC signal but allows the DC signal, while the capacitor blocks the DC signal but allows the AC signal, achieving superposition of the two signals. The first modulation circuit 4 transmits the superimposed signal to the first LED lamp 5. According to the circuit superposition principle, the voltage across the LED is equal to the sum of the DC bias voltage and the AC digital signal voltage. When the AC signal is high, the total voltage of the LED increases, enhancing its luminous intensity. When the AC signal is low, the total voltage decreases, weakening its luminous intensity. In this manner, the LED is driven to produce light and dark variations with a frequency of up to 1GHz, achieving OOK modulation. The entire modulation process is implemented entirely with passive components, avoiding the noise and nonlinear distortion issues associated with active components and ensuring that the signal quality meets gigabit-class transmission requirements.

[0058] Furthermore, the first filter 7 and the second filter 16 are both band-pass filters for the blue light band, and their passband wavelength range is 400nm-480nm; the first LED lamp 5 and the second LED lamp 10 emit blue light through semiconductors and excite yellow phosphors to produce yellow light mixed into white light, and the first filter 7 and the second filter 16 respectively filter out the yellow light and only pass the blue light, thereby avoiding the corresponding avalanche photodiode from being unable to operate in the linear region due to the DC component generated by the yellow light, thereby improving the signal-to-noise ratio.

[0059] In this embodiment of the present invention, both the first filter 7 and the second filter 16 utilize multilayer dielectric film interference filter technology. High-refractive-index and low-refractive-index dielectric materials are alternately deposited on an optical glass substrate through a vacuum coating process, forming a precisely controlled film structure. The filter's passband wavelength range is strictly controlled between 400nm and 480nm, with a cutoff depth reaching OD5 (i.e., 99.999% attenuation of light outside the passband). The first LED lamp 5 and the second LED lamp 10 utilize white light technology, in which a blue light chip excites a yellow phosphor. The emitted mixed light contains a significant amount of blue light components around 450nm and yellow light components around 550nm. When light passes through the filters, the multilayer dielectric film structure selectively allows the blue light to pass through through interference effects, while reflecting or absorbing light of other wavelengths, such as yellow light. In this way, only the blue light component reaches the avalanche photodiode, avoiding the influence of the DC component in the yellow light on the detector. Since the response characteristics of the avalanche photodiode are more sensitive in the blue light band and the high-frequency characteristics of blue light are more suitable for high-speed data transmission, the signal-to-noise ratio and transmission performance of the system are effectively improved through filtering processing.

[0060] Furthermore, the first avalanche photodiode 8 and the second avalanche photodiode 17 both serve as spatial light detectors, which output voltage signals of different amplitudes through a transresistance amplifier circuit according to the different received light illuminations. The output voltage range is 0.01V-1.5V, and the blue light signals passing through the corresponding filters are converted into analog electrical signals.

[0061] In an embodiment of the present invention, both the first avalanche photodiode 8 and the second avalanche photodiode 17 employ a semiconductor photodetector structure with an internal gain mechanism. When blue light strikes the photosensitive surface of the detector, photons are absorbed and generate electron-hole pairs. Under the action of a high reverse bias, these carriers gain sufficient energy and collide with the lattice, generating more electron-hole pairs and forming an avalanche multiplication effect, thereby significantly improving the sensitivity of the detector. The weak current signal output by the detector is converted into a voltage signal by a transimpedance amplifier circuit. This circuit is composed of a low-noise operational amplifier and a precision feedback resistor. The feedback resistor value is set to 10kΩ, ensuring stable signal amplification within a bandwidth range of 1GHz-1.2GHz. When the received light intensity changes, the current output by the detector changes accordingly, and after transimpedance amplification, a voltage signal in the range of 0.01V-1.5V is output. By precisely controlling the avalanche gain and amplification factor, the output voltage signal can accurately reflect the intensity changes of the input light signal, achieving linear conversion from the light signal to the analog electrical signal, and providing a high-quality input signal for subsequent digital signal recovery.

[0062] Furthermore, the first digital signal recovery circuit 9 and the second digital signal recovery circuit 18 both include a high-speed decision device with a bandwidth of 1.2GHz-1.8GHz; the high-speed decision device adopts a zero-crossing decision circuit with hysteresis decision, which filters noise and maintains high sensitivity by controlling the comparison level, and converts the analog signals output by the corresponding avalanche photodiode into CMOS-level digital signals.

[0063] In this embodiment of the present invention, the high-speed decision makers of the first digital signal recovery circuit 9 and the second digital signal recovery circuit 18 both employ a hysteresis comparator architecture, with a ±200mV hysteresis voltage set via a precision resistor network. A Schottky diode protection circuit is employed at the input stage to limit the input voltage range to -0.5V to +2.0V to prevent overvoltage damage. The decision maker's reference level is set to 0.75V via a high-precision voltage divider circuit, ensuring operation near the CMOS threshold. When the analog signal exceeds the reference level, the output transitions to a high level (3.3V); when the signal falls below the reference level minus the hysteresis voltage, the output transitions to a low level (0V). This hysteresis mechanism effectively filters noise interference within the ±200mV range while maintaining detection sensitivity for weak signals. To meet bandwidth requirements of 1.2GHz-1.8GHz, the circuit employs a multi-stage differential amplifier structure, with each amplifier stage designed to have a gain-bandwidth product of 3GHz. Interstage connections are achieved via capacitive coupling to ensure a flat signal response across the entire bandwidth. The output stage adopts a push-pull structure and can directly drive a 50Ω load. The rise and fall times of the output signal are controlled within 200ps, ensuring that the edge steepness of the digital signal meets the requirements of high-speed communication.

[0064] Furthermore, in the PCB design, the characteristic impedance of the transmission line is maintained at 48Ω-52Ω through calculation, SMA RF connectors are used for input and output, and coaxial RF cables are used to connect different modules or PCBs; the first LED lamp 5 and the second LED lamp 10 are each connected in series with a 50R resistor, and the first modulation circuit 4 and the second modulation circuit 11 both use bias ties in a compact package to achieve good insertion loss and isolation performance over a wide frequency band of 400kHz-3GHz, so as to achieve impedance matching during signal transmission.

[0065] In an embodiment of the present invention, in the PCB design, the transmission line adopts a microstrip line structure, and the substrate material is FR-4 material with a dielectric constant of 4.4, and the thickness is controlled at 0.8mm. The microstrip line width is calculated to be 2.0mm, ensuring that the characteristic impedance is 50Ω, and the error is controlled within the range of ±2Ω. All signal lines are routed at 45° angles to avoid right-angle reflections, and the spacing between adjacent lines is maintained at more than 3mm to reduce crosstalk. When the SMA RF connector is soldered to the PCB, the center pin of the connector is directly connected to the microstrip line, and the outer conductor and the ground plane of the PCB are connected at low impedance through multiple vias. The coaxial RF line connecting different modules uses RG-316 type cable with a characteristic impedance of 50Ω, an outer diameter of 2.2mm, and an attenuation of no more than 0.4dB / m at 1GHz. The first LED lamp 5 and the second LED lamp 10 are each connected in series with a 50Ω precision resistor. The resistor uses a 1206 package with a temperature coefficient of ±50ppm / ℃ to ensure the stability of the LED operating current under different temperature environments. The bias transistors of the first modulation circuit 4 and the second modulation circuit 11 are manufactured using the LTCC process, with multi-layer inductors and capacitors integrated inside. The insertion loss is less than 0.5dB in the frequency range of 400kHz-3GHz, and the isolation is greater than 20dB, effectively achieving separation and impedance matching of AC and DC signals.

[0066] Furthermore, the shell has a size of 10x9x14cm, and is equipped with two sets of light-emitting lenses and light-receiving lenses, each with a size of 6cm; the first LED lamp 5 and the second avalanche photodiode 17 are respectively fixed at the focus of one set of light-emitting lenses and light-receiving lenses, and the second LED lamp 10 and the first avalanche photodiode 8 are respectively fixed at the focus of another set of light-emitting lenses and light-receiving lenses; a power management module, a first digital terminal 2 and a second digital terminal 13 are placed at the bottom of the shell, and two gigabit network ports and a power interface are led out on the shell to realize the two-way communication integration and convenient use of the equipment.

[0067] In the embodiment of the present invention, the device shell is made of aluminum alloy material and is formed by CNC precision processing. The size is strictly controlled to 10x9x14cm. The internal light emitting lens and light receiving lens group are both aspherical in design, with a diameter of 6cm and a focal length of 5cm. They are manufactured by molded glass process and coated with anti-reflection film on the surface. The transmittance is greater than 95%. The first LED lamp 5 and the second avalanche photodiode 17 are respectively fixed at the focal position of the first group of light emitting lens and light receiving lens by precision positioning fixtures. The position error is controlled within ±50μm. The second LED lamp 10 and the first avalanche photodiode 8 are fixed at the focus of the second group of lenses in the same way. The bottom of the shell is designed with heat dissipation fins, and the power management module Thermally conductive silicone is attached to the heat sink fins to ensure effective heat dissipation during operation. The first digital terminal 2 and the second digital terminal 13 are fixed to the bottom of the casing with an L-shaped bracket. Shock-absorbing rubber pads are used between the bracket and the PCB to reduce the impact of mechanical vibration on the circuit. Two RJ45 gigabit network ports and a DC power interface are connected to the front of the casing. The network port adopts a metal shell shielding design and is connected to the internal circuit through an isolation transformer to ensure electrical isolation and anti-interference capabilities. The power interface adopts an anti-reverse connection design and a built-in overcurrent protection circuit. When the current exceeds 3A, the power supply is automatically cut off to ensure safe operation of the equipment. The entire device has achieved the integration of two-way communication functions through structural optimization while maintaining ease of use.

[0068] The present invention is therefore intended to be illustrative and non-restrictive in all respects, with the scope of the invention being defined by the appended claims rather than the foregoing description, and all changes that come within the meaning and range of equivalents of the application documents are intended to be embraced therein.

[0069] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown herein, but is to be construed in the widest possible manner consistent with the principles and novel features disclosed herein.

Claims

1. Gigabit visible light network communication equipment, characterized by: It includes a bidirectional transmitting and receiving system and a housing, wherein the bidirectional transmitting and receiving system includes a first signal transmission link and a second signal transmission link, and is used to realize bidirectional conversion and transmission of Ethernet signals and visible light signals, and the housing is used to integrate the bidirectional transmitting and receiving system; The first signal transmission link includes a Gigabit Ethernet, a first digital terminal, a first linear power amplifier, a first modulation circuit, and a first LED lamp connected in sequence. The Gigabit Ethernet is used to access Ethernet signals. The first digital terminal converts the Ethernet signal of the Gigabit Ethernet RG45 interface into a serial differential digital signal, and converts the serial differential digital signal into a single-ended signal through an integrated differential-to-single-ended function. The first linear power amplifier amplifies the single-ended signal and reduces the output impedance. The first modulation circuit modulates the amplified digital signal to the first LED lamp through DC-AC coupling, so that the first LED lamp acts as an optical antenna to transmit a visible light signal. The second signal transmission link includes a second optical filter, a second avalanche photodiode, a second digital signal recovery circuit, and a Gigabit Ethernet network connected in sequence; the second optical filter only passes blue light in the visible light band, the second avalanche photodiode converts the weak visible light signal transmitted through the second optical filter into an analog electrical signal, and the second digital signal recovery circuit converts the analog electrical signal into a CMOS-level digital signal, sends the digital signal to the second digital terminal, converts it into an Ethernet signal, and then outputs it via the Gigabit Ethernet network; The first signal transmission link and the second signal transmission link are symmetrical in structure, and a corresponding sending and receiving relationship is formed between the first LED lamp and the second filter, and between the first filter and the second LED lamp.

2. The Gigabit visible light network communication device according to claim 1, wherein: The first digital terminal and the second digital terminal are both self-developed modules with an operating voltage of 3.0V-3.6V, and both include an RG45 interface, a power interface, an RX serial interface and a TX serial interface; the RG45 interface of the first digital terminal is connected to the Gigabit Ethernet to access the Ethernet signal, and the TX serial interface outputs the serial differential digital signal; the RX serial interface of the second digital terminal receives the digital signal output by the second digital signal recovery circuit, and its RG45 interface is connected to the Gigabit Ethernet to output the Ethernet signal.

3. The Gigabit visible light network communication device according to claim 2, wherein: The differential-to-single-ended functions integrated in the first digital terminal and the second digital terminal are both implemented by a balun; the left side of the balun is a 90Ω-110Ω differential input interface for receiving the serial differential digital signal output by the corresponding digital terminal, and the right side is a 45Ω-55Ω single-ended output interface for outputting the converted single-ended signal to the corresponding linear power amplifier, realizing impedance conversion from differential signal to single-ended signal and matching the impedance of the front and back ends.

4. The Gigabit visible light network communication device according to claim 3, wherein: The first linear power amplifier and the second linear power amplifier are both wide-bandwidth RF amplifiers, and their input and output impedances are both 48Ω-52Ω; the first linear power amplifier amplifies the single-ended signal output by the first digital terminal to increase the signal power and reduces the output impedance to achieve impedance matching with the first modulation circuit; the second linear power amplifier amplifies the single-ended signal output by the second digital terminal to achieve impedance matching with the second modulation circuit.

5. The Gigabit visible light network communication device according to claim 4, wherein: Both the first modulation circuit and the second modulation circuit couple the transmitted AC digital signal and the DC bias voltage together, do not contain any active devices, and have a bandwidth of 1GHz-1.2GHz; the first modulation circuit, based on the circuit superposition principle, makes the voltage value acting on both ends of the first LED lamp equal to the sum of the DC signal and the AC signal voltage values, driving the first LED lamp to produce light and dark changes that are imperceptible to the naked eye, thereby realizing OOK modulation; the second modulation circuit drives the second LED lamp to perform signal modulation using the same principle.

6. The Gigabit visible light network communication device according to claim 1, wherein: The first filter and the second filter are both band-pass filters for the blue light band, and their passband wavelength range is 400nm-480nm; the first LED lamp and the second LED lamp emit blue light through semiconductors and excite yellow phosphors to produce yellow light mixed into white light. The first filter and the second filter respectively filter out the yellow light and only pass the blue light, avoiding the corresponding avalanche photodiode from being unable to operate in the linear region due to the DC component generated by the yellow light, thereby improving the signal-to-noise ratio.

7. The gigabit visible light network communication device according to claim 6, wherein: The first avalanche photodiode and the second avalanche photodiode both serve as spatial light detectors. Depending on the received light intensity, they output voltage signals of different amplitudes through a transresistance amplifier circuit. The output voltage range is 0.01V-1.5V, and the blue light signals passing through the corresponding filters are converted into analog electrical signals.

8. The Gigabit visible light network communication device according to claim 7, wherein: The first digital signal recovery circuit and the second digital signal recovery circuit both include a high-speed decision device with a bandwidth of 1.2GHz-1.8GHz; the high-speed decision device adopts a zero-crossing decision circuit with hysteresis decision, which filters noise and maintains high sensitivity by controlling the comparison level, and converts the analog signals output by the corresponding avalanche photodiode into CMOS-level digital signals.

9. The gigabit visible light network communication device according to claim 8, characterized in that: In the PCB design, the characteristic impedance of the transmission line is maintained at 48Ω-52Ω through calculation, SMA RF connectors are used for input and output, and coaxial RF cables are used to connect different modules or PCBs. The first and second LED lamps are both connected in series with a 50R resistor, and the first and second modulation circuits both use bias tees in compact packages to achieve good insertion loss and isolation performance over a wide frequency band of 400kHz-3GHz, thereby realizing impedance matching during signal transmission.

10. The Gigabit visible light network communication device according to claim 1, wherein: The shell measures 10x9x14cm, and is internally provided with two sets of light-emitting lenses and light-receiving lenses, each with a size of 6cm; the first LED lamp and the second avalanche photodiode are respectively fixed at the focus of one set of light-emitting lenses and light-receiving lenses, and the second LED lamp and the first avalanche photodiode are respectively fixed at the focus of the other set of light-emitting lenses and light-receiving lenses; a power management module, a first digital terminal and a second digital terminal are placed at the bottom of the shell, and two gigabit network ports and a power interface are led out on the shell to realize the two-way communication integration and convenient use of the equipment.

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