Direct multi-channel signal hybrid modulation and demodulation method suitable for photoelectric communication application

Abstract

The invention relates to the field of photoelectric communication, and discloses a direct multipath signal hybrid modulation and demodulation method suitable for photoelectric communication application, which comprises the following steps: S1, signal modulation: a transmitting end uses a high data rate signal as a carrier wave, and transmits a low speed signal by changing the amplitude of the high data rate signal; s2, signal encoding and transmission: encoding a low-speed signal and a high-speed signal, the low-speed signal being expressed as a least significant bit, the high-speed signal being expressed as a most significant bit, and generating a plurality of non-return-to-zero code signals for transmission; the current intensity of the transmitting end is controlled through the generated NRZ signal, and a mixed modulation signal is generated; at a transmitting end, a current source is adjusted to generate a modulation signal. The low-speed signal and the high-speed signal are effectively mixed and modulated, so that the number of optical fibers required for transmission is greatly reduced, a plurality of signals can be transmitted in a superposed manner, the limited transmission bandwidth is efficiently utilized, and the channel efficiency of the whole system is improved.

Description

Technical Field

[0001] The invention relates to the field of optoelectronic communication, and in particular to a direct multi-path signal hybrid modulation and demodulation method suitable for optoelectronic communication applications. Background Art

[0002] With the rapid development of modern communication technology, optoelectronic communication has gradually become the mainstream in high-speed and large-capacity data transmission. Especially in application scenarios such as data centers, long-distance transmission and high-speed interconnection, optical communication technology has gradually replaced the traditional electrical signal transmission method with its low loss and high bandwidth characteristics. However, although optical communication has significant advantages in large data rates and long-distance transmission, in some scenarios, such as the mixed transmission of low-speed control signals and high-speed data signals, there are still problems of channel resource waste and high cost. Take existing consumer electronic products as an example, such as high-speed interfaces such as USB, the transmission rate of a single channel has reached 20Gbps. When transmitting through copper wires, even when a signal re-timer is used, the maximum transmission distance is usually no more than 3 meters. In the field of data communication, the transmission rate has reached 112Gbps or even 224Gbps, however, the maximum distance of transmission using passive copper cables is still limited to only about 2 meters. This poses a challenge to many application scenarios that require longer distance transmission but cannot significantly increase costs. To solve this problem, optical fiber transmission has become a very promising option.

[0003] However, in optical communication applications, there are various types of transmission signals, including high-speed signals and low-speed control signals. If an optical channel is allocated separately for each signal, the system complexity and cost will increase significantly. High-speed signals can be transmitted through optical fibers, but the transmission rate of low-speed signals such as control signals (CC) and sub-low-speed signals (SBU) is low, and they do not occupy channel resources for a long time. If an optical fiber is configured separately for each low-speed signal, it not only increases the number of transmission channels, but also greatly increases the system cost and design complexity. Existing modulation technologies, such as pulse amplitude modulation (PAM) and non-return-to-zero code (NRZ), have better performance when processing high-speed data transmission, but are not efficient for processing low-speed signals, especially in the case of mixed transmission of asynchronous low-speed signals and high-speed signals. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a direct multi-channel signal mixing modulation and demodulation method suitable for optoelectronic communication applications, which solves the problem that the existing modulation technology has better performance when processing high-speed data transmission, but is not efficient in processing low-speed signals, especially in the case of mixed transmission of asynchronous low-speed signals and high-speed signals.

[0005] To achieve the above objectives, the present invention is implemented by the following technical scheme: a direct multi-channel signal hybrid modulation and demodulation method suitable for optoelectronic communication applications, comprising the following steps:

[0006] S1. Signal modulation

[0007] The transmitter uses the high data rate signal as a carrier and transmits the low-speed signal by changing the amplitude of the high data rate signal;

[0008] S2. Signal Coding and Transmission

[0009] Encoding the low-speed signal and the high-speed signal, wherein the low-speed signal is represented as the least significant bit and the high-speed signal is represented as the most significant bit, and generating a plurality of non-return-to-zero code signals for transmission;

[0010] The current intensity of the transmitting end is controlled by the generated NRZ signal to generate a mixed modulation signal;

[0011] At the transmitting end, the current source is adjusted to generate a modulation signal, and the generated modulation signal is converted into an optical signal for transmission to the receiving end.

[0012] Preferably, the receiving end performs the following steps:

[0013] Optical signal conversion to electrical signal: The received optical signal is converted into an electrical signal through a photodiode, and the electrical signal is amplified using a transimpedance amplifier and an automatic gain controller;

[0014] Electrical signal differential processing: convert the amplified electrical signal into a differential signal for processing.

[0015] Preferably, the receiving end recovers the least significant bit and the most significant bit signals through an envelope detector and a limiting amplifier, and extracts the high-order modulation signal using an adaptive reference voltage circuit.

[0016] Preferably, the transmitting end adjusts the amplitude of the modulation signal through a pre-distortion processing technology to compensate for the nonlinear distortion of the modulation signal during the transmission process.

[0017] Preferably, the transmitting end generates a non-return-to-zero code signal according to the following coding rules: when the most significant bit and the least significant bit are both 0, the output signal is a first level; when the most significant bit is 0 and the least significant bit is 1, the output signal is a second level; when the most significant bit is 1 and the least significant bit is 0, the output signal is a third level; when the most significant bit and the least significant bit are both 1, the output signal is a fourth level.

[0018] Preferably, the envelope detector samples the received signal level by using an adaptive voltage generation module, and dynamically adjusts the reference voltage according to the sampling result to accurately restore the most significant bit signal.

[0019] Preferably, the transmitting end and the receiving end optimize power consumption by dynamically adjusting the current source and gain control according to the signal transmission rate and transmission conditions.

[0020] Preferably, the receiving end enhances the anti-interference capability of the signal by introducing an error detection and correction module in combination with a digital signal processing algorithm.

[0021] Preferably, the direct multi-channel signal hybrid modulation and demodulation method suitable for optoelectronic communication applications supports multi-level pulse amplitude modulation, and improves the spectrum utilization of the channel by increasing the modulation level of the signal.

[0022] Preferably, the transmitting end and the receiving end adaptively adjust the modulation depth, coding method and power setting of the signal through a real-time feedback loop to adapt to changes in channel conditions.

[0023] The invention provides a direct multi-channel signal mixing modulation and demodulation method suitable for photoelectric communication applications.

[0024] It has the following beneficial effects:

[0025] 1. The present invention significantly reduces the number of optical fibers required for transmission by effectively mixing and modulating low-speed signals with high-speed signals. In traditional solutions, allocating an optical path for each signal individually will lead to a waste of optical fiber resources, while this method can transmit multiple signals in a superimposed manner, achieving efficient utilization of limited transmission bandwidth, thereby improving the channel efficiency of the entire system.

[0026] 2. The present invention effectively reduces the number of channels required in the system by directly mixing multiple asynchronous signals for modulation. Compared with the traditional solution of allocating optical channels for each signal, this method significantly reduces the complexity of system design. At the same time, the reduced number of optical channels also greatly reduces the hardware cost of the optoelectronic communication system, which is particularly suitable for cost-sensitive consumer electronics and data communication scenarios.

[0027] 3. The present invention uses pre-distortion technology to compensate for the nonlinear distortion of the modulated signal before signal transmission, thereby obtaining more accurate signal recovery at the receiving end. This technology effectively improves the stability and quality of signal transmission, is particularly suitable for long-distance high-frequency transmission, and reduces the bit error rate caused by signal distortion.

[0028] 4. The present invention adopts a dynamic power regulation mechanism to automatically adjust power consumption according to the signal transmission rate and transmission conditions. When the system is in a low-speed transmission state, power consumption is reduced; and when it is in a high-speed transmission state, sufficient power is provided to ensure signal quality, thereby optimizing the energy consumption of the overall system without affecting performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the Tx timing diagram of the present invention;

[0030] Figure 2 This is the Tx principle diagram of the present invention;

[0031] Figure 3 This is the Rx principle diagram of the present invention;

[0032] Figure 4 is a principle block diagram of the envelope detector of the present invention;

[0033] Figure 5 This is an example diagram of the envelope detection and its corresponding reference voltage of the present invention. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Please refer to the attached Figure 1 -Attached Figure 5 The embodiment of the present invention provides a direct multi-channel signal mixing modulation and demodulation method suitable for optoelectronic communication applications, comprising the following steps:

[0036] S1. Signal modulation

[0037] The transmitter uses the high data rate signal as a carrier and transmits the low-speed signal by changing the amplitude of the high data rate signal;

[0038] S2. Signal Coding and Transmission

[0039] Encoding the low-speed signal and the high-speed signal, wherein the low-speed signal is represented as the least significant bit and the high-speed signal is represented as the most significant bit, and generating a plurality of non-return-to-zero code signals for transmission;

[0040] The current intensity of the transmitting end is controlled by the generated NRZ signal to generate a mixed modulation signal;

[0041] At the transmitting end, the current source is adjusted to generate a modulation signal, and the generated modulation signal is converted into an optical signal for transmission to the receiving end.

[0042] Specifically, the basic process of the whole method is described, which is mainly divided into two steps (S1 and S2). In S1, the high-speed data signal is used as a carrier, and its amplitude is modulated to transmit the low-speed signal. S2 involves encoding and transmission, and multiple NRZ signals are generated by encoding the low-speed signal (LSB) and the high-speed signal (MSB) respectively for transmission.

[0043] S1: Signal modulation: This part is the core step in optoelectronic communication. By using high-speed signals as carriers, low-speed signals can be effectively transmitted. The use of amplitude modulation (AM) technology allows high-frequency signals to be used as the main carrier, while embedding low-speed signals by changing their amplitude, reducing the complexity of the channel.

[0044] S2: Signal encoding and transmission: By encoding LSB and MSB to generate NRZ signal for transmission, bandwidth can be effectively saved and signal conflicts can be reduced. NRZ signal is a commonly used digital signal encoding method. It has no return to zero state, so it is more stable during transmission.

[0045] The receiving end performs the following steps:

[0046] Optical signal conversion to electrical signal: The received optical signal is converted into an electrical signal through a photodiode, and the electrical signal is amplified using a transimpedance amplifier and an automatic gain controller;

[0047] Electrical signal differential processing: convert the amplified electrical signal into a differential signal for processing.

[0048] Specifically, the conversion of optical signals into electrical signals through photodiodes (PDs) is a basic operation in optical communication systems. PDs can transmit the data carried in optical signals in the form of current. TIA and AGC are key devices for amplifying electrical signals. TIA increases signal strength through transimpedance conversion, while AGC is used to dynamically adjust signal gain to ensure that the signal remains stable in subsequent processing to avoid distortion.

[0049] The receiving end recovers the least significant bit and most significant bit signals through an envelope detector and a limiting amplifier, and uses an adaptive reference voltage circuit to extract high-order modulation signals.

[0050] Specifically, the envelope detector can recover the original modulated signal by extracting the envelope information of the signal, and the limiting amplifier helps to enhance the signal amplitude to ensure the accurate recovery of the LSB and MSB signals. The adaptive reference voltage system can adjust the voltage threshold in real time to ensure that the modulated signal can be correctly demodulated under different transmission conditions.

[0051] The transmitter adjusts the amplitude of the modulated signal through pre-distortion processing technology to compensate for the nonlinear distortion of the modulated signal during the transmission process.

[0052] Specifically, in optical communications, due to the nonlinear effects of optical fibers or transmitters, the transmitted signal may be distorted. Pre-distortion technology is to compensate for the distortion that may occur during the transmission process by adjusting the signal in reverse before the signal is sent, ensuring that the signal received by the receiving end is closer to the original signal.

[0053] The transmitter generates a non-return-to-zero code signal according to the following coding rules: when the most significant bit and the least significant bit are both 0, the output signal is at a first level; when the most significant bit is 0 and the least significant bit is 1, the output signal is at a second level; when the most significant bit is 1 and the least significant bit is 0, the output signal is at a third level; when the most significant bit and the least significant bit are both 1, the output signal is at a fourth level.

[0054] Specifically, this coding rule defines the relationship between the combination of MSB and LSB and the output signal level. This clear coding scheme ensures that the signal level is accurately generated at the transmitter and reduces signal interference during transmission. The level change of the NRZ signal will affect the decoding at the receiver, so the accuracy of the coding rule is very important.

[0055] The envelope detector samples the received signal level using an adaptive voltage generation module and dynamically adjusts the reference voltage based on the sampling result to accurately recover the most significant bit signal.

[0056] Specifically, the adaptive voltage generation module can adjust the reference voltage in real time according to the level fluctuation of the received signal to ensure the accurate recovery of the MSB signal. This dynamic adjustment mechanism is very critical for dealing with signal changes caused by external factors such as temperature and noise in optical fiber communication, and can improve the signal's anti-interference ability.

[0057] The transmitter and receiver optimize power consumption by dynamically adjusting the current source and gain control according to the signal transmission rate and transmission conditions.

[0058] Specifically, dynamic power adjustment technology can adjust power output in real time according to the current transmission rate and transmission conditions. For example, when the signal transmission rate is low, the power consumption of the transmitter and receiver is reduced to save energy; when the signal rate is high, the power is increased to ensure the quality of the signal. This method can not only optimize power consumption, but also improve the overall efficiency of the system.

[0059] The receiving end enhances the signal's anti-interference capability by introducing an error detection and correction module and combining it with a digital signal processing algorithm.

[0060] Specifically, the FEC module can detect and correct errors that occur during transmission through certain redundant coding during the signal reception process. By introducing redundant information into the signal, even if the optical signal is interfered during transmission, the receiving end can restore the original signal through the FEC module. This greatly improves the system's anti-interference ability and reduces the bit error rate.

[0061] The direct multi-channel signal mixing modulation and demodulation method suitable for optoelectronic communication applications supports multi-level pulse amplitude modulation. By increasing the modulation level of the signal, the spectrum utilization of the channel is improved and a higher data transmission rate is provided under the same bandwidth.

[0062] Specifically, multi-level pulse amplitude modulation (such as PAM-4 and PAM-8) allows multiple levels to be transmitted in each signal cycle, increasing the amount of information that each symbol can carry. Compared with traditional NRZ modulation, multi-level modulation can significantly improve the spectrum utilization of the channel, thereby achieving a higher data transmission rate within a limited bandwidth.

[0063] The transmitter and receiver adaptively adjust the signal's modulation depth, coding method and power setting through a real-time feedback loop to adapt to changes in channel conditions.

[0064] Specifically, the introduction of the feedback loop allows the system to adjust the transmission and reception parameters in real time according to the actual channel conditions. For example, when the channel conditions deteriorate, the system can reduce the modulation depth or change the encoding method through the feedback loop to ensure that the signal can be transmitted normally. When the channel conditions improve, the system can restore high-depth modulation to increase the data rate. This adaptive adjustment mechanism ensures the stability of the system and the reliability of transmission.

[0065] Taking the optical communication network as an example, the following explanation is given:

[0066] First, taking the mixing of two NRZ signals as an example, the signal with a higher data rate is used as a carrier during normal transmission, and the signal with a lower data rate is transmitted by changing the amplitude of the signal with a higher data rate. Figure 1 ITX is shown in the figure. After the two signals are superimposed, the generated signal has four levels in total. The difference from the PAM-4 signal in the usual sense is that since the two signals are asynchronous burst NRZ signals, the superimposed signal eye diagram has no fixed frequency characteristics except for the middle eye, and therefore does not have a fixed eye width. The eye height is determined according to the level corresponding to the output current.

[0067] In order to further compensate for the possible nonlinear characteristics of the receiving end, it is necessary to perform pre-distortion processing at the transmitting end and make the relative proportions of the four levels into an adjustable coding form. The method is as follows:

[0068] The two signals are represented by LSB and MSB respectively according to the transmission data rate, and the corresponding expressions are:

[0069] D2=MSB·LSB

[0070] D1=LSB

[0071]

[0072] The truth table of the above expression is shown in Table 1. After encoding, the MSB and LSB are output as three NRZ signals D0, D1 and D2. These three signals are used to control the unit current respectively to achieve the purpose of signal mixing. That is, the MSB signal is transmitted at the same time as the LSB signal, and the MSB and LSB can be asynchronous signals:

[0073] When the MSB is 0, the swing of the LSB is between 1 and 21.

[0074] When the MSB is 1, the swing of the LSB is between 0 and 31.

[0075] The corresponding Tx implementation is shown in Fig.2.

[0076] The current source IBIAS generates a basic bias current to put the VCSEL in working state. On this basis, the formation of the modulation signal is controlled by adjusting the on-off of the current of ID0~ID2; the "eye height" is fine-tuned by adjusting the current size of each bit, as shown in Fig.2. Then it is converted into an optical signal.

[0077] The receiving end (Rx) schematic diagram is as follows Figure 3 As shown in the figure, before the formal signal is received, Tx and Rx work in the training mode. The signal sent by Tx is irradiated on the photodiode through the optical fiber to stimulate the photosensitive current. After being amplified by TIA and AGC, the signal is converted into a differential signal by the S2D circuit. In order to ensure that TIA is at a suitable static operating point, a DC control loop (DCC) is required to assist in generating a suitable pull-down current. After the DCC loop is stable, it enters the task mode and starts to transmit data. In the training mode, the signal encoding sent by the transmitter has a DC balance feature, which is convenient for DCC convergence.

[0078] In task mode, the input optical signal is amplified by TIA and AGC, and then converted into a differential signal by the S2D circuit, which is sent to the limiting amplifier (Limiting AMP) and envelope detector (Envelope Detector) respectively. After the burrs are removed by the burr removal circuit, the MSB and LSB are finally restored to do_env and do signals respectively.

[0079] The envelope detector is composed of three slicers and their corresponding feedback logic and reference voltage generation circuit (Vref Gen.). Figure 4 As shown, they are used to adaptively sample V3 and V4 of the PAM-4 signal, and the voltage Vref_env corresponding to the mean value obtained by adaptive sampling is used as the reference voltage for extracting the envelope, such as Figure 5 To cope with PVT changes, Vref_env needs to be adaptively adjusted even in mission mode to ensure that the voltage value is between V3 and V4.

[0080] Table 1 Signal encoding method

[0081]

[0082]

[0083] Table field explanation:

[0084] MSB (Most Significant Bit):

[0085] Indicates "most significant bit", which is the most important bit in the transmitted data and usually represents the greatest weight in the data. In this table, the MSB can take the value of 0 or 1, indicating different signal states.

[0086] LSB (Least Significant Bit):

[0087] Stands for "least significant bit," which is the bit with the lowest weight in the transmitted data. LSB can also take the value 0 or 1 in this table, determining part of the output signal.

[0088] D:

[0089] This is the third output signal after encoding. It is determined by the MSB and LSB and is used to indicate the state of the mixed signal. In this table, the value of D depends on the combination of the MSB and LSB, which is 1 or 0 in a specific case.

[0090] D:

[0091] This is the second output signal after encoding. Similar to D, it also determines the output state of the signal through the combination of MSB and LSB. This bit is used to represent a certain level or state of the modulated signal.

[0092] D:

[0093] This is the first output signal after encoding. The output value of D is also based on the combination of MSB and LSB. The table shows the output results of D under different combinations.

[0094] Specific table data explanation:

[0095] First row (MSB = 0, LSB = 0): In this combination, D and D outputs are 0, while D output is 1, indicating a specific signal level or amplitude in this state.

[0096] Second row (MSB = 0, LSB = 1): In this combination, D and D outputs are 1, and D output is 0, indicating another signal state.

[0097] The third row (MSB = 1, LSB = 0): In this combination, all D, D, and D are output as 0, indicating the lowest signal state or amplitude.

[0098] Fourth row (MSB=1, LSB=1): When both MSB and LSB are 1, D, D, and D are all output as 1, indicating the highest signal level in this state.

[0099] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A direct multi-channel signal mixing modulation and demodulation method suitable for optoelectronic communication applications, characterized in that: The following steps are involved: S1. Signal modulation The transmitter uses the high data rate signal as a carrier and transmits the low-speed signal by changing the amplitude of the high data rate signal; S2. Signal Coding and Transmission Encoding the low-speed signal and the high-speed signal, wherein the low-speed signal is represented as the least significant bit and the high-speed signal is represented as the most significant bit, and generating a plurality of non-return-to-zero code signals for transmission; The current intensity of the transmitting end is controlled by the generated NRZ signal to generate a mixed modulation signal; At the transmitting end, the current source is adjusted to generate a modulation signal, and the generated modulation signal is converted into an optical signal for transmission to the receiving end.

2. The direct multi-channel signal mixing modulation and demodulation method suitable for optoelectronic communication applications according to claim 1, characterized in that: The receiving end performs the following steps: Optical signal conversion to electrical signal: The received optical signal is converted into an electrical signal through a photodiode, and the electrical signal is amplified using a transimpedance amplifier and an automatic gain controller; Electrical signal differential processing: convert the amplified electrical signal into a differential signal for processing.

3. The direct multi-channel signal mixing modulation and demodulation method suitable for optoelectronic communication applications according to claim 1, characterized in that: The receiving end recovers the least significant bit and the most significant bit signals through an envelope detector and a limiting amplifier, and extracts the high-order modulation signal using an adaptive reference voltage circuit.

4. The direct multi-channel signal mixing modulation and demodulation method suitable for optoelectronic communication applications according to claim 1, characterized in that: The transmitting end adjusts the amplitude of the modulated signal through a pre-distortion processing technology to compensate for the nonlinear distortion of the modulated signal during the transmission process.

5. The direct multi-channel signal mixing modulation and demodulation method suitable for optoelectronic communication applications according to claim 1, characterized in that: The transmitting end generates a non-return-to-zero code signal according to the following coding rules: when the most significant bit and the least significant bit are both 0, the output signal is a first level; when the most significant bit is 0 and the least significant bit is 1, the output signal is a second level; when the most significant bit is 1 and the least significant bit is 0, the output signal is a third level; when the most significant bit and the least significant bit are both 1, the output signal is a fourth level.

6. The direct multi-channel signal mixing modulation and demodulation method suitable for optoelectronic communication applications according to claim 3, characterized in that: The envelope detector samples the received signal level by using an adaptive voltage generation module and dynamically adjusts the reference voltage according to the sampling result to accurately restore the most significant bit signal.

7. The direct multi-channel signal mixing modulation and demodulation method suitable for optoelectronic communication applications according to claim 1, characterized in that: The transmitting end and the receiving end optimize power consumption by dynamically adjusting the current source and gain control according to the signal transmission rate and transmission conditions.

8. The direct multi-channel signal mixing modulation and demodulation method suitable for optoelectronic communication applications according to claim 1, characterized in that: The receiving end enhances the anti-interference capability of the signal by introducing an error detection and correction module and combining a digital signal processing algorithm.

9. The direct multi-channel signal mixing modulation and demodulation method suitable for optoelectronic communication applications according to claim 1, characterized in that: The direct multi-channel signal hybrid modulation and demodulation method suitable for optoelectronic communication applications supports multi-level pulse amplitude modulation and improves the spectrum utilization of the channel by increasing the modulation level of the signal.

10. The direct multi-channel signal mixing modulation and demodulation method suitable for optoelectronic communication applications according to claim 1, characterized in that: The transmitting end and the receiving end adaptively adjust the modulation depth, coding mode and power setting of the signal through a real-time feedback loop to adapt to changes in channel conditions.

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