WO2022249458A1 - 光伝送装置、システム、方法、及び非一時的なコンピュータ可読媒体 - Google Patents
光伝送装置、システム、方法、及び非一時的なコンピュータ可読媒体 Download PDFInfo
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- the present disclosure relates to an optical transmission device, system, method, and non-transitory computer-readable medium, and in particular, an optical transmission device capable of reducing noise generated by IQ mixing in subcarrier multiplexing.
- Systems, methods, and non-transitory computer-readable media are examples of optical transmission devices, and in particular, reducing noise generated by IQ mixing in subcarrier multiplexing.
- a digital coherent optical transmission system that achieves a communication speed of 1 Tbps (Tera Bps) or higher requires a digital subcarrier (SC) multiplexing method.
- SC digital subcarrier
- the delay difference between the in-phase (I) component and the quadrature (Q) component, the amplitude error, and the difference in the frequency characteristics, etc. cause paired subs.
- noise is generated in the carrier due to IQ mixing, and reception characteristics are degraded due to the noise.
- the MIMO (Multi Input Multi Output) equalizer provided on the receiving side to compensate for the frequency characteristic difference between the in-phase component and the quadrature component is in a state where noise due to IQ mixing is included.
- the filter coefficients of the FIR (Finite Impulse Response) filter are derived, reception characteristics deteriorate.
- the in-phase component is sometimes called I-lane
- the quadrature component is sometimes called Q-lane.
- Non-patent document 1 in radio communication, the pilot signal of one side subcarrier of OFDM (Orthogonal Frequency Division Multiplexing) is periodically and alternately set to zero to avoid the influence of IQ mixing, and the optimum filter coefficient for transmission and reception It is disclosed to derive Non-Patent Document 1 does not disclose reduction of noise generated by IQ mixing in a multiple subcarrier multiplexing digital coherent optical transmission system.
- OFDM Orthogonal Frequency Division Multiplexing
- Non-Patent Document 2 discloses that in single-carrier digital coherent optical transmission, 8x2 MIMO provided on the receiving side is used to compensate for the frequency characteristics of a transmitting/receiving device. Non-Patent Document 2 does not disclose reduction of noise generated by IQ mixing in a multiple subcarrier multiplexing digital coherent optical transmission system.
- Non-Patent Document 3 discloses that in single-carrier digital coherent optical transmission, 4x2 MIMO provided on the receiving side is used to compensate for the frequency characteristics of a receiving device. Non-Patent Document 3 does not disclose reduction of noise generated by IQ mixing in a multiple subcarrier multiplexing digital coherent optical transmission system.
- the SC multiplexing method used in the digital coherent optical transmission system for high-speed communication has the problem that reception characteristics deteriorate due to noise caused by IQ mixing that occurs in paired subcarriers.
- An object of the present disclosure is to provide an optical transmission device, system, method, and non-transitory computer-readable medium that solve the above-described problems.
- An optical transmission device includes: pilot adding means for adding a first pilot signal to the first data signal to generate a first digital signal and adding a second pilot signal to the second data signal to generate a second digital signal; optically modulating the first digital signal with a first subcarrier included in a frequency band negative with respect to the center frequency of the used frequency band; optical modulation means for optically modulating the second digital signal with two subcarriers to generate an optically modulated signal and transmitting the optically modulated signal; with The pilot adding means is not transmitting the second pilot signal during transmission of the first pilot signal; The first pilot signal is not transmitted while the second pilot signal is being transmitted.
- An optical transmission device includes: adding a first pilot signal to the first data signal to generate a first digital signal; adding a second pilot signal to the second data signal to generate a second digital signal; and adding a third pilot signal to the third data signal.
- pilot adding means for adding the signal to generate a third digital signal and adding a fourth pilot signal to the fourth data signal to generate a fourth digital signal; optically modulating the first digital signal with an X-polarized wave using a first subcarrier contained in a frequency band that is negative with respect to the center frequency of the used frequency band; optically modulating the second digital signal with X polarization using a second subcarrier included in the frequency band to generate an X optical modulated signal; and generating the third digital signal with Y polarization using the first subcarrier optically modulating a signal, optically modulating the fourth digital signal with a Y polarization using the second subcarrier to generate a Y optically modulated signal, and converting the X optically modulated signal and the Y optically modulated signal
- An optical transmission device includes: adding a first pilot signal to the first data signal to generate a first digital signal; adding a second pilot signal to the second data signal to generate a second digital signal; and adding a third pilot signal to the third data signal.
- pilot adding means for adding the signal to generate a third digital signal and adding a fourth pilot signal to the fourth data signal to generate a fourth digital signal; optically modulating the first digital signal with a first subcarrier included in a frequency band negative with respect to the center frequency of the used frequency band; Optically modulating the second digital signal with two subcarriers, optically modulating the third digital signal with a third subcarrier included in a positive frequency band with respect to the center frequency of the working frequency band, and optically modulating the working frequency optical modulation means for optically modulating the fourth digital signal with a fourth subcarrier included in a positive frequency band with respect to the center frequency of the band to generate an optically modulated signal and transmitting the optically modulated signal; with The pilot adding means is During transmission of the first pilot,
- a system includes: an optical transmission device; another optical transmission device that receives an optical modulated signal from the optical transmission device via an optical transmission line; with The optical transmission device is pilot adding means for adding a first pilot signal to the first data signal to generate a first digital signal and adding a second pilot signal to the second data signal to generate a second digital signal; optically modulating the first digital signal with a first subcarrier included in a frequency band negative with respect to the center frequency of the used frequency band; optical modulation means for optically modulating the second digital signal with two subcarriers to generate the optically modulated signal and transmitting the optically modulated signal; has The pilot adding means is not transmitting the second pilot signal during transmission of the first pilot signal; not transmitting the first pilot signal while transmitting the second pilot signal; Another optical transmission device, optical signal receiving means for receiving the first digital signal obtained by coherently detecting the modulated optical signal and the second digital signal obtained by coherently detecting the modulated optical signal; position detection means for detecting the position of the first pilot signal within the first digital signal and the
- a method includes: adding a first pilot signal to the first data signal to generate a first digital signal and adding a second pilot signal to the second data signal to generate a second digital signal; optically modulating the first digital signal with a first subcarrier included in a frequency band negative with respect to the center frequency of the used frequency band; optically modulating the second digital signal with two subcarriers to generate an optically modulated signal, and transmitting the optically modulated signal; not transmitting the second pilot signal during transmission of the first pilot signal; not transmitting the first pilot signal while transmitting the second pilot signal; Prepare.
- a non-transitory computer-readable medium includes: adding a first pilot signal to the first data signal to generate a first digital signal and adding a second pilot signal to the second data signal to generate a second digital signal; optically modulating the first digital signal with a first subcarrier included in a frequency band negative with respect to the center frequency of the used frequency band; optically modulating the second digital signal with two subcarriers to generate an optically modulated signal, and transmitting the optically modulated signal; not transmitting the second pilot signal during transmission of the first pilot signal; not transmitting the first pilot signal while transmitting the second pilot signal;
- a program that causes a computer to execute is stored.
- an optical transmission device, system, method, and non-transitory computer-readable medium capable of reducing noise generated by IQ mixing in subcarrier multiplexing.
- FIG. 1 is a block diagram illustrating a digital coherent optical transmission system
- FIG. FIG. 4 is a schematic diagram illustrating waveforms after subcarrier synthesis
- FIG. 4 is a schematic diagram illustrating waveforms after subcarrier synthesis
- 3 is a block diagram illustrating a MIMO equalizer of an optical transmission device and its inputs and outputs
- FIG. 1 is a block diagram illustrating an optical transmission device according to Embodiment 1
- FIG. 1 is a block diagram illustrating an optical transmission device according to Embodiment 1
- FIG. 1 is a block diagram illustrating an optical transmission device according to Embodiment 1
- FIG. 1 is a block diagram illustrating a system according to Embodiment 1;
- FIG. 1 is a block diagram illustrating a MIMO equalizer according to Embodiment 1;
- FIG. 4 is a schematic diagram illustrating how pilot signals are transmitted according to Embodiment 1.
- FIG. 2 is a schematic diagram illustrating an example of a MIMO equalizer and its inputs and outputs in the optical transmission device according to Embodiment 1;
- FIG. 2 is a schematic diagram illustrating an example of a MIMO equalizer and its inputs and outputs in the optical transmission device according to Embodiment 1;
- FIG. 1 is a block diagram illustrating a MIMO equalizer according to Embodiment 1;
- FIG. 1 is a block diagram illustrating a MIMO equalizer according to Embodiment 1;
- FIG. 8 is a block diagram illustrating a 2 ⁇ 2 MIMO equalizer according to Embodiment 2;
- FIG. 12 is a block diagram illustrating a 4 ⁇ 2 MIMO equalizer according to Embodiment 3;
- FIG. 12 is a block diagram illustrating a 4 ⁇ 2 MIMO equalizer according to Embodiment 4;
- FIG. 11 is a schematic diagram illustrating part of a receiving unit of an optical transmission device according to Embodiment 5;
- FIG. 14 is a schematic diagram illustrating a part of a transmission means of an optical transmission device according to Embodiment 5;
- FIG. 13 is a schematic diagram illustrating part of a receiving means of an optical transmission device according to a sixth embodiment;
- FIG. 14 is a schematic diagram illustrating a part of a transmission means of an optical transmission device according to Embodiment 6;
- FIG. 13 is a schematic diagram illustrating how pilot signals are transmitted according to Embodiment 7;
- FIG. 13 is a schematic diagram illustrating how pilot signals are transmitted according to Embodiment 7;
- FIG. 13 is a schematic diagram illustrating how pilot signals are transmitted according to Embodiment 7;
- FIG. 1 is a block diagram illustrating a digital coherent optical transmission system.
- the transmission means of the optical transmission device of the optical transmission system performs processing such as encoding on information to be transmitted to generate a data signal.
- the transmission means of the optical transmission apparatus receives from the data signal the I component SC1-XI of the X-polarized wave of the first subcarrier, the Q component SC1-XQ of the X-polarized wave of the first subcarrier, and the Y-polarized wave of the first subcarrier.
- An I component SC1-YI and a Q component SC1-YQ of the Y-polarized wave of the first subcarrier are generated.
- the transmission means of the optical transmission device optically modulates each of these components with a Mach-Zender (MZ) type modulator to generate an optically modulated signal.
- MZ Mach-Zender
- the transmission means of the optical transmission device polarization-multiplexes the generated optical modulated signal and transmits the resultant to another optical transmission device via the optical transmission line.
- the I component is sometimes called an in-phase component
- the Q component is sometimes called a quadrature component
- An optical transmission line is sometimes called an optical fiber.
- Receiving means of another optical transmission device depolarizes the modulated optical signal received from the optical transmission device, and then uses a 90-degree hybrid to demultiplex the I component of the X-polarized wave of the first subcarrier and the X-polarized wave of the first subcarrier. and the Q component of the polarization.
- a receiving means of another optical transmission apparatus converts the I component of the Y-polarized wave of the first subcarrier and the Q component of the Y-polarized wave of the first subcarrier using another 90-degree hybrid.
- a receiving means of another optical transmission device coherently detects these converted components (signals), converts them into electrical signals, and samples these electrical signals using a high-speed ADC (Analog Digital Converter).
- the receiving means of the optical transmission apparatus performs digital signal processing on the sampled signal to correct waveform distortion.
- waveform distortion is corrected using a MIMO equalizer, which will be described later.
- the receiving means of the optical transmission apparatus performs error correction on the corrected data to reproduce the information.
- FIG. 2 is a schematic diagram illustrating waveforms after subcarrier synthesis.
- FIG. 2 shows the waveform after combining the first subcarrier and the second subcarrier.
- FIG. 3 is a schematic diagram illustrating waveforms after subcarrier synthesis.
- FIG. 3 shows the waveform after combining the first subcarrier and the second subcarrier.
- FIG. 3 shows a case where the frequency characteristic of the I lane ⁇ the frequency characteristic of the Q lane.
- the horizontal axis shown in FIGS. 2 and 3 indicates frequency, and the vertical axis indicates power.
- FIG. 4 is a block diagram illustrating a MIMO equalizer of an optical transmission device and its inputs and outputs.
- IQ mixing performs the first A conjugate component SC2 * of the second subcarrier is generated in the first subcarrier SC1. Also, due to IQ mixing, a conjugate component SC1 * of the first subcarrier is generated in the second subcarrier SC2. That is, IQ mixing occurs due to conjugated components of mutual subcarriers SC. Note that IQ mixing occurs between pairs of subcarriers SC (first subcarrier SC1 and second subcarrier SC2 in FIG. 3) due to differences in delay, amplitude, frequency characteristics, etc. between I and Q lanes. do.
- a conjugate component SC2 * of the second subcarrier and a conjugate component SC1 * of the first subcarrier are generated by IQ mixing.
- a signal having a waveform as shown in FIG. input As a result, a signal having a waveform as shown in FIG. input.
- the conjugate component SC2 * of the second subcarrier and the conjugate component SC1 * of the first subcarrier become interference or noise.
- a MIMO equalizer is a device for compensating for the frequency characteristic difference between the IQs of the receivers of the optical transmission device. Therefore, in an environment where noise is input to the MIMO equalizer, it is difficult to compensate for the frequency characteristic difference between the IQs of the receiver using the MIMO equalizer.
- Embodiment 1 even if the conjugate component SC2 * of the second subcarrier and the conjugate component SC1 * of the first subcarrier are generated by IQ mixing, the MIMO equalizer is not affected by it. make it A specific configuration for preventing the MIMO equalizer from being affected by IQ mixing will be described in the first embodiment.
- FIG. 5 is a block diagram illustrating an optical transmission device according to Embodiment 1.
- FIG. 5 shows the minimum configuration of the optical transmission device according to the first embodiment. For simplicity, FIG. 5 shows only the configuration of the transmission means of the optical transmission device.
- the optical transmission device 11 includes pilot addition means 111 and optical modulation means 112 .
- the pilot adding means 111 adds (inserts) the first pilot signal to the first data signal to generate a first digital signal, adds (inserts) the second pilot signal to the second data signal, and generates a second digital signal. to generate
- the optical transmission device 11 may include data signal generating means for performing processing such as encoding on information to be transmitted to generate a data signal.
- the data signal includes a first data signal and a second data signal.
- the pilot adding means may be called pilot inserting means.
- the first pilot signal and the second pilot signal may be collectively referred to as pilot signals.
- the pilot signal is a known signal that is required to reproduce the data signal.
- the optical modulating means 112 optically modulates the digital subcarrier-multiplexed signal as follows.
- the optical modulating means 112 optically modulates the first digital signal with a first subcarrier SC1 included in a frequency band negative with respect to the center frequency of the frequency band in use, and modulates the first digital signal in a frequency band positive with respect to the center frequency of the frequency band in use.
- the optical modulating means 112 optically modulates the in-phase component SC1-I and the quadrature component SC1-Q of the first digital signal using the first subcarrier SC1, and modulates the second digital signal using the second subcarrier SC2.
- Optical modulation signals are generated by optically modulating the in-phase component SC2-I and the quadrature component SC2-Q. After that, the optical modulation means 112 transmits the generated optical modulation signal.
- the frequency band negative with respect to the center frequency indicates a frequency band lower than the center frequency.
- the positive frequency band with respect to the center frequency indicates a frequency band equal to or higher than the center frequency.
- the optical modulating means 112 may optically modulate each of the first digital signal and the second digital signal using a phase modulation method or a quadrature modulation method.
- the optical modulating means 112 may optically modulate with a Mach-Zender (MZ) type modulator.
- MZ Mach-Zender
- the pilot addition means 111 does not transmit the second pilot signal during transmission of the first pilot signal. Further, the pilot adding means 111 does not transmit the first pilot signal while transmitting the second pilot signal.
- the conjugate component SC2 * of the second subcarrier due to IQ mixing is not generated during the transmission of the first pilot signal of the first subcarrier SC1.
- the conjugate component SC1 * of the first subcarrier due to IQ mixing does not occur.
- the MIMO equalizer can derive the optimum filter coefficients, Reception characteristics do not deteriorate (degrade).
- Embodiment 1 it is possible to provide an optical transmission apparatus, system, method, and non-transitory computer-readable medium capable of reducing noise generated by IQ mixing in a subcarrier multiplexing system. can be done.
- the optical transmission device 11 includes first IQ conversion means for converting the first digital signal into an in-phase component and a quadrature component, and second IQ conversion means for converting the second digital signal into an in-phase component and a quadrature component.
- the optical modulating means 112 optically modulates the in-phase and quadrature components of the first digital signal using the first subcarrier SC1, and modulates the in-phase and quadrature components of the second digital signal using the second subcarrier SC2. is optically modulated to generate an optically modulated signal.
- the optical transmission device 11 may include subcarrier generating means for generating a plurality of subcarriers.
- the first subcarrier SC1 and the second subcarrier SC2 may be selected from a plurality of subcarriers.
- optical modulation means 112 of the optical transmission device 11 may further include optical signal synthesis means for synthesizing the in-phase component and the quadrature component of the optical modulated signal after optical modulation.
- the optical transmission device 11 may also include pilot signal generation means for generating the first pilot signal and the second pilot signal.
- the pilot adding means 111 may alternately transmit the first pilot signal and the second pilot signal.
- the pilot adding means 111 may determine the length of the transmission time for transmitting the first data signal and the length of the transmission time for transmitting the first pilot signal based on the data amount of the first data signal. good. For example, when the data amount of the first data signal is larger than the data amount of the first pilot signal, the pilot adding means 111 sets the length of the transmission time for transmitting the first data signal to the transmission time for transmitting the first pilot signal. Make it longer than the length of time.
- FIG. 6 is a block diagram illustrating an optical transmission device according to Embodiment 1.
- FIG. 6 shows the 2SC XY polarization configuration of the optical transmission device according to the first embodiment.
- FIG. 6 shows only the configuration of the transmission section of the optical transmission device.
- the optical transmission device 11 with a 2SC XY polarization configuration includes pilot addition means 111 , optical modulation means 112 and polarization combining means 113 .
- the pilot adding means 111 adds a first pilot signal to the first data signal to generate a first digital signal, and adds a second pilot signal to the second data signal to generate a second digital signal.
- the pilot addition means 111 adds a third pilot signal to the third data signal to generate a third digital signal, and adds a fourth pilot signal to the fourth data signal to generate a fourth digital signal.
- the optical modulating means 112 optically modulates the first digital signal with the X-polarized wave using the first subcarrier SC1 included in the negative frequency band with respect to the center frequency of the used frequency band, and modulates the first digital signal to the center frequency of the used frequency band.
- the second subcarrier SC2 included in the positive frequency band is used to optically modulate the second digital signal with the X polarization to generate the X optical modulated signal.
- the optical modulating means 112 optically modulates the in-phase component SC1-XI and the quadrature component SC1-XQ of the first digital signal with the X polarization using the first subcarrier SC1, and modulates the second subcarrier SC2. are used to optically modulate the in-phase component SC2-XI and the quadrature component SC2-XQ of the second digital signal with the X-polarized wave to generate an optical modulated signal.
- the optical modulating means 112 optically modulates the third digital signal with the Y-polarized wave using the first subcarrier SC1 included in the negative frequency band with respect to the center frequency of the used frequency band, and modulates the third digital signal to the center frequency of the used frequency band.
- the second subcarrier SC2 included in the positive frequency band is used to optically modulate the fourth digital signal with the Y polarization to generate the Y optical modulated signal.
- the optical modulating means 112 optically modulates the in-phase component SC1-YI and the quadrature component SC1-YQ of the third digital signal with the Y polarization using the first subcarrier SC1, and modulates the second subcarrier SC2. are used to optically modulate the in-phase component SC2-YI and the quadrature component SC2-YQ of the fourth digital signal with the Y-polarization to generate an optical modulated signal.
- the optical modulation means 112 transmits the generated X optical modulated signal and Y optical modulated signal.
- the polarization synthesizing means 113 synthesizes the X optical modulated signal and the Y optical modulated signal.
- the pilot addition means 111 does not transmit the second pilot signal and the fourth pilot signal during transmission of the first pilot signal and the third pilot signal. Also, the pilot adding means 111 does not transmit the first pilot signal and the third pilot signal during transmission of the second pilot signal and the fourth pilot signal.
- FIG. 7 is a block diagram illustrating an optical transmission device according to Embodiment 1.
- FIG. FIG. 7 shows a 4SC configuration of the optical transmission device according to the first embodiment.
- FIG. 7 shows only the configuration of the transmission section of the optical transmission device.
- the 4SC optical transmission device 11 includes pilot addition means 111 and optical modulation means 112 .
- the pilot adding means 111 adds a first pilot signal to the first data signal to generate a first digital signal, and adds a second pilot signal to the second data signal to generate a second digital signal.
- the pilot addition means 111 adds a third pilot signal to the third data signal to generate a third digital signal, and adds a fourth pilot signal to the fourth data signal to generate a fourth digital signal.
- the optical modulating means 112 optically modulates the first digital signal with a first subcarrier SC1 included in a frequency band negative with respect to the center frequency of the used frequency band, optically modulate the second digital signal with the second subcarrier SC2 included in the used frequency band, optically modulate the third digital signal with the third subcarrier SC3 included in the positive frequency band with respect to the center frequency of the used frequency band, and use
- An optically modulated signal is generated by optically modulating the fourth digital signal with a fourth subcarrier SC4 included in a positive frequency band with respect to the center frequency of the frequency band.
- the optical modulating means 112 optically modulates the in-phase component SC1-I and the quadrature component SC1-Q of the first digital signal using the first subcarrier SC1, and modulates the second digital signal using the second subcarrier SC2.
- the in-phase component SC2-I and the quadrature component SC2-Q are each optically modulated, the in-phase component SC3-I and the quadrature component SC3-Q of the third digital signal are optically modulated with the third subcarrier SC3, and the fourth subcarrier SC4 is optically modulates the in-phase component SC4-I and the quadrature component SC4-Q of the fourth digital signal to generate an optically modulated signal.
- the optical modulation means 112 transmits the generated optical modulation signal.
- the pilot adding means 111 does not transmit the third pilot signal and the fourth pilot signal during transmission of the first pilot signal and the second pilot signal. Further, the pilot adding means 111 does not transmit the first pilot signal and the second pilot signal during transmission of the third pilot signal and the fourth pilot signal.
- FIG. 8 is a block diagram illustrating a system according to Embodiment 1.
- FIG. 8 is a block diagram illustrating a system according to Embodiment 1.
- the system 10 includes an optical transmission device 11 and another optical transmission device 12 that receives an optical modulated signal from the optical transmission device 11 via an optical transmission line. Since the optical transmission device 11 has already been explained, the explanation is omitted. An optical transmission device and another optical transmission device have the same function.
- the system may also be referred to as an optical transmission system.
- Another optical transmission device 12 comprises optical signal receiving means 126 , position detecting means 127 and frequency characteristic difference compensating means 128 .
- the optical signal receiving means 126 receives the first digital signal obtained by coherently detecting the modulated optical signal and the second digital signal obtained by coherently detecting the modulated optical signal.
- the position detection means 127 detects the position of the first pilot signal within the first digital signal and the position of the second pilot signal within the second digital signal.
- the frequency characteristic difference compensating means 128 uses the first pilot signal to compensate for the frequency characteristic difference between the in-phase component and the quadrature component of the first data signal.
- the frequency characteristic difference compensating means 128 uses the second pilot signal to compensate for the frequency characteristic difference between the in-phase component and the quadrature component of the second data signal.
- the frequency characteristic difference compensating means 128 has a MIMO (Multi Input Multi Output) equalizer for obtaining the frequency characteristic difference and compensating based on the frequency characteristic difference.
- a MIMO equalizer compensates for the frequency characteristic difference between the in-phase and quadrature components.
- FIG. 9 is a block diagram illustrating a MIMO equalizer according to Embodiment 1.
- FIG. 9 shows a 2x2 MIMO equalizer.
- FIG. 9 shows the case where the first subcarrier SC1 is on and the second subcarrier SC2 is off.
- the frequency characteristic difference compensator 128 has a MIMO (Multi Input Multi Output) equalizer.
- a MIMO equalizer has a plurality of FIR (Finite Impulse Response) filters for compensating for frequency characteristic differences.
- Each of the plurality of FIR filters has filter coefficients.
- h 11 , h 12 , h 21 and h 22 denote filter coefficients of the FIR filter.
- the frequency characteristic difference compensating means 128 uses a MIMO equalizer to detect the frequency characteristic difference of the pilot signal.
- the frequency characteristic difference compensator 128 uses a MIMO equalizer to compensate for the frequency characteristic difference of the data signal based on the detected frequency characteristic difference.
- the frequency characteristic difference between the in-phase component and the quadrature component is mainly due to the devices (parts) mounted in the optical transmission apparatus. Therefore, the fluctuation period of the frequency characteristic difference is in units of minutes or hours. Therefore, adaptive equalization such as a MIMO equalizer is not necessary, and an equalizer with fixed filter coefficients (fixed equalizer) may be used.
- the frequency characteristic difference compensating means 128 may obtain predetermined filter coefficients using a MIMO equalizer in advance before operating the system. Further, the frequency characteristic difference compensating means 128 may acquire predetermined filter coefficients during system operation.
- a MIMO equalizer that uses predetermined filter coefficients obtained in advance in this way is called a fixed equalizer.
- the frequency characteristic difference compensating means 128 may detect the frequency characteristic difference by operating a MIMO equalizer using predetermined filter coefficients obtained in advance. Also, the frequency characteristic difference compensator 128 compensates for the frequency characteristic difference of the data signal based on the detected frequency characteristic difference.
- FIG. 10 is a schematic diagram illustrating how pilot signals are transmitted according to Embodiment 1.
- FIG. The horizontal axis of FIG. 10 indicates time, and the vertical axis indicates frequency.
- 11 is a schematic diagram illustrating an example of a MIMO equalizer and its inputs and outputs in the optical transmission device according to Embodiment 1.
- FIG. 11 shows how the first pilot signal is transmitted.
- 12 is a schematic diagram illustrating the MIMO equalizer and its inputs and outputs in the optical transmission device according to the first embodiment;
- FIG. FIG. 12 shows how the second pilot signal is transmitted.
- IQ mixing occurs between paired subcarriers SC around DC, for example, between the first subcarrier SC1 and the second subcarrier SC2 (see FIG. 3).
- the optical transmission apparatus 11 transmits the first pilot signal of the first subcarrier SC1 while transmitting the first pilot signal of the second subcarrier SC2. 2 Do not transmit pilot signals. Also, the optical transmission device 11 does not transmit the first pilot signal of the first subcarrier SC1 while transmitting the second pilot signal of the second subcarrier SC2. That is, the optical transmission device 11 alternately sets the pairs of subcarriers SC (the first subcarrier SC1 and the second subcarrier SC2) at symmetrical positions with respect to DC on the frequency axis to zero on the time axis. A subcarrier multiplexed signal is generated and transmitted.
- the number of subcarriers SC is not limited to two.
- the number of subcarriers SC may be a number other than 2 as long as it is a multiple of 2 (an even number).
- the optical transmission device 11 periodically and alternately sets the pilot signal of one subcarrier SC to zero, so that the received first subcarrier SC1r has a conjugate of the second subcarrier as shown in FIG. SC2r * is not included. Also, as shown in FIG. 12, the received second subcarrier SC2r does not contain the conjugate SC1r * of the first subcarrier.
- Embodiment 1 it is possible to provide an optical transmission apparatus, system, method, and non-transitory computer-readable medium capable of reducing noise generated by IQ mixing in a subcarrier multiplexing system. can be done.
- the pilot signal may be periodically inserted into the data signal.
- the optical transmission device 11 may sequentially update the filter coefficients of the MIMO equalizer using the pilot signal. Further, since the transmission time of the pilot signal with respect to the entire transmission time is fixed, even if the transmission of the pilot signal of one subcarrier SC is turned off, the transmission capacity of the data signal does not change.
- the first subcarrier SC1r received by another optical transmission device 12 and the conjugate SC1r * of the first subcarrier are input to the MIMO equalizer of the frequency characteristic difference compensation means 128.
- the second subcarrier SC2 is not transmitted during transmission of the first subcarrier SC1 (see FIG. 10). Therefore, the second subcarrier SC2r and the conjugate SC2r * of the second subcarrier are not input to the MIMO equalizer.
- the MIMO equalizer compensates for the frequency characteristic difference between the receivers (receiving units) of another optical transmission device 12.
- the MIMO equalizer compensates for the frequency characteristic difference between IQ based on the pilot signal included in the received first subcarrier SC1r.
- Equation 1 shows the relationship between the first subcarrier SC1 and the received subcarrier SC1r.
- Equation 2 shows the relationship between the second subcarrier SC2 and the received subcarrier SC1r.
- h 11 , h 21 , h 12 , and h 22 denote the filter coefficients of the FIR filters of the MIMO equalizer.
- SC2 0.
- FIG. 13 is a block diagram illustrating a MIMO equalizer according to Embodiment 1.
- FIG. 13 shows a 2x2 MIMO equalizer.
- FIG. 13 shows the case where the first subcarrier SC1 is off and the second subcarrier SC2 is on.
- the second subcarrier SC2r received by another optical transmission device 12 and the conjugate SC2r * of the second subcarrier are input to the MIMO equalizer.
- the first subcarrier SC1 is not transmitted during transmission of the second subcarrier SC2 (see FIG. 10). Therefore, the first subcarrier SC1r and the conjugate SC1r * of the first subcarrier are not input to the MIMO equalizer.
- the MIMO equalizer compensates for the frequency characteristic difference between the receivers (receiving units) of another optical transmission device 12.
- the MIMO equalizer compensates for the frequency characteristic difference between IQ based on the pilot signal contained in the received second subcarrier SC2r.
- Equation 3 shows the relationship between the first subcarrier SC1 and the received subcarrier SC1r.
- SC2 h12SC2r ** + h22SC2r (equation 4)
- the MIMO equalizer obtains the filter coefficients of the FIR filter based on Equations 1, 2, 3 and 4.
- the MIMO equalizer compensates for the frequency characteristic difference between the IQ of the receiving means using the obtained filter coefficients of the FIR filter.
- FIG. 14 is a block diagram illustrating a MIMO equalizer according to Embodiment 1.
- FIG. 14 shows a 4 ⁇ 4 MIMO equalizer for polarization multiplexing of XY polarizations.
- the X-polarized wave SC1xr of the first subcarrier, the Y-polarized wave SC1yr of the first subcarrier, and the X-polarized wave of the second subcarrier are conjugated.
- SC2xr * and the Y-polarized conjugate SC2yr * of the second subcarrier are input.
- the conjugate SC1xr* of the X-polarization of the first subcarrier and the conjugate SC1yr * of the Y-polarization of the first subcarrier and the X-polarization SC2xr* of the second subcarrier are added during another period . and the Y-polarized wave SC2yr of the second subcarrier are input.
- Equation 5 shows the relationship between the X-polarized wave SC1x of the first subcarrier and the received subcarriers (SC1xr, SC1yr, SC2xr * , SC2yr * ).
- Equation 6 shows the relationship between the Y-polarized wave SC1y of the first subcarrier and the received subcarrier.
- Equation 7 shows the relationship between the X-polarized wave SC2x of the second subcarrier and the received subcarrier.
- Equation 8 shows the relationship between the Y-polarized wave SC2y of the second subcarrier and the received subcarrier.
- h11 to h44 indicate the filter coefficients of the FIR filter of the MIMO equalizer.
- SC1x h 11 SC1xr + h 21 SC1yr + h 31 SC2xr * + h 41 SC2yr * (equation 5)
- SC1y h 12 SC1xr + h 22 SC1yr + h 32 SC2xr * + h 42 SC2yr * (equation 6)
- SC2x h13SC1xr * + h23SC1yr * + h33SC2xr + h43SC2yr (equation 7)
- SC2y h14SC1xr * + h24SC1yr * + h34SC2xr + h44SC2yr (equation 8)
- the X-polarized and Y-polarized subcarriers are paired.
- the pilot signals of the X-polarized and Y-polarized subcarriers SC are on/off controlled at the same timing. Specifically, the X polarized wave SC1x of the first subcarrier and the Y polarized wave SC1y of the first subcarrier are on, and the X polarized wave SC2x of the second subcarrier and the Y polarized wave SC2y of the second subcarrier are off. Become.
- the X-polarized wave SC1x of the first subcarrier and the Y-polarized wave SC1y of the first subcarrier are turned off, and the X-polarized wave SC2x of the second subcarrier and the Y-polarized wave SC2y of the second subcarrier are turned on. Since IQ mixing occurs between the I component and the Q component of the X polarized wave and between the I component and the Q component of the Y polarized wave, the X polarized wave and the Y polarized wave may be on/off controlled independently. Specifically, the X-polarized wave SC1x of the first subcarrier is turned on and the X-polarized wave SC2x of the second subcarrier is turned off.
- the Y-polarized wave SC1y of the first subcarrier is turned on and the Y-polarized wave SC2y of the second subcarrier is turned off.
- the subcarrier ON/OFF conditions are not limited to the above conditions. For example, any one subcarrier may be on and all other subcarriers off.
- the MIMO equalizer obtains the filter coefficients of the FIR filter based on Equations 5, 6, 7, 8, and subcarrier on/off conditions.
- the MIMO equalizer uses the obtained filter coefficients of the FIR filter to compensate for the frequency characteristic difference between the IQ of the receiver.
- XY polarization multiplexing can also be supported by using a 4x4 MIMO equalizer.
- the number of subcarriers SC can correspond to an integer multiple of 2 (2, 4, 6, . . . ).
- 2x2 MIMO is used for each set of subcarriers SC.
- one set of 2x2 MIMO is used, and for four subcarriers, two sets of 2x2 MIMO are used.
- the system 20 according to the second embodiment differs from the system 10 according to the first embodiment in that another optical transmission device 12 has light source error compensation means.
- the light source error compensation means compensates for the frequency error between the modulation light source that the optical transmission device 11 has for optical modulation and the detection light source that another optical transmission device 12 has for coherent detection.
- FIG. 15 is a block diagram illustrating a 2 ⁇ 2 MIMO equalizer according to Embodiment 2.
- FIG. A 2 ⁇ 2 MIMO equalizer according to the second embodiment includes frequency error detection means, compensation means, and light source error compensation means.
- Equation 9 shows the relationship between the first subcarrier SC1 and the received subcarriers (SC1r, SC2r * ). Equation 9 shows the relationship between the second subcarrier SC2 and the received subcarriers (SC1r * , SC2r).
- SC1 ( ⁇ fh 11 - ⁇ fh 13 ) SC1r + ( ⁇ fh 21 - ⁇ fh 23 ) SC2r * (equation 9)
- SC2 ( ⁇ fh 12 ⁇ fh 14 )SC1r * +( ⁇ fh 22 ⁇ fh 24 )SC2r (equation 10)
- ⁇ f indicates the frequency error between the light source of the transmitting means of the optical transmission device 11 and the light source of the receiving means of another optical transmission device 12 .
- the MIMO equalizer according to Embodiment 2 uses the obtained filter coefficients of the FIR filter to compensate for the difference in frequency characteristics between the IQs of the transmitting means (transmitting section) and the receiving means (receiving section).
- a system 30 according to the third embodiment differs from the system 10 according to the first embodiment in that another optical transmission device 12 has chromatic dispersion compensating means.
- the chromatic dispersion compensator compensates for the in-phase component and the quadrature component of chromatic dispersion generated by the transmission of the modulated optical signal through the optical transmission line.
- FIG. 16 is a block diagram illustrating a 4 ⁇ 2 MIMO equalizer according to Embodiment 3.
- the first subcarrier SC1 is divided into an in-phase component I SC1 and a quadrature component Q SC1
- the second subcarrier SC2 is divided into an in-phase component I SC2 and a quadrature component Q SC2 .
- the components after passing through a chromatic dispersion compensator (CDC: Chromatic Dispersion Compensation) (components after chromatic dispersion compensation) are I SC1c , Q SC1c , I SC2c and Q SC2 .
- the 4x2 MIMO equalizer according to the third embodiment includes frequency error detection means, compensation means (CDC: Chromatic Dispersion Compensation).
- the chromatic dispersion compensator uses a chromatic dispersion compensator (CDC: Chromatic Dispersion Compensation) to use the in-phase component I SC1 and the quadrature component Q SC1 of the chromatic dispersion of the first subcarrier SC1 and the second
- the in-phase component I SC2 and the quadrature component Q SC2 of the chromatic dispersion of the subcarrier SC2 are compensated.
- a chromatic dispersion compensator is placed, for example, in front of a 4 ⁇ 2 MIMO equalizer.
- the chromatic dispersion compensator may compensate for chromatic dispersion using, for example, a chromatic dispersion compensating filter.
- Embodiment 3 When an IQ signal in which an in-phase component and a quadrature component are mixed is compensated by a chromatic dispersion compensator, IQ mixing occurs. Therefore, in Embodiment 3, the in-phase component (I signal) and the quadrature component (Q signal) are separately compensated for dispersion. This can reduce the occurrence of IQ mixing.
- a first subcarrier SC1, a post-CDC component I SC1c of the received in-phase component of the first subcarrier SC1, a post-CDC component Q SC1c of the quadrature component, and a post-CDC component of the received in-phase component of the second subcarrier SC2 Equation 11 shows the relationship between I SC2c and the component Q SC2c after CDC of the quadrature component.
- the second subcarrier SC2 shows the relationship between the component I SC2c of the quadrature component and the component Q SC2c after CDC of the quadrature component.
- SC1 (h 11 I SC1c + jh 21 Q SC1c ) + (h 31 I * SC2c + jh 41 Q * SC2c ) (Formula 11)
- SC2 ( h12I * SC1c + jh22Q * SC1c ) + ( h32ISC2c + jh42QSC2c ) (Formula 12)
- a system 40 according to the fourth embodiment is a system to which the system 20 according to the second embodiment and the system according to the third embodiment are simultaneously applied.
- FIG. 17 is a block diagram illustrating a 4 ⁇ 2 MIMO equalizer according to Embodiment 4.
- FIG. A 4 ⁇ 2 MIMO equalizer according to Embodiment 4 is preceded by a chromatic dispersion compensator and compensates for the frequency characteristic difference between IQ on the transmitter side and the receiver side.
- Equation 13 The relationship between the first subcarrier SC1, the received in-phase component I SC1 and quadrature component Q SC1 of the first sub-carrier SC1, and the received in-phase component I SC2 and quadrature component Q SC2 of the second sub-carrier SC2 is given by Equation 13. show. Also, the relationship between the second subcarrier SC2, the received in-phase component I SC1 and quadrature component Q SC1 of the first sub-carrier SC1, and the received in-phase component I SC2 and quadrature component Q SC2 of the second sub-carrier SC2 is expressed by the following formula: 14.
- SC1 (( ⁇ fh 11 ⁇ fh 13 )I SC1c +j( ⁇ fh 21 ⁇ fh 23 )Q SC1c ) + (( ⁇ fh 31 ⁇ fh 33 )I * SC2c +j( ⁇ fh 41 ⁇ fh 43 )Q * SC2c ) (Formula 13)
- SC2 (( ⁇ fh 12 ⁇ fh 14 )I * SC1c +j( ⁇ fh 22 ⁇ fh 24 )Q * SC1c ) + (( ⁇ fh 32 ⁇ fh 34 )I SC2c +j( ⁇ fh 42 ⁇ fh 44 )Q SC2c ) (Formula 14)
- Embodiment 5 The system 50 according to Embodiment 5 detects and compensates for the frequency characteristic difference using an equalizer while the plurality of subcarriers SC are independent. For example, when an equalizer is provided in the receiving means of the optical transmission device, the equalizer is provided after separating the plurality of subcarriers SC. Further, for example, when an equalizer is provided in the transmission means of the optical transmission device, the equalizer is provided before combining the plurality of subcarriers SC. Combining may also be referred to as multiplexing.
- FIG. 18 is a schematic diagram illustrating part of the receiving means of the optical transmission device according to the fifth embodiment.
- the received first subcarrier is indicated as SC1r
- the received second subcarrier is indicated as SC2r.
- the second pilot signal of the second subcarrier SC2r is not received while the first pilot signal of the first subcarrier SC1r is received
- the second pilot signal of the second subcarrier SC2r is received while the second pilot signal of the second subcarrier SC2r is received. It does not receive the first pilot signal of 1 subcarrier SC1r.
- FIG. 18 shows the waveform during reception of the first subcarrier SC1r and the waveform during reception of the second subcarrier SC2r. Both the first data signal of the first subcarrier SC1r and the second data signal of the second subcarrier SC1r are received.
- the equalizer compensates for the frequency characteristic difference after separating into the first subcarrier SC1r and the second subcarrier SC2r.
- a first subcarrier SC1 contains a first digital signal and a second subcarrier SC2 contains a second digital signal.
- the IQ mixing is device specific and does not require adaptive equalization like a MIMO equalizer. Therefore, the equalizer according to the fifth embodiment is assumed to be a fixed equalizer.
- a fixed equalizer uses predetermined filter coefficients as equalizer filter coefficients.
- values calculated by an external calculator are used based on the output data of the ADC (see FIG. 1).
- For the filter coefficients of the fixed equalizer for example, values calculated by an external computer in advance by performing the processing of the MIMO equalizer according to any one of the first to fourth embodiments described above are used.
- FIG. 19 is a schematic diagram illustrating part of the transmission means of the optical transmission device according to the fifth embodiment.
- the transmission means of the optical transmission device has a transmission side MIMO.
- An equalizer may be provided.
- An optical transmission apparatus uses an equalizer to compensate for frequency characteristic differences in transmission means.
- the frequency characteristic difference is, for example, the difference in delay and amplitude frequency characteristics between the in-phase component and the quadrature component of the first pilot signal. Also, for example, the frequency characteristic difference is the difference in delay and amplitude frequency characteristics between the in-phase component and the quadrature component of the second pilot signal.
- the optical transmission device has a transmitting side frequency characteristic difference compensating means on the transmitting side in the same way as on the receiving side.
- the transmitting side frequency characteristic difference compensating means uses the first pilot signal to compensate for the transmitting side frequency characteristic difference between the in-phase component and the quadrature component of the first data signal, and uses the second pilot signal to compensate for the transmitting side frequency characteristic difference. Compensating for the transmitter frequency characteristic difference between the in-phase component and the quadrature component of the second data signal.
- the transmitting side frequency characteristic difference compensating means has a transmitting side MIMO equalizer.
- the transmission-side MIMO equalizer has a plurality of transmission-side FIR (Finite Impulse Response) filters for compensating transmission-side frequency characteristic differences.
- Each of the plurality of transmit FIR filters has transmit filter coefficients.
- the transmitting side frequency characteristic difference compensating means compensates for the transmitting side frequency characteristic difference using the transmitting side MIMO equalizer instead of the frequency characteristic difference compensating means of the optical transmission device that receives the subcarrier SC.
- the equalizer according to the fifth embodiment is an equalizer with fixed filter coefficients (fixed equalizer).
- the transmission-side frequency characteristic difference compensating means obtains predetermined transmission-side filter coefficients in advance using the transmission-side MIMO equalizer. Specifically, a value calculated by an external calculator based on the ADC output data (see FIG. 1) is used as the predetermined transmission-side filter coefficient. For the predetermined transmission-side filter coefficient, for example, a value calculated by an external computer in advance by performing the processing of the MIMO equalizer of the above-described second or fourth embodiment is used. After that, the transmitting side frequency characteristic difference compensating means operates the transmitting side MIMO equalizer using the obtained predetermined transmitting side filter coefficient to compensate for the transmitting side frequency characteristic difference.
- the transmitting-side MIMO equalizer (fixed equalizer) set with a predetermined transmitting-side filter coefficient combines the first digital signal of the first subcarrier SC1 and the second digital signal of the second subcarrier SC2. Before, the frequency characteristic difference on the transmitting side is compensated.
- Embodiment 6 The system 60 according to Embodiment 6 compensates for frequency characteristic differences using an equalizer in a state where a plurality of subcarriers SC are multiplexed (combined). For example, when an equalizer is provided in the receiving means of the optical transmission device, the equalizer is provided before separating the plurality of subcarriers SC. Further, for example, when an equalizer is provided in the transmission means of the optical transmission device, the equalizer is provided after combining the plurality of subcarriers SC. Note that multiplexing is sometimes referred to as synthesis.
- FIG. 20 is a schematic diagram illustrating part of the receiving means of the optical transmission device according to the sixth embodiment.
- the received first subcarrier is indicated as SC1r
- the received second subcarrier is indicated as SC2r.
- the second pilot signal of the second subcarrier SC2r is not received while the first pilot signal of the first subcarrier SC1r is received
- the second pilot signal of the second subcarrier SC2r is received while the second pilot signal of the second subcarrier SC2r is received. It does not receive the first pilot signal of 1 subcarrier SC1r.
- the waveform during reception of the first subcarrier SC1r and the waveform during reception of the second subcarrier SC2r are shown superimposed. Both the first data signal of the first subcarrier SC1r and the second data signal of the second subcarrier SC1r are received.
- the SC batch equalizer compensates for the frequency characteristic difference before separating into the first digital signal of the first subcarrier SC1r and the second digital signal of the second subcarrier SC2r.
- the IQ mixing is device specific and does not require adaptive equalization like a MIMO equalizer. Therefore, the SC batch equalizer according to Embodiment 6 is assumed to be a fixed equalizer.
- a fixed equalizer uses predetermined filter coefficients as equalizer filter coefficients. As the filter coefficients of the fixed equalizer, values calculated by an external calculator are used based on the output data of the ADC (see FIG. 1).
- filter coefficients of the fixed equalizer for example, values calculated by an external computer in advance by performing the processing of the MIMO equalizer according to any one of the first to fourth embodiments described above are used. Predetermined filter coefficients are used as the filter coefficients of the SC batch equalizer, and the SC batch equalizer is operated as a fixed equalizer to perform SC batch compensation for the frequency characteristic difference between IQ. Note that the filter coefficients of the SC batch equalizer (fixed equalizer) may be updated periodically.
- FIG. 21 is a schematic diagram exemplifying part of the transmission means of the optical transmission device according to the sixth embodiment.
- the second pilot signal of the second subcarrier SC2 is not transmitted during transmission of the first pilot signal of the first subcarrier SC1
- the second pilot signal of the second subcarrier SC2 is transmitted during transmission of the second pilot signal.
- the first pilot signal of one subcarrier SC1 is not transmitted. Both the first data signal on the first subcarrier SC1 and the second data signal on the second subcarrier SC1 are received.
- the SC batch equalizer on the transmitting side combines the first digital signal of the first subcarrier SC1 and the second digital signal of the second subcarrier SC2, and then calculates the frequency characteristic difference on the transmitting side. Compensate.
- the IQ mixing is device specific and does not require adaptive equalization like a MIMO equalizer. Therefore, the SC batch equalizer on the transmission side according to Embodiment 6 is assumed to be a fixed equalizer.
- a fixed equalizer uses predetermined filter coefficients as equalizer filter coefficients. As the filter coefficients of the fixed equalizer, values calculated by an external calculator are used based on the output data of the ADC (see FIG. 1).
- filter coefficients of the fixed equalizer for example, values calculated by an external computer in advance through the processing of the MIMO equalizer of the second or fourth embodiment are used. Predetermined filter coefficients are used as the filter coefficients of the SC batch equalizer, and the SC batch equalizer is operated as a fixed equalizer to perform SC batch compensation for the frequency characteristic difference between IQ. Note that the filter coefficients of the SC batch equalizer (fixed equalizer) may be updated periodically.
- FIG. 22 is a schematic diagram illustrating how pilot signals are transmitted according to the seventh embodiment.
- FIG. 23 is a schematic diagram illustrating how pilot signals are transmitted according to the seventh embodiment.
- 24 is a schematic diagram illustrating how pilot signals are transmitted according to Embodiment 7.
- FIG. 22 to 24 the horizontal axis indicates time, and the vertical axis indicates frequency.
- the optical transmission device 71 transmits a data signal and a pilot signal in a pattern in which a pilot signal is inserted between a data signal and another data signal.
- the optical transmission device 71 may transmit a pilot signal at all times for the purpose of calibrating a device that causes a frequency characteristic difference between IQs. This transmission pattern is called a first transmission pattern.
- the optical transmission device 71 may transmit pilot signals at all times.
- This transmission pattern is called a second transmission pattern.
- the switching cycle from the first subcarrier SC1 to the second subcarrier SC2 in the second transmission pattern is longer than that in the first transmission pattern.
- the present invention has been described as a hardware configuration in the above embodiment, the present invention is not limited to this.
- the present invention can also be realized by causing a CPU (Central Processing Unit) to execute a computer program to process each component.
- a CPU Central Processing Unit
- Non-transitory computer readable media include various types of tangible storage media.
- Examples of non-transitory computer-readable media include magnetic recording media (specifically flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (specifically magneto-optical discs), CD-ROMs (Read Only Memory ), CD-R, CD-R/W, semiconductor memory (specifically, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM)), flash ROM, and RAM (Random Access Memory).
- the program may also be delivered to the computer on various types of transitory computer readable medium. Examples of transitory computer-readable media include electrical signals, optical signals, and electromagnetic waves. Transitory computer-readable media can deliver the program to the computer via wired channels, such as wires and optical fibers, or wireless channels.
- pilot adding means for adding a first pilot signal to the first data signal to generate a first digital signal and adding a second pilot signal to the second data signal to generate a second digital signal; optically modulating the first digital signal with a first subcarrier included in a frequency band negative with respect to the center frequency of the used frequency band; optical modulation means for optically modulating the second digital signal with two subcarriers to generate an optically modulated signal and transmitting the optically modulated signal; with The pilot adding means is not transmitting the second pilot signal during transmission of the first pilot signal; not transmitting the first pilot signal while transmitting the second pilot signal; Optical transmission equipment.
- Appendix 2 further comprising data signal generating means for generating a data signal by performing encoding processing on information to be transmitted; said data signal comprises said first data signal and said second data signal;
- the optical transmission device according to appendix 1.
- Appendix 3 a first IQ conversion means for converting the first digital signal into an in-phase component and a quadrature component; a second IQ conversion means for converting the second digital signal into an in-phase component and a quadrature component; further comprising
- the light modulating means is optically modulating each of the in-phase component and the quadrature component of the first digital signal with the first subcarrier, and optically modulating each of the in-phase component and the quadrature component of the second digital signal with the second subcarrier; generating a modulated signal, 3.
- the optical transmission device according to appendix 1 or 2.
- the optical modulating means has an optical signal synthesizing means for synthesizing an in-phase component and a quadrature component of the optical modulated signal after optical modulation, 4.
- the optical transmission device according to any one of Appendices 1 to 3.
- (Appendix 5) Further comprising subcarrier generation means for generating a plurality of subcarriers, the first subcarrier and the second subcarrier are selected from within the plurality of subcarriers; 5.
- the optical transmission device according to any one of Appendices 1 to 4.
- the optical modulating means optically modulates each of the first digital signal and the second digital signal by a phase modulation method or a quadrature modulation method, 6.
- the optical transmission device according to any one of Appendices 1 to 5.
- the light modulating means modulates light with a Mach-Zender (MZ) type modulator.
- the optical transmission device according to any one of Appendices 1 to 6.
- Appendix 8) Further comprising pilot signal generating means for generating the first pilot signal and the second pilot signal, 8.
- the optical transmission device according to any one of Appendices 1 to 7.
- the pilot adding means alternately transmits the first pilot signal and the second pilot signal, 9.
- the optical transmission device according to any one of Appendices 1 to 8.
- the pilot adding means determines the length of transmission time for transmitting the first data signal and the length of transmission time for transmitting the first pilot signal based on the data amount of the first data signal; 10.
- the optical transmission device according to any one of Appendices 1 to 9.
- (Appendix 11) adding a first pilot signal to the first data signal to generate a first digital signal; adding a second pilot signal to the second data signal to generate a second digital signal; and adding a third pilot signal to the third data signal.
- pilot adding means for adding the signal to generate a third digital signal and adding a fourth pilot signal to the fourth data signal to generate a fourth digital signal; optically modulating the first digital signal with an X-polarized wave using a first subcarrier contained in a frequency band that is negative with respect to the center frequency of the used frequency band; optically modulating the second digital signal with X polarization using a second subcarrier included in the frequency band to generate an X optical modulated signal; and generating the third digital signal with Y polarization using the first subcarrier optically modulating a signal, optically modulating the fourth digital signal with a Y polarization using the second subcarrier to generate a Y optically modulated signal, and converting the X optically modulated signal and the Y optically modulated signal; optical modulating means for transmitting; polarization synthesis means for synthesizing the X optical modulated signal and the Y optical modulated signal; with The pilot adding means is During transmission of the first pilot signal and the third pilot signal, the second pilot
- pilot adding means for adding the signal to generate a third digital signal and adding a fourth pilot signal to the fourth data signal to generate a fourth digital signal; optically modulating the first digital signal with a first subcarrier included in a frequency band negative with respect to the center frequency of the used frequency band; Optically modulating the second digital signal with two subcarriers, optically modulating the third digital signal with a third subcarrier included in a positive frequency band with respect to the center frequency of the working frequency band, and optically modulating the working frequency optical modulation means for optically modulating the fourth digital signal with a fourth subcarrier included in a positive frequency band with respect to the center frequency of the band to generate an optically modulated signal and transmitting the optically modulated signal; with The pilot adding means is During transmission of the first pilot signal and the second pilot
- an optical transmission device an optical transmission device; another optical transmission device that receives an optical modulated signal from the optical transmission device via an optical transmission line; with The optical transmission device is pilot adding means for adding a first pilot signal to the first data signal to generate a first digital signal and adding a second pilot signal to the second data signal to generate a second digital signal; optically modulating the first digital signal with a first subcarrier included in a frequency band negative with respect to the center frequency of the used frequency band; optical modulation means for optically modulating the second digital signal with two subcarriers to generate the optically modulated signal and transmitting the optically modulated signal; has The pilot adding means is not transmitting the second pilot signal during transmission of the first pilot signal; not transmitting the first pilot signal while transmitting the second pilot signal; Another optical transmission device, optical signal receiving means for receiving the first digital signal obtained by coherently detecting the modulated optical signal and the second digital signal obtained by coherently detecting the modulated optical signal; position detection means for detecting the position of the first pilot signal within the first digital signal and the position of the
- Another optical transmission device includes light source error compensating means for compensating for a frequency error between a modulation light source for optical modulation of the optical transmission device and a detection light source for coherent detection.
- the optical signal receiving means has chromatic dispersion compensating means for compensating in-phase and quadrature components of chromatic dispersion generated when the modulated optical signal is transmitted through the optical transmission line. 15. The system of clause 13 or 14.
- the chromatic dispersion compensation means uses a chromatic dispersion compensator (CDC: Chromatic Dispersion Compensation) to compensate for in-phase and quadrature components of the chromatic dispersion. 16.
- the system of clause 15. (Appendix 17)
- the frequency characteristic difference compensation means has a MIMO (Multi Input Multi Output) equalizer,
- the MIMO equalizer has a plurality of FIR (Finite Impulse Response) filters for compensating for the frequency characteristic difference, each of the plurality of FIR filters has a filter coefficient;
- the frequency characteristic difference compensation means compensates for the frequency characteristic difference using the MIMO equalizer. 14.
- the frequency characteristic difference compensating means includes: Obtaining predetermined said filter coefficients using said MIMO equalizer; operating the MIMO equalizer using the predetermined filter coefficients to compensate for the frequency characteristic difference; 18.
- the system of clause 17. The MIMO equalizer compensates for the frequency characteristic difference after separating the first digital signal and the second digital signal. 19. The system of clause 17 or 18.
- the MIMO equalizer compensates for the frequency characteristic difference before separating the first digital signal and the second digital signal. 19. The system of clause 17 or 18.
- the first pilot signal is used to compensate for a transmitting side frequency characteristic difference between an in-phase component and a quadrature component of the first data signal
- the second pilot signal is used to transmitting side frequency characteristic difference compensating means for compensating for a transmitting side frequency characteristic difference between the in-phase component and the quadrature component of the second data signal
- the transmitting side frequency characteristic difference compensating means has a transmitting side MIMO equalizer
- the transmitting side MIMO equalizer has a plurality of transmitting side FIR (Finite Impulse Response) filters for compensating for the transmitting side frequency characteristic difference, each of the plurality of transmitter FIR filters has a transmitter filter coefficient
- the transmitting side frequency characteristic difference compensating means compensates for the transmitting side frequency characteristic difference using the transmitting side MIMO equalizer instead of the frequency characteristic difference compensating means of another optical transmission device.
- FIR Finite Impulse Response
- the transmitting side frequency characteristic difference compensating means includes: Obtaining the predetermined transmitting-side filter coefficients using the transmitting-side MIMO equalizer; compensating for the transmission-side frequency characteristic difference by operating the transmission-side MIMO equalizer using the predetermined transmission-side filter coefficients; 22.
- the transmitting side MIMO equalizer compensates for the transmitting side frequency characteristic difference before combining the first digital signal and the second digital signal. 23.
- the system of clause 22. (Appendix 24)
- the transmitting-side MIMO equalizer compensates for the transmitting-side frequency characteristic difference after combining the first digital signal and the second digital signal. 23.
- optical transmission device 111 pilot adding means 112: optical modulation means 113: polarization combining means 12: another optical transmission device 126: optical signal receiving means 127 : position detection means 128: frequency characteristic difference compensation means SC: subcarrier SC1: first subcarrier SC2: second subcarrier SC3: third subcarrier SC4: fourth subcarrier
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Abstract
Description
第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成するパイロット付加手段と、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調して光変調信号を生成し、前記光変調信号を送信する光変調手段と、
を備え、
前記パイロット付加手段は、
前記第1パイロット信号の送信中は、前記第2パイロット信号を送信せず、
前記第2パイロット信号を送信中は、前記第1パイロット信号を送信しない。
第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成し、第3データ信号に第3パイロット信号を付加して第3デジタル信号を生成し、第4データ信号に第4パイロット信号を付加して第4デジタル信号を生成するパイロット付加手段と、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアを使用しX偏波で前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアを使用しX偏波で前記第2デジタル信号を光変調してX光変調信号を生成し、前記第1サブキャリアを使用しY偏波で前記第3デジタル信号を光変調して、前記第2サブキャリアを使用しY偏波で前記第4デジタル信号を光変調してY光変調信号を生成し、前記X光変調信号と前記Y光変調信号とを送信する光変調手段と、
前記X光変調信号と、前記Y光変調信号と、を合成する偏波合成手段と、
を備え、
前記パイロット付加手段は、
前記第1パイロット信号と前記第3パイロット信号の送信中は、前記第2パイロット信号と前記第4パイロット信号を送信せず、
前記第2パイロット信号と前記第4パイロット信号の送信中は、前記第1パイロット信号と前記第3パイロット信号を送信しない。
第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成し、第3データ信号に第3パイロット信号を付加して第3デジタル信号を生成し、第4データ信号に第4パイロット信号を付加して第4デジタル信号を生成するパイロット付加手段と、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して負の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第3サブキャリアで前記第3デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第4サブキャリアで前記第4デジタル信号を光変調して光変調信号を生成し、前記光変調信号を送信する光変調手段と、
を備え、
前記パイロット付加手段は、
前記第1パイロット信号と前記第2パイロット信号の送信中は、前記第3パイロット信号と前記第4パイロット信号を送信せず、
前記第3パイロット信号と前記第4パイロット信号の送信中は、前記第1パイロット信号と前記第2パイロット信号を送信しない。
光伝送装置と、
前記光伝送装置から光伝送路を介して光変調信号を受光する別の前記光伝送装置と、
を備え、
前記光伝送装置は、
第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成するパイロット付加手段と、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調して前記光変調信号を生成し、前記光変調信号を送信する光変調手段と、
を有し、
前記パイロット付加手段は、
前記第1パイロット信号の送信中は、前記第2パイロット信号を送信せず、
前記第2パイロット信号を送信中は、前記第1パイロット信号を送信せず、
別の前記光伝送装置は、
前記光変調信号をコヒーレント検波した前記第1デジタル信号と、前記光変調信号を前記コヒーレント検波した前記第2デジタル信号と、を受信する光信号受信手段と、
前記第1デジタル信号内の前記第1パイロット信号の位置と、前記第2デジタル信号内の前記第2パイロット信号の位置と、を検出する位置検出手段と、
前記第1パイロット信号と前記第2パイロット信号とを用いて、前記第1データ信号の同相成分と直交成分との間の周波数特性差と、前記第2データ信号の同相成分と直交成分との間の周波数特性差と、を補償する周波数特性差補償手段と、
を有する。
第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成することと、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調して光変調信号を生成し、前記光変調信号を送信することと、
前記第1パイロット信号の送信中は、前記第2パイロット信号を送信しないことと、
前記第2パイロット信号を送信中は、前記第1パイロット信号を送信しないことと、
を備える。
第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成することと、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調して光変調信号を生成し、前記光変調信号を送信することと、
前記第1パイロット信号の送信中は、前記第2パイロット信号を送信しないことと、
前記第2パイロット信号を送信中は、前記第1パイロット信号を送信しないことと、
をコンピュータに実行させるプログラムが格納される。
先ず、課題の詳細を説明する。
図1は、デジタルコヒーレント光伝送システムを例示するブロック図である。
図2は、第1サブキャリアと第2サブキャリアとを合成した後の波形を示す。
図2は、Iレーンの周波数特性=Qレーンの周波数特性の場合を示す。
図3は、サブキャリア合成後の波形を例示する模式図である。
図3は、第1サブキャリアと第2サブキャリアとを合成した後の波形を示す。
図3は、Iレーンの周波数特性≠Qレーンの周波数特性の場合を示す。
図2及び図3に示す横軸は周波数を示し、縦軸は電力を示す。
図4は、光伝送装置のMIMO等化器とその入出力を例示するブロック図である。
<装置の構成:2SC構成(最小構成)>
図5は、実施の形態1に係る光伝送装置を例示するブロック図である。
図5は、実施の形態1に係る光伝送装置の最小構成を示す。
図5は、簡単のため、光伝送装置の送信手段の構成だけを示す。
光変調手段112は、使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアSC1で第1デジタル信号を光変調し、使用周波数帯域の中心周波数に対して正の周波数帯域に含まれる第2サブキャリアSC2で第2デジタル信号を光変調して光変調信号を生成する。具体的には、光変調手段112は、第1サブキャリアSC1で第1デジタル信号の同相成分SC1-Iと直交成分SC1-Qをそれぞれ光変調し、第2サブキャリアSC2で第2デジタル信号の同相成分SC2-Iと直交成分SC2-Qをそれぞれ光変調して光変調信号を生成する。その後、光変調手段112は、生成した光変調信号を送信する。なお、中心周波数に対して負の周波数帯域とは、中心周波数よりも低い周波数帯域を示す。また、中心周波数に対して正の周波数帯域とは、中心周波数以上の周波数帯域を示す。
2サブキャリアのXY偏波構成の場合を説明する。
図6は、実施の形態1に係る光伝送装置を例示するブロック図である。
図6は、実施の形態1に係る光伝送装置の2SCのXY偏波構成を示す。
図6は、簡単のため、光伝送装置の送信部の構成だけを示す。
4サブキャリア構成の場合を説明する。
図7は、実施の形態1に係る光伝送装置を例示するブロック図である。
図7は、実施の形態1に係る光伝送装置の4SC構成を示す。
図7は、簡単のため、光伝送装置の送信部の構成だけを示す。
システム構成を説明する。
図8は、実施の形態1に係るシステムを例示するブロック図である。
図9は、2x2MIMO等化器を示す。
図9は、第1サブキャリアSC1がオンで第2サブキャリアSC2がオフの場合を示す。
実施の形態1に係る光伝送装置の動作を説明する。
図10は、実施の形態1に係るパイロット信号の送信の様子を例示する模式図である。
図10の横軸は時間を示し、縦軸は周波数を示す。
図11は、実施の形態1に係る光伝送装置のMIMO等化器とその入出力を例示する模式図である。
図11は、第1パイロット信号の送信時の様子を示す。
図12は、実施の形態1に係る光伝送装置のMIMO等化器とその入出力を例示する模式図である。
図12は、第2パイロット信号の送信時の様子を示す。
<2x2MIMО>
ここで、別の光伝送装置12(光伝送装置11でもよい)に設けられるMIMО等化器の具体例について説明する。2x2MIMОを説明する。
SC2=h12SC1r*+h22SC1r*=0 (式2)
図13は、2x2MIMO等化器を示す。
図13は、第1サブキャリアSC1がオフで第2サブキャリアSC2がオンの場合を示す。
SC2=h12SC2r**+h22SC2r (式4)
4x4MIMОを説明する。
図14は、実施の形態1に係るMIMО等化器を例示するブロック図である。
図14は、XY偏波の偏波多重の場合の4x4MIMO等化器を示す。
=h11SC1xr+h21SC1yr+h31SC2xr*+h41SC2yr* (式5)
SC1y
=h12SC1xr+h22SC1yr+h32SC2xr*+h42SC2yr* (式6)
SC2x
=h13SC1xr*+h23SC1yr*+h33SC2xr+h43SC2yr (式7)
SC2y
=h14SC1xr*+h24SC1yr*+h34SC2xr+h44SC2yr (式8)
実施の形態2に係るシステム20は、実施の形態1に係るシステム10と比べて、別の光伝送装置12が光源誤差補償手段を有する点が異なる。光源誤差補償手段は、光伝送装置11が光変調するために有する変調用光源と、別の光伝送装置12がコヒーレント検波するために有する検波用光源と、の間の周波数誤差を補償する。
実施の形態2に係る2x2MIMO等化器は、周波数誤差検出手段と補償手段と光源誤差補償手段とを含む。
=(Δfh11-Δfh13)SC1r+(Δfh21-Δfh23)SC2r* (式9)
SC2
=(Δfh12-Δfh14)SC1r*+(Δfh22-Δfh24)SC2r (式10)
ただし、Δfは、光伝送装置11の送信手段の光源と、別の光伝送装置12の受信手段の光源と、の間の周波数誤差を示す。
実施の形態2に係るMIMО等化器は、求めたFIRフィルタのフィルタ係数を用いて送信手段(送信部)と受信手段(受信部)それぞれのIQ間の周波数特性差を補償する。
実施の形態3に係るシステム30は、実施の形態1に係るシステム10と比べて、別の光伝送装置12が波長分散補償手段を有する点が異なる。波長分散補償手段は、光変調信号が光伝送路を伝送することよって発生する波長分散の同相成分と直交成分とを補償する。
図16では、第1サブキャリアSC1を同相成分ISC1と直交成分QSC1とに分け、第2サブキャリアSC2を同相成分ISC2と直交成分QSC2とに分けた。また、波長分散補償器(CDC:Chromatic Dispersion Compensation)を通過した後の成分(波長分散補償後の成分)をISC1c、QSC1c、ISC2c、QSC2とした。
実施の形態3に係る4x2MIMO等化器は、周波数誤差検出手段と補償手段と(CDC:Chromatic Dispersion Compensation)とを含む。
=(h11ISC1c+jh21QSC1c)+(h31I* SC2c+jh41Q* SC2c)
(式11)
SC2
=(h12I* SC1c+jh22Q* SC1c)+(h32ISC2c+jh42QSC2c)
(式12)
実施の形態4に係るシステム40は、実施の形態2に係るシステム20と実施の形態3に係るシステムとを同時に適用したシステムである。
実施の形態4に係る4x2MIMO等化器は、波長分散補償器が前段に配置され、送信機側と受信機側のIQ間の周波数特性差を補償する。
=((Δfh11-Δfh13)ISC1c+j(Δfh21-Δfh23)QSC1c)
+((Δfh31-Δfh33)I* SC2c+j(Δfh41-Δfh43)Q* SC2c)
(式13)
SC2
=((Δfh12-Δfh14)I* SC1c+j(Δfh22-Δfh24)Q* SC1c)
+((Δfh32-Δfh34)ISC2c+j(Δfh42-Δfh44)QSC2c)
(式14)
実施の形態5に係るシステム50は、複数のサブキャリアSCがそれぞれ独立している状態で等化器を用いて周波数特性差を検出し補償する。例えば、光伝送装置の受信手段に等化器が設けられる場合、複数のサブキャリアSCの分離後に等化器が設けられる。また、例えば、光伝送装置の送信手段に等化器が設けられる場合、複数のサブキャリアSCの合成前に等化器が設けられる。なお、合成を多重と称することもある。
等化器が複数のサブキャリアSCの分離後に設けられる場合を説明する。
図18は、実施の形態5に係る光伝送装置の受信手段の一部を例示する模式図である。
図18では、受信した第1サブキャリアをSC1rとし、受信した第2サブキャリアをSC2rとして示す。
実施の形態5では、第1サブキャリアSC1rの第1パイロット信号の受信中は第2サブキャリアSC2rの第2パイロット信号を受信せず、第2サブキャリアSC2rの第2パイロット信号の受信中は第1サブキャリアSC1rの第1パイロット信号を受信しない。図18では、簡単のため、第1サブキャリアSC1rの受信中の波形と、第2サブキャリアSC2rの受信中の波形と、を重ねて示す。なお、第1サブキャリアSC1rの第1データ信号と第2サブキャリアSC1rの第2データ信号は、どちらも受信する。
等化器が複数のサブキャリアSCの合成前に設けられる場合を説明する。
図19は、実施の形態5に係る光伝送装置の送信手段の一部を例示する模式図である。
実施の形態6に係るシステム60は、複数のサブキャリアSCが多重(合成)した状態で等化器を用いて周波数特性差を補償する。例えば、光伝送装置の受信手段に等化器が設けられる場合、複数のサブキャリアSCの分離前に等化器が設けられる。また、例えば、光伝送装置の送信手段に等化器が設けられる場合、複数のサブキャリアSCの合成後に等化器が設けられる。なお、多重を合成と称することもある。
等化器が複数のサブキャリアSCの分離前に設けられる場合を説明する。
図20は、実施の形態6に係る光伝送装置の受信手段の一部を例示する模式図である。
図20では、受信した第1サブキャリアをSC1rとし、受信した第2サブキャリアをSC2rとして示す。
実施の形態6では、第1サブキャリアSC1rの第1パイロット信号の受信中は第2サブキャリアSC2rの第2パイロット信号を受信せず、第2サブキャリアSC2rの第2パイロット信号の受信中は第1サブキャリアSC1rの第1パイロット信号を受信しない。図20では、簡単のため、第1サブキャリアSC1rの受信中の波形と、第2サブキャリアSC2rの受信中の波形と、を重ねて示す。なお、第1サブキャリアSC1rの第1データ信号と第2サブキャリアSC1rの第2データ信号は、どちらも受信する。
等化器が複数のサブキャリアSCの合成後に設けられる場合を説明する。
実施の形態6では、第1サブキャリアSC1の第1パイロット信号の送信中は第2サブキャリアSC2の第2パイロット信号を送信せず、第2サブキャリアSC2の第2パイロット信号の送信中は第1サブキャリアSC1の第1パイロット信号を送信しない。なお、第1サブキャリアSC1の第1データ信号と第2サブキャリアSC1の第2データ信号は、どちらも受信する。
実施の形態7に係る光伝送装置71は、サブキャリアSCの送信パターンに特徴がある。
図22は、実施の形態7に係るパイロット信号の送信の様子を例示する模式図である。
図23は、実施の形態7に係るパイロット信号の送信の様子を例示する模式図である。
図24は、実施の形態7に係るパイロット信号の送信の様子を例示する模式図である。
図22から図24の横軸は時間を示し、縦軸は周波数を示す。
(付記1)
第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成するパイロット付加手段と、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調して光変調信号を生成し、前記光変調信号を送信する光変調手段と、
を備え、
前記パイロット付加手段は、
前記第1パイロット信号の送信中は、前記第2パイロット信号を送信せず、
前記第2パイロット信号を送信中は、前記第1パイロット信号を送信しない、
光伝送装置。
(付記2)
送信すべき情報に符号化処理をしてデータ信号を生成するデータ信号生成手段をさらに備え、
前記データ信号は前記第1データ信号と前記第2データ信号とを含む、
付記1に記載の光伝送装置。
(付記3)
前記第1デジタル信号を同相成分と直交成分とに変換する第1IQ変換手段と、
前記第2デジタル信号を同相成分と直交成分とに変換する第2IQ変換手段と、
をさらに備え、
前記光変調手段は、
前記第1サブキャリアで前記第1デジタル信号の同相成分と直交成分のそれぞれを光変調し、前記第2サブキャリアで前記第2デジタル信号の同相成分と直交成分のそれぞれを光変調して前記光変調信号を生成する、
付記1又は2に記載の光伝送装置。
(付記4)
前記光変調手段は、光変調後の前記光変調信号の同相成分と直交成分とを合成する光信号合成手段を有する、
付記1から3のいずれか1つに記載の光伝送装置。
(付記5)
複数のサブキャリアを生成するサブキャリア生成手段をさらに備え、
前記第1サブキャリアと前記第2サブキャリアは、前記複数のサブキャリア内から選択される、
付記1から4のいずれか1つに記載の光伝送装置。
(付記6)
前記光変調手段は、前記第1デジタル信号と前記第2デジタル信号のそれぞれを位相変調方式又は直交変調方式で光変調する、
付記1から5のいずれか1つに記載の光伝送装置。
(付記7)
前記光変調手段は、マッハツェンダー(MZ:Mach-Zender)型変調器で光変調する、
付記1から6のいずれか1つに記載の光伝送装置。
(付記8)
前記第1パイロット信号と前記第2パイロット信号とを生成するパイロット信号生成手段をさらに備える、
付記1から7のいずれか1つに記載の光伝送装置。
(付記9)
前記パイロット付加手段は、前記第1パイロット信号と前記第2パイロット信号とを、交互に送信する、
付記1から8のいずれか1つに記載の光伝送装置。
(付記10)
前記パイロット付加手段は、前記第1データ信号のデータ量に基づいて、前記第1データ信号を送信する送信時間の長さと、前記第1パイロット信号を送信する送信時間の長さと、を決定する、
付記1から9のいずれか1つに記載の光伝送装置。
(付記11)
第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成し、第3データ信号に第3パイロット信号を付加して第3デジタル信号を生成し、第4データ信号に第4パイロット信号を付加して第4デジタル信号を生成するパイロット付加手段と、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアを使用しX偏波で前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアを使用しX偏波で前記第2デジタル信号を光変調してX光変調信号を生成し、前記第1サブキャリアを使用しY偏波で前記第3デジタル信号を光変調して、前記第2サブキャリアを使用しY偏波で前記第4デジタル信号を光変調してY光変調信号を生成し、前記X光変調信号と前記Y光変調信号とを送信する光変調手段と、
前記X光変調信号と、前記Y光変調信号と、を合成する偏波合成手段と、
を備え、
前記パイロット付加手段は、
前記第1パイロット信号と前記第3パイロット信号の送信中は、前記第2パイロット信号と前記第4パイロット信号を送信せず、
前記第2パイロット信号と前記第4パイロット信号の送信中は、前記第1パイロット信号と前記第3パイロット信号を送信しない、
光伝送装置。
(付記12)
第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成し、第3データ信号に第3パイロット信号を付加して第3デジタル信号を生成し、第4データ信号に第4パイロット信号を付加して第4デジタル信号を生成するパイロット付加手段と、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して負の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第3サブキャリアで前記第3デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第4サブキャリアで前記第4デジタル信号を光変調して光変調信号を生成し、前記光変調信号を送信する光変調手段と、
を備え、
前記パイロット付加手段は、
前記第1パイロット信号と前記第2パイロット信号の送信中は、前記第3パイロット信号と前記第4パイロット信号を送信せず、
前記第3パイロット信号と前記第4パイロット信号の送信中は、前記第1パイロット信号と前記第2パイロット信号を送信しない、
光伝送装置。
(付記13)
光伝送装置と、
前記光伝送装置から光伝送路を介して光変調信号を受光する別の前記光伝送装置と、
を備え、
前記光伝送装置は、
第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成するパイロット付加手段と、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調して前記光変調信号を生成し、前記光変調信号を送信する光変調手段と、
を有し、
前記パイロット付加手段は、
前記第1パイロット信号の送信中は、前記第2パイロット信号を送信せず、
前記第2パイロット信号を送信中は、前記第1パイロット信号を送信せず、
別の前記光伝送装置は、
前記光変調信号をコヒーレント検波した前記第1デジタル信号と、前記光変調信号を前記コヒーレント検波した前記第2デジタル信号と、を受信する光信号受信手段と、
前記第1デジタル信号内の前記第1パイロット信号の位置と、前記第2デジタル信号内の前記第2パイロット信号の位置と、を検出する位置検出手段と、
前記第1パイロット信号を用いて前記第1データ信号の同相成分と直交成分との間の周波数特性差を補償し、前記第2パイロット信号とを用いて前記第2データ信号の同相成分と直交成分との間の周波数特性差を補償する周波数特性差補償手段と、
を有する、
システム。
(付記14)
別の前記光伝送装置は、前記光伝送装置が光変調するために有する変調用光源と、前記コヒーレント検波するための検波用光源と、の間の周波数誤差を補償するための光源誤差補償手段を有する、
付記13に記載のシステム。
(付記15)
前記光信号受信手段は、前記光変調信号が前記光伝送路を伝送することよって発生する波長分散の同相成分と直交成分とを補償する波長分散補償手段を有する、
付記13又は14に記載のシステム。
(付記16)
前記波長分散補償手段は、波長分散補償器(CDC:Chromatic Dispersion Compensation)を用いて、前記波長分散の同相成分と直交成分を補償する、
付記15に記載のシステム。
(付記17)
前記周波数特性差補償手段は、MIMO(Multi Input Multi Output)等化器を有し、
前記MIMО等化器は、前記周波数特性差を補償するための複数のFIR(Finite Impulse Response)フィルタを有し、
複数の前記FIRフィルタのそれぞれは、フィルタ係数を有し、
前記周波数特性差補償手段は、前記MIMО等化器を用いて、前記周波数特性差を補償する、
付記13に記載のシステム。
(付記18)
前記周波数特性差補償手段は、
前記MIMО等化器を用いて所定の前記フィルタ係数を求め、
所定の前記フィルタ係数を用いて前記MIMО等化器を動作させて前記周波数特性差を補償する、
付記17に記載のシステム。
(付記19)
前記MIMО等化器は、前記第1デジタル信号と前記第2デジタル信号に分離した後に、前記周波数特性差を補償する、
付記17又は18に記載のシステム。
(付記20)
前記MIMО等化器は、前記第1デジタル信号と前記第2デジタル信号に分離する前に、前記周波数特性差を補償する、
付記17又は18に記載のシステム。
(付記21)
前記光伝送装置は、送信側において、前記第1パイロット信号を用いて前記第1データ信号の同相成分と直交成分との間の送信側周波数特性差を補償し、前記第2パイロット信号を用いて前記第2データ信号の同相成分と直交成分との間の送信側周波数特性差を補償する送信側周波数特性差補償手段を有し、
前記送信側周波数特性差補償手段は、送信側MIMO等化器を有し、
前記送信側MIMO等化器は、前記送信側周波数特性差を補償するための複数の送信側FIR(Finite Impulse Response)フィルタを有し、
複数の前記送信側FIRフィルタのそれぞれは、送信側フィルタ係数を有し、
前記送信側周波数特性差補償手段は、別の前記光伝送装置の前記周波数特性差補償手段の代わりに前記送信側MIMO等化器を用いて、前記送信側周波数特性差を補償する、
付記13に記載のシステム。
(付記22)
前記送信側周波数特性差補償手段は、
前記送信側MIMO等化器を用いて所定の前記送信側フィルタ係数を求め、
所定の前記送信側フィルタ係数を用いて前記送信側MIMO等化器を動作させて前記送信側周波数特性差を補償する、
付記21記載のシステム。
(付記23)
前記送信側MIMO等化器は、前記第1デジタル信号と前記第2デジタル信号に合成する前に、前記送信側周波数特性差を補償する、
付記22に記載のシステム。
(付記24)
前記送信側MIMO等化器は、前記第1デジタル信号と前記第2デジタル信号を合成した後に、前記送信側周波数特性差を補償する、
付記21又は22に記載のシステム。
(付記25)
第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成することと、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調して光変調信号を生成し、前記光変調信号を送信することと、
前記第1パイロット信号の送信中は、前記第2パイロット信号を送信しないことと、
前記第2パイロット信号を送信中は、前記第1パイロット信号を送信しないことと、
を備える方法。
(付記26)
第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成することと、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調して光変調信号を生成し、前記光変調信号を送信することと、
前記第1パイロット信号の送信中は、前記第2パイロット信号を送信しないことと、
前記第2パイロット信号を送信中は、前記第1パイロット信号を送信しないことと、
をコンピュータに実行させるプログラムが格納される非一時的なコンピュータ可読媒体。
11、71:光伝送装置
111:パイロット付加手段
112:光変調手段
113:偏波合成手段
12:別の光伝送装置
126:光信号受信手段
127:位置検出手段
128:周波数特性差補償手段
SC:サブキャリア
SC1:第1サブキャリア
SC2:第2サブキャリア
SC3:第3サブキャリア
SC4:第4サブキャリア
Claims (26)
- 第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成するパイロット付加手段と、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調して光変調信号を生成し、前記光変調信号を送信する光変調手段と、
を備え、
前記パイロット付加手段は、
前記第1パイロット信号の送信中は、前記第2パイロット信号を送信せず、
前記第2パイロット信号を送信中は、前記第1パイロット信号を送信しない、
光伝送装置。 - 送信すべき情報に符号化処理をしてデータ信号を生成するデータ信号生成手段をさらに備え、
前記データ信号は前記第1データ信号と前記第2データ信号とを含む、
請求項1に記載の光伝送装置。 - 前記第1デジタル信号を同相成分と直交成分とに変換する第1IQ変換手段と、
前記第2デジタル信号を同相成分と直交成分とに変換する第2IQ変換手段と、
をさらに備え、
前記光変調手段は、
前記第1サブキャリアで前記第1デジタル信号の同相成分と直交成分のそれぞれを光変調し、前記第2サブキャリアで前記第2デジタル信号の同相成分と直交成分のそれぞれを光変調して前記光変調信号を生成する、
請求項1又は2に記載の光伝送装置。 - 前記光変調手段は、光変調後の前記光変調信号の同相成分と直交成分とを合成する光信号合成手段を有する、
請求項1から3のいずれか1つに記載の光伝送装置。 - 複数のサブキャリアを生成するサブキャリア生成手段をさらに備え、
前記第1サブキャリアと前記第2サブキャリアは、前記複数のサブキャリア内から選択される、
請求項1から4のいずれか1つに記載の光伝送装置。 - 前記光変調手段は、前記第1デジタル信号と前記第2デジタル信号のそれぞれを位相変調方式又は直交変調方式で光変調する、
請求項1から5のいずれか1つに記載の光伝送装置。 - 前記光変調手段は、マッハツェンダー(MZ:Mach-Zender)型変調器で光変調する、
請求項1から6のいずれか1つに記載の光伝送装置。 - 前記第1パイロット信号と前記第2パイロット信号とを生成するパイロット信号生成手段をさらに備える、
請求項1から7のいずれか1つに記載の光伝送装置。 - 前記パイロット付加手段は、前記第1パイロット信号と前記第2パイロット信号とを、交互に送信する、
請求項1から8のいずれか1つに記載の光伝送装置。 - 前記パイロット付加手段は、前記第1データ信号のデータ量に基づいて、前記第1データ信号を送信する送信時間の長さと、前記第1パイロット信号を送信する送信時間の長さと、を決定する、
請求項1から9のいずれか1つに記載の光伝送装置。 - 第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成し、第3データ信号に第3パイロット信号を付加して第3デジタル信号を生成し、第4データ信号に第4パイロット信号を付加して第4デジタル信号を生成するパイロット付加手段と、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアを使用しX偏波で前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアを使用しX偏波で前記第2デジタル信号を光変調してX光変調信号を生成し、前記第1サブキャリアを使用しY偏波で前記第3デジタル信号を光変調して、前記第2サブキャリアを使用しY偏波で前記第4デジタル信号を光変調してY光変調信号を生成し、前記X光変調信号と前記Y光変調信号とを送信する光変調手段と、
前記X光変調信号と、前記Y光変調信号と、を合成する偏波合成手段と、
を備え、
前記パイロット付加手段は、
前記第1パイロット信号と前記第3パイロット信号の送信中は、前記第2パイロット信号と前記第4パイロット信号を送信せず、
前記第2パイロット信号と前記第4パイロット信号の送信中は、前記第1パイロット信号と前記第3パイロット信号を送信しない、
光伝送装置。 - 第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成し、第3データ信号に第3パイロット信号を付加して第3デジタル信号を生成し、第4データ信号に第4パイロット信号を付加して第4デジタル信号を生成するパイロット付加手段と、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して負の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第3サブキャリアで前記第3デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第4サブキャリアで前記第4デジタル信号を光変調して光変調信号を生成し、前記光変調信号を送信する光変調手段と、
を備え、
前記パイロット付加手段は、
前記第1パイロット信号と前記第2パイロット信号の送信中は、前記第3パイロット信号と前記第4パイロット信号を送信せず、
前記第3パイロット信号と前記第4パイロット信号の送信中は、前記第1パイロット信号と前記第2パイロット信号を送信しない、
光伝送装置。 - 光伝送装置と、
前記光伝送装置から光伝送路を介して光変調信号を受光する別の前記光伝送装置と、
を備え、
前記光伝送装置は、
第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成するパイロット付加手段と、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調して前記光変調信号を生成し、前記光変調信号を送信する光変調手段と、
を有し、
前記パイロット付加手段は、
前記第1パイロット信号の送信中は、前記第2パイロット信号を送信せず、
前記第2パイロット信号を送信中は、前記第1パイロット信号を送信せず、
別の前記光伝送装置は、
前記光変調信号をコヒーレント検波した前記第1デジタル信号と、前記光変調信号を前記コヒーレント検波した前記第2デジタル信号と、を受信する光信号受信手段と、
前記第1デジタル信号内の前記第1パイロット信号の位置と、前記第2デジタル信号内の前記第2パイロット信号の位置と、を検出する位置検出手段と、
前記第1パイロット信号を用いて前記第1データ信号の同相成分と直交成分との間の周波数特性差を補償し、前記第2パイロット信号とを用いて前記第2データ信号の同相成分と直交成分との間の周波数特性差を補償する周波数特性差補償手段と、
を有する、
システム。 - 別の前記光伝送装置は、前記光伝送装置が光変調するために有する変調用光源と、前記コヒーレント検波するための検波用光源と、の間の周波数誤差を補償するための光源誤差補償手段を有する、
請求項13に記載のシステム。 - 前記光信号受信手段は、前記光変調信号が前記光伝送路を伝送することよって発生する波長分散の同相成分と直交成分とを補償する波長分散補償手段を有する、
請求項13又は14に記載のシステム。 - 前記波長分散補償手段は、波長分散補償器(CDC:Chromatic Dispersion Compensation)を用いて、前記波長分散の同相成分と直交成分を補償する、
請求項15に記載のシステム。 - 前記周波数特性差補償手段は、MIMO(Multi Input Multi Output)等化器を有し、
前記MIMО等化器は、前記周波数特性差を補償するための複数のFIR(Finite Impulse Response)フィルタを有し、
複数の前記FIRフィルタのそれぞれは、フィルタ係数を有し、
前記周波数特性差補償手段は、前記MIMО等化器を用いて、前記周波数特性差を補償する、
請求項13に記載のシステム。 - 前記周波数特性差補償手段は、
前記MIMО等化器を用いて所定の前記フィルタ係数を求め、
所定の前記フィルタ係数を用いて前記MIMО等化器を動作させて前記周波数特性差を補償する、
請求項17に記載のシステム。 - 前記MIMО等化器は、前記第1デジタル信号と前記第2デジタル信号に分離した後に、前記周波数特性差を補償する、
請求項17又は18に記載のシステム。 - 前記MIMО等化器は、前記第1デジタル信号と前記第2デジタル信号に分離する前に、前記周波数特性差を補償する、
請求項17又は18に記載のシステム。 - 前記光伝送装置は、送信側において、前記第1パイロット信号を用いて前記第1データ信号の同相成分と直交成分との間の送信側周波数特性差を補償し、前記第2パイロット信号を用いて前記第2データ信号の同相成分と直交成分との間の送信側周波数特性差を補償する送信側周波数特性差補償手段を有し、
前記送信側周波数特性差補償手段は、送信側MIMO等化器を有し、
前記送信側MIMO等化器は、前記送信側周波数特性差を補償するための複数の送信側FIR(Finite Impulse Response)フィルタを有し、
複数の前記送信側FIRフィルタのそれぞれは、送信側フィルタ係数を有し、
前記送信側周波数特性差補償手段は、別の前記光伝送装置の前記周波数特性差補償手段の代わりに前記送信側MIMO等化器を用いて、前記送信側周波数特性差を補償する、
請求項13に記載のシステム。 - 前記送信側周波数特性差補償手段は、
前記送信側MIMO等化器を用いて所定の前記送信側フィルタ係数を求め、
所定の前記送信側フィルタ係数を用いて前記送信側MIMO等化器を動作させて前記送信側周波数特性差を補償する、
請求項21記載のシステム。 - 前記送信側MIMO等化器は、前記第1デジタル信号と前記第2デジタル信号に合成する前に、前記送信側周波数特性差を補償する、
請求項22に記載のシステム。 - 前記送信側MIMO等化器は、前記第1デジタル信号と前記第2デジタル信号を合成した後に、前記送信側周波数特性差を補償する、
請求項21又は22に記載のシステム。 - 第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成することと、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調して光変調信号を生成し、前記光変調信号を送信することと、
前記第1パイロット信号の送信中は、前記第2パイロット信号を送信しないことと、
前記第2パイロット信号を送信中は、前記第1パイロット信号を送信しないことと、
を備える方法。 - 第1データ信号に第1パイロット信号を付加して第1デジタル信号を生成し、第2データ信号に第2パイロット信号を付加して第2デジタル信号を生成することと、
使用周波数帯域の中心周波数に対して負の周波数帯域に含まれる第1サブキャリアで前記第1デジタル信号を光変調し、前記使用周波数帯域の前記中心周波数に対して正の周波数帯域に含まれる第2サブキャリアで前記第2デジタル信号を光変調して光変調信号を生成し、前記光変調信号を送信することと、
前記第1パイロット信号の送信中は、前記第2パイロット信号を送信しないことと、
前記第2パイロット信号を送信中は、前記第1パイロット信号を送信しないことと、
をコンピュータに実行させるプログラムが格納される非一時的なコンピュータ可読媒体。
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