KR102515056B1 - Optical Transmission Apparatus And Method Capable Of Mitigating Inter-Dimensional Interference - Google Patents

Abstract

Provided in the present invention is an optical transmission apparatus and a method thereof, which may comprise: an optical modulation unit which outputs an optical signal by modulating the intensity and the phase of light applied from a light source in response to an intensity signal and a phase signal; a symbol conversion unit which analyzes the generation frequency of a plurality of codes acquired by coding a data bit string to be transmitted in a predetermined method, and maps the plurality of codes into a plurality of symbols of constellation in a predetermined intensity and phase modulation method according to the analyzed generation frequency; and a waveform generator which acquires the intensity signal to control the intensity modulation and the phase signal to control the phase modulation in response to each of the plurality of symbols mapped at each of the plurality of codes. Therefore, the bandwidth may be efficiently used without changes in the structure of a receiving device.

Description

Optical Transmission Apparatus And Method Capable Of Mitigating Inter-Dimensional Interference

The present invention relates to an optical transmission device and method, and relates to an optical transmission device and method capable of mitigating interdimensional interference.

The next-generation optical subscriber network system is developing in the direction of providing various quality services to users and building an integrated network, and traffic is gradually increasing. As a method to solve this problem, coherent optical transmission having high reception sensitivity and multidimensional optical transmission having high frequency efficiency have been suggested as alternatives. However, in the case of coherent optical transmission, an expensive system using a separate light source and a complicated transceiver structure is required. Accordingly, direct detection-based multidimensional optical transmission technology is being actively researched.

Multi-dimensional optical transmission technology is a technology capable of improving bandwidth efficiency of optical transmission by using different dimensional elements such as intensity and phase of an optical signal. Multidimensional optical transmission technologies include ASK-DPSK (Amplitude Shift Keying-Differential Phase-Shift Keying) and QAM-DPSK (Quadrature Amplitude Modulation-Differential Phase-Shift Keying), which simultaneously modulate and transmit the intensity and phase of light to increase transmission capacity. There is a technique. However, since ASK-DPSK and QAM-DPSK using a single modulator are basically based on DPSK, the phase modulation level is limited to two levels, so there is also a limit to increase in transmission capacity. Accordingly, QAM-MDPSK (Quadrature Amplitude Modulation - M-ary Differential Phase Shift Keying), which modulates in multiple levels during phase modulation, has recently been proposed.

However, in the currently most commonly used Intensity Modulation/Direct Detection (IM/DD) technique, there is a limitation in that performance is limited due to occurrence of inter-dimensional interference according to a reception structure.

In an optical communication system based on IM/DD (Intensity Modulation/Direct Detection), when light intensity and phase are simultaneously modulated and transmitted, the light intensity and light phase are separately detected. At this time, the light intensity can be directly detected from the received optical signal, but in the case of the optical phase, beating between the non-delayed and delayed optical signals using a delay interferometer configuration such as MZDI (Mach-Zehnder Delay Interferometer) It is possible to detect after converting into an optical signal converted to an intensity by using . That is, a method of detecting the conversion into an optical signal having an intensity indicating a phase difference between a previously applied and delayed optical signal and a later applied optical signal is used.

In this way, when the intensity and phase are simultaneously modulated and detected by dividing the light intensity and the light phase from the transmitted light signal, the light phase modulation does not affect the detected light intensity, whereas the light intensity modulation affects the detected light phase. will affect This is because, as described above, when the optical receiver delays and beats the intensity-modulated light by using the delay interferometer configuration, a change appears in the beating result between the non-delayed light and the delayed light due to the modulated intensity. The effect of this optical intensity modulation on the optical phase signal is limited in modulation techniques such as ASK-DPSK and QAM-DPSK that generate a large phase difference, whereas modulation that generates a phase difference at multiple levels such as QAM-MDPSK In the technique, there is a problem that a transmission error may occur because the phase difference between each level is not large.

Korean Registered Patent No. 10-1382619 (registered on 2014.04.01)

An object of the present invention is to provide an optical transmission apparatus and method capable of minimizing inter-dimensional interference by geometrically and probabilistically optimizing the constellation of a transmission signal.

Another object of the present invention is to provide an optical transmission device and method capable of securing high bandwidth efficiency without changing the structure of a receiving device by reducing inter-dimensional interference.

An optical transmission apparatus and method according to an embodiment of the present invention for achieving the above object includes an optical modulator for outputting an optical signal by intensity-modulating and phase-modulating light applied from a light source in response to an intensity signal and a phase signal; The frequency of occurrence of a plurality of codes obtained by coding a data bit stream to be transmitted in a predetermined manner is analyzed, and the plurality of codes are assigned to a plurality of symbols of a constellation according to a predetermined intensity and phase modulation method according to the analyzed frequency of occurrence. a symbol conversion unit for mapping; and a waveform generator for obtaining the intensity signal for controlling intensity modulation and the phase signal for controlling phase modulation corresponding to each of a plurality of symbols mapped to each of the plurality of codes.

The symbol converter includes a coding unit receiving the data bit stream and coding it in a predetermined manner to obtain the plurality of codes; a distribution analysis unit analyzing occurrence frequencies of each of the plurality of codes; a symbol selector selecting a symbol having a smaller amplitude among the plurality of symbols of the constellation as the frequency of occurrence of each code in the plurality of codes increases; and a symbol mapping unit for mapping selected symbols corresponding to each of the plurality of codes.

The symbol mapping unit may map the plurality of codes to the symbols according to a QAM-MDPSK (Quadrature Amplitude Modulation - M-ary Differential Phase Shift Keying) modulation technique.

The symbol mapping unit may map each of the plurality of codes with a selected symbol among a plurality of symbols based on hexa-QAM having a hexagonal shape in a decision region.

The light modulator may include a light intensity modulator configured to output a light intensity signal by modulating the intensity of light applied from the light source in response to the intensity signal; and an optical phase modulator for outputting the optical signal by modulating a phase of the optical intensity signal applied from the optical intensity modulator in response to the phase signal.

An optical transmission apparatus and method according to another embodiment of the present invention for achieving the above object analyzes the occurrence frequency of a plurality of codes obtained by coding a data bit stream to be transmitted in a predetermined manner, and mapping a plurality of codes to a plurality of symbols of a constellation according to predetermined intensity and phase modulation schemes; obtaining an intensity signal for controlling intensity modulation and a phase signal for controlling phase modulation corresponding to each of a plurality of symbols mapped to each of the plurality of codes; and outputting an optical signal by intensity-modulating and phase-modulating the light applied from the light source in response to the intensity signal and the phase signal.

Therefore, the optical transmission apparatus and method according to an embodiment of the present invention transmits a transmission signal by geometrically and probabilistically optimizing the constellation so that the deviation of the beating signal is reduced and inter-dimensional interference is minimized, thereby preventing transmission errors even at high symbol density. It is possible to prevent this from occurring, so that the bandwidth can be efficiently used without changing the structure of the receiving device.

1 shows a schematic structure of an optical transmission device according to an embodiment of the present invention.
2 shows a schematic structure of an optical receiving device of an optical communication system according to an embodiment of the present invention.
Figure 3 shows the change of the phase optical signal according to the amplitude of the amplitude modulation.
4 shows an example of a QAM-DPSK constellation used by the symbol mapping unit of FIG. 1 .
FIG. 5 shows the amplitude of each QAM symbol according to the QAM-DPSK constellation of FIG. 4 .
6 shows a light transmission method according to an embodiment of the present invention.

In order to fully understand the present invention and its operational advantages and objectives achieved by the practice of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the present invention will be described in detail by describing preferred embodiments of the present invention with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the described embodiments. And, in order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals in the drawings indicate the same members.

Throughout the specification, when a part "includes" a certain component, it means that it may further include other components, not excluding other components unless otherwise stated. In addition, terms such as "... unit", "... unit", "module", and "block" described in the specification mean a unit that processes at least one function or operation, which is hardware, software, or hardware. And it can be implemented as a combination of software.

1 shows a schematic structure of an optical transmission device according to an embodiment of the present invention, FIG. 2 shows a schematic structure of an optical reception device of an optical communication system according to an embodiment of the present invention, and FIG. It represents the change of the phase optical signal with the amplitude.

Referring to FIG. 1 , the light transmission device 100 according to the present embodiment may include a light source 110, a symbol converter 120, a waveform generator 130, and a light modulator 140.

The light source 110 generates and emits light having a predetermined wavelength and waveform. For example, the light source may generate and emit light in a continuous wave mode, and may be implemented as a laser diode or the like.

The symbol conversion unit 120 receives data to be transmitted and converts it into a symbol signal according to a modulation method.

In this embodiment, it is assumed that the optical transmitter 100 transmits light after intensity and phase modulation corresponding to data, and here, as an example, it is assumed that the symbol converter 120 converts data into signals according to a QAM-MDPSK modulation technique. to explain. Accordingly, the symbol conversion unit 120 checks a symbol representing the intensity and phase corresponding to the data, and outputs a signal corresponding to the checked symbol. The symbol converter 120 may output first and second signals respectively corresponding to the strength and phase of the checked symbol.

In particular, in this embodiment, the symbol conversion unit 120 uses a Hexagonal-QAM-based Geometric Constellation Shaping (GCS) technique to increase symbol density, and at the same time, a signal with a large amplitude By adjusting the symbol distribution using a probabilistic constellation shaping (PCS) technique to reduce the probability of occurrence, the possibility of an error due to intensity modulation when detecting a phase-modulated signal is reduced. That is, it is possible to achieve high bandwidth efficiency by reducing the interference of the intensity dimension to the phase dimension.

A detailed description of the symbol conversion unit 120 will be described later.

The waveform generator 130 generates and outputs intensity and phase signals of waveforms corresponding to the first and second signals, respectively. That is, the waveform generator 130 receives a first signal to be modulated and transmitted according to the intensity modulation method, generates an intensity signal of a corresponding waveform, receives a second signal to be modulated and transmitted according to the phase modulation method, and receives a corresponding waveform A phase signal of is generated and transmitted to the light modulator 140. Here, the waveform generator 130 may be implemented as, for example, an arbitrary waveform generator (AWG).

The light modulator 140 receives intensity and phase signals from the waveform generator 130, and intensity- and phase-modulates light applied from the light source 110 according to the applied intensity and phase signals to generate an optical signal. and outputs it to an optical receiving device through an optical fiber.

The light modulator 140 may include a light intensity modulator 141 and an light phase modulator 142 . The light intensity modulator 141 intensity-modulates light applied from the light source 110 according to the intensity signal applied from the waveform generator 130 and outputs a light intensity signal. Here, the light intensity modulator 141 may be implemented as, for example, a Mach-Zehnder Modulator (MZM).

Further, the optical phase modulator 142 modulates the phase of the light intensity signal that is intensity-modulated by the light intensity modulator 141 according to the phase signal applied from the waveform generator 130 and outputs an intensity- and phase-modulated optical signal. .

Meanwhile, referring to FIG. 2 , the light receiving device 200 may include an optical splitter 210, a delay interferometer 220, an optical detector 230, a signal discriminator 240, and a data acquisition unit 250. .

The optical splitter 210 receives and distributes an optical signal transmitted through an optical fiber to the optical transmission device 100 and outputs two received optical signals. Here, the optical splitter 210 may be implemented as an optical coupler, for example, and the two received optical signals may have the same intensity and phase.

The delay interferometer 220 delays and beats one of the two received optical signals distributed by the optical splitter 210 (herein, the second received optical signal as an example). The delay interferometer 220 may be implemented as an example of a Mach-Zehnder Delay Interferometer (MZDI).

The delay interferometer 220 implemented with MZDI causes the received optical signal to pass through a delay path and a non-delay path, respectively, so that the received optical signal delayed by the delay path and the received optical signal not delayed in the non-delay path are mutually beat. By doing so, a phased optical signal having light intensity according to the phase difference between the delayed received optical signal and the non-delayed received optical signal is output. That is, the delay interferometer 220 converts the phase difference of the received optical signal into an intensity to obtain a phase optical signal.

Meanwhile, the optical detector 230 receives the received optical signal directly applied from the optical splitter 210 and the phase optical signal obtained from the delay interferometer 220, and receives a predetermined optical signal for each of the received optical signal and the phase optical signal. First and second received signals are obtained by accumulatively detecting the light intensity during the symbol period T. The photodetector 230 receives the received optical signal and detects the cumulative optical intensity during the symbol period (T) to obtain the first received signal and the first photodetector 231 to obtain the phased optical signal and detects the accumulated light intensity during the symbol period (T). It may include a second photodetector 232 for obtaining a second received signal by detecting the cumulative light intensity during the operation. Here, the first and second photodetectors 231 and 232 may be implemented as a photo diode or the like.

The signal determination unit 240 receives the amplified first and second received signals and determines the amplified first and second received signals. The signal discrimination unit 240 determines the signal level of the phased optical signal based on which section among a plurality of predetermined intensity sections includes the intensity of the applied phased optical signal. Here, the signal discrimination unit may be implemented as an example of a DPO (Digital Phosphor Oscilloscope).

The data acquisition unit 250 restores the data transmitted from the optical transmission device 100 based on the signal level determined by the signal determination unit 240 . Here, since the first received signal is a signal corresponding to the strength of the symbol and the second received signal is a signal corresponding to the phase of the symbol, the data acquisition unit 250 determines based on the modulation technique applied to the optical transmission device 100. Data may be restored by extracting symbols from the first and second received signals.

If the intensity of the received optical signal is uniform, the difference in intensity between the delayed received optical signal and the non-delayed received signal in the delay interferometer 220 of the optical receiving device 200 is generated only by phase modulation. Intensity is also detected at a specified specific level. However, since the intensity and phase modulation are simultaneously performed by the optical transmission device 100 in the present embodiment, the intensity of the received optical signal continuously changes. will appear as Therefore, the level of the second received signal may be erroneously determined due to the change in intensity of the received optical signal.

In the case of the first received signal in the light receiving device 200, since it is a signal directly extracted from the intensity of the received optical signal, it is hardly affected by intensity modulation. However, in the case of the second received signal, since it is a signal extracted from an optical intensity difference obtained by beating continuously received received optical signals, it is greatly affected by intensity modulation.

Specifically, the phase light signal I(t) applied to the second photodetector 232 during the symbol period T, that is, the second received signal is obtained as in Equation 1.

(Where P is the average power of the light source, R is the response sensitivity of the photodetector, and k is a predetermined proportional constant. And φ _n (t) and φ _n-1 (t) are the nth represents the phase of the symbol and the n-1th symbol, and A _m (t) and A _m-1 (t) respectively represent the amplitudes of the m-th symbol and the m-1th symbol according to amplitude modulation.)

According to Equation 1, the second received signal is not only the phase difference between symbols (φ _n (t) - φ _n-1 (t)) according to the phase modulation, but also the amplitude of the m th symbol and the m-1 th symbol (A _m (t), A _m-1 (t)). That is, as described above, when the optical communication system performs communication according to the QAM-MDPSK modulation scheme, MDPSK reception performance is affected by the QAM symbol, which can be regarded as inter-dimensional interference.

3 shows the change of the phase light signal I(t) when the amplitudes of the QAM symbols according to QAM modulation are different from each other, and the area of the phase light signal I(t) can be regarded as the second received signal. .

In FIG. 3, (a) and (b) show the maximum and minimum values of the second received signal when the amplitude change due to QAM modulation is not large, respectively, and (c) and (d) respectively show the case where the amplitude change is large. Indicates the maximum and minimum values of the second received signal.

Comparing (a) and (c), the maximum value of the second received signal appears larger when the amplitude change is greater than when the amplitude change due to QAM modulation is not large, and the minimum value is (b) and (d) ), it can be seen that it appears smaller. That is, when the amplitude change due to the QAM modulation is large, the deviation between the maximum value and the minimum value of the second received signal becomes larger. This means that the larger the amplitude change due to the QAM modulation, the more the QAM modulation component affects the second received signal.

의 편차를 줄인다면, 위상 변조에 대한 진폭 변조의 간섭, 즉 차원간 간섭을 줄여 오류를 저감시킬 수 있다. 이는 MDPSK 변조된 심볼을 더욱 정확하게 추출할 수 있도록 하거나, MDPSK 변조 레벨을 확장시켜 대역폭 효율을 높일 수 있도록 한다.Therefore, in Equation 1, the interference component due to QAM modulation

If the deviation of is reduced, the error can be reduced by reducing interference of amplitude modulation with respect to phase modulation, that is, inter-dimensional interference. This makes it possible to more accurately extract the MDPSK modulated symbol or to increase the bandwidth efficiency by extending the MDPSK modulation level.

Accordingly, the optical transmission apparatus according to the present embodiment minimizes interference with respect to MDPSK by reducing a distance between QAM symbols during QAM-MDPSK modulation. In particular, by applying the geometric constellation shaping technique and the stochastic constellation shaping technique together during QAM modulation, the possibility of a QAM symbol having a large amplitude is greatly reduced.

Referring back to FIG. 1 , the symbol conversion unit 120 may include a coding unit 121, a symbol mapping unit 122, a distribution analysis unit 123, and a symbol selection unit 124.

First, when data D to be transmitted is applied, the coding unit 121 codes a bit string of the applied data in a predetermined manner to obtain a code.

The symbol mapping unit 122 maps the obtained code to symbols representing strength and phase according to the QAM-MDPSK modulation scheme, and outputs a signal corresponding to the mapped symbol. The symbol mapping unit 122 may output first and second signals respectively corresponding to the strength and phase of the checked symbol.

FIG. 4 shows an example of a QAM-DPSK constellation used by the symbol mapping unit of FIG. 1, and FIG. 5 shows the amplitude of each QAM symbol according to the QAM-DPSK constellation of FIG.

Referring to FIG. 4, the symbol mapping unit 122 acquires symbols represented by coordinates on a 3D constellation consisting of a phase axis and a QAM plane represented by QAM-I and QAM-Q constituting two axes of intensity. Code can be mapped.

In the QAM modulation technique, a corresponding symbol is obtained by mapping a code using a geometric constellation formation technique based on square-QAM, such as 4-QAM, 16-QAM, and 64-QAM. However, as described above, in order to reduce inter-dimensional interference, it is necessary to reduce the amplitude change due to QAM modulation, and accordingly, it is necessary to reduce the distance between QAM symbols. That is, the symbol density should be increased.

Therefore, in this embodiment, as shown in FIG. 4, the symbol mapping unit 122 maps codes using a geometric constellation formation technique based on Hexagonal-QAM, which exhibits higher symbol density than square-QAM. .

In the hexa-QAM-based geometric constellation technique, a constellation diagram consisting of a honeycomb-shaped decision area as a whole is used in which the decision area that distinguishes each symbol on the QAM plane is composed of a hexagonal shape rather than a square of square-QAM. In the case of using such a hexa-QAM-based geometric constellation technique, one symbol is allocated to the origin on the QAM-I and QAM-Q planes, and 6 symbols are allocated at the same distance (d1) from the origin around the symbol of the origin. It has a structure in which 7 symbols are added and 19 symbols can be allocated according to the distance range from the origin. Therefore, Hexa-QAM can allocate more symbols than Square-QAM, which can allocate symbols in the order of 4 or 16 according to the distance from the origin, and thus can have high symbol density. In other words, when the same number of symbols are mapped, it means that the deviation between the maximum value and the minimum value due to QAM modulation is smaller.

In FIG. 4, black dots represent constellations for general 19 hexa-QAM symbols, and red dots represent complementary hexa-QAM with the largest inter-symbol distance from typical 19 hexa-QAM symbols represented by black dots ( Complement Hexagonal-QAM) symbol. Since the inter-symbol distance includes all QAM-I, QAM-Q, and phase information during actual signal reception, even if the density of QAM symbols is increased through the proposed Hexagonal-QAM-based GCS, performance at reception can be secured.

Therefore, the symbol mapping unit 122 reduces the deviation of the maximum and minimum values of the second received signal and increases the symbol distance by using the hexa-QAM-based geometric constellation formation technique, compared to the case of using the square-QAM. MDPSK signal detection error due to QAM modulation can be reduced.

In particular, in this embodiment, the symbol mapping unit 122 maps the obtained code to the symbol selected by the symbol selection unit 124 to more effectively reduce an MDPSK signal detection error due to QAM modulation.

To this end, the distribution analysis unit 123 analyzes the frequency of occurrence of the obtained code. The distribution analyzer 123 analyzes the frequency of occurrence of codes to be mapped to symbols and distinguishes codes having a high frequency of occurrence and a code having a low frequency of occurrence. That is, codes with a high probability of occurrence and codes with a low probability of occurrence are distinguished.

This is because the larger the maximum magnitude of the amplitude according to QAM modulation, the larger the deviation between the maximum and minimum values of the amplitude, so that a symbol with a large amplitude is not selected as much as possible to minimize the probability of occurrence of the symbol, thereby reducing the MDPSK signal due to QAM modulation This is to reduce the possibility of detection errors as much as possible.

Accordingly, the symbol selector 124 determines that a code with a high frequency of occurrence among a plurality of symbols of the symbol mapping unit 122 has a lower amplitude during QAM modulation, based on the frequency of occurrence of the code analyzed by the distribution analyzer 123. Select a symbol to be mapped so that it can be mapped to a symbol having That is, the symbol selector 124 selects a symbol to be mapped on the basis of the probability of occurrence of each code so that a code with a high probability is mapped to a symbol with a low amplitude and a code with a low probability is mapped to a symbol with a higher amplitude. do.

Referring to FIGS. 4 and 5, a total of 31 hexa-QAM symbols at phase modulation levels 0 and 1 are shown in FIG. 4, and the amplitudes of each of these symbols are shown in FIG. As shown in FIG. 5, when symbol indices are sequentially allocated from the origin to the outer periphery of the QAM plane having a phase modulation level of 0, the larger the symbol index, the larger the amplitude.

Accordingly, the symbol selection unit 124 sequentially selects higher index symbols having high amplitudes from the lowest index symbol, which is a symbol having the lowest amplitude, in the order of a code having the highest frequency of occurrence to a code having a low frequency of occurrence, and the symbol mapping unit 122 ) causes each code to be mapped to a selected symbol.

As a result, the symbol conversion unit 120 of the present embodiment, based on the frequency of occurrence of the code corresponding to data, sequentially maps from a code having a high frequency of occurrence to a symbol having a low amplitude in a hexa-QAM-based geometric constellation. , the deviation between the maximum value and the minimum value of the amplitude according to the intensity modulation is reduced, so that the effect on the phase modulation is reduced. That is, interdimensional interference can be reduced.

6 shows a light transmission method according to an embodiment of the present invention.

Referring to the optical transmission method of FIG. 6 with reference to FIGS. 1 to 5, first, a bit stream of data to be transmitted is received, coded, and converted into a code (S10). Then, the occurrence frequency of the converted code is analyzed (S20). When the frequency of occurrence of codes corresponding to the data is analyzed, codes are selected in order of highest frequency of occurrence (S30). In addition, each of the codes sequentially selected according to the frequency of occurrence is mapped to a symbol having the lowest QAM amplitude among a plurality of pre-designated symbols based on hexa-QAM on the QAM-MDPSK constellation (S40).

When each code is mapped to a symbol in an order of decreasing QAM amplitude based on the frequency of occurrence, an intensity signal and a phase signal respectively corresponding to the intensity and phase of the mapped symbol are obtained (S50). When the intensity signal and the phase signal are acquired, the light intensity signal is acquired by intensity modulating the light applied from the light source according to the acquired intensity signal (S50). Thereafter, the optical intensity-modulated optical intensity signal is optically phase-modulated according to the compensated phase signal, and an intensity- and phase-modulated optical signal is output (S60).

The method according to the present invention may be implemented as a computer program stored in a medium for execution on a computer. Here, computer readable media may be any available media that can be accessed by a computer, and may also include all computer storage media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, including read-only memory (ROM) dedicated memory), random access memory (RAM), compact disk (CD)-ROM, digital video disk (DVD)-ROM, magnetic tape, floppy disk, optical data storage device, and the like.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is only exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom.

Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

100: light transmission device 110: light source
120: symbol conversion unit 121: coding unit
122: symbol mapping unit 123: distribution analysis unit
124: symbol selection unit 130: waveform generator
140: light modulator 200: light receiving device
210: optical splitter 220: delay interferometer
230: light detection unit 240: signal determination unit
250: data acquisition unit

Claims (10)

a light modulator configured to output an optical signal by intensity-modulating and phase-modulating the light applied from the light source in response to the intensity signal and the phase signal;
The frequency of occurrence of a plurality of codes obtained by coding a data bit stream to be transmitted in a predetermined manner is analyzed, and the plurality of codes are assigned to a plurality of symbols of a constellation according to a predetermined intensity and phase modulation method according to the analyzed frequency of occurrence. a symbol conversion unit for mapping; and
A waveform generator for acquiring the intensity signal for controlling intensity modulation and the phase signal for controlling phase modulation corresponding to each of a plurality of symbols mapped to each of the plurality of codes,
The symbol conversion unit
a coding unit receiving the data bit stream and coding it in a predetermined manner to obtain the plurality of codes;
a distribution analysis unit analyzing occurrence frequencies of each of the plurality of codes;
a symbol selector selecting a symbol having a smaller amplitude among the plurality of symbols of the constellation as the frequency of occurrence of each code in the plurality of codes increases; and
and a symbol mapping unit for mapping selected symbols corresponding to each of the plurality of codes.

delete The method of claim 1, wherein the symbol mapping unit
An optical transmission device for mapping the plurality of codes to the symbols according to a QAM-MDPSK (Quadrature Amplitude Modulation - M-ary Differential Phase Shift Keying) modulation technique. The method of claim 3, wherein the symbol mapping unit
An optical transmission device for mapping each of the plurality of codes with a selected symbol among a plurality of symbols based on hexa-QAM having a hexagonal shape in a decision area. The method of claim 1, wherein the light modulator
a light intensity modulator configured to output a light intensity signal by modulating the intensity of light applied from the light source in response to the intensity signal; and
and an optical phase modulator for outputting the optical signal by modulating a phase of the optical intensity signal applied from the optical intensity modulator in response to the phase signal. The frequency of occurrence of a plurality of codes obtained by coding a data bit stream to be transmitted in a predetermined manner is analyzed, and the plurality of codes are assigned to a plurality of symbols of a constellation according to a predetermined intensity and phase modulation method according to the analyzed frequency of occurrence. mapping;
obtaining an intensity signal for controlling intensity modulation and a phase signal for controlling phase modulation corresponding to each of a plurality of symbols mapped to each of the plurality of codes; and
In response to the intensity signal and the phase signal, intensity and phase modulation of the light applied from the light source to output an optical signal,
The step of mapping to the plurality of symbols
acquiring the plurality of codes by receiving the data bit stream and coding it in a predetermined manner;
analyzing a frequency of occurrence of each of the plurality of codes;
selecting a symbol having a smaller amplitude from among the plurality of symbols of the constellation as the frequency of occurrence of each code in the plurality of codes increases; and
and mapping selected symbols corresponding to each of the plurality of codes.
delete 7. The method of claim 6, wherein mapping the selected symbols
An optical transmission method of mapping the plurality of codes to the symbols according to QAM-MDPSK (Quadrature Amplitude Modulation - M-ary Differential Phase Shift Keying) modulation technique. 9. The method of claim 8, wherein the mapping of the selected symbols comprises:
An optical transmission method of mapping each of the plurality of codes with a symbol selected from among a plurality of symbols based on hexa-QAM in which a decision area has a hexagonal shape. 7. The method of claim 6, wherein outputting the optical signal comprises:
outputting a light intensity signal by modulating the intensity of light applied from the light source in response to the intensity signal; and
and receiving the light intensity signal in response to the phase signal, modulating a phase, and outputting the light signal.

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