A four-level modulation receiving device and method based on double polarization double binary superposition

Abstract

The application relates to the field of optical communication technology, and provides a four-level modulation receiving device and method based on double-polarization double-binary superposition, which comprises a transmitting module, a transmission link and a receiving module; the transmitting module is used for outputting a first binary baseband signal, outputting a first three-level double-binary electrical signal, outputting a second binary baseband signal, outputting a second three-level double-binary electrical signal, performing polarization orthogonal superposition on the first three-level double-binary electrical signal and the second three-level double-binary electrical signal, and outputting one superimposed optical signal; the transmission link is used for transmitting the one superimposed optical signal; and the receiving module is used for receiving the one superimposed optical signal and restoring the one superimposed optical signal into the first binary baseband signal and the second binary baseband signal. The application realizes effective unification of high dispersion tolerance and high spectral efficiency by superimposing two double-binary signals on orthogonal polarization states.

Description

Technical Field

[0001] This invention belongs to the field of optical communication technology, and particularly relates to a four-level modulation receiving device and method based on dual polarization dual binary superposition. Background Technology

[0002] In optical communication systems, as the transmission symbol rate increases, the signal bandwidth also increases synchronously. However, the impact of fiber dispersion on the signal is positively correlated with bandwidth, leading to a significant reduction in the system's dispersion tolerance. This has become a core bottleneck limiting the transmission distance and speed of high-speed systems. Optical dual binary modulation technology introduces correlation between adjacent symbols through partial response coding, resulting in significantly better dispersion resistance than traditional binary modulation, making it one of the effective solutions to alleviate the dispersion problem. However, limited by its modulation principle, each symbol can only carry 1 bit of information, resulting in a spectral efficiency of only 1 bit / s / Hz. Furthermore, it is difficult to further increase the rate by increasing the modulation order, failing to fully meet the urgent needs for high speed and high spectral efficiency in scenarios such as 5G transport and data center interconnection.

[0003] On the other hand, although coherent detection technology can compensate for dispersion and support multi-dimensional modulation, its receiver relies on a complex polarization demultiplexing module and multiple photodetectors (PDs), resulting in a cumbersome system structure and high cost, which limits its application in cost-sensitive short-distance transmission scenarios.

[0004] Therefore, the industry urgently needs a modulation and reception scheme that achieves a better balance between structural complexity, cost, dispersion tolerance, and spectral efficiency. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the present invention proposes a four-level modulation receiving device based on dual-polarization dual-binary superposition, the technical solution of which includes:

[0006] Transmitting module, transmission link, and receiving module;

[0007] The transmitting module includes a first binary signal source, a second binary signal source, a first dual binary encoder, a second dual binary encoder, a polarization beam splitter, and a polarization beam combiner;

[0008] The first binary signal source is used to output the first binary baseband signal;

[0009] The first dual binary encoder is used to encode the first binary baseband signal and output the first three-level dual binary electrical signal;

[0010] The second binary signal source is used to output a second binary baseband signal;

[0011] The second dual binary encoder is used to encode the second binary baseband signal and output the second three-level dual binary electrical signal;

[0012] The polarization beam splitter and polarization beam combiner are used to perform polarization orthogonal superposition of the first three-level dual binary electrical signal and the second three-level dual binary electrical signal to output a superimposed optical signal.

[0013] The transmission link is used to transmit one superimposed optical signal;

[0014] The receiving module is used to receive one superimposed optical signal and recover it into a first binary baseband signal and a second binary baseband signal.

[0015] Preferably, the binary baseband signals output by the first binary signal source and the second binary signal source have the same rate.

[0016] Preferably, both the first dual binary encoder and the second dual binary encoder are configured to perform response encoding, the encoding process including pre-encoding and correlation encoding;

[0017] The precoding process is defined by the following formula:

[0018]

[0019] In the formula, For the nth pre-coded data, For modulo-2 operations, This represents the original binary data of the nth input.

[0020] The relevant encoding process is described in the following formula:

[0021]

[0022] In the formula, This is the nth output three-level dual binary electrical signal.

[0023] Preferably, the transmitting module further includes an optical modulation unit;

[0024] The optical modulation unit is used to modulate the first three-level dual binary electrical signal and the second three-level dual binary electrical signal onto the optical carrier, respectively.

[0025] The bias point of the optical modulation unit is set at the point of lowest power in its transmission curve.

[0026] Preferably, the receiving module includes a single photodetector and a signal processing unit;

[0027] The single photodetector is used to receive one superimposed optical signal and convert its optical power into a four-level electrical signal.

[0028] The signal processing unit is used to perform threshold decision and decoding on the four-level electrical signal to restore it into the first binary baseband signal and the second binary baseband signal.

[0029] Preferably, the signal processing unit further includes an equalizer;

[0030] The equalizer is used to perform equalization processing on four-level electrical signals.

[0031] Preferably, the present invention further proposes a four-level modulation receiving method based on dual-polarization dual-binary superposition, comprising:

[0032] Output the first binary baseband signal;

[0033] The first binary baseband signal is encoded to output the first three-level dual binary electrical signal.

[0034] Output the second binary baseband signal;

[0035] The second binary baseband signal is encoded to output a second three-level dual binary electrical signal.

[0036] The first three-level dual binary electrical signal and the second three-level dual binary electrical signal are polarized orthogonally superimposed to output a superimposed optical signal.

[0037] Transmit one superimposed optical signal;

[0038] It receives one superimposed optical signal and restores it to the first binary baseband signal and the second binary baseband signal.

[0039] Beneficial effects:

[0040] 1. The two orthogonally polarized dual binary signals of this application inherit the dispersion suppression characteristics of optical dual binary modulation. After superposition, the intersymbol interference of the signal is further reduced to reduce the sensitivity of fiber dispersion, and the dispersion tolerance is significantly higher than that of traditional single polarization four-level pulse amplitude modulation.

[0041] 2. The dual-polarization state dual binary signals of this application completely overlap in the spectrum. After superposition, the spectral width of the signal is the same as that of a single dual binary signal, thereby achieving a multiplied spectral efficiency.

[0042] 3. The receiving end of this application only requires a single photodetector and a matching signal processing unit, without the need for a polarization demultiplexing module and multiple parallel detectors, which greatly simplifies the hardware structure and reduces system cost and debugging difficulty. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the device structure according to a preferred embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of the bit error rate-dispersion curve of a preferred embodiment of the present invention. Detailed Implementation

[0045] The embodiments of the present invention will be described in detail below. The embodiments described below are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the embodiments described below.

[0046] This invention designs a four-level modulation receiving device based on dual-polarization dual-binary superposition, such as... Figure 1 As shown, the technical solution specifically includes:

[0047] Transmitting module, transmission link, and receiving module;

[0048] The transmitting module includes a first binary signal source, a second binary signal source, a first dual binary encoder, a second dual binary encoder, a polarization beam splitter, and a polarization beam combiner;

[0049] The first binary signal source is used to output the first binary baseband signal;

[0050] The first dual binary encoder is used to encode the first binary baseband signal and output the first three-level dual binary electrical signal.

[0051] The second binary signal source is used to output the second binary baseband signal;

[0052] The second dual binary encoder is used to encode the second binary baseband signal and output the second three-level dual binary electrical signal;

[0053] The polarization beam splitter and polarization beam combiner are used to perform polarization orthogonal superposition of the first three-level dual binary electrical signal and the second three-level dual binary electrical signal, and output a superimposed optical signal.

[0054] The transmission link is used to transmit one superimposed optical signal;

[0055] The receiving module is used to receive one superimposed optical signal and restore it to the first binary baseband signal and the second binary baseband signal.

[0056] Specifically, polarization beam splitters are used to ensure that the polarization states of optical signals modulated by two dual binary electrical signals are orthogonal.

[0057] In addition, the dual binary encoding uses a three-level encoding, with the three levels represented by E, 0, and -E in terms of light intensity, where "E" and "-E" represent "1" level and "0" represents "0" level. The encoding rule is: when there are an odd number of "0"s between two "1" bits, the light phase is reversed, and the relevant encoding is implemented by 1-bit delay addition or analog low-pass filtering.

[0058] In addition, the optical power of the superimposed optical signal satisfies: ,in To carry the optical signal power of the first dual binary electrical signal, The optical signal power is used to carry the second dual binary electrical signal. and The power levels of the "0" and "1" levels of the dual binary signals correspond to the total optical power after superposition. There are four combinations, corresponding to four optical power levels.

[0059] In addition, the transmission link is a single-mode fiber.

[0060] Preferably, the binary baseband signals output by the first binary signal source and the second binary signal source have the same rate.

[0061] Specifically, such as Figure 2 As shown, in one application example, the output rate of both the first and second binary signal sources is 40 Gbit / s, the signal code is NRZ code, and the total system transmission rate reaches 80 Gbit / s; the optical power carrying the first dual binary electrical signal... , The optical power carrying the second dual binary electrical signal , The optical powers of the four levels after superposition are as follows: , , , The signal processing unit sets decision thresholds of 2mW, 3mW, and 4mW, dividing the electrical signal into four intervals, corresponding to... to Tests showed that the device can tolerate a dispersion of 210 ps / nm at a bit error rate threshold of 1E-2.

[0062] Preferably, both the first dual binary encoder and the second dual binary encoder are configured to perform response encoding, the encoding process including pre-encoding and correlation encoding;

[0063] The precoding process is described in the following formula:

[0064]

[0065] In the formula, For the nth pre-coded data, For modulo-2 operations, This represents the original binary data of the nth input.

[0066] The relevant encoding process, as shown in the formula below:

[0067]

[0068] In the formula, This is the nth output three-level dual binary electrical signal.

[0069] Preferably, the transmitting module further includes an optical modulation unit;

[0070] The optical modulation unit is used to modulate the first three-level dual binary electrical signal and the second three-level dual binary electrical signal onto the optical carrier, respectively;

[0071] The bias point of the optical modulation unit is set at the point of lowest power on its transmission curve.

[0072] Specifically, at this bias point, the electric fields corresponding to "+1" and "-1" are opposite but the optical power is the same, and the modulator output is a binary optical signal.

[0073] Preferably, the receiving module includes a single photodetector and a signal processing unit;

[0074] A single photodetector is used to receive one superimposed optical signal and convert its optical power into a four-level electrical signal.

[0075] The signal processing unit is used to perform threshold decision and decoding on the four-level electrical signal, and restore it to the first binary baseband signal and the second binary baseband signal.

[0076] Specifically, since light only beats between the same polarization states, the electrical signal output by a single photodetector is the superposition of the photocurrents generated by the two polarization states, and is proportional to the total optical power. This converts the four combinations of optical power into corresponding four-level electrical signals.

[0077] In addition, the signal processing unit reverse-engineers the original levels of the two dual binary electrical signals based on the different values ​​of the four levels, and then recovers the original binary baseband signal through dual binary inverse encoding.

[0078] Preferably, the signal processing unit further includes an equalizer;

[0079] An equalizer is used to equalize four-level electrical signals.

[0080] Specifically, the equalizer can use a forward feedback filter.

[0081] Preferably, the present invention further proposes a four-level modulation receiving method based on dual-polarization dual-binary superposition, comprising:

[0082] Output the first binary baseband signal;

[0083] The first binary baseband signal is encoded to output the first three-level dual binary electrical signal.

[0084] Output the second binary baseband signal;

[0085] The second binary baseband signal is encoded to output a second three-level dual binary electrical signal.

[0086] The first three-level dual binary electrical signal and the second three-level dual binary electrical signal are polarized orthogonally superimposed to output a superimposed optical signal.

[0087] Transmit one superimposed optical signal;

[0088] It receives one superimposed optical signal and restores it to the first binary baseband signal and the second binary baseband signal.

[0089] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A four-level modulation receiving device based on dual-polarization dual-binary superposition, characterized in that, include: Transmitting module, transmission link, and receiving module; The transmitting module includes a first binary signal source, a second binary signal source, a first dual binary encoder, a second dual binary encoder, a polarization beam splitter, and a polarization beam combiner; The first binary signal source is used to output the first binary baseband signal; The first dual binary encoder is used to encode the first binary baseband signal and output the first three-level dual binary electrical signal; The second binary signal source is used to output a second binary baseband signal; The second dual binary encoder is used to encode the second binary baseband signal and output the second three-level dual binary electrical signal; The polarization beam splitter and polarization beam combiner are used to perform polarization orthogonal superposition of the first three-level dual binary electrical signal and the second three-level dual binary electrical signal to output a superimposed optical signal. The transmission link is used to transmit one superimposed optical signal; The receiving module is used to receive one superimposed optical signal and recover it into a first binary baseband signal and a second binary baseband signal.

2. The four-level modulation receiving device based on dual-polarization dual-binary superposition according to claim 1, characterized in that, The binary baseband signals output by the first binary signal source and the second binary signal source have the same rate.

3. The four-level modulation receiving device based on dual-polarization dual-binary superposition according to claim 1, characterized in that, Both the first dual binary encoder and the second dual binary encoder are configured to perform response encoding, the encoding process including pre-encoding and correlation encoding; The precoding process is defined by the following formula: ， In the formula, For the nth pre-coded data, For modulo-2 operations, This represents the original binary data of the nth input. The relevant encoding process is described in the following formula: ， In the formula, This is the nth output three-level dual binary electrical signal.

4. The four-level modulation receiving device based on dual-polarization dual-binary superposition according to claim 1, characterized in that, The transmitting module also includes an optical modulation unit; The optical modulation unit is used to modulate the first three-level dual binary electrical signal and the second three-level dual binary electrical signal onto the optical carrier, respectively. The bias point of the optical modulation unit is set at the point of lowest power in its transmission curve.

5. A four-level modulation receiving device based on dual-polarization dual-binary superposition according to claim 1, characterized in that, The receiving module includes a single photodetector and a signal processing unit; The single photodetector is used to receive one superimposed optical signal and convert its optical power into a four-level electrical signal. The signal processing unit is used to perform threshold decision and decoding on the four-level electrical signal to restore it into the first binary baseband signal and the second binary baseband signal.

6. A four-level modulation receiving device based on dual-polarization dual-binary superposition according to claim 5, characterized in that, The signal processing unit also includes an equalizer; The equalizer is used to perform equalization processing on four-level electrical signals.

7. A four-level modulation receiving method based on dual-polarization dual-binary superposition, applied to the four-level modulation receiving device based on dual-polarization dual-binary superposition as described in claim 1, characterized in that, include: Output the first binary baseband signal; The first binary baseband signal is encoded to output the first three-level dual binary electrical signal. Output the second binary baseband signal; The second binary baseband signal is encoded to output a second three-level dual binary electrical signal. The first three-level dual binary electrical signal and the second three-level dual binary electrical signal are polarized orthogonally superimposed to output a superimposed optical signal. Transmit one superimposed optical signal; It receives one superimposed optical signal and restores it to the first binary baseband signal and the second binary baseband signal.

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