JP7067393B2 - Optical transmission device, transmission signal generation method, and transmission signal extraction method - Google Patents

Description

The present invention relates to an optical transmission device, a transmission signal generation method, and a transmission signal extraction method, and can be applied to, for example, an optical transmission device using an optical coherent detection method in a subscriber optical network communication.

In recent years, communication demand has been rapidly increasing due to the development of mobile applications such as smartphones and the emergence of IoT (Internet of Things) technology, and there is a demand for larger capacities in optical transmission devices of subscriber optical networks. Therefore, research is underway to apply the coherent optical transmission device, which has been conventionally applied to the backbone optical network, to the subscriber optical network. Coherent optical transmission uses both the amplitude and phase of the signal light to send and receive information, so it is carried per unit time compared to the intensity-modulated direct detection method optical transmission used in existing subscriber optical networks. This method has a large amount of information and is suitable for large-capacity communication.

An optical transmission system called PON (Passive Optical Network) is applied to an existing subscriber optical network. In communication from the station side to the subscriber side (downlink communication), the optical transmission method is continuous signal transmission. On the other hand, in the communication from the subscriber side to the station side (uplink communication), the optical transmission method is intermittent (burst) signal transmission. The backbone optical network is composed of devices using only the continuous signal transmission method, and burst signal transmission is an important issue in considering the application of coherent optical transmission to the subscriber optical network.

As one of the key techniques for ensuring desired transmission quality in optical transmission, there is waveform distortion compensation in a receiving device, and for example, a compensation circuit using adaptive signal processing is often used. Adaptive signal processing is a feedback configuration and uses past signal waveform information directly or indirectly to compensate for the signal waveform. In burst signal transmission, unlike continuous signal transmission, the signal is continuous for only a finite time, so the signal waveform must be compensated using only the past signal waveform information for the shortest possible time (that is, short-time convergence is required). Will be).

In Non-Patent Document 1, a double-multiplexed optical transmission experiment using a coherent transmission method for uplink communication is carried out, and the transmission speed (~ We have confirmed offline operation of 100 Gb / s per wavelength, which exceeds 10 Gb / s). In this system, the optical modulation / demodulation method is QPSK (Quaternary Phase Shift Keying), and polarization multiplexing is performed to speed up information transfer while suppressing the operating speed of the transmission device. In addition, a burst optical signal is configured by arranging control information in front of the information to be transmitted and received (paptail), and the receiving side immediately uses the pilot signal, which is one of the control information, to perform polarization separation and polarization channel. By compensating for waveform distortion each time, the adaptive signal processing for compensating for waveform distortion is shortened.

A polarization multiplex separation using a pilot signal will be described. FIG. 14 is a block diagram showing an example of a conventional optical transmission system (optical transmission device).

In FIG. 14, the optical transmission system 1 has the configuration of the transmission side 10, x-polarized channel transmission means 101-1, y-polarized channel transmission means 101-2, light source 102, polarization branching means 103, and x-polarized channel optical modulation means 104. -1 The optical coherent detection means 110-1 and the optical coherent detection means 110-2 of the Y polarized channel are provided. In the optical transmission system 1, optical signals are transmitted and received via the optical transmission line 106.

On the transmitting side 10, an electric signal corresponding to each of the polarized channels (represented as x and y) is generated by using the x polarized channel transmitting means 101-1 and the y polarized channel transmitting means 101-2. Here, on the transmitting side 10, a single-frequency sine wave called a pilot signal and a payload signal are time-divided and transmitted. The frequencies of the pilot signals correspond to the respective polarization channels (x, y) and are different from each other. On the other hand, from the continuous light generated from the light source 102, continuous light having two polarization axes x and y orthogonal to each other is generated by using the polarization branching means 103. On the transmitting side 10, the continuous light for each polarization is separately modulated by using the x-polarized channel light modulation means 104-1 and the y-polarized channel light modulation means 104-2 by using those electric signals. Then, the polarized light coupling means 105 is used to combine the modulated lights and send them to the optical transmission line 106.

In the uplink communication, the optical signals transmitted from the subscribers (each transmitting side 10) are combined on the optical transmission line 106, and the combined optical signals are transmitted to the stationer side (reception side 15). At this time, the transmission timing of the transmission means of each subscriber is set so that the optical signals transmitted from each subscriber do not overlap in time. On the other hand, in downlink communication, optical signals transmitted from the station building are branched on the optical transmission line 106, and the branched optical signals are transmitted to the subscriber side.

On the receiving side 15, the optical signal transmitted from the optical transmission line 106 is branched into an optical signal having two polarization axes X and Y orthogonal to each other by using the first polarization branching means 107. Here, the polarization axis (x, y) on the transmitting side and the polarization axis (X, Y) on the receiving side are generally different. This is because the polarization axes are set independently on the transmitting side and the receiving side. Therefore, signals transmitted from the x and y polarized channels on the transmitting side can be detected in both the X and Y polarized channels on the receiving side. On the other hand, from the continuous light generated from the light source 108, the second polarization branching means 109 is used to generate continuous light having two polarization axes X and Y orthogonal to each other. The optical coherent detection means 110-1 of the X-polarized channel and the optical coherent detection means 110-2 of the Y-polarized channel use continuous light for each of the polarized channels to light the received signal obtained from the first polarized branching means 107. Coherent detection is performed and output as an electric signal. The receiving means 111 processes those electrical signals and restores the transmitted information.

The electrical signals that modulate the continuous light of the x and y polarized channels on the transmitting side 10 are s _x and _sy , respectively, and the electrical signals detected from the X and Y polarized channels on the receiving side 15 are r _X and r _Y , respectively. In the time during which the pilot signal is transmitted and received, for example, as shown in Non-Patent Document 2, the following parameters are estimated from the received signal.

Here, in the above equations (1) to (6), α _x and δ _x are estimated values of the power ratio and the phase difference when the signal of the x polarized channel is branched into the X and Y polarized channels, respectively. α _y and δ _y are estimated values of the power ratio and the phase difference when the signal of the y polarized channel is branched into the X and Y polarized channels, respectively. By compensating the received signal using the above parameters, an estimated value of the transmitted signal after the reception time of the pilot signal can be obtained on the receiving side.

Here, in order for the above parameters to be estimated, it is necessary to create a situation in which either s _x or _sy is zero. Non-Patent Document 1 creates a situation in which either s _x or _sy becomes zero by frequency-separating the frequency-multiplexed pilot signal in the electric signal region in the electric region on the receiving side.

By the way, due to the polarization multiplexing separation described above, the optical burst signal is a form in which the control signal and the payload are time-multiplexed. In order to properly extract the pilot signal on the receiving side, it is necessary to extract timing information from the received signal. For example, in Non-Patent Document 1, although this function is realized in the form of frame synchronization using autocorrelation before polarization separation, the details are unknown.

Further, in Non-Patent Document 3, a waveform in which the same pattern is repeated twice is used as one of the control signals, the timing metric of the signal is calculated on the receiving side, and the timing information is extracted by detecting the peak. The timing metric is a correlation function between a signal and a signal obtained by delaying the signal by a time of a pattern repetition interval, and is a parameter having the same meaning as an autocorrelation function. Since the waveform is irregular at times other than the part where the same pattern is repeated twice in the received signal waveform, when the above timing metric is calculated, a peak is generated from the part where the same pattern is repeated twice. Will be done.

R. Matsumoto, et al. , "Burst-Mode Coherent Detection Fast-Fitting Pilot Sequence for 100-Gb / s / λ Coherent TDM-PON System," EuropeanConference onCommunication. K. Kikuchi and S. Tsukamoto, "Evaluation of Sensitivity of the Digital Coherent Receiver," Journal of Lightwave Technology, vol. 26, no. 13, pp. 1817-1822, Jul. 1,2008. T. M. Schmidl and D. C. Cox, "Robust Frequency and Timing Synchronization for OFDM," IEEE Transitions on Communications, vol. 45, no. 12, pp. 1613-1621, Dec. 1997.

By the way, in the above-mentioned prior art, a pilot signal frequency-multiplexed corresponding to both polarization axes is used as a control signal for polarization multiplexing separation. When separating them on the receiving side, frequency discrimination means are required. For example, a Fourier transform means may be used to convert the received signal waveform in the time domain into a signal spectrum in the frequency domain to separate and extract a single frequency sinusoidal pilot, or a bandpass filter may be used to separate and extract a single frequency sinusoidal pilot. Need to be extracted.

Further, in the above-mentioned prior art, a method of calculating a timing metric that takes a peak value at a desired timing for timing information extraction is described, but a specific means for detecting a peak from the obtained timing metric. Is not mentioned.

Therefore, an optical transmission device, a transmission signal generation method, and a transmission signal extraction method that can extract transmission information while reducing the circuit scale for timing information extraction and polarization separation are desired.

The first invention is an optical transmission device that multiplexes and transmits a first polarized channel and a second polarized channel, and (1) the first polarized channel having a finite time width. The waveform of the above is repeated three times to generate a first control signal, and in the second polarization channel, the second waveform having the same time width as the first waveform is repeated twice, and then the second waveform is repeated. A control signal generation means that generates a second control signal by combining the sign inversion waveforms of the waveform, (2) a payload signal generation means that generates a polarization-multiplexed payload signal, and (3) the first control signal and The polarized multiplex signal transmitting means for transmitting the polarized multiplex signal by time-multiplexing the second control signal and the polarization-multiplexed payload signal generated by the payload signal generation means, and (4) the polarized multiplex signal. The waveform sum and waveform difference between the received signal received and the delayed received signal obtained by delaying the received signal by the finite time width are calculated to calculate the waveform sum and waveform difference of the first control signal and the second control signal. Estimated by the control signal extraction means for extracting the time position, (5) the polarization state estimation means for estimating the polarization branching ratio and the phase difference between polarizations in the transmission path of the polarization multiplex signal, and (6) the polarization state estimation means. It is characterized by comprising a transmission information extraction means for extracting transmission information of each polarization channel from the received signal based on the polarization branching ratio and the phase difference between polarizations.

The second invention is a transmission signal generation method used for an optical transmission device that multiplexes a first polarization channel and a second polarization channel to transmit a signal, and comprises a control signal generation means and a payload signal generation means. (1) The control signal generation means generates a first control signal by repeating a first waveform having a finite time width three times in the first polarization channel, and generates the second polarization channel. In, after repeating the second waveform having the same time width as the first waveform twice, the code inversion waveform of the second waveform is combined to generate a second control signal, and (2) the payload. The signal generation means is characterized in that it generates a polarization-multiplexed payload signal.

A third aspect of the present invention is a transmission signal extraction method used for an optical receiving device that receives a signal in which a first polarization channel and a second polarization channel are multiplexed, and is a control signal extraction means, a polarization state estimation means, and a polarization state estimation means. The received signal received by the optical receiving device is the first control signal in which the first waveform having a finite time width is repeated three times in the first polarizing channel. In the second polarization channel, a second control signal having the same time width as the first waveform is repeated twice, and then the code inversion waveform of the second waveform is combined with the second control signal. The polarization-multiplexed payload signal is a time-multiplexed polarization-multiplexed signal, and (2) the control signal extraction means delays the received signal and the received signal by the finite time width. The time positions of the first control signal and the second control signal are extracted by calculating the sum of waveforms and the waveform difference between the above and (3) the polarization state estimation means is a polarization branch in the transmission path of the received signal. The ratio and the phase difference between polarizations are estimated, and (4) the transmission information extraction means of each polarization channel from the received signal based on the polarization branching ratio and the phase difference between polarizations estimated by the polarization state estimation means. It is characterized by extracting transmission information.

According to the present invention, transmission information can be extracted while reducing the circuit scale for timing information extraction and polarization separation.

It is a block diagram which shows the whole structure of the receiving means which concerns on 1st Embodiment. It is explanatory drawing which shows the form of the transmission signal which concerns on 1st Embodiment. It is a block diagram which shows the detailed structure of the common variable generation means which concerns on 1st Embodiment. It is a block diagram which shows the detailed structure of the timing signal generation means which concerns on 1st Embodiment. It is a block diagram which shows the detailed structure of the intermediate variable generation means of the X polarization channel (intermediate variable generation means of the Y polarization channel) which concerns on 1st Embodiment. It is a block diagram which shows the detailed structure of the polarization channel separation means which concerns on 1st Embodiment. It is explanatory drawing which shows the mathematical expression model of the polarization multiplex transmission system which concerns on 1st Embodiment. It is explanatory drawing (the 1) which shows the result of the calculated intermediate variable which concerns on 1st Embodiment. It is explanatory drawing (the 2) which shows the result of the calculated intermediate variable which concerns on 1st Embodiment. It is explanatory drawing which shows the waveform of the calculated intermediate variable which concerns on 1st Embodiment. It is a block diagram which shows the detailed structure of the timing signal generation means which concerns on 2nd Embodiment. It is explanatory drawing which shows the waveform of the calculated intermediate variable which concerns on 2nd Embodiment. It is a block diagram which shows the detailed structure of the intermediate variable generation means of the X polarization channel (intermediate variable generation means of the Y polarization channel) which concerns on 3rd Embodiment. It is a block diagram which shows an example of the conventional optical transmission system (optical transmission apparatus).

(A) First Embodiment In the following, the first embodiment of the optical transmission device, the transmission signal generation method, and the transmission signal extraction method according to the present invention will be described in detail with reference to the drawings.

(A-1) Configuration of First Embodiment (A-1-1) Overall Configuration The optical transmission system 1 of the first embodiment is basically the same as the configuration shown in FIG. However, in the optical transmission system 1 of the first embodiment, the receiving means 300 described later is applied instead of the receiving means 111. Further, the format of the signal (optical burst) transmitted from the transmitting side 10 to the receiving side 15 is also different.

FIG. 2 is an explanatory diagram showing a format of a transmission signal according to the first embodiment.

As shown in FIG. 2, the transmission signals s _x (t) and _sy (t) include control information B _x (t), By (t), payload C _x (t), _{Cy (} t), and the like. Information A _x (t) and _Ay (t). Further, it is assumed that the beginning of the optical burst is at a time less than 0 and the end of the optical burst is at a time exceeding 3T.

A _x (t), A _y (t), B _x (t), By (t), C _x (t), and _{Cy (} t) have different waveforms and have the same average power. B _x (t) and _{By (} t) are control information for timing information extraction and polarization separation, and C _x (t) and _Cy (t) are payloads. Further, A _x (t) and A _y (t) are other information such as preambles.

As shown in FIG. 2, in s _x (t), the same pattern _BX is repeated three times from time 0. Let T be the repetition interval. In _sy (t), the same pattern By is repeated twice from time ₀ , and immediately after that, _−By follows. The third _BX at s _x (t) and the _-By pattern at _sy (t) are followed by the payloads C _x and _Cy , respectively.

The transmitting side 10 (x-polarized channel transmitting means 101-1, y-polarized channel transmitting means 101-2) controls to transmit an optical signal according to the format shown in FIG. 2 above.

(A-1-2) Detailed Configuration of Receiving Means FIG. 1 is a block diagram showing an overall configuration of the receiving means according to the first embodiment. In FIG. 1, the receiving means 300 includes a common variable generating means 302, a timing signal generating means 303, an intermediate variable generating means 304-1 for an X polarized channel, an intermediate variable generating means 304-2 for a Y polarized channel, and a polarizing channel separating means. Has 305.

The common variable generation means 302 inputs the received signal 301-1 of the X-polarized channel and the received signal 301-2 of the Y polarized channel, generates (calculates) 10 intermediate signals, and outputs the generated signals.

The timing signal generation means 303 inputs the fifth intermediate signal 308-5 and the sixth intermediate signal 308-6 among the intermediate signals output from the common variable generation means 302, and generates and generates the timing signal 306. Output the signal.

The intermediate variable generation means 304-1 of the X polarization channel follows the timing signal 306, and among the intermediate signals output from the common variable generation means 302, the first intermediate signal 308-1, the second intermediate signal 308-2, The third intermediate signal 308-3 and the fourth intermediate signal 308-4 are input, the eleventh intermediate signal 309-1 and the twelfth intermediate signal 309-2 are generated, and the generated signals are output.

The intermediate variable generation means 304-2 of the Y polarization channel follows the timing signal 306, and among the intermediate signals output from the common variable generation means 302, the seventh intermediate signal 308-7, the eighth intermediate signal 308-8, 3. Input the 9th intermediate signal 308-9 and the 10th intermediate signal 308-10 to generate the 13th intermediate signal 309-3 and the 14th intermediate signal 309-4, and output the generated signals. do.

The polarizing channel separating means 305 includes the eleventh intermediate signal 309-1 and the twelfth intermediate signal 309-2 output from the intermediate variable generating means 304-1 of the X polarized channel, and the intermediate variable generating means 304 of the Y polarized channel. The thirteenth intermediate signal 309-3 and the fourteenth intermediate signal 309-4 output from -2 are input to generate the x-polarized channel estimation signal 307-1 and the y-polarized channel estimation signal 307.2. , Output the generated signal.

FIG. 3 is a block diagram showing a detailed configuration of the common variable generation means according to the first embodiment.

In FIG. 3, the common variable generation means 302 is the first delay means 402-1, the second delay means 402-2, the first addition means 403-1 and the second addition means 403-2, the first. Subtraction means 404-1, second subtraction means 404-2, first absolute value calculation means 405-1, second absolute value calculation means 405-2, third absolute value calculation means 405-3, fourth It has an absolute value calculation means 405-4, a third addition means 406-1, and a fourth addition means 406-2.

The first delay means 402-1 and the second delay means 402-2 use the received signal 301-1 of the X-polarized channel and the received signal 301-2 of the Y polarized channel of the waveform pattern for extracting the timing information, respectively. Output with a delay equal to the repetition interval.

The first adding means 403-1 adds the complex numerical value of the received signal 301-1 of the X-polarized channel and the complex numerical value of the output signal of the first delay means 402-1. The first addition means 403-1 outputs the calculated signal to the first absolute value calculation means 405-1, and also outputs the calculated signal to the intermediate variable generation means 304-1 of the X-polarized channel as the first intermediate signal 308-1. Output.

The second adding means 403-2 adds the complex value of the received signal 301-2 of the Y polarized channel and the complex value of the output signal of the second delay means 402-2. The second addition means 403-2 outputs the calculated signal to the second absolute value calculation means 405-2, and also outputs the calculated signal to the intermediate variable generation means 304-1 of the X-polarized channel as the second intermediate signal 308-2. Output.

The first subtracting means 404-1 subtracts the complex numerical value of the output signal of the first delay means 402-1 from the complex numerical value of the received signal 301-1 of the X-polarized channel. The first subtraction means 404-1 outputs the calculated signal to the third absolute value calculation means 405-3, and also outputs the calculated signal to the Y polarized channel intermediate variable generation means 304-2 as the seventh intermediate signal 308-7. Output.

The second subtracting means 404-2 subtracts the complex numerical value of the output signal of the second delay means 402-2 from the complex numerical value of the received signal 301-2 of the Y polarized channel. The second subtraction means 404-2 outputs the calculated signal to the fourth absolute value calculation means 405-4, and also outputs the calculated signal to the intermediate variable generation means 304-2 of the Y polarized channel as the eighth intermediate signal 308-8. Output.

The first absolute value calculation means 405-1 calculates the absolute value of the complex numerical value of the output signal of the first addition means 403-1. The first absolute value calculation means 405-1 outputs the calculated signal to the third addition means 406-1, and also outputs the calculated signal to the intermediate variable generation means 304-1 of the X-polarized channel as the third intermediate signal 308-3. Output.

The second absolute value calculation means 405-2 calculates the absolute value of the complex numerical value of the output signal of the second addition means 403-2. The second absolute value calculation means 405-2 outputs the calculated signal to the third addition means 406-1, and also outputs the calculated signal to the intermediate variable generation means 304-1 of the X-polarized channel as the fourth intermediate signal 308-4. Output.

The third absolute value calculation means 405-3 calculates the absolute value of the complex numerical value of the output signal of the first subtraction means 404-1. The third absolute value calculation means 405-3 outputs the calculated signal to the fourth addition means 406-2, and also as the ninth intermediate signal 308-9 to the intermediate variable generation means 304-2 of the Y polarized channel. Output.

The fourth absolute value calculation means 405-4 calculates the absolute value of the complex numerical value of the output signal of the second subtraction means 404-2. The fourth absolute value calculation means 405-4 outputs the calculated signal to the fourth addition means 406-2, and also as the tenth intermediate signal 308-10 to the intermediate variable generation means 304-2 of the Y polarized channel. Output.

The third addition means 406-1 adds the real value of the output signal of the first absolute value calculation means 405-1 and the real value of the output signal of the second absolute value calculation means 405-2. The third adding means 406-1 outputs the calculated signal to the timing signal generating means 303 as the fifth intermediate signal 308-5.

The fourth addition means 406-2 adds the real value of the output signal of the third absolute value calculation means 405-3 and the real value of the output signal of the fourth absolute value calculation means 405-4. The fourth adding means 406-2 outputs the calculated signal to the timing signal generating means 303 as the sixth intermediate signal 308-6.

FIG. 4 is a block diagram showing a detailed configuration of the timing signal generation means according to the first embodiment.

In FIG. 4, the timing signal generating means 303 includes a pulse generating means 501, a first integrating means 502-1, a second integrating means 502-2, a constant multiple means 503, a comparison means 504, a minimum value detecting means 505, and a minimum value detecting means 505. It has a logical product means 506. Further, the fifth intermediate signal 308-5 and the sixth intermediate signal 308-6, which are output signals of the common variable generation means 302, are real value signals.

The pulse generation means 501 periodically generates a pulse signal at intervals of twice the repetition interval (T) of the waveform pattern for extracting timing information.

The first integrating means 502-1 integrates the fifth intermediate signal 308-5 for a time equal to the repetition interval of the waveform pattern for timing information extraction. The first integrating means 502-1 outputs the calculated signal to the constant multiple means 503.

The second integrating means 502-2 integrates the sixth intermediate signal 308-6 for a time equal to the repetition interval of the waveform pattern for timing information extraction. The second integrating means 502-2 outputs the calculated signal to the comparing means 504 and the minimum value detecting means 505.

The constant multiplying means 503 multiplies the output signal of the first integrating means 502-1 by a real constant (eg, 0.5) greater than 0 and less than 1. The constant multiple means 503 outputs the calculated signal to the comparison means 504.

In the comparison means 504, the output signal of the constant multiple means 503 is used as the first input, the output signal of the second integrating means 502-2 is used as the second input, and the real value of the first input signal is the second input signal. A binary signal asserted in a time larger than the real value of is output to the logical product means 506.

In the minimum value detecting means 505, the real value of the output signal of the second integrating means 502-2 is the minimum value in the time from the beginning of the pulse to immediately before the next beginning in each cycle of the pulse signal. The binary signal asserted by the time taken is output to the AND means 506.

The logical product means 506 takes a logical product of the value of the output signal of the comparison means 504 and the value of the output signal of the minimum value detection means 505. The AND means 506 outputs the calculated signal as a timing signal 306 to the intermediate variable generation means 304-1 of the X-polarized channel, the intermediate variable generating means 304-2 of the Y polarized channel, and the like.

FIG. 5 is a block diagram showing a detailed configuration of an intermediate variable generation means for the X-polarized channel (intermediate variable generating means for the Y-polarized channel) according to the first embodiment. The intermediate variable generation means 304-1 of the X-polarized channel and the intermediate variable-generating means 304-2 of the Y polarized channel have the same configuration.

In FIG. 5, the intermediate variable generation means 304-1 of the X polarization channel (intermediate variable generation means 304-2 of the Y polarization channel) is the first division means 603-1, the second division means 603-2, and the third. Division means 603-3, first square root calculation means 604-1, second square root calculation means 604-2, multiplication means 605, first storage means 606-1, and second storage means 606-2. Have. Further, the 15th intermediate signal 601-1 and the 16th intermediate signal 601-2 are complex numerical signals, and the 17th intermediate signal 601-1, the 18th intermediate signal 601-4, and the 19th intermediate signal 601-5 is a real value signal.

Further, as shown below, in the X-polarized intermediate variable generation means 304-1, the fifteenth intermediate signal 601-1, the sixteenth intermediate signal 601-2, the seventeenth intermediate signal 601-3, and the eighteenth intermediate signal 601-1. The intermediate signals 601-4, the 19th intermediate signal 601-1-5, the 20th intermediate signal 607-1, the 21st intermediate signal 607-2, and the timing signal 602 are the first intermediate signal 3081 and the first intermediate signal 602, respectively. 2 intermediate signal 308-2, 3rd intermediate signal 308-3, 4th intermediate signal 308-4, 5th intermediate signal 308-5, 11th intermediate signal 309-1, 12th intermediate signal 309 -2 and the timing signal 306.

On the other hand, in the Y-polarized intermediate variable generation means 304-2, the fifteenth intermediate signal 601-1, the sixteenth intermediate signal 601-2, the seventeenth intermediate signal 601-3, the eighteenth intermediate signal 601-4, The 19th intermediate signal 601-5, the 20th intermediate signal 607-1, the 21st intermediate signal 607-2, and the timing signal 602 are the 7th intermediate signal 308-7 and the 8th intermediate signal 308-, respectively. 8, 9th intermediate signal 308-9, 10th intermediate signal 308-10, 6th intermediate signal 308-6, 13th intermediate signal 309-3, 14th intermediate signal 309-4, and timing signal. It is set to 306.

The first dividing means 603-1 divides the complex value of the fifteenth intermediate signal 601-1 by the complex value of the sixteenth intermediate signal 601-2. The first division means 603-1 outputs the calculated signal to the multiplication means 605.

The second dividing means 603-2 divides the real value of the 17th intermediate signal 601-3 by the real value of the 19th intermediate signal 601-5. The second division means 603-2 outputs the calculated signal to the first square root calculation means 604-1.

The third dividing means 603-3 divides the real value of the 18th intermediate signal 601-4 by the real value of the 19th intermediate signal 601-5. The third division means 603-3 outputs the calculated signal to the second square root calculation means 604-2.

The first square root calculation means 604-1 calculates the square root of the real value of the output signal of the second division means 603-2. The first square root calculating means 604-1 outputs the calculated signal to the multiplying means 605.

The second square root calculation means 604-2 calculates the square root of the real value of the output signal of the third division means 603-3. The second square root calculation means 604-2 outputs the calculated signal to the second storage means 606-2.

The multiplying means 605 multiplies the complex value of the output signal of the first dividing means 603-1 with the real value of the first square root calculating means 604-1. The multiplying means 605 outputs the calculated signal to the first storage means 606-1.

The first storage means 606-1 writes a complex numerical value of the output signal of the multiplying means 605 at the time when the timing signal 602 (timing signal 306) is asserted, and holds the value. The first storage means 606-1 outputs the output signal of the first storage means 606-1 to the polarizing channel separation means 305 as the 20th intermediate signal 607-1.

The second storage means 606-2 writes the real value of the output signal of the second square root calculation means 604-2 at the time when the timing signal 602 is asserted, and holds the value. The second storage means 606-2 outputs the output signal of the second storage means 606-2 to the polarization channel separation means 305 as the 21st intermediate signal 607-2.

FIG. 6 is a block diagram showing a detailed configuration of the polarizing channel separating means according to the first embodiment.

In FIG. 6, the polarization channel separating means 305 includes a first multiplying means 703-1, a second multiplying means 703-2, a third multiplying means 703-3, a fourth multiplying means 703-4, and a fifth. Multiplying means 703-5, 6th multiplying means 703-6, 1st subtracting means 704-1, 2nd subtracting means 704-2, 3rd subtracting means 704-3, 1st dividing means 705-1 , And a second dividing means 705-2.

The first multiplying means 703-1 multiplies the complex value of the received signal 301-1 of the X-polarized channel with the complex value of the thirteenth intermediate signal 309-3. The first multiplying means 703-1 outputs the calculated signal to the first subtracting means 704-1.

The second multiplying means 703-2 multiplies the complex value of the received signal 301-1 of the X-polarized channel with the real value of the 14th intermediate signal 309-4. The second multiplying means 703-2 outputs the calculated signal to the first subtracting means 704-1.

The third multiplying means 703-3 multiplies the complex value of the eleventh intermediate signal 309-1 and the complex value of the thirteenth intermediate signal 309-3. The third multiplying means 703-3 outputs the calculated signal to the second subtracting means 704-2.

The fourth multiplying means 703-4 multiplies the real value of the twelfth intermediate signal 309-2 with the real value of the fourteenth intermediate signal 309-4. The fourth multiplying means 703-4 outputs the calculated signal to the second subtracting means 704-2.

The fifth multiplying means 703-5 multiplies the complex value of the received signal 301-2 of the Y polarized channel with the complex value of the eleventh intermediate signal 309-1. The fifth multiplying means 703-5 outputs the calculated signal to the third subtracting means 704-3.

The sixth multiplying means 703-6 multiplies the complex value of the received signal 301-2 of the Y polarized channel with the real value of the 14th intermediate signal 309-4. The sixth multiplying means 703-6 outputs the calculated signal to the third subtracting means 704-3.

The first subtracting means 704-1 subtracts the complex numerical value of the output signal of the second multiplying means 703-2 from the complex numerical value of the output signal of the first multiplying means 703-1. The first subtraction means 704-1 outputs the calculated signal to the first division means 705-1.

The second subtracting means 704-2 subtracts the real value of the output signal of the fourth multiplying means 703-4 from the complex numerical value of the output signal of the third multiplying means 703-3. The second subtraction means 704-2 outputs the calculated signal to the first division means 705-1 and the second division means 705-2.

The third subtracting means 704-3 subtracts the complex numerical value of the output signal of the sixth multiplying means 703-6 from the complex numerical value of the output signal of the fifth multiplying means 703-5. The third subtraction means 704-3 outputs the calculated signal to the second division means 705-2.

The first dividing means 705-1 divides the complex value of the output signal of the first subtracting means 704-1 by the real value of the output signal of the second subtracting means 704-2. The first division means 705-1 outputs the calculated signal as an estimated signal 307-1 of the x-polarized channel.

The second dividing means 705-2 divides the complex value of the output signal of the third subtracting means 704-3 by the real value of the output signal of the second subtracting means 704-2. The second dividing means 705-2 outputs the calculated signal as the estimated signal 307-2 of the y-polarized channel.

(A-2) Operation of the First Embodiment Next, the operation of the optical transmission system 1 (mainly the receiving means 300) of the first embodiment having the above configuration will be described with reference to the drawings. ..

First, using FIG. 7 (mathematical model of the polarized multiplex transmission system), the signal relationship between transmission and reception in the polarized multiplex transmission system is derived.

Time is represented by t, and electrical signals that modulate the continuous light of the x and y polarized channels on the transmitting side 10 are detected from s _x (t) and _sy (t), respectively, and from the X and Y polarized channels on the receiving side 15. Let the electrical signals be r _X (t) and r _Y (t), respectively. Further, let s _x (t), _sy (t), r _X (t), and r _Y (t) be complex numbers. α _x and δ _x are the power ratio and phase difference when the signal of the x polarized channel is branched into the polarized channels of X and Y, respectively, and α _y and δ _y are the signals of the y polarized channel of X and Y, respectively. Represents the power ratio and phase difference when branching into the polarization channel of. Further, α _x , δ _x , α _y , and δ _y are real numbers.

Note that in a coherent optical transmission system, the complex amplitude of an electrical signal is proportional to the electric field amplitude of the corresponding optical signal, and the square of the electric field amplitude of the optical signal is proportional to its optical power. Ignoring the noise added in the transmission line, the following equations (7) to (8) are obtained.

From the received signal, the common variable generation means 302 includes the first delay means 402-1, the second delay means 402-2, the first addition means 403-1 and the second addition means 403-2, the first. The following quantities are calculated using the subtracting means 404-1 and the second subtracting means 404-2.

When the format of the transmission signals s _x (t) and _sy (t) is the format shown in FIG. 2, the above _{FX (t), FX (t), GX (t), and G Y ( t )} . ) Is shown in FIG.

When the modulation signal format is a method such as QPSK in which the waveform amplitude does not become zero, considering the duration of the optical burst, in the time range of _T≤t <2T, GX (t) and _GY (t) The value of is 0. In the other time range, the values of _{GX (t) and G Y (} t) do not become 0 continuously in the time width T. In all time zones, the values of _FX (t) and _FY (t) do not become zero consecutively in the time width T. This property is used for timing information extraction.

Further, in the time range of 2T ≦ t <3T, the information of the transmission signal _sy (t) is not included in the values of _FX (t) and _{FY (t), and GX (t) and G Y are not} included. The value of (t) does not include the information of the transmission signal _sy (t). This property is used for polarization separation.

Subsequently, the operation of timing information extraction will be described. From the above _{FX (t), FY (t), GX (t), and G Y ( t )} , the common variable generation means 302 is the first absolute value calculation means 405-1 and the second absolute value calculation. Using means 405-2, a third absolute value calculation means 405-3, a fourth absolute value calculation means 405-4, a third addition means 406-1, and a fourth addition means 406-2, | F. _Find the values of _X (t) | ² + | FY (t) | ² and | _GX (t) | ² + | G _Y (t) | ² .

Then, the timing signal generating means 303 integrates the calculated value in the range of time T by using the first integrating means 502-1 and the second integrating means 502-2. For example, in the time range of t <0, | _FX (t) | ² is expressed by the following equation (13).

In the above equation (13), "￣" represents the complex conjugate and Re [] represents the real part. For example, when a modulated signal format having an origin-symmetrical constellation such as QPSK is adopted, different waveform patterns (A _x (t) and A _y (t), A _x (t) and A _x (t-T)) are adopted. , Etc.) is zero. When correlating in the range of finite time T, it is not exactly zero, but it is sufficiently smaller than the square of the absolute value of the same signal. Therefore, if the above equation (13) is integrated in the range of time T, the term of 2Re [] can be ignored. Then, | _FX (t) | ² can be regarded as the following equation (14). Further, the same calculation can be performed for | _FY (t) | ^{2, | GX (t) | 2} _, ^and | G _Y (t) | ² . Then, the values of | _FX (t) | ^{2 + | FY (t) | 2 and | GX (t) | 2} ₊ ^| _G ^Y ₍ t) | ² obtained as a result of the same calculation are shown in FIG. As shown in.

FIG. 10 is an explanatory diagram showing the waveform of the calculated intermediate variable according to the first embodiment. FIG. 10A shows the waveforms of | _FX (t) | ² + | _FY (t) | ² . FIG. 10B shows the waveforms of | _GX (t) | ² + | G _Y (t) | ² . FIG. 10 (c) shows a waveform obtained by integrating the waveform shown in FIG. 10 (a) in the range of time T. FIG. 10 (d) shows a waveform obtained by integrating the waveform shown in FIG. 10 (b) in the range of time T.

Both the waveforms of FIGS. 10 (c) and 11 (d) take almost constant values except in the time range of 0 ≦ t <2T in the time T before the end of the optical burst from the beginning of the optical burst. The amplitudes of the waveforms in FIGS. 10 (c) and 10 (d) are equal in the time range of t <0 and 3T ≦ t. In the time range of 2T ≦ t <3T, the amplitudes of the waveforms in FIGS. 10 (c) and 10 (d) are almost the same. Then, the waveform of FIG. 10D has a peak (minimum value) at time T in the duration of the optical burst, and the peak value becomes 0.

The timing signal generating means 303 uses the minimum value detecting means 505 for the signal obtained by integrating | _GX (t) | ² + | _GH (t) | ² , and covers the range of time 2T every cycle of time 2T. Detect the minimum value. The detection time range and timing are set by the pulse generation means 501. The minimum value obtained in the period in which the waveform peak exists is the desired minimum value, but the minimum value obtained in the other periods is not the desired minimum value. The undesired minimum value is removed as follows.

The timing signal generation means 303 uses the comparison means 504 to compare the detected minimum value with a certain threshold value, and considers the minimum value as a desired peak only when the minimum value is less than the threshold value. Therefore, the logical product means 506 takes the logical product of the threshold value determination result and the binary signal representing the time for taking the minimum value. The time when the peak exists is the reference for specifying the time position of the payload. The beginning of the payload is the time 2T after the peak existence time.

The above "certain threshold value" is K times (0) of the signal value obtained by integrating | _FX (t) | ² + | _FY (t) | ² at the minimum value detection time, for example, using the constant multiple means 503. It can be set to <K <1). As described above, the time for detecting an undesired minimum value is a time zone in which the signal obtained by integrating | _GX (t) | ² + | _GY (t) | ² changes almost constantly, and in that time zone | Because the signal value obtained by integrating G _X (t) | ² + | G _Y (t) | ² | and the signal value obtained by integrating | _FX (t) | ² + | _FY (t) | ² are almost equal. be.

Next, the operation of polarization separation will be described. In the time range of 2T ≦ t <3T, the values of _{FX (t), FY (t), GX (t), and G Y ( t )} are shown in FIG. 8 above and (15) to (18) below. ) Will be shown in the equation.

From the above equations (15) to (18), the estimated values of α _x , δ _x , α _y , and δ _y can be obtained by the following equations (19) to (24). It should be noted that the hat (^) indicating that it is an estimated value of α _x in the following equations (19) to (24) is not the upper part of α _x but is like ^ α _x (t) due to the regulation on the notation. It shall be shown on the left side. Similarly, the estimated values of δ _x , α _y , and δ _y shall be indicated as ^ δ _x (t), ^ α _y (t), and ^ δ _y (t). The same applies to the variables in).

The division means 603 executes the above equations (19) to (24). These are the values at the temporary point t. Since ^ α _x (t), ^ δ _x (t), ^ α _y (t), and ^ δ _y (t) required for polarization separation are values obtained in the time range of 2T ≦ t <3T, The ^ α _x (t), ^ δ _x (t), ^ α _y (t), and ^ δ _y (t) obtained in the time range of 2T ≦ t <3T are stored.

Here, the variables finally required for the polarization channel separation are A to D shown in the following equations (25) to (28).

Therefore, the intermediate variable generation means 304 calculates the values of the following equations (29) to (32) using the square root calculation means 604 and the multiplication means 605, and uses the storage means 606 to calculate the values (A (A). Store t) to D (t)).

Hereinafter, the obtained estimated values are expressed as ^ α _x , ^ δ _x , ^ α _y , and ^ δ _y . When, for example, the ZF (zero-force) method is adopted as the reception signal estimation method, the estimated value of the transmission signal obtained from the reception signals r _x (t) and r _Y (t) for a time of t ≧ 3T ^ s _x (t) and ^ s _y (t) are the following (33) and (34) by solving the above equations (7) and (8) for s _x (t) and _sy (t). It is calculated like an expression. The following calculations of equations (33) and (34) are performed by the polarizing channel separating means 305.

(A-3) Effect of the first embodiment According to the first embodiment, the following effects are obtained.

The circuit scales of the receiving means of the conventional example and the receiving means of the present embodiment are compared. Since both methods use timing signal generation means, intermediate variable generation means for both polarization channels, and polarization separation means, the circuit scales related to these means may be the same.

In the conventional example, the timing metric is calculated in order to extract the timing information. This calculation formula is shown by the formula (5) of Non-Patent Document 3. Assuming that r (t) is the received signal and P (t) is the timing metric, it is expressed as the following equations (35) and (36). Therefore, in the case of digital signal processing, the number of calculations is N for complex multiplication. It is necessary to calculate the absolute value of complex numbers N times and the sum of N real numbers (corresponding to the integral) once.

Here, N is the number of sample values included in the time T. If, for example, the M-point Fast Fourier Transform (FFT) is used for frequency discrimination of the pilot signal, which is executed to estimate the polarization parameters (α _x , δ _x , α _y , δ _y ) in the conventional example, it is complex. Both addition and complex multiplication require _Mlog 2M times.

In this embodiment, _{FX (t), FY (t), GX (t), and G Y ( t )} are calculated for timing information extraction and polarization separation. In the case of digital signal processing, the number of calculations is N times for complex addition (subtraction is considered as addition with sign-inverted numerical value), N times for complex number absolute value calculation, and 1 time for sum of N real numbers (corresponding to integration). is necessary.

In places where there are multiple circuits with the same configuration and input / output of the same format, if there is a margin in timing constraints, the input / output signals can be time-division-multiplexed to combine multiple circuits into one. Circuits with the same format of input / output are counted as one in the configuration.

Therefore, in the receiving means of the present embodiment, the number of complex multiplication circuits is reduced as compared with the conventional example.

As described above, according to the first embodiment, the calculation formula is modified to standardize the means required for timing information extraction and the means required for polarization separation, and thus the timing information is integrated. The effect of reducing the circuit scale for extraction and polarization separation is obtained.

(B) Second Embodiment Hereinafter, a second embodiment of the optical transmission device, the transmission signal generation method, and the transmission signal extraction method according to the present invention will be described in detail with reference to the drawings.

(B-1) Configuration of Second Embodiment The overall configuration of the receiving means 300 of the second embodiment can also be shown with reference to FIG. 1 described above. Hereinafter, the configuration of the receiving means 300 of the second embodiment will be described focusing on the difference (timing signal generating means) from the receiving means 300 of the first embodiment.

FIG. 11 is a block diagram showing a detailed configuration of the timing signal generation means according to the second embodiment. In FIG. 11, the same or corresponding configurations as those in FIG. 4 according to the first embodiment are designated by the same reference numerals. Further, detailed description of the same or corresponding configuration of FIG. 4 according to the first embodiment will be omitted.

In FIG. 11, the timing signal generation means 303A according to the second embodiment has the third delay means 701 added to the configuration of the timing signal generation means 303 according to the first embodiment, and is the minimum of the first embodiment. The first embodiment is in that the value detecting means 505 is replaced with the first minimum value detecting means 702 and the second minimum value detecting means 703, and the logical product means 506 of the first embodiment is replaced with the logical product means 506A. Is different from.

The third delay means 701 gives the output pulse signal of the pulse generation means 501 a delay of a time equal to the repetition interval of the waveform pattern for timing information extraction.

The first minimum value detection means 702 outputs the output of the second integration means 502-2 in the time from the beginning of the pulse to immediately before the next beginning in each cycle of the output pulse signal of the pulse generation means 501. Outputs a binary signal that is asserted at the time when the real value of the signal takes the minimum value.

The second minimum value detection means 703 is a second integration means 502-2 in the time from the beginning of the pulse to immediately before the next beginning in each cycle of the output pulse signal of the third delay means 701. Outputs a binary signal that is asserted at the time when the real value of the output signal takes the minimum value.

The logical product means 506A takes a logical product with the values of the output signals of the comparison means 504, the first minimum value detection means 702, and the second minimum value detection means 70-3. The AND means 506A outputs the calculated signal as a timing signal 306.

(B-2) Operation of the Second Embodiment Next, the operation of the optical transmission system 1 (mainly the timing signal generation means 303A) of the second embodiment having the above configuration is described with reference to the drawings. I will explain while. Hereinafter, the operation peculiar to the timing signal generation means 303A will be described while comparing with the timing signal generation means 303 of the first embodiment.

In the first embodiment, in the timing signal generating means 303, the minimum value of the output signal of the second integrating means 502-2 is detected over the range of the time 2T every cycle of the time 2T, and the comparison means 504 is detected. When the minimum value of the output signal of is detected within the asserted time, the timing signal 306 is asserted. If the output signal of the second integrating means 502-2 peaks near the middle of the 2T time range for detecting the minimum value, the timing signal 306 is asserted at the desired time. However, if the output signal of the second integrating means 502-2 peaks near the end of the 2T time range for detecting the minimum value, then the timing signal 306 is within the desired time and adjacent minimum detection time range. May be asserted in time. The timing signal generation means 303A of the second embodiment takes this point into consideration.

FIG. 12 is an explanatory diagram showing the waveform of the calculated intermediate variable according to the second embodiment.

FIG. 12A shows the waveform of the output signal of the second integrating means 502-2 (waveform W1 shown by the solid line) and the waveform of the output signal of the constant multiple means 503 (W2 shown by the broken line). The output signal of the comparison means 504 is asserted in such a time that the value of the solid line (value of W1) becomes smaller than the value of the broken line (value of W2).

When the minimum value detection time range generated for each cycle of time 2T is as shown in FIG. 12 (b) (in the case of the minimum value detection time range Sr1-1 to Sr1-5), the timing signal 306 is the first. The next minimum detection time of the minimum detection time range (minimum detection time range Sr1-2) including the time when the value of the output signal of the integration means 502-2 of 2 peaks (desired timing) and the peak time. It is asserted in two times, that is, the time when the value of the output signal of the second integrating means 502-2 becomes the minimum in the range (minimum value detection time range Sr1-3). This is because the value of the solid line (value of W1) is smaller than the value of the broken line (value of W2) even at the other assert time, as a matter of course, at the desired timing.

FIG. 12 (c) shows the waveform of the timing signal 306 when the minimum value detection time range is time-shifted by T from the case of FIG. 12 (b). In this case, in addition to the desired timing, the second is in the minimum value detection time range (minimum value detection time range Sr2-1) before the minimum value detection time range (minimum value detection time range Sr2-2) including the peak time. The timing signal 306 is asserted at the time when the value of the output signal of the integrating means 502-2 is minimized. This is because the value of the solid line is smaller than the value of the broken line in the other assert time as well as the desired timing.

The timing signal 306 may be asserted only at a desired timing depending on the time relationship between the minimum value detection time and the output signal of the second integrating means 502-2. Further, since the minimum value detection time range is set to 2T, the timing signal 306 is not asserted at an undesired time in both the minimum value detection time range before and after the minimum value detection time range including the desired timing.

Therefore, the timing signal output from the timing signal generation means such as the timing signal generation means 303 and the timing signal output from the timing signal generation means obtained by shifting the minimum value detection time by T time from the timing signal generation means. The logical product gives a timing signal that is asserted only at the desired timing. The waveform is shown in FIG. 12 (d). FIG. 12 (d) shows, as an example, a signal obtained by taking a logical product of the timing signal of FIG. 12 (b) and the timing signal of FIG. 12 (c).

The signal of FIG. 12B is the logical product of the values of the output signals of the comparison means 504 and the minimum value detection means (first minimum value detection means 702), and the signal of FIG. 12C is different from the comparison means 504. The result of taking the logical product of the value of the output signal of the minimum value detection means (second minimum value detection means 703) is shown, and the result of taking the logical product of those two binary signals is shown in FIG. 12 (d). Is the output of. Therefore, the logical product means 506A may take the logical product of the three output signals of the comparison means 504, the first minimum value detection means 702, and the second minimum value detection means 703. As shown in FIG. 12 (d), the time T with the peak P is the reference timing.

(B-3) Effect of Second Embodiment According to the second embodiment, in addition to the effect of the first embodiment, the possibility of erroneous detection of timing information can be reduced.

(C) Third Embodiment Hereinafter, a second embodiment of the optical transmission device, the transmission signal generation method, and the transmission signal extraction method according to the present invention will be described in detail with reference to the drawings.

(C-1) Configuration of Third Embodiment The overall configuration of the receiving means 300 of the third embodiment can also be shown with reference to FIG. 1 described above. Hereinafter, the configuration of the receiving means 300 of the third embodiment will be described focusing on the difference (intermediate variable generating means) from the receiving means 300 of the first embodiment.

FIG. 13 is a block diagram showing a detailed configuration of an intermediate variable generation means for the X-polarized channel (intermediate variable generating means for the Y-polarized channel) according to the third embodiment. In FIG. 13, the same or corresponding configurations as those in FIG. 5 according to the first embodiment are designated by the same reference numerals. Further, detailed description of the same or corresponding configuration of FIG. 5 according to the first embodiment will be omitted.

The X-polarized channel intermediate variable generating means 304A-1 (Y polarized channel intermediate variable generating means 304A-2) according to the third embodiment is the X-polarized channel intermediate variable generating means 304- according to the first embodiment. The first averaging means 801-1 and the second averaging means 801-2 are added to the configuration of 1 (intermediate variable generation means 304-2 of the Y polarization channel).

The first averaging means 801-1 averages the output signal of the multiplying means 605 over a time equal to or less than the repetition interval of the waveform pattern for timing information extraction. The first averaging means 801-1 outputs the calculated (averaging) signal to the first storage means 606-1.

The second averaging means 801-2 averages the output signal of the second square root calculating means 604-2 over a time equal to or less than the repetition interval of the waveform pattern for timing information extraction. The second averaging means 801-2 outputs the calculated (averaging) signal to the second storage means 606-2.

(C-2) Operation of the Third Embodiment Next, the optical transmission system 1 of the third embodiment having the above configuration (mainly, the intermediate variable generation means 304A-1 of the X polarization channel and the Y polarization). The operation of the channel intermediate variable generation means 304A-2) will be described with reference to the drawings. Hereinafter, the intermediate variable generation of the X-polarized channel of the third embodiment is compared with the intermediate variable generation means 304-1 of the X-polarized channel of the first embodiment (intermediate variable generation means 304-2 of the Y polarized channel). The operation peculiar to the means 304A-1 (intermediate variable generation means 304A-2 of the Y polarized channel) will be described.

In the first embodiment, among the X-polarized intermediate variable generating means 304-1 and the Y-polarized intermediate variable generating means 304-2, the intermediate variables ^ α _x , ^ δ _x , ^ α _y , ^ δ _y The value was calculated. Since noise is generally added to the received signal, there is an error in the above estimated value. In order to reduce the influence of the error, it is desirable to average each estimated value over a time of T or less within a time of 2T ≦ t <3T.

The averaging calculation formula used in the first averaging means 801-1 and the second averaging means 801-2 is defined by the following formula (37).

Here, u (t) is an input signal to the averaging means, v (t) is an output signal from the averaging means, T ₀ is a time, and 0 <T ₀ ≦ T is satisfied.

Since the operations of the intermediate variable generation means 304A-1 for the X-polarized channel and the intermediate variable generating means 304A-2 for the Y polarized channel other than the above are the same as those in the first embodiment, the description thereof will be omitted.

(C-3) Effect of the third embodiment According to the second embodiment, in addition to the effect of the first embodiment, the intermediate variables ^ α _x , ^ δ _x , ^ α _y , ^ δ _y The estimation accuracy can be improved.

(D) Other Embodiments Although various modified embodiments have been mentioned in the above-mentioned first to third embodiments, the present invention can also be applied to the following modified embodiments.

(D-1) In the first to third embodiments described above, as a method of realizing the polarizing channel separating means 305, the ZF method of polarizing channel separation has been described as an example. As another implementation method, the polarizing channel separating means 305 may adopt a method such as an MMSE (minimum likelihood estimation) method or an MLD (maximum likelihoodhod detection) method. Compared to the ZF method, the MMSE method has better signal estimation accuracy when receiving at a lower signal-to-noise ratio (SN ratio), but it cannot completely eliminate interference between polarized channels, and it is necessary to estimate the SN ratio on the receiving side. There is a drawback that a circuit for that purpose is required. On the other hand, the MLD method has better signal estimation accuracy than the above two types of methods, but has a drawback that the circuit scale increases. Whichever method is adopted for the polarizing channel separating means 305 has advantages and disadvantages, and therefore, it is desired to appropriately select the method according to the specifications required for the system.

(D-2) In the first to third embodiments described above, as the transmission signal format (FIG. 2), control information for timing information extraction and polarization channel separation is provided immediately before the payload after the beginning of the burst. It was assumed that it would be sent and received. Of course, the control information may be inserted into one place or a plurality of places of the transmission signal at any timing.

(D-3) The receiving means 300 of the first to third embodiments described above may be configured by hardware for each part thereof, or may be configured by software for some configurations.

(D-4) An example in which the receiving means 300 of the first to third embodiments described above is applied to the station side has been described, but as a modified example, it is mounted on a device on the subscriber side (in other words, continuous signal transmission). It may be applied to the optical transmission method of.

1 ... Optical transmission system, 300 ... Receiving means, 302 ... Common variable generating means, 303, 303A ... Timing signal generating means, 304, 304A ... Intermediate variable generating means, 305 ... Polarized channel separating means, 402-1 ... First Delay means, 402-2 ... second delay means, 403-1 ... first addition means, 4032 ... second addition means, 404-1 ... first subtraction means, 404-2 ... second Subtraction means, 405-1 ... 1st absolute value calculation means, 405-2 ... 2nd absolute value calculation means, 405-3 ... 3rd absolute value calculation means, 405-4 ... 4th absolute value calculation means , 406-1 ... 3rd adding means, 406-2 ... 4th adding means, 501 ... pulse generating means, 502-1 ... 1st integrating means, 502-2 ... 2nd integrating means, 503 ... constant Multiplying means, 504 ... comparison means, 505 ... minimum value detecting means, 506, 506A ... logical product means, 603 ... dividing means, 603-1 ... first dividing means, 603-2 ... second dividing means, 603- 3 ... Third subtraction means, 604 ... Square root calculation means, 604-1 ... First square root calculation means, 604-2 ... Second square root calculation means, 605 ... Multiplying means, 606 ... Storage means, 606-1 ... 1st storage means, 606-2 ... 2nd storage means, 701 ... 3rd delay means, 702 ... 1st minimum value detection means, 703 ... 2nd minimum value detection means, 703-1 ... 1st 703-2 ... 2nd multiplying means, 703-3 ... 3rd multiplying means, 703-4 ... 4th multiplying means, 703-5 ... 5th multiplying means, 703-6 ... 6th Multiplying means, 704-1 ... 1st subtracting means, 704-2 ... 2nd subtracting means, 704-3 ... 3rd subtracting means, 705-1 ... 1st dividing means, 705-2 ... 2nd Dividing means, 801-1 ... 1st averaging means, 801-2 ... 2nd averaging means.

Claims (3)

An optical transmission device that multiplexes and transmits a first polarized channel and a second polarized channel.
In the first polarization channel, the first waveform having a finite time width is repeated three times to generate a first control signal, and in the second polarization channel, the same time width as the first waveform is obtained. A control signal generation means for generating a second control signal by combining the sign inversion waveforms of the second waveform after repeating the second waveform having the second waveform twice.
A payload signal generation means that generates a polarized and multiplexed payload signal,
A polarized multiplexed signal transmitting means for transmitting a polarized multiplexed signal by time-multiplexing the first control signal, the second control signal, and the polarized multiplexed payload signal generated by the payload signal generating means.
The first control signal and the first control signal and the first control signal are calculated by calculating the waveform sum and waveform difference between the received signal and the delayed received signal obtained by delaying the received signal by the finite time width after receiving the polarized multiplex signal. A control signal extraction means for extracting the time position of the control signal of 2 and
A polarization state estimation means for estimating the polarization branching ratio and the phase difference between polarizations in the transmission path of the polarization multiplex signal,
An optical transmission apparatus comprising: a transmission information extraction means for extracting transmission information of each polarization channel from the received signal based on the polarization branching ratio estimated by the polarization state estimation means and the phase difference between the polarizations. .. A transmission signal generation method used in an optical transmitter that multiplexes a first polarized channel and a second polarized channel to transmit a signal.
Equipped with control signal generation means and payload signal generation means,
The control signal generation means repeats the first waveform having a finite time width three times in the first polarization channel to generate a first control signal, and in the second polarization channel, the first control signal is generated. After repeating the second waveform having the same time width as that of the waveform twice, the code inversion waveform of the second waveform is combined to generate the second control signal.
The payload signal generation means is a transmission signal generation method, characterized in that a payload signal that is polarized and multiplexed is generated. A transmission signal extraction method used in an optical receiver that receives a signal in which a first polarized channel and a second polarized channel are multiplexed.
The received signal received by the optical receiver provided with the control signal extraction means, the polarization state estimation means, and the transmission information extraction means repeats the first waveform having a finite time width three times in the first polarization channel. The first control signal and the second waveform having the same time width as the first waveform are repeated twice in the second polarization channel, and then the sign inversion waveform of the second waveform is combined. The second control signal and the polarization-multiplexed payload signal are time-multiplexed polarization-multiplexed signals.
The control signal extraction means calculates the waveform sum and waveform difference between the received signal and the delayed received signal obtained by delaying the received signal by the finite time width, and calculates the waveform sum and the waveform difference of the first control signal and the second. Extract the time position of the control signal of
The polarization state estimation means estimates the polarization branching ratio and the phase difference between polarizations in the transmission line of the received signal.
The transmission information extraction means extracts transmission information of each polarization channel from the received signal based on the polarization branching ratio and the phase difference between the polarizations estimated by the polarization state estimation means. Method.

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