CN109565337B - Optical transmission method, device and system - Google Patents
Optical transmission method, device and system Download PDFInfo
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- CN109565337B CN109565337B CN201680087737.9A CN201680087737A CN109565337B CN 109565337 B CN109565337 B CN 109565337B CN 201680087737 A CN201680087737 A CN 201680087737A CN 109565337 B CN109565337 B CN 109565337B
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/54—Intensity modulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
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Abstract
The embodiment of the invention provides an optical transmission method, an optical transmission device and an optical transmission system, and relates to the technical field of communication. The method comprises the following steps: encoding an N-level pulse amplitude modulation (PAM-N) signal to be transmitted to obtain a first encoded signal, wherein the first encoded signal comprises N-1 first positive integer levels, 1 zero level and N-1 negative integer levels, N is not less than 3, and N is an integer; shifting the N-1 first positive integer levels or the N-1 negative integer levels by a first offset, respectively, to convert the first encoded signal to a second encoded signal, the first offset being a fractional number; modulating the second encoded signal into an optical signal; and transmitting the optical signal to an optical receiver. By the method, the optical receiver can demodulate the PAM-N optical signal in a direct detection mode when the coded signal of the PAM-N signal comprises a negative level, so that the complexity of an optical transmitter and the complexity of the optical receiver are reduced.
Description
Technical Field
The present invention relates to the field of communications technologies, and in particular, to an optical transmission method, apparatus, and system.
Background
In an optical transmission system, a multi-level (three or more) pulse amplitude modulation (PAM-N) is a commonly used modulation signal for modulating data to be transmitted. After acquiring the PAM-N signal to be transmitted, the optical transmitter encodes the PAM-N signal, modulates the encoded signal into an optical signal, and transmits the optical signal to the optical receiver through an optical fiber. When the optical receiver receives the optical signal, the PAM-N signal is obtained by demodulating the optical signal into an electrical signal and decoding the electrical signal.
Currently, an optical receiver may demodulate an optical signal by using a direct detection method or a coherent detection method. The direct detection means that the level information carried in the optical signal is squared by a photodetector to obtain an electrical signal (the level value in the electrical signal is the square value of the level information). Coherent detection is to obtain an electrical signal by performing a series of processing such as mixing a local oscillation signal with the optical signal.
Generally, the optical transmitter uses different encoding methods, and the encoded signal may include different level information, such as only 0 level and positive level, or 0 level, positive level and negative level. When the coded signal only includes a 0 level and a positive level, since the absolute values of 0 and a positive integer are still 0 and a positive integer, the optical receiver can demodulate the optical signal received by the optical receiver in a direct detection manner. When the coded signal further includes a negative level, the optical receiver needs to demodulate the optical signal by coherent detection since the direct detection cannot obtain the negative level.
However, when the coded signal includes a negative level, if the optical Receiver needs to demodulate the optical signal by Coherent detection, the optical transmitter and the optical Receiver need to add a Digital Signal Processing (DSP) module, an Integrated Coherent Receiver (ICR) module, a Local Oscillator (LO) module, and other modules, so that the design of the optical Receiver and the optical transmitter is more complicated, and the power consumption of the optical transmitter and the optical Receiver is increased, and the cost is increased.
Disclosure of Invention
Embodiments of the present invention provide an optical transmission method, apparatus, and system, so that an optical receiver can demodulate a PAM-N optical signal in a direct detection manner when an encoded signal of the PAM-N signal includes a negative level, thereby reducing the complexity of an optical transmitter and the optical receiver.
In order to achieve the above purpose, the embodiment of the invention adopts the following technical scheme:
in a first aspect, an embodiment of the present invention provides an optical transmission method, including:
coding an N-level pulse amplitude modulation (PAM-N) signal to be transmitted to obtain a first coded signal, wherein the first coded signal comprises N-1 first positive integer levels, 1 zero level and N-1 negative integer levels, N is more than or equal to 3, and N is an integer; shifting the N-1 first positive integer levels or the N-1 negative integer levels by a first offset, respectively, to convert the first encoded signal to a second encoded signal, the first offset being a fractional number; modulating the second encoded signal into an optical signal; the optical signal is transmitted to an optical receiver.
The embodiment of the invention provides an optical transmission method, an optical transmitter can shift a first positive integer level or a negative integer level in a first coded signal of a PAM-N signal through a first offset with a fractional value to obtain a second coded signal, and modulate the second coded signal into an optical signal to be sent to a receiver, so that the optical receiver directly detects and judges the optical signal, the obtained 2N-1 levels comprise N-1 positive fractional levels, therefore, when the optical receiver recovers the 2N-1 levels, the N-1 positive fractional levels are converted into N-1 recovered negative integer levels, a zero level in the 2N-1 levels is determined to be a recovered zero level, and N-1 positive integer levels in the 2N-1 levels are determined to be recovered N-1 first positive integer levels, so as to obtain a recovered first coded signal, or convert the N-1 positive fractional levels into recovered N-1 first positive integer levels, determine a zero level in the 2N-1 levels as a recovered zero level, and convert N-1 second positive integer levels in the 2N-1 levels into recovered N-1 negative integer levels, so as to obtain a recovered first coded signal, and then the optical receiver can decode the recovered first coded signal, so as to obtain a recovered PAM-N signal. Namely, the optical transmission method enables the optical receiver to demodulate the PAM-N optical signal by adopting a direct detection mode when the coded signal of the PAM-N signal comprises a negative level, thereby reducing the complexity of the optical transmitter and the optical receiver and reducing the power consumption of the optical transmitter and the optical receiver.
Optionally, the first offset is a fractional number between-1 and 1.
In a second aspect, an embodiment of the present invention provides an optical transmission method, including:
receiving an optical signal sent by an optical transmitter; directly detecting and judging the optical signal to obtain 2N-1 levels, wherein the 2N-1 levels comprise N-1 second positive integer levels, 1 zero level and N-1 positive decimal levels, N is not less than 3, and N is an integer; restoring the 2N-1 levels to obtain a restored first coded signal, wherein the restored first coded signal comprises restored N-1 first positive integer levels, restored 1 zero level and restored N-1 negative integer levels; the recovered N-1 first positive integer levels are the N-1 second positive integer levels, the recovered 1 zero levels are the 1 zero levels, and the recovered N-1 negative integer levels are obtained by converting the N-1 positive decimal levels; or the recovered N-1 first positive integer levels are converted from the N-1 positive decimal levels, the recovered 1 zero levels are the 1 zero levels, and the recovered N-1 negative integer levels are converted from the N-1 second positive integer levels; and decoding the recovered first coded information coded signal to obtain a recovered PAM-N signal.
An embodiment of the present invention provides an optical transmission method, in which an optical receiver is capable of directly detecting an optical signal of a PAM-N signal to obtain 2N-1 levels, and an optical transmitter offsets a negative integer level or a positive integer level of a first encoded signal of the PAM-N signal by using a first offset having a fractional value before modulating an encoded signal of the PAM-N signal into the optical signal, so that the 2N-1 levels obtained by the optical receiver include N-1 positive fractional levels, and thus when the 2N-1 levels are restored, the optical receiver may convert the N-1 positive fractional levels into N-1 restored negative integer levels, determine a zero point in the 2N-1 levels as a restored zero level, and determine N-1 positive integer levels in the 2N-1 levels as N-1 first restored positive integer levels Counting the levels to obtain recovered first coded signals, or converting the N-1 positive fractional levels into recovered N-1 first positive integer levels, determining zero levels in the 2N-1 levels as recovered zero levels, and converting N-1 second positive integer levels in the 2N-1 levels into recovered N-1 negative integer levels to obtain recovered first coded signals, and then decoding the recovered first coded signals by the optical receiver to obtain recovered PAM-N signals. Namely, the optical transmission method enables the optical receiver to demodulate the PAM-N optical signal by adopting a direct detection mode when the coded signal of the PAM-N signal comprises a negative level, thereby reducing the complexity of the optical transmitter and the optical receiver and reducing the power consumption of the optical transmitter and the optical receiver.
Optionally, the optical signal is a signal obtained by modulating a second encoded signal by the optical transmitter, where the second encoded signal is a signal obtained by shifting, by the optical transmitter, N-1 first positive integer levels or N-1 negative integer levels in the first encoded signal by a first offset amount, respectively, and the first offset amount is a decimal number.
Optionally, the restoring 2N-1 levels includes: determining N-1 second positive integer levels as recovered N-1 first positive integer levels; determining 1 zero level as the recovered 1 zero level; and respectively shifting the N-1 positive decimal levels by a first offset to obtain N-1 third positive integer levels, and respectively negating the N-1 third positive integer levels to obtain recovered N-1 negative integer levels, wherein the first offset is a decimal.
Optionally, the restoring 2N-1 levels includes:
respectively negating the N-1 second positive integer levels to obtain recovered N-1 negative integer levels; determining 1 zero level as the recovered 1 zero level; and respectively shifting the N-1 positive decimal levels by a first offset to obtain recovered N-1 first positive integer levels, wherein the first offset is a decimal.
Optionally, the first offset is a fractional number between-1 and 1.
In a third aspect, an embodiment of the present invention provides an optical transmitter, including: the PAM-N signal is coded to obtain a first coded signal, wherein the first coded signal comprises N-1 first positive integer levels, 1 zero level and N-1 negative integer levels, N is not less than 3, and N is an integer; the processing unit is further configured to shift the N-1 first positive integer levels or the N-1 negative integer levels by first offsets, respectively, to convert the first encoded signal into a second encoded signal, where the first offsets are decimals; the modulation unit is used for modulating the second coded signal converted by the processing unit into an optical signal; the communication unit is used for sending the optical signal modulated by the modulation unit to an optical receiver.
The embodiment of the invention provides an optical transmitter, which can shift a first positive integer level or a negative integer level in a first coded signal of a PAM-N signal through a first offset with a fractional value to obtain a second coded signal, modulate the second coded signal into an optical signal and transmit the optical signal to a receiver, so that the optical receiver directly detects and judges the optical signal, obtains 2N-1 levels including N-1 positive fractional levels, so that the optical receiver can convert the N-1 positive fractional levels into N-1 recovered negative integer levels when recovering the 2N-1 levels, determine a zero level in the 2N-1 levels as a recovered zero level, and determine N-1 positive integer levels in the 2N-1 levels as the recovered N-1 first positive integer levels, so as to obtain a recovered first coded signal, or convert the N-1 positive fractional levels into recovered N-1 first positive integer levels, determine a zero level in the 2N-1 levels as a recovered zero level, and convert N-1 second positive integer levels in the 2N-1 levels into recovered N-1 negative integer levels, so as to obtain a recovered first coded signal, and then the optical receiver can decode the recovered first coded signal, so as to obtain a recovered PAM-N signal. Namely, the optical transmission method enables the optical receiver to demodulate the PAM-N optical signal by adopting a direct detection mode when the coded signal of the PAM-N signal comprises a negative level, thereby reducing the complexity of the optical transmitter and the optical receiver and reducing the power consumption of the optical transmitter and the optical receiver.
Optionally, the first offset is a fractional number between-1 and 1.
In a fourth aspect, an embodiment of the present invention provides an optical receiver, including a communication unit, a photodetection unit, and a processing unit, where the communication unit is configured to receive an optical signal sent by an optical transmitter; the photoelectric detection unit is used for directly detecting and judging the optical signal received by the communication unit to obtain 2N-1 levels, wherein the 2N-1 levels comprise N-1 second positive integer levels, 1 zero level and N-1 positive decimal levels, N is not less than 3, and N is an integer; the processing unit is configured to recover the 2N-1 levels obtained by the photodetecting unit to obtain a recovered first encoded signal, where the recovered first encoded signal includes N-1 recovered first positive integer levels, 1 recovered zero level, and N-1 recovered negative integer levels; the recovered N-1 first positive integer levels are the N-1 second positive integer levels, the recovered 1 zero levels are the 1 zero levels, and the recovered N-1 negative integer levels are obtained by converting the N-1 positive decimal levels; or the recovered N-1 first positive integer levels are converted from the N-1 positive decimal levels, the recovered 1 zero levels are the 1 zero levels, and the recovered N-1 negative integer levels are converted from the N-1 second positive integer levels; the processing unit is further configured to decode the recovered first encoded signal, and obtain a recovered PAM-N signal.
In the optical receiver according to the embodiment of the present invention, the optical receiver can directly detect an optical signal of a PAM-N signal and obtain 2N-1 levels, and since the optical transmitter shifts a negative integer level or a positive integer level of a first encoded signal of the PAM-N signal by using a first offset amount having a fractional value before modulating an encoded signal of the PAM-N signal into the optical signal, the 2N-1 levels obtained by the optical receiver include N-1 positive fractional levels, so that the optical receiver can convert the N-1 positive fractional levels into N-1 restored negative integer levels when restoring the 2N-1 levels, determine a zero point in the 2N-1 levels as a restored zero level, and determine N-1 positive integer levels in the 2N-1 levels as N-1 first restored positive integer levels Counting the levels to obtain recovered first coded signals, or converting the N-1 positive fractional levels into recovered N-1 first positive integer levels, determining zero levels in the 2N-1 levels as recovered zero levels, and converting N-1 second positive integer levels in the 2N-1 levels into recovered N-1 negative integer levels to obtain recovered first coded signals, and then decoding the recovered first coded signals by the optical receiver to obtain recovered PAM-N signals. Namely, the optical transmission method enables the optical receiver to demodulate the PAM-N optical signal by adopting a direct detection mode when the coded signal of the PAM-N signal comprises a negative level, thereby reducing the complexity of the optical transmitter and the optical receiver and reducing the power consumption of the optical transmitter and the optical receiver.
Optionally, the optical signal is a signal obtained by modulating a second encoded signal by the optical transmitter, where the second encoded signal is a signal obtained by shifting, by the optical transmitter, N-1 first positive integer levels or N-1 negative integer levels in the first encoded signal by a first offset amount, respectively, and the first offset amount is a decimal number.
Optionally, the processing unit is specifically configured to determine that the N-1 second positive integer levels are N-1 first positive integer levels, shift the N-1 positive fractional levels by the first offset amount respectively, obtain N-1 third positive integer levels, and negate the N-1 third positive integer levels respectively, obtain N-1 negative integer levels, where the first offset amount is a fractional number.
Optionally, the processing unit is specifically configured to respectively negate the N-1 second positive integer levels, obtain N-1 negative integer levels, respectively shift the N-1 positive fractional levels by a first offset, and obtain N-1 first positive integer levels, where the first offset is a fractional number.
In a fifth aspect, an embodiment of the present invention provides an optical transmission system, including the optical transmitter according to the third aspect and the optical receiver according to the fourth aspect or any optional manner of the fourth aspect.
Based on the optical transmission system provided by the embodiment of the present invention, the optical transmitter can shift the positive integer level or the negative integer level in the first encoded signal of the PAM-N signal by the first offset with a fractional value to obtain the second encoded signal, and modulate the second encoded signal into the optical signal to be sent to the optical receiver, so that the optical receiver directly detects and decides the optical signal, and then obtains 2N-1 levels including N-1 positive fractional levels, so that the optical receiver can convert the N-1 positive fractional levels into N-1 recovered negative integer levels when recovering the 2N-1 levels, determine the zero level in the 2N-1 levels as the recovered zero level, and determine the N-1 positive integer levels in the 2N-1 levels as the recovered N-1 first positive integer levels, so as to obtain a recovered first coded signal, or convert the N-1 positive fractional levels into recovered N-1 first positive integer levels, determine a zero level in the 2N-1 levels as a recovered zero level, and convert N-1 second positive integer levels in the 2N-1 levels into recovered N-1 negative integer levels, so as to obtain a recovered first coded signal, and then the optical receiver can decode the recovered first coded signal, so as to obtain a recovered PAM-N signal. Namely, the optical transmission method enables the optical receiver to demodulate the PAM-N optical signal by adopting a direct detection mode when the coded signal of the PAM-N signal comprises a negative level, thereby reducing the complexity of the optical transmitter and the optical receiver and reducing the power consumption of the optical transmitter and the optical receiver.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention.
FIG. 1 is a diagram of an optical transmission system in the prior art;
fig. 2 is an interaction diagram of an optical transmission method according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of an optical transmitter according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of an optical receiver according to an embodiment of the present invention;
fig. 5 is a schematic diagram of an optical transmission system according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.
As shown in fig. 1, the conventional optical transmission network architecture includes an optical transmitter and an optical receiver, which are connected by an optical fiber. The optical transmitter is used for modulating an electric signal to be transmitted into an optical signal and transmitting the optical signal to an optical fiber for transmission. After receiving the optical signal, the optical receiver recovers the optical signal into an electrical signal.
At present, when a PAM-N signal is used for data transmission, if a coded signal of the PAM-N signal includes a negative level, when an optical receiver receives an optical signal modulated by the coded signal, the optical receiver needs to demodulate the optical signal by using a coherent detection method. However, if the optical receiver demodulates the optical signal by coherent detection, the optical transmitter and the optical receiver need to add modules, ICRs, LOs, and other devices, so that the designs of the optical receiver and the optical transmitter are more complicated, and the power consumption of the optical transmitter and the optical receiver is increased, resulting in higher cost.
To this end, embodiments of the present invention provide an optical transmission method, so that an optical receiver can demodulate a PAM-N optical signal in a direct detection manner even when a coded signal of the PAM-N signal includes a negative level, and recover the negative level in the coded signal, thereby reducing power consumption of an optical transmitter and the optical receiver.
As shown in fig. 2, an embodiment of the present invention provides an optical transmission method, which may include:
s101, an optical transmitter encodes a PAM-N signal to be transmitted to obtain a first encoded signal, wherein the first encoded signal comprises N-1 first positive integer levels, 1 zero level and N-1 negative integer levels, N is more than or equal to 3, and N is an integer.
In the embodiment of the present invention, the PAM-N signal may be a PAM-3 signal, a PAM-4 signal, a PAM-5 signal, or the like. The optical transmitter may encode the PAM-N signal using a multiple binary (english) modulation coding technique to obtain 2N-1 levels, i.e., a first encoded signal. Specifically, the 2N-1 levels are-N +1 volts (V), -N +2V, … …, 0V, … …, N-2V, and N-1V, respectively, i.e., the 2N-1 levels include N-1 first positive integer levels, 1 zero level, and N-1 negative integer levels.
Illustratively, taking the PAM-4 signal as an example, the PAM-4 signal includes 4 levels, which are 0V, 1V, 2V, and 3V, respectively. After the PAM-4 signal is coded by the optical transmitter by adopting a multi-binary modulation coding method, 7 levels can be obtained, wherein the levels comprise 3 levels with negative integer levels of-3V, -2V and-1V, 1 level with 0V and 3 levels with first positive integer levels of 1V, 2V and 3V.
Specifically, the process of the optical transmitter encoding the PAM-N signal may be described in detail in the ethernet standard (ieee802.3bj), and is not described herein again.
S102, the optical transmitter shifts the N-1 first positive integer levels or the N-1 negative integer levels by a first offset respectively to convert the first coded signal into a second coded signal, wherein the first offset is a decimal number.
In embodiments of the present invention, the first offset may be a positive or negative fraction, and the optical transmitter may mark N-1 positive integer levels in the first encoded signal with a fraction or mark N-1 negative integer levels in the first encoded signal with a fraction.
Specifically, if the optical transmitter marks the N-1 first positive integer levels with a decimal, the optical transmitter may shift the N-1 first positive integer levels in the first encoded signal by a first offset amount, so that the N-1 first positive integer levels are converted into N-1 decimal levels, thereby converting the first encoded signal into a second encoded signal, that is, the second encoded signal includes the N-1 decimal levels, 1 zero level, and N-1 negative integer levels.
Illustratively, the first encoded signal obtained after encoding the PAM-4 signal includes 7 levels, which are-3V, -2V, -1V, 0V, 1V, 2V and 3V, respectively, and assuming that the first offset is-0.5, the optical transmitter shifts 3 first positive integer levels in the first encoded signal by-0.5, and converts the 3 positive integer levels into 3 decimal levels, which are 0.5V, 1.5V and 2.5V, respectively, so that the 7 levels included in the second encoded signal corresponding to the PAM-4 signal are-3V, -2V, -1V, 0V, 0.5V, 1.5V and 2.5V, respectively.
Optionally, if the optical transmitter marks the N-1 negative-positive integer levels with a decimal, the optical transmitter may shift the N-1 negative integer levels in the first encoded signal by a first offset amount, so that the N-1 negative integer levels are converted into N-1 decimal levels, so that the first encoded signal is converted into a second encoded signal, that is, the second encoded signal includes the N-1 decimal levels, 1 zero level, and N-1 first positive integer levels.
Illustratively, assuming that the first offset amount is +0.3, the optical transmitter may shift all 3 negative integer levels in the first encoded signal of the PAM-4 signal by +0.3 to 3 decimal levels of-2.7V, -1.7V, and-0.7V, respectively, such that the second encoded signal corresponding to the PAM-4 signal includes 7 levels of-2.7V, -1.7V, -0.7V, 0V, 1V, 2V, and 3V, respectively.
It should be noted that, the N-1 decimal levels obtained by shifting the N-1 first positive or negative integer levels may be all positive decimal levels, may also be all negative decimal levels, and may also include positive decimal levels and negative decimal levels. The specific result is associated with a first offset. For example, the first offset is 1.5, and N-1 negative integer levels are inexpensive, including-1.5V, -0.5V, and 0.5V.
Preferably, in the embodiment of the present invention, the first offset may be a decimal between-1 and 1, so that no matter the N-1 integer levels are offset or the N-1 negative integer levels are offset, after the offset, the sign of the levels can be kept unchanged, thereby reducing the probability of the disorder between the negative levels and the positive levels.
S103, the optical transmitter modulates the second coded signal into an optical signal.
Specifically, in the embodiment of the present invention, the optical transmitter may input the second encoded signal to a push-pull modulator, such as a Mach-Zehnder modulator (MZM), for modulation. Further, in the implementation of the present invention, after the optical transmitter inputs the second encoded signal into the MZM, the second encoded signal may be modulated by using a zero-crossing point modulation method. Because the amplitude of the modulation of the second encoding signal by the zero-crossing point modulation is large, the performance of the modulated optical signal against the Relative Intensity Noise (RIN) of the light source is stronger. And it can be understood that the carrier wave can be suppressed by adopting the zero-crossing point modulation mode, thereby reducing the transmission power when the optical transmitter transmits the optical signal and improving the performance of the optical transmission system.
It should be noted that, after the optical receiver directly detects the received optical signal, the square value of the value corresponding to the level information carried in the optical signal is obtained, so in the embodiment of the present invention, when the optical transmitter modulates the second encoded signal into the optical signal, the optical transmitter needs to perform the squaring processing on the second encoded signal, that is, the values of 2N-1 levels in the second encoded signal are respectively squared, and then convert the squared second encoded signal into the optical signal, so that the optical receiver receives the optical signal and can obtain an effective electrical signal after directly detecting the optical signal.
For example, if 7 levels in the second encoded signal of the PAM-4 signal are-2.7V, -1.7V, -0.7V, 0V, 1V, 2V, and 3V, respectively, then the 7 levels in the second encoded signal after the squaring process are each set to be the same
0V、1V、
And
if the 7 levels in the second coded signal are-3V, -2V, -1V, 0V, 0.5V, 1.5V and 2.5V, respectively, after the evolution process
0V、
And
the specific way of modulating the second encoded signal into the optical signal by the push-pull modulator using the zero-crossing point modulation method may refer to a process of modulating the encoded signal by the push-pull modulator in the prior art, and is not described herein again.
S104, the optical transmitter transmits the optical signal to the optical receiver.
It will be appreciated that, once the optical transmitter acquires the optical signal, the optical signal is transmitted to the corresponding optical fiber and transmitted to the optical receiver.
And S105, the optical receiver receives the optical signal sent by the optical transmitter.
S106, the optical receiver directly detects and judges the optical signal to obtain 2N-1 levels, wherein the 2N-1 levels comprise N-1 second positive integer levels, 1 zero level and N-1 positive decimal levels.
In the embodiment of the invention, after receiving the optical signal, the optical receiver directly detects the optical signal, that is, the optical signal is directly input into the photoelectric detector, the photoelectric detector detects the level information carried in the optical signal, and the detected level information is judged to obtain the 2N-1 levels.
It is understood that, due to the influence of system performance or due to the difference in the receiving power of the optical receiver, the level information obtained after the optical signal is detected by the optical receiver may have an error from the level information transmitted by the optical transmitter. Therefore, the optical receiver needs to make a decision on the detected level information.
For example, if the level information originally required to be transmitted by the optical transmitter is 0V and 1V, the determination criterion may be 0.5, and the level information detected by the optical receiver is 0.2V and 1.2V, that is, if the detected level information is shifted by 0.2V compared to the level information transmitted by the optical transmitter, when the optical receiver determines the detected level information, the levels smaller than 0.5 are all determined to be 0V, and the levels larger than 0.5 are all determined to be 1V. Wherein, the decision criterion can be set according to actual needs.
Further, in order to avoid distortion of the level information obtained after the optical receiver directly detects the optical signal, the optical receiver may perform clock algorithm processing and equalization algorithm processing on the detected level information.
For specific implementation of clock algorithm processing, equalization algorithm processing, and decision on the level information, reference may be made to related descriptions in the prior art, and details are not described here.
For example, suppose that the optical signal received by the optical receiver is modulated by the second coded signal of the PAM-4 signal after the square root processing, if 7 levels in the second coded signal are respectively
0V、1V、
And
the optical receiver directly detects the optical signal and determines that the obtained 7 levels are 2.7V, 1.7V, 0.7V, 0V, 1V, 2V and 3V in sequence. If 7 levels in the second encoded signal are respectively
0V、
And
the 7 levels obtained after the optical receiver directly detects and decides the optical signal are 3V, 2V, 1V, 0V, 0.5V, 1.5V and 2.5V in sequence. That is, the 7 levels obtained by the optical receiver through direct detection of the optical signal include 3 positive fractional levels, 1 zero level and 3 second positive integer levels.
S107, the optical receiver recovers the 2N-1 levels to obtain a recovered first coded signal, wherein the recovered first coded signal comprises recovered N-1 first positive integer levels, recovered 1 zero level and recovered N-1 negative integer levels; the recovered N-1 first positive integer levels are the N-1 second positive integer levels, the recovered 1 zero levels are the 1 zero levels, and the recovered N-1 negative integer levels are obtained by converting the N-1 positive decimal levels; or the recovered N-1 first positive integer levels are converted from the N-1 positive decimal levels, the recovered 1 zero levels are the 1 zero levels, and the recovered N-1 negative integer levels are converted from the N-1 second positive integer levels.
In the embodiment of the present invention, since the optical receiver on the receiving side (i.e., the optical receiver) does not necessarily have to be able to completely recover the first encoded signal on the transmitting side (i.e., the optical transmitter), in order to distinguish the first encoded signal on the transmitting side from the first encoded signal recovered on the receiving side, the first encoded signal on the transmitting side is also referred to as the first encoded signal, and the first encoded signal recovered on the receiving side is referred to as the recovered first encoded signal. Similarly, the first positive integer level recovered by the receiving end is called the recovered first positive integer level, the negative integer level recovered by the receiving end is called the recovered negative integer level, and the zero level recovered by the receiving end is called the recovered zero level.
Further, if the optical transmitter marks the negative integer level with the decimal, the optical receiver needs to convert N-1 positive decimal levels of the 2N-1 levels into N-1 negative integer levels after recovery when recovering the detected 2N-1 levels.
Specifically, the optical receiver recovers the 2N-1 levels, specifically, the optical receiver determines that the N-1 second positive integer levels are the recovered N-1 first positive integer levels; determining the 1 zero level as a recovered zero level; and shifting the N-1 positive decimal levels by the first offset respectively to obtain N-1 third positive integer levels, and negating the N-1 third positive integer levels respectively to obtain recovered N-1 negative integer levels.
Illustratively, after directly detecting and determining the received optical signal, the optical receiver obtains 7 levels of 2.7V, 1.7V, 0.7V, 0V, 1V, 2V, and 3V in sequence, and the optical receiver may keep 3 second positive integer levels of the 7 levels unchanged, that is, determine that the 3 second positive integer levels are the recovered first positive integer levels, respectively. The optical receiver shifts 3 positive decimal levels of the 7 levels according to a first offset value, namely +0.3, adopted by the optical transmitter to convert the 3 positive decimal levels into 3 third positive integer levels, wherein the 3 third positive integer levels are 3V, 2V and 1V in sequence, and then the 3 third positive integer levels are inverted in sequence to obtain 3 recovered negative integer levels which are-3V, -2V and-1V in sequence. Then, the optical receiver recovers the obtained 7 levels, that is, the 7 levels in the recovered first encoded signal are-3V, -2V, -1V, 0V, 1V, 2V, and 3V, respectively, that is, in the embodiment of the present invention, the optical receiver can obtain the recovered first encoded signal of the PAM-4 signal.
Optionally, if the optical transmitter marks the positive integer level with the decimal, when the optical receiver recovers the detected 2N-1 levels, the optical receiver needs to convert N-1 positive decimal levels in the 2N-1 levels into N-1 second integer levels after recovery.
Specifically, the optical receiver may specifically recover the 2N-1 levels by inverting the N-1 second positive integer levels respectively to obtain the recovered N-1 negative integer levels, and offsetting the N-1 positive fractional levels by a first offset respectively to obtain the recovered N-1 first positive integer levels.
Illustratively, after directly detecting and deciding a received optical signal, the optical receiver obtains 7 levels, which are 3V, 2V, 1V, 0V, 0.5V, 1.5V and 2.5V in sequence, and the optical receiver can respectively invert 3 second positive integer levels of the 7 levels to obtain 3 negative integer levels, which are-3V, -2V and-1V in sequence, where the 3 negative integer levels are the recovered 3 negative integer levels. The optical receiver sequentially performs reverse direction offset on 3 positive fractional levels of the 7 levels according to a first offset amount, namely-0.5, adopted by the optical transmitter, so as to convert the 3 positive fractional levels into 3 positive integer levels, namely levels of 1V, 2V and 3V, wherein the 3 positive integer levels are the recovered 3 first positive integer levels. Then, after the optical receiver recovers the obtained 7 levels, the optical receiver may obtain the 7 levels in the recovered first encoded signal of the PAM-4 signal, that is, in the embodiment of the present invention, the optical receiver may obtain the recovered first encoded signal. The reverse direction offset refers to that when the optical transmitter uses the decimal mark positive integer level, if the optical transmitter shifts N-1 positive integer levels in the first coded signal by + M, the optical receiver shifts the detected N-1 positive decimal levels by-M, where M is the first offset.
S108, the optical receiver decodes the recovered first coded signal to obtain a recovered PAM-N signal.
Correspondingly, the optical receiver may employ a duobinary coded modulation technique to decode the recovered first encoded signal to obtain a recovered PAM-N signal.
It is understood that since the recovered first encoded signal may have a slight error from the first encoded signal, a PAM-N signal obtained by decoding the recovered first encoded signal may also have a slight error. In the embodiment of the invention, the PAM-N signal recovered by optical reception is called a recovered PAM-N signal.
Specifically, the process of decoding the recovered first encoded signal by the optical receiver can be referred to in the prior art, and is not described in detail herein.
In summary, with the optical transmission method provided by the embodiment of the present invention, the optical receiver can demodulate the PAM-N optical signal by using a direct detection method when the coded signal of the PAM-N signal includes a negative level, so as to reduce the complexity of the optical transmitter and the optical receiver and reduce the power consumption of the optical transmitter and the optical receiver.
Further, in the embodiment of the present invention, because the encoding scheme (e.g., the encoding scheme in ieee802.3bj) adopted when the optical transmitter encodes the PAM-N signal can reduce the bandwidth requirements of the optical transmitter and the optical receiver, based on the optical transmission method provided in the embodiment of the present invention, the optical transmitter and the optical receiver at 10GHz can be used to implement 40-50Gbps modulation, or the optical transmitter and the optical receiver at 25GHz can be used to implement 100Gbps modulation, and compared with the conventional modulation and demodulation scheme, the carrier-signal power ratio (carrier-signal power ratio) of the optical signal corresponding to the encoded signal is also reduced, thereby improving the system performance.
By adopting the optical transmission method provided by the embodiment of the invention, the optical transmitter and the optical receiver are simple in design, and the low-power-consumption optical module can be packaged, such as small Form-factor plug transceivers (SFP) with the power consumption requirement lower than 1.5W, or quad Small Form-factor plug (QSFP) interfaces with the power consumption requirement lower than 3.5W.
As shown in fig. 3, an embodiment of the present invention provides an optical transmitter, including: the processing unit 10, the modulation unit 11, and the communication unit 12 may be connected through a communication bus 13, and the system bus 13 may include a data bus, a power bus, a control bus, a signal status bus, and the like, and for convenience of illustration, only one thick line is shown in fig. 3, but only one bus or one type of bus is not shown.
The processing unit 10 may be an encoder, a Central Processing Unit (CPU), or other special purpose processors, general purpose processors, Digital Signal Processors (DSP), Application Specific Integrated Circuits (ASIC), Field Programmable Gate Arrays (FPGA), or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, or the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The modulation unit 11 may be a push-pull modulator.
The communication unit 12 may be a transceiver, a transceiver circuit, or a communication interface, etc. and is used to support information interaction between an optical transmitter and an optical receiver.
The optical transmitter may further include a storage unit 14 for storing a code program and data in the optical transmitter, and the storage unit 14 may include a volatile memory (RAM), such as a random-access memory (random-access memory); the memory 14 may also include a non-volatile memory (ROM), such as a read-only memory (read-only memory), a flash memory (flash memory), a hard disk (HDD) or a solid-state drive (SSD); the memory 14 may also comprise a combination of memories of the kind described above. Which may implement or perform the various illustrative logical blocks, modules, and circuits described in connection with the disclosure. The processing unit may also be a combination of computing functions, e.g., comprising one or more microprocessors, a combination of a DSP and a microprocessor, or the like.
Specifically, in the embodiment of the present invention, the processing unit 10 is configured to encode an N-level pulse amplitude modulation PAM-N signal to be transmitted to obtain a first encoded signal, where the first encoded signal includes N-1 first positive integer levels, 1 zero level, and N-1 negative integer levels, where N is greater than or equal to 3, and N is an integer.
The processing unit 10 is further configured to shift the N-1 first positive integer levels or the N-1 negative integer levels by a first shift amount respectively to convert the first encoded signal into a second encoded signal, where the first shift amount is a fractional number.
The modulation unit 11 is configured to modulate the second encoded signal converted by the processing unit 10 into an optical signal.
The communication unit 12 is configured to send the optical signal modulated by the modulation unit 11 to an optical receiver.
Optionally, the first offset is a fractional number between-1 and 1.
The optical transmitter according to the embodiment of the present invention is capable of shifting a first positive integer level or a negative integer level in a first coded signal of a PAM-N signal by a first offset having a fractional value to obtain a second coded signal, and modulating the second coded signal into an optical signal to be transmitted to a receiver, so that the optical receiver directly detects and decides the optical signal, and then obtains 2N-1 levels including N-1 positive fractional levels, so that the optical receiver can convert the N-1 positive fractional levels into N-1 recovered negative integer levels, determine a zero level of the 2N-1 levels as a recovered zero level, and determine N-1 positive integer levels of the 2N-1 levels as N-1 recovered first positive integer levels when the 2N-1 levels are recovered, so as to obtain a recovered first coded signal, or convert the N-1 positive fractional levels into recovered N-1 first positive integer levels, determine a zero level in the 2N-1 levels as a recovered zero level, and convert N-1 second positive integer levels in the 2N-1 levels into recovered N-1 negative integer levels, so as to obtain a recovered first coded signal, and then the optical receiver can decode the recovered first coded signal, so as to obtain a recovered PAM-N signal. Namely, the optical transmission method enables the optical receiver to demodulate the PAM-N optical signal by adopting a direct detection mode when the coded signal of the PAM-N signal comprises a negative level, thereby reducing the complexity of the optical transmitter and the optical receiver and reducing the power consumption of the optical transmitter and the optical receiver.
As shown in fig. 4, an embodiment of the present invention provides an optical receiver, including: the system comprises a communication unit 20, a photoelectric detection unit 21 and a processing unit 22, wherein the communication unit 20, the photoelectric detection unit 21 and the processing unit 22 can be connected through a communication bus 23, the system bus 23 can comprise a data bus, a power bus, a control bus, a signal state bus and the like, and for convenience of representation, only one thick line is used for representation in fig. 4, but only one bus or one type of bus is not shown.
The communication unit 20 may be a transceiver, a transceiver circuit, a communication interface, or the like, and is used to support information interaction between the optical receiver and the optical transmitter.
The photo detection unit 21 may include a photo detector, a decision module, and the like.
The processing unit 22 may be a decoder, a CPU, or other special purpose processor, general purpose processor, DSP, ASIC, FPGA or other programmable logic device, discrete gate or transistor logic device, discrete hardware component, or the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The optical receiver may further comprise a storage unit 24 for storing the code program and data in the optical transmitter, which storage unit 24 may be a device comprising a volatile memory, such as a RAM; the memory 24 may also include a non-volatile memory such as a ROM, a flash memory, an HDD, or an SSD; the memory 24 may also comprise a combination of memories of the kind described above. Which may implement or perform the various illustrative logical blocks, modules, and circuits described in connection with the disclosure. The processing unit may also be a combination of computing functions, e.g., comprising one or more microprocessors, a combination of a DSP and a microprocessor, or the like.
Specifically, in the present embodiment, the communication unit 20 is configured to receive an optical signal sent by an optical transmitter.
The photodetection unit 21 is configured to directly detect and determine the optical signal received by the communication unit 20, and obtain 2N-1 levels, where the 2N-1 levels include N-1 second positive integer levels, 1 zero level, and N-1 positive decimal levels, where N is greater than or equal to 3, and N is an integer.
The processing unit 22 is configured to recover the 2N-1 levels obtained by the photodetecting unit 21 to obtain a recovered first encoded signal, where the recovered first encoded signal includes recovered N-1 first positive integer levels, recovered 1 zero level, and recovered N-1 negative integer levels; the recovered N-1 first positive integer levels are the N-1 second positive integer levels, the recovered 1 zero levels are the 1 zero levels, and the recovered N-1 negative integer levels are obtained by converting the N-1 positive decimal levels; or the recovered N-1 first positive integer levels are converted from the N-1 positive fractional levels, the recovered 1 zero levels are the 1 zero levels, and the recovered N-1 negative integer levels are converted from the N-1 second positive integer levels.
The processing unit 22 is further configured to decode the recovered first encoded signal, and obtain a recovered N-level pulse amplitude modulation PAM-N signal.
Optionally, the optical signal is a signal obtained by modulating a second encoded signal by the optical transmitter, the second encoded signal is a signal obtained by shifting, by the optical transmitter, N-1 first positive integer levels or N-1 negative integer levels in the first encoded signal by a first offset respectively, and the first offset is a fractional number.
Optionally, the processing unit 22 is specifically configured to determine that the N-1 second positive integer levels are the recovered N-1 first positive integer levels; determining the 1 zero level as the recovered 1 zero level; and respectively shifting the N-1 positive decimal levels by a first offset to obtain N-1 third positive integer levels, and respectively negating the N-1 third positive integer levels to obtain the recovered N-1 negative integer levels, wherein the first offset is a decimal number.
Optionally, the processing unit 22 is specifically configured to respectively negate the N-1 second positive integer levels, and obtain the recovered N-1 negative integer levels; determining the 1 zero level as the recovered 1 zero level; and respectively offsetting the N-1 positive decimal levels by a first offset to obtain the recovered N-1 first positive integer levels, wherein the first offset is a decimal.
Optionally, the first offset is a fractional number between-1 and 1.
In the optical receiver according to the embodiment of the present invention, the optical receiver can directly detect an optical signal of a PAM-N signal and obtain 2N-1 levels, and since the optical transmitter shifts a negative integer level or a positive integer level of a first encoded signal of the PAM-N signal by using a first offset amount having a fractional value before modulating an encoded signal of the PAM-N signal into the optical signal, the 2N-1 levels obtained by the optical receiver include N-1 positive fractional levels, so that the optical receiver can convert the N-1 positive fractional levels into N-1 restored negative integer levels when restoring the 2N-1 levels, determine a zero point in the 2N-1 levels as a restored zero level, and determine N-1 positive integer levels in the 2N-1 levels as N-1 first restored positive integer levels Counting the levels to obtain recovered first coded signals, or converting the N-1 positive fractional levels into recovered N-1 first positive integer levels, determining zero levels in the 2N-1 levels as recovered zero levels, and converting N-1 second positive integer levels in the 2N-1 levels into recovered N-1 negative integer levels to obtain recovered first coded signals, and then decoding the recovered first coded signals by the optical receiver to obtain recovered PAM-N signals. Namely, the optical transmission method enables the optical receiver to demodulate the PAM-N optical signal by adopting a direct detection mode when the coded signal of the PAM-N signal comprises a negative level, thereby reducing the complexity of the optical transmitter and the optical receiver and reducing the power consumption of the optical transmitter and the optical receiver.
As shown in fig. 5, an embodiment of the present invention provides an optical transmission system, including: an optical transmitter as described in fig. 3, an optical receiver as described in fig. 4.
The optical transmitter and the optical receiver in the optical transmission system provided by the embodiment of the present invention can perform the optical transmission method as described in fig. 2. For a specific payment method, reference may be made to the related description in the embodiment shown in fig. 2, and details are not repeated here.
Based on the optical transmission system provided by the embodiment of the present invention, the optical transmitter can shift the positive integer level or the negative integer level in the first coded signal of the PAM-N signal by the first offset with a fractional value to obtain the second coded signal, and modulate the second coded signal into the optical signal to be sent to the optical receiver, so that the optical receiver directly detects and decides the optical signal, and then obtains 2N-1 positive fractional levels, so that the optical receiver can convert the N-1 positive fractional levels into N-1 recovered negative integer levels, determine the zero point level in the 2N-1 levels as the recovered zero level, and determine the N-1 positive integer levels in the 2N-1 levels as the recovered N-1 first positive integer levels, so as to obtain a recovered first coded signal, or convert the N-1 positive fractional levels into recovered N-1 first positive integer levels, determine a zero level in the 2N-1 levels as a recovered zero level, and convert N-1 second positive integer levels in the 2N-1 levels into recovered N-1 negative integer levels, so as to obtain a recovered first coded signal, and then the optical receiver can decode the recovered first coded signal, so as to obtain a recovered PAM-N signal. Namely, the optical transmission method enables the optical receiver to demodulate the PAM-N optical signal by adopting a direct detection mode when the coded signal of the PAM-N signal comprises a negative level, thereby reducing the complexity of the optical transmitter and the optical receiver and reducing the power consumption of the optical transmitter and the optical receiver.
It will be clear to those skilled in the art that, for convenience and simplicity of description, the foregoing division of the functional modules is merely used as an example, and in practical applications, the above function distribution may be performed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to perform all or part of the above described functions. For the specific working processes of the system, the apparatus and the unit described above, reference may be made to the corresponding processes in the foregoing method embodiments, and details are not described here again.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the modules or units is only one logical division, and there may be other divisions when actually implemented, for example, a plurality of units or components may be combined or may be integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit may be implemented in the form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, all or part of the technical solution can be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) or a processor to execute all or part of the steps of the method according to the embodiments of the present invention. The storage medium is a non-transient (English) medium, comprising: flash memory, removable hard drive, read only memory, random access memory, magnetic or optical disk, and the like.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (13)
1. An optical transmission method, comprising:
encoding an N-level pulse amplitude modulation (PAM-N) signal to be transmitted to obtain a first encoded signal, wherein the first encoded signal comprises N-1 first positive integer levels, 1 zero level and N-1 negative integer levels, N is not less than 3, and N is an integer;
shifting the N-1 first positive integer levels or the N-1 negative integer levels by a first offset, respectively, to convert the first encoded signal to a second encoded signal, the first offset being a fractional number;
modulating the second encoded signal into an optical signal;
and transmitting the optical signal to an optical receiver.
2. The method of claim 1,
the first offset is a fractional number between-1 and 1.
3. An optical transmission method, comprising:
receiving an optical signal sent by an optical transmitter;
directly detecting and judging the optical signal to obtain 2N-1 levels, wherein the 2N-1 levels comprise N-1 second positive integer levels, 1 zero level and N-1 positive decimal levels, N is not less than 3, and N is an integer;
restoring the 2N-1 levels to obtain a restored first coded signal, wherein the restored first coded signal comprises restored N-1 first positive integer levels, restored 1 zero level and restored N-1 negative integer levels; the recovered N-1 first positive integer levels are the N-1 second positive integer levels, the recovered 1 zero levels are the 1 zero levels, and the recovered N-1 negative integer levels are obtained by converting the N-1 positive decimal levels; or the recovered N-1 first positive integer levels are converted from the N-1 positive decimal levels, the recovered 1 zero levels are the 1 zero levels, and the recovered N-1 negative integer levels are converted from the N-1 second positive integer levels;
decoding the recovered first coded signal to obtain a recovered N-level pulse amplitude modulation (PAM-N) signal;
the optical signal is a signal obtained by modulating a second coded signal by the optical transmitter, the second coded signal is a signal obtained by shifting N-1 first positive integer levels or N-1 negative integer levels in a first coded signal by a first offset respectively by the optical transmitter, and the first offset is a fractional number.
4. The method of claim 3, wherein said recovering said 2N-1 levels comprises:
determining the N-1 second positive integer levels as the recovered N-1 first positive integer levels;
determining the 1 zero level as the recovered 1 zero level;
and respectively shifting the N-1 positive decimal levels by a first offset to obtain N-1 third positive integer levels, and respectively negating the N-1 third positive integer levels to obtain the recovered N-1 negative integer levels, wherein the first offset is a decimal number.
5. The method of claim 3, wherein said recovering said 2N-1 levels comprises:
respectively negating the N-1 second positive integer levels to obtain the recovered N-1 negative integer levels;
determining the 1 zero level as the recovered 1 zero level;
and respectively offsetting the N-1 positive decimal levels by a first offset to obtain the recovered N-1 first positive integer levels, wherein the first offset is a decimal.
6. The method according to claim 4 or 5,
the first offset is a fractional number between-1 and 1.
7. An optical transmitter is characterized by comprising a processing unit, a modulation unit and a communication unit,
the processing unit is used for encoding an N-level pulse amplitude modulation (PAM-N) signal to be transmitted to obtain a first encoded signal, wherein the first encoded signal comprises N-1 first positive integer levels, 1 zero level and N-1 negative integer levels, N is more than or equal to 3, and N is an integer;
the processing unit is further configured to shift the N-1 first positive integer levels or the N-1 negative integer levels by first offsets, respectively, so as to convert the first encoded signal into a second encoded signal, where the first offsets are decimal numbers;
the modulation unit is used for modulating the second coded signal converted by the processing unit into an optical signal;
and the communication unit is used for sending the optical signal modulated by the modulation unit to an optical receiver.
8. The optical transmitter of claim 7,
the first offset is a fractional number between-1 and 1.
9. An optical receiver is characterized by comprising a communication unit, a photoelectric detection unit and a processing unit,
the communication unit is used for receiving an optical signal sent by the optical transmitter;
the photoelectric detection unit is used for directly detecting and judging the optical signal received by the communication unit to obtain 2N-1 levels, wherein the 2N-1 levels comprise N-1 second positive integer levels, 1 zero level and N-1 positive decimal levels, N is not less than 3, and N is an integer;
the processing unit is configured to restore the 2N-1 levels obtained by the photodetection unit to obtain a restored first encoded signal, where the restored first encoded signal includes N-1 restored first positive integer levels, 1 restored zero level, and N-1 restored negative integer levels; the recovered N-1 first positive integer levels are the N-1 second positive integer levels, the recovered 1 zero levels are the 1 zero levels, and the recovered N-1 negative integer levels are obtained by converting the N-1 positive decimal levels; or the recovered N-1 first positive integer levels are converted from the N-1 positive decimal levels, the recovered 1 zero levels are the 1 zero levels, and the recovered N-1 negative integer levels are converted from the N-1 second positive integer levels;
the processing unit is further configured to decode the recovered first encoded signal to obtain a recovered N-level pulse amplitude modulation PAM-N signal;
the optical signal is a signal obtained by modulating a second coded signal by the transmitter, the second coded signal is a signal obtained by shifting N-1 first positive integer levels or N-1 negative integer levels in a first coded signal by a first offset respectively by the transmitter, and the first offset is a decimal number.
10. The optical receiver of claim 9,
the processing unit is specifically configured to determine that the N-1 second positive integer levels are the recovered N-1 first positive integer levels; determining the 1 zero level as the recovered 1 zero level; and respectively shifting the N-1 positive decimal levels by a first offset to obtain N-1 third positive integer levels, and respectively negating the N-1 third positive integer levels to obtain the recovered N-1 negative integer levels, wherein the first offset is a decimal number.
11. The optical receiver of claim 9,
the processing unit is specifically configured to respectively negate the N-1 second positive integer levels, and obtain the recovered N-1 negative integer levels; determining the 1 zero level as the recovered 1 zero level; and respectively offsetting the N-1 positive decimal levels by a first offset to obtain the recovered N-1 first positive integer levels, wherein the first offset is a decimal.
12. The optical receiver according to claim 10 or 11,
the first offset is a fractional number between-1 and 1.
13. An optical transmission system, comprising:
an optical transmitter according to claim 7 or 8 and an optical receiver according to any of claims 9-12.
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| PCT/CN2016/091963 WO2018018477A1 (en) | 2016-07-27 | 2016-07-27 | Optical transmission method, apparatus and system |
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| KR20090049290A (en) * | 2007-11-13 | 2009-05-18 | 삼성전자주식회사 | Multi-level pulse amplitude modulation transceiver and method for transmitting and receiving data |
| US8964818B2 (en) * | 2012-11-30 | 2015-02-24 | Broadcom Corporation | Use of multi-level modulation signaling for short reach data communications |
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| US20160072651A1 (en) * | 2014-09-04 | 2016-03-10 | Luxtera, Inc. | Method and system for a multi-level encoded data path with decoder |
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