CN115118339A - Extra-long distance unrepeatered optical transmission system - Google Patents
Extra-long distance unrepeatered optical transmission system Download PDFInfo
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- CN115118339A CN115118339A CN202210741831.9A CN202210741831A CN115118339A CN 115118339 A CN115118339 A CN 115118339A CN 202210741831 A CN202210741831 A CN 202210741831A CN 115118339 A CN115118339 A CN 115118339A
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Abstract
The invention provides an ultra-long distance unrepeatered optical transmission system aiming at the technical problems in the prior art, which comprises a first optical signal modulator, an optical signal encoder, a first optical amplifier, an optical signal decoder, a second optical amplifier, a photoelectric converter, a first low-pass filter, a second optical signal modulator and a second low-pass filter; with the rapid development of the optical fiber communication technology, the ultra-long distance non-relay optical transmission system adopts an end-to-end direct path, the whole transmission line does not need relaying, and the ultra-long distance non-relay optical transmission system has the outstanding characteristics of high reliability, low construction cost, rapid opening, convenient maintenance and the like, and is very suitable for communication of part of side sea defense sentries. Based on the one-dimensional strict optimal optical orthogonal code, an OCDMA (optical code division multiple Access) ultra-long distance unrepeatered optical transmission system designed by using an optical fiber Bragg grating as an encoder and using an optical fiber time delay line as a decoder realizes 400-kilometer unrepeatered transmission of 155Mbps user optical signals.
Description
Technical Field
The invention relates to the technical field of optical transmission, in particular to an ultra-long distance unrepeatered optical transmission system.
Background
The China has long border defense lines, a plurality of border defense sentries are hundreds of kilometers away from a communication hub station, communication basically depends on wireless communication, the wireless communication bandwidth is narrow, the communication requirements of the border defense sentries cannot be met at present, therefore, an optical communication transmission system is required, the theoretical value of the optical transmission relay distance is 100 kilometers under general conditions, a plurality of relay stations need to be established between the sentries and the communication hub station, and the construction and maintenance cost of the optical communication system is increased.
An ultra-long distance refers to an optical transmission system relaying distances greater than 200 km. The basic factors limiting the relay distance of fiber optic communications are two, the first being limited by line attenuation and the second being limited by line dispersion and dispersion due to various types of noise. The ultra-long distance optical transmission system needs a narrower signal spectrum width and a sufficiently high fiber-entering power, so that energy is more concentrated when the signal light and the pump light are transmitted in the optical fiber, and the nonlinear effect of the optical fiber is more easily caused.
At present, the G.652 optical fiber is mainly used in China, the attenuation is 0.2dB/km when the optical wavelength is 1550nm, and the attenuation reaches 40dB when the transmission distance is 200 km.
Disclosure of Invention
The invention provides an ultra-long distance unrepeatered optical transmission system aiming at the technical problems in the prior art, along with the rapid development of the optical fiber communication technology, the ultra-long distance unrepeatered optical transmission system adopts an end-to-end direct path, the whole transmission line does not need relaying, and the ultra-long distance unrepeatered optical transmission system has the outstanding characteristics of high reliability, low construction cost, rapid opening, convenient maintenance and the like, and is very suitable for the communication of part of border defense sentries.
According to a first aspect of the present invention, there is provided an ultra-long distance unrepeatered optical transmission system comprising a first optical signal modulator, an optical signal encoder, a first optical amplifier, an optical signal decoder, a second optical amplifier, an optical-to-electrical converter, a first low-pass filter, a second optical signal modulator, and a second low-pass filter; the input end of the first optical signal modulator is connected with a user optical signal, the output end of the first optical signal modulator is connected with the input end of an optical signal encoder, the output end of the optical signal encoder is connected with the input end of a first optical amplifier, the output end of the first optical amplifier is connected with the input end of an optical signal decoder, the output end of the optical signal decoder is connected with the input end of a second optical amplifier, the output end of the second optical amplifier is connected with the input end of a photoelectric converter, the output end of the photoelectric converter is connected with the photoelectric input end of a first low-pass filter, the output end of the first low-pass filter is connected with the input end of a second optical signal modulator, the input end of the second optical signal modulator is also connected with a local electrical signal, and the output end of the second optical signal modulator is connected with the input end of a second low-pass filter.
According to the technical scheme of the invention, the following improvements can be made:
optionally, the optical signal encoder adopts a bragg grating encoder, and the optical signal decoder adopts a light delay line decoder.
Optionally, the optical signal decoder is an optical fiber delay decoder with a parallel structure.
Optionally, the first optical amplifier is a raman amplifier.
Optionally, the second optical amplifier is an erbium-doped fiber amplifier.
Optionally, the user optical signal rate is 155Mbps, the transmission rate is 2.015Gbps, and the local electrical signal is 2.015 Gbps.
The invention provides an ultra-long distance unrepeatered optical transmission system, which adopts an end-to-end direct path along with the rapid development of an optical fiber communication technology, does not need relaying in the whole transmission line, has the outstanding characteristics of high reliability, low construction cost, rapid opening, convenient maintenance and the like, and is very suitable for the communication of part of side-to-side sea defense sentries. The invention relates to an OCDMA (optical code division multiple Access) ultra-long distance unrepeatered optical transmission system which is designed by using an optical fiber Bragg grating as an encoder and an optical fiber time delay line as a decoder on the basis of one-dimensional strict optimal optical orthogonal codes, and realizes 400-kilometer unrepeatered transmission of 155Mbps user optical signals.
Drawings
Fig. 1 is a schematic block diagram of an ultra-long distance unrepeatered optical transmission system according to an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a bragg grating encoder of an ultra-long-distance unrepeatered optical transmission system according to an embodiment of the present invention.
Fig. 3 is a schematic structural diagram of an optical fiber delay line decoder of an ultra-long distance unrepeatered optical transmission system according to an embodiment of the present invention.
Fig. 4 is a general simulation design diagram of an ultra-long distance unrepeatered optical transmission system according to an embodiment of the present invention.
Fig. 5 is a waveform diagram of a user optical signal of an ultra-long distance unrepeatered optical transmission system according to an embodiment of the present invention.
Fig. 6 is a signal diagram i after modulation of a user optical signal of an ultra-long-distance unrepeatered optical transmission system according to an embodiment of the present invention.
Fig. 7 is a signal diagram ii after modulation of a user optical signal of an ultra-long-distance unrepeatered optical transmission system according to an embodiment of the present invention.
Fig. 8 is a signal diagram after encoding of an ultra-long-distance unrepeatered optical transmission system according to an embodiment of the present invention.
Fig. 9 is a decoded signal diagram of an ultra-long distance unrepeatered optical transmission system according to an embodiment of the present invention.
Fig. 10 is a signal diagram of an ultra-long distance unrepeatered optical transmission system modulated by a local electrical signal according to an embodiment of the present invention.
Fig. 11 is a signal processing diagram of the ultra-long distance unrepeatered optical transmission system processed by the second low-pass filter according to the embodiment of the present invention.
Detailed Description
The following detailed description of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Examples
As shown in fig. 1-11:
the embodiment provides an ultra-long distance unrepeatered optical transmission system, which comprises a first optical signal modulator, an optical signal encoder, a first optical amplifier, an optical signal decoder, a second optical amplifier, an optical-to-electrical converter, a first low-pass filter, a second optical signal modulator and a second low-pass filter; the input end of the first optical signal modulator is connected with a user optical signal, the output end of the first optical signal modulator is connected with the input end of an optical signal encoder, the output end of the optical signal encoder is connected with the input end of a first optical amplifier, the output end of the first optical amplifier is connected with the input end of an optical signal decoder, the output end of the optical signal decoder is connected with the input end of a second optical amplifier, the output end of the second optical amplifier is connected with the input end of a photoelectric converter, the output end of the photoelectric converter is connected with the photoelectric input end of a first low-pass filter, the output end of the first low-pass filter is connected with the input end of a second optical signal modulator, the input end of the second optical signal modulator is also connected with a local electric signal, and the output end of the second optical signal modulator is connected with the input end of a second low-pass filter.
It is understood that, in the present embodiment, as shown in fig. 1, the first optical signal modulator, the optical signal encoder, the first optical amplifier, the optical signal decoder, the second optical amplifier, the optical-to-electrical converter, the first low-pass filter, the second optical signal modulator, and the second low-pass filter are connected end to end, the user optical signal is input at the input end of the first optical signal modulator, the user optical signal rate is 155Mbps, the transmission rate is 2.015Gbps, and the local electrical signal is input at the second optical signal modulator, the local electrical signal is 2.015Gbps, and the address code is (0, 1, 3, 9) of the strictly optimal (13, 4, 1). The optical signal decoder adopts an optical fiber delay decoder with a parallel structure. The first optical amplifier adopts a Raman amplifier. The second optical amplifier is an erbium-doped fiber amplifier.
It will be appreciated that in the present example, the determination of the address code takes the following form:
the optical orthogonal code is a group of (0, 1) sequences with good autocorrelation, cross correlation and code word capacity characteristics, and the characteristic improves the number of asynchronous users of an OCDMA system, so that the data transmission is more efficient, and the flexibility of system networking is improved; the autocorrelation characteristic of high peak value and low sidelobe is beneficial to the detection of the data at the receiving end; the low cross-correlation peak value reduces the multiple access interference of the system; the larger codeword capacity increases the number of concurrent users of the system. Therefore, in the optical code division multiple access system, the optical orthogonal code is the best choice at present.
One-dimensional optical orthogonal code design parameter (L, omega, lambda) a ,λ c ) Where L is the codeword length, i.e., the number of "0" s and "1" s in the (0, 1) sequence (the chip total); ω is the codeword weight, i.e., the number of "l" in the sequence; lambda [ alpha ] a Being the autocorrelation limit, λ, of the code word c The self-correlation side lobe and the maximum cross-correlation peak of the code word are respectively expressed as the code word cross-correlation limit: when lambda is a ≠λ c Then, the orthogonal code of this type is called equal-weight asymmetric optical orthogonal code. When lambda is a ＝λ c When λ is defined, the orthogonal code of this type is called an equisymmetric optical orthogonal code, and in this case, it can be abbreviated as Φ (L, ω, λ). Let X be { X ═ X 1 ,x 2 ,…,x n }，Y＝{y 1 ,y 2 ,…,y n The self-correlation and cross-correlation functions are defined as follows:
the autocorrelation function:
cross-correlation function:
where C represents the address code (v, k, λ) code set.
As can be seen from the autocorrelation and cross-correlation functional expressions of the above expressions (4) and (5), since there is an autocorrelation side lobe when f ≠ 0, the optical address code selected in the optical code division multiple access system should satisfy the following condition: the autocorrelation peak value is large; the cross-correlation peak is as small as possible; the autocorrelation sidelobes are smaller. Therefore, the signal-to-noise ratio is improved, and meanwhile, the sending end and the receiving end are easy to synchronize. Based on the relationship of code length, code capacity and code weight, if v, k and | C | satisfy the relationship:
(v-1)(v-2)…(v-λ)＝|C|k(k-1)(k-2)…(k-λ)
then | C | is called the strictly optimal (v, k, λ) optical orthogonal code.
The required address code is constructed by a direct construction method, and the main idea of the direct construction method is to form the address code based on a constraint relation between a difference set and a V-element integer set V which are defined on a code word set. By means of computer aided design, the optical orthogonal code meeting the requirement of relevant characteristic may be obtained.
Let v, k (v > k) be positive integers, and the set D ═ a 1 ,a 2 ,…,a i ,…a k Contains mutually different elements of cowpea k, in which a i E.g. V (1 ≦ i ≦ k), V ═ 0,1, …, V-1 }. If D is the codeword set of the strictly optimal (V, k,1) optical orthogonal code with capacity l, the difference set Δ D is V- {0 }. Thus, for any element pair (a) i ,a j ),a i ,a j E.g. D, assuming that the difference between them, modulo v, is equal to D 1 And d 2 Then there is d 1 ,d 2 E.g., V- {0}, and d 1 +d 2 ＝v。
The direct construction method comprises the following specific operation steps:
the first step is as follows: the code weight k is defined, and the code length v ═ k (k-1) + i +1 is determined, where 0 < i < k (k-1) is an integer. For the 1 st element in D, let p s And p e Respectively represents the position number (from l) of the element in V, and is 1 ≦ p s ≤p e V-1 is an integer, and V is {0,1, …, V-1 }.
The second step is that: definition of d 1 Maximum value of d max . I.e. by
1≤d 1 ≤d max ,d max ＝v-1-V(p s ),V(p s ) Represents the p-th in the set V s And (4) each element.
The third step: the first two elements in D are set as: d (1) ═ V (p) s )，D(2)＝V(p s +d 1 ) And, the next element in D, D (n) V (l), where 3. ltoreq. n.ltoreq.k and 1. ltoreq. l.ltoreq.v are integers, is also provided.
The fourth step: and determining a difference set delta D of the n-element set D, and if all elements in the delta D are different from each other, making n equal to n +1 and l equal to 1, and otherwise, making l equal to l + 1.
The fifth step: if n < k and l > v, let d 1 ＝d 1 +1. When d is 1 ＞d max . When it is, let p s ＝p s +1, the second, third and fourth steps are repeated. When d is 1 ≤d max And repeating the third step and the fourth step.
And a sixth step: if p is s ＞p e Then the construction method cannot get the codeword set of the quasi-optimal or strictly optimal (v, k,1) optical orthogonal code. If n > k, D is the set of codewords of the quasi-optimal or strictly optimal (v, k,1) optical orthogonal code obtained by the construction method.
A set of strictly optimal (13, 4, 1) address codes {0,1, 3, 9} is obtained through calculation.
In this embodiment, a Fiber Bragg Grating (FBG) is a short period grating, which is an optical reflection type band-stop filter centered on the bragg wavelength. Due to the good reflection and frequency selection functions, fig. 2 shows a cascaded bragg grating encoder structure, and the encoder is composed of a group of FBGs with specific reflection wavelengths. The input signal passes through the optical circulator, the cascaded FBGs arranged according to a specific relation carry out frequency division on the optical signal, and the time delay is carried out by the optical fiber delay line, so that the coding of a time domain and a frequency domain is completed.
At present, there are three main structures of an optical fiber delay line decoder: parallel structure, trapezoidal structure and adjustable structure. In the present embodiment, a parallel structure is mainly used. The parallel structure of the optical fiber delay line decoder is shown in fig. 3, and an encoded signal is divided into omega narrow optical pulse signals by a 1 × ω optical splitter. These ω narrow optical pulse signals correspond to ω "1" s in the user-assigned codeword in the system and determine the fiber length l based on the relative position of "l". Due to the unequal delay lengths of the optical fibers, when the optical signals are transmitted to the omega x 1 optical combiner, the omega narrow optical pulse signals separated in the time domain form a coded optical pulse sequence. This type of codec is simple in structure and easy to set.
Based on the technical scheme of the embodiment, the optical fiber Bragg grating is used as an encoder, and the optical fiber delay line is used as a decoder to form an ultra-long-distance optical transmission system, and the simulation is carried out by Optisystem7.0 simulation software. The overall system design is shown in fig. 3, wherein the user rate is 155Mbps and the transmission rate is 2.015 Gbps. The address code uses (0, 1, 3, 9) of the strict optimum (13, 4, 1). And the Matlab assembly in the design drawing realizes the noise reduction of the electric signals.
Fig. 4 is a general schematic diagram of a simulation system, a waveform of a user optical signal is shown in fig. 5, an optical modulation signal passing through a first optical signal modulator is shown in fig. 6, a signal modulated by the user optical signal is shown in fig. 7, after the modulation signal passes through an FBG, one optical pulse is changed to be shown in fig. 8, and encoding of the optical signal is achieved, and the light emitting power is 12.76 dBm. After 400 km transmission, optical signals firstly enter a raman amplifier for amplification and then enter an optical fiber delay line decoder for decoding, the decoded signals are shown in fig. 9, and then the optical signals enter an erbium-doped optical fiber amplifier for re-amplification. The optical signal is converted into an electrical signal by the photoelectric converter, the noise is filtered by the low-pass filter, the signal is modulated with the local electrical signal of 2.015Gbps, the modulated signal is shown in fig. 10, and the modulated signal passes through the low-pass filter, and is shown in fig. 11.
In the embodiment, the ultra-long distance unrepeatered optical transmission system adopts an end-to-end direct path, the whole transmission line does not need relaying, and the ultra-long distance unrepeatered optical transmission system has the outstanding characteristics of high reliability, low construction cost, rapid opening, convenient maintenance and the like, and is very suitable for communication of part of border sea defense sentries. The invention relates to an OCDMA ultra-long distance unrepeatered optical transmission system which is designed by using an optical fiber Bragg grating as an encoder and an optical fiber time delay line as a decoder on the basis of one-dimensional strict optimal optical orthogonal code, and realizes the unrepeatered transmission of an optical signal of a user of 155Mbps for 400 kilometers.
It should be noted that, in the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and reference may be made to relevant descriptions of other embodiments for parts that are not described in detail in a certain embodiment.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (6)
1. The super-long distance unrepeatered optical transmission system is characterized by comprising a first optical signal modulator, an optical signal encoder, a first optical amplifier, an optical signal decoder, a second optical amplifier, an optical-to-electrical converter, a first low-pass filter, a second optical signal modulator and a second low-pass filter; the input end of the first optical signal modulator is connected with a user optical signal, the output end of the first optical signal modulator is connected with the input end of an optical signal encoder, the output end of the optical signal encoder is connected with the input end of a first optical amplifier, the output end of the first optical amplifier is connected with the input end of an optical signal decoder, the output end of the optical signal decoder is connected with the input end of a second optical amplifier, the output end of the second optical amplifier is connected with the input end of a photoelectric converter, the output end of the photoelectric converter is connected with the photoelectric input end of a first low-pass filter, the output end of the first low-pass filter is connected with the input end of a second optical signal modulator, the input end of the second optical signal modulator is also connected with a local electrical signal, and the output end of the second optical signal modulator is connected with the input end of a second low-pass filter.
2. The system of claim 1, wherein the optical signal encoder is a bragg grating encoder and the optical signal decoder is a light delay line decoder.
3. The system of claim 2, wherein the optical signal decoder is a parallel-structured fiber delay decoder.
4. The system of claim 1, wherein the first optical amplifier is a raman amplifier.
5. The system of claim 4, wherein the second optical amplifier is an erbium doped fiber amplifier.
6. The ultra-long distance unrepeatered optical transmission system of claim 1, wherein the user optical signal rate is 155Mbps, the transmission rate is 2.015Gbps, and the local electrical signal is 2.015 Gbps.
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| CN209844964U (en) * | 2019-05-31 | 2019-12-24 | 无锡瀚诺光电科技有限公司 | Optical transmission system for extending unrepeatered transmission distance |
| CN113676256A (en) * | 2021-08-23 | 2021-11-19 | 重庆邮电大学 | Safe optical transmission method based on superstructure fiber Bragg grating |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US20030161636A1 (en) * | 2002-02-26 | 2003-08-28 | Nec Corporation | Optical packet header identifier, optical router incorporating the same therein, and optical routing method using the router |
| CN104639247A (en) * | 2015-01-22 | 2015-05-20 | 中航光电科技股份有限公司 | Optical fiber transmission system of super long distance non-repeater radio frequency signal |
| CN209844964U (en) * | 2019-05-31 | 2019-12-24 | 无锡瀚诺光电科技有限公司 | Optical transmission system for extending unrepeatered transmission distance |
| CN113676256A (en) * | 2021-08-23 | 2021-11-19 | 重庆邮电大学 | Safe optical transmission method based on superstructure fiber Bragg grating |
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