WO2010073990A1 - 光送信器及び光ofdm通信システム - Google Patents
光送信器及び光ofdm通信システム Download PDFInfo
- Publication number
- WO2010073990A1 WO2010073990A1 PCT/JP2009/071139 JP2009071139W WO2010073990A1 WO 2010073990 A1 WO2010073990 A1 WO 2010073990A1 JP 2009071139 W JP2009071139 W JP 2009071139W WO 2010073990 A1 WO2010073990 A1 WO 2010073990A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- signal
- unit
- optical
- distortion
- inverse fft
- Prior art date
Links
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/548—Phase or frequency modulation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03343—Arrangements at the transmitter end
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03821—Inter-carrier interference cancellation [ICI]
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2626—Arrangements specific to the transmitter only
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2697—Multicarrier modulation systems in combination with other modulation techniques
Definitions
- the present invention relates to an optical transmitter and an optical OFDM communication system, and more particularly to an optical transmitter of an optical communication system using a multicarrier, and more specifically, an optical OFDM (Orthogonal Frequency Division) using a direct detection reception method.
- the present invention relates to an optical transmitter and an optical OFDM communication system that reduce the influence of intersubcarrier interference in a (Multiplexing, Orthogonal Frequency Division Multiplexing) communication system.
- An optical communication system that has been put into practical use so far employs a binary modulation / demodulation technique using light intensity. Specifically, digital information “0” and “1” are converted to on / off of light intensity on the transmitting side and transmitted to the optical fiber, and the light propagated in the optical fiber is photoelectrically converted on the receiving side. The original information is restored.
- the communication capacity required for optical communication systems has increased dramatically.
- the demand for higher communication capacity has been met by increasing the speed at which light is turned on and off, that is, the modulation speed.
- the technique of increasing the modulation speed to realize a large capacity generally has the following problems.
- the transmittable distance limited by the chromatic dispersion of the optical fiber is shortened.
- the transmission distance limited by chromatic dispersion is shortened by the square of the bit rate. That is, when the bit rate is doubled, the transmission distance limited by chromatic dispersion becomes 1/4.
- the modulation speed is increased, there is a problem that the transmission distance limited by the polarization dispersion of the optical fiber is shortened.
- the transmission distance limited by the polarization dispersion is halved. Specifically, the influence of chromatic dispersion is shown.
- the transmission distance limited by chromatic dispersion is 60 km, but when the system has a bit rate of 40 Gbps, the distance is approximately It becomes as short as 4km. Further, in the case of the next-generation 100 Gbps system, the transmission distance limited by chromatic dispersion is 0.6 km, and a trunk optical communication system with a transmission distance of about 500 km cannot be realized as it is.
- a special optical fiber called a dispersion compensating fiber having negative chromatic dispersion is installed in a repeater or transmitter / receiver to cancel the chromatic dispersion of the transmission line. Yes.
- This special fiber is expensive and requires a sophisticated design of how much dispersion compensation fiber is installed at each site (the length of the dispersion compensation fiber). Both of these increase the price of optical communication systems. Yes.
- An optical OFDM communication system is a communication system to which OFDM technology is applied using light as a carrier.
- OFDM technology as described above, a large number of subcarriers are used, and for each subcarrier, a modulation scheme such as 4-QAM, 8-PSK, or 16-QAM can be applied. Therefore, one symbol time is much longer than the reciprocal of the bit rate.
- the transmission distance limited by the above-mentioned chromatic dispersion and polarization dispersion is sufficiently longer than the transmission distance assumed in an optical communication system (for example, 500 km in a domestic trunk line system), and the above-mentioned dispersion compensation fiber is not required. It becomes.
- a low-cost optical communication system can be realized.
- an optical communication system with a bit rate of 10 Gbps is realized by optical OFDM technology. If the number of subcarriers is 10 and the modulation of each subcarrier is 4-QAM, the 1-symbol rate is 500 MBaud.
- a domestic trunk line system with a transmission distance of 500 km can be realized without using an expensive dispersion compensating fiber, and a low-cost optical communication system can be constructed.
- the optical OFDM communication system can be classified into two types according to the optical signal reception method. One is a direct detection reception system, and the other is a coherent reception system.
- the present invention relates to an optical OFDM communication system using a direct detection reception system.
- Fig. 3 shows the configuration of this system.
- data to be originally communicated is input to the transmitter 1 from the input terminal 9, it is converted into a baseband OFDM signal by the transmission signal processing unit 100 inside the transmitter 1, and this signal is amplified by the driver amplifier 2 and amplified by the optical modulator 4.
- an optical OFDM signal is generated by being placed on the light that is a carrier.
- This optical OFDM signal reaches the receiver 6 through the optical fiber 5 serving as a transmission path.
- the optical OFDM signal is directly detected and received by the photodiode 7 and converted into an electric signal.
- This electric signal is ideally the above-described baseband OFDM signal, which is amplified by the preamplifier 6 and demodulated into data to be originally communicated by the reception signal processing unit 200 and output from the output terminal 10.
- FIG. 5 is a functional configuration diagram of the transmission signal processing unit 100
- FIG. 6 is a functional configuration diagram of the reception signal processing unit 200.
- Data to be communicated is first converted into 2N parallel data by the serial-parallel converter 110.
- N is the number of subcarriers that carry data.
- the subcarrier modulation is 4-QAM
- the subcarrier modulation is 16-QAM
- the number is 4N. That is, the serial data is converted into parallel data of “number of bits per symbol ⁇ number of subcarriers”.
- the subcarrier modulation unit 120 modulates N subcarriers using the parallel data.
- the modulated subcarrier is converted into time-axis data by the inverse FFT unit 130 and converted into serial data by the parallel-serial conversion unit 140.
- the serial data is cyclically inserted by the cyclic prefix insertion unit 150, passes through the D / A conversion unit 160, and is sent to the driver amplifier as an analog signal.
- the received electrical signal amplified by the preamplifier is converted into a digital signal by the A / D conversion unit 210, the cyclic prefix is deleted by the cyclic prefix deletion unit 220, and the serial-parallel conversion unit 230 Converted to N parallel data.
- These parallel data are separated into N subcarrier signals by the FFT unit 240, the data on each subcarrier is demodulated by the subcarrier demodulating unit 250, and converted into serial data by the parallel-serial converting unit 260. Is done.
- the spectrum of the optical OFDM signal propagating through the optical fiber 5 uses a single sideband modulation method in order to avoid the influence of chromatic dispersion of the optical fiber.
- the optical spectrum of the optical OFDM signal in this case is shown in FIG.
- Subcarrier signals are arranged on the high frequency side of the optical carrier (subcarriers may be arranged on the low frequency side).
- the optical spectrum of this optical OFDM signal has a plurality of subcarrier signals arranged at equal intervals with an inverse ⁇ of the symbol time Ts.
- the signal band B occupied by the optical OFDM signal is approximately N ⁇ ⁇ where N is the number of subcarriers.
- the beat signal (beat signal) between the subcarriers is generated by the direct detection performed by the photodiode, that is, photoelectric conversion, which interferes with the subcarrier signal to be originally received, and the received signal.
- reception sensitivity is deteriorated.
- FIGS. 10A and 10B respectively show a schematic diagram of a spectrum of a baseband OFDM signal generated by this method and a schematic diagram of a spectrum of a received electrical signal generated when this signal is directly detected and received.
- a guard band is provided by separating a subcarrier signal carrying a signal to be originally communicated from a direct current by a signal band B only. This is converted into an optical OFDM signal and transmitted for direct detection.
- inter-subcarrier interference occurs between the direct current and the signal band B, and has a frequency different from that of the subcarrier carrying the data originally intended to communicate, and does not cause interference.
- the second method is a guard band method shown in Non-Patent Document 2.
- the guard band is provided in the spectrum of the baseband OFDM signal in the same manner as in the first method, but in this method, the bias point of the optical modulator 4 is used as a so-called transmission characteristic in which no optical carrier is generated. Is set to the zero point (transmittance null), and a frequency band component with a baseband (for example, -fc) is used as a carrier, a guard band is set from this carrier by the signal bandwidth B, and a signal is placed on the higher frequency side. Arrange subcarriers.
- FIGS. 10B and FIG. 11B A schematic diagram of the spectrum of a specific baseband OFDM signal and the spectrum of an electric signal when this signal is optically transmitted and directly received are shown in FIGS.
- the difference between this method and the first method described above is that the spectrum of the baseband OFDM signal is shifted by ⁇ fc. Therefore, the spectrum of the electrical signal directly received by detection is the same (see FIG. 10B and FIG. 11B).
- the third method is also shown in Non-Patent Document 2.
- a signal in which the guard bands of the first and second methods are arranged between subcarriers carrying signals is used. Specific frequency arrangements are shown in FIGS. 12 (a) and 12 (b).
- the interval between the subcarriers carrying the signal is set to 2 ⁇ ⁇ .
- An electric signal spectrum generated by converting this signal into an optical OFDM signal, transmitting it, and directly detecting and receiving it is shown in FIG.
- Inter-subcarrier interference (ICI) occurs between subcarrier components on which the signal is carried, and does not interfere with the signal.
- Non-Patent Document 3 The fourth method is shown in Non-Patent Document 3, and the spectrum of the optical OFDM signal remains as in FIG.
- the receiver performs normal signal processing to demodulate subcarriers, then uses the demodulated data to generate distortion components of intersubcarrier interference by signal processing, and subtracts them from the received signal This is a technique for reducing the influence of inter-subcarrier interference.
- the band of the transmission signal is expanded to twice the band B that the signal originally has by using the guard band.
- this optical OFDM transmission technique is applied to a wavelength division multiplexing transmission system, there is a problem that the total transmission capacity that can be sent by one optical fiber is halved.
- the fourth method since the distortion component due to the inter-subcarrier interference is extracted from the demodulated signal, the distortion component is extracted using the wrong demodulated signal due to noise. There is a problem that the component cannot be extracted.
- the present invention has been made in view of the above points, and in an optical OFDM communication system using a direct detection reception method, received signal distortion due to inter-subcarrier interference is not affected by noise in a transmission path or a receiver.
- One of the objects is to provide an optical transmitter and an optical OFDM communication system that can reduce the reception sensitivity degradation.
- Another object of the present invention is to perform communication while maintaining the original spectral bandwidth B of the optical OFDM signal.
- the present invention aims to double the transmission capacity that can be communicated by one optical fiber to that of an optical OFDM communication system that uses a conventional guard band when a wavelength division multiplexing communication system is constructed using this technology.
- the present invention does not depend on individual differences in characteristics of devices used in an optical OFDM communication system, such as photodiodes, optical modulators, driver amplifiers, preamplifiers, characteristic changes due to environmental changes such as temperature, and changes over time.
- One of the objects is to reduce the influence of inter-subcarrier interference generated by photoelectric conversion.
- a transmission signal processing unit generates a distortion component of inter-subcarrier interference generated at the time of photoelectric conversion, and subtracts this from a subcarrier signal carrying data to be transmitted, and transmits the subcarrier signal.
- the optical spectrum of the optical OFDM signal of the present invention is the same as that shown in FIG. 8, and the one-sided spectrum of the baseband OFDM signal is shown in FIG. The means for solving the problem will be described more specifically below.
- a transmission signal processing unit in the transmitter is provided with a distortion generation circuit (distortion generation unit), and a subcarrier signal modulated with data is used as an input signal of this circuit.
- the distortion generator uses this input signal to generate a baseband OFDM signal by inverse FFT operation, takes the square of the absolute value of this signal to perform the same operation as photoelectric conversion, and returns it to the subcarrier signal by FFT operation . Since this signal includes inter-subcarrier interference generated by photoelectric conversion, distortion components generated by inter-sub-carrier interference can be taken out when taking a difference from the input signal, that is, a signal to be communicated.
- the output of the distortion generator is the distortion component of each subcarrier.
- a signal obtained by subtracting this from a subcarrier signal modulated with data to be originally communicated is defined as a transmission signal.
- the transmission signal is transmitted in a distorted state, but when photoelectric conversion is performed by the photodiode of the receiver, the inter-subcarrier interference of the electric signal generated as a result is not subjected to the above signal processing.
- c 0 represents the optical carrier amplitude
- c k represents the modulation component (eg, 4-QAM) of each subcarrier
- ⁇ represents the subcarrier frequency difference
- f 0 represents the optical carrier frequency.
- the photocurrent can be expressed by the following equation (2).
- R is a proportional constant including the quantum efficiency of the photodiode and the optical coupling efficiency between the optical fiber and the photodiode, and * represents a complex conjugate.
- ⁇ k is given by the following equation.
- Equation (2) in the photocurrent directly detected and received, an extra component of ⁇ k is generated in addition to the original signal ck to be communicated.
- this extra component is the sum of beat signals between carriers.
- This is a distortion component generated by direct detection reception.
- the distortion component ⁇ k is generated by a distortion generation circuit inside the transmitter, and is subtracted from the information signal ck that is originally desired to be transmitted, so that the distortion component is kept small.
- a signal V (t) converted into a serial signal after modulating each subcarrier in the transmitter can be expressed by the following equation.
- the following equation is obtained.
- a distortion component ⁇ 1 is generated as a component of the frequency ⁇ in addition to c 1 .
- the distortion component ⁇ 1 is It is. From this, it can be seen that the distortion equation (3) due to the inter-carrier interference generated by the direct detection reception obtained by the equation (3) is generated.
- This distortion component ⁇ 1 is subtracted from the signal c 1 that is originally intended to be sent as information.
- the subtraction signal of the distortion and d 1. Since signal c 2 is not distorted, d 2 c 2 .
- Optical OFDM communication is performed using the distorted signals (d 1 , d 2 ).
- the optical OFDM signal in this case is expressed by the following equation. That is, It is.
- the photocurrent obtained by directly detecting and receiving this is Here, as the component of the frequency ⁇ , when using the equations (6) and (7), Thus, the distortion component ⁇ 1 is certainly gone.
- 2 >>
- the distortion component cancellation by the predistortion of the present invention does not depend on R in equation (2).
- the present invention operates independently of the characteristics of the direct receiver, such as the quantum efficiency of the photodiode and the optical coupling efficiency between the optical fiber and the photodiode. It is also apparent from the above description of the principle that it does not depend on characteristics such as the operating point of the transmitter device, for example, the modulator, and the drive amplitude.
- An optical transmitter maps and modulates digital data into a plurality of subcarriers orthogonal to each other over a symbol time, transmits the optical data as an optical signal through an optical fiber
- the optical transmitter in an optical OFDM communication system in which an optical receiver photoelectrically converts an optical signal propagated through the optical fiber by a photodiode and directly detects and receives it, and demodulates each subcarrier signal to reproduce the original digital data
- a modulator that maps and modulates digital data onto a plurality of subcarriers orthogonal to each other over a symbol time, and outputs a modulated subcarrier signal
- a distortion generation unit that performs an inverse FFT operation on the subcarrier signal to generate a baseband OFDM signal, squares an absolute value of the baseband OFDM signal, and generates a distortion component due to intersubcarrier interference
- a subtraction unit that obtains a transmission signal by subtracting the distortion component generated by the distortion generation unit from the subcarrier signal output from the modulation unit;
- a baseband OFDM signal is generated by performing an inverse FFT operation on the transmission signal obtained by the subtracting unit, an absolute value of the baseband OFDM signal is squared, and the transmission signal
- a second distortion generation unit that generates a second distortion component due to intersubcarrier interference
- a third subtraction unit that obtains a transmission signal by subtracting the second distortion component generated by the second distortion generation unit from the output of the subtraction unit
- the inverse FFT unit performs an inverse FFT operation on the transmission signal from which the distortion component and the second distortion component have been subtracted to convert it into a time-axis signal.
- An optical transmitter maps and modulates digital data into a plurality of subcarriers orthogonal to each other over a symbol time, transmits the optical data as an optical signal through an optical fiber
- the optical transmitter in an optical OFDM communication system in which an optical receiver photoelectrically converts an optical signal propagated through the optical fiber by a photodiode and directly detects and receives it, and demodulates each subcarrier signal to reproduce the original digital data
- a modulator that maps and modulates digital data onto a plurality of subcarriers orthogonal to each other over a symbol time, and outputs a modulated subcarrier signal
- a predistortion unit for generating a transmission signal obtained by subtracting distortion components due to intersubcarrier interference
- An inverse FFT unit that performs an inverse FFT operation on the transmission signal to generate a baseband OFDM signal
- a transmitter that transmits an optical signal based on the baseband OFDM signal generated by the inverse FFT unit to the optical receiver via the optical fiber;
- a first switch in an
- An optical transmitter that maps and modulates digital data into a plurality of subcarriers orthogonal to each other over a symbol time, and transmits the optical data via an optical fiber;
- An optical receiver that directly detects and receives an optical signal propagated through the optical fiber by photoelectric conversion with a photodiode, and demodulates each subcarrier signal to reproduce the original digital data;
- the optical transmitter is A modulator that maps and modulates digital data onto a plurality of subcarriers orthogonal to each other over a symbol time, and outputs a modulated subcarrier signal;
- a distortion generation unit that performs an inverse FFT operation on the subcarrier signal to generate a baseband OFDM signal, squares an absolute value of the baseband OFDM signal, and generates a distortion component due to intersubcarrier interference;
- a subtraction unit that obtains a transmission signal by subtracting the distortion component generated by the distortion generation unit from the subcarrier signal output from the modulation unit;
- An inverse FFT unit that performs an inverse
- a baseband OFDM signal is generated by performing an inverse FFT operation on the transmission signal obtained by the subtracting unit, an absolute value of the baseband OFDM signal is squared, and a second distortion caused by inter-subcarrier interference of the transmission signal.
- a second distortion generator for generating a component;
- a third subtraction unit that obtains a transmission signal by subtracting the second distortion component generated by the second distortion generation unit from the output of the subtraction unit;
- the inverse FFT unit performs an inverse FFT operation on the transmission signal from which the distortion component and the second distortion component have been subtracted to convert it into a time-axis signal.
- An optical transmitter that maps and modulates digital data into a plurality of subcarriers orthogonal to each other over a symbol time, and transmits the optical data via an optical fiber;
- An optical receiver that directly detects and receives an optical signal propagated through the optical fiber by photoelectric conversion with a photodiode, and demodulates each subcarrier signal to reproduce the original digital data;
- the optical transmitter is A modulator that maps and modulates digital data onto a plurality of subcarriers orthogonal to each other over a symbol time, and outputs a modulated subcarrier signal;
- a predistortion unit for generating a transmission signal obtained by subtracting distortion components due to intersubcarrier interference;
- An inverse FFT unit that performs an inverse FFT operation on the transmission signal to generate a baseband OFDM signal;
- a transmitter that transmits an optical signal based on the baseband OFDM signal generated by the inverse FFT unit to the optical receiver via the optical fiber;
- a first switch that selects either the output of the modul
- optical signal that can reduce distortion of a received signal due to inter-subcarrier interference without being affected by noise in a transmission path or a receiver, and can reduce reception sensitivity deterioration.
- a transmitter and an optical OFDM communication system can be provided.
- communication can be performed with the spectral bandwidth of the optical OFDM signal as it is, the original signal bandwidth B. For this reason, when a wavelength division multiplexing communication system is constructed using this technology, the transmission capacity that can be communicated with one optical fiber can be doubled that of an optical OFDM communication system that uses a conventional guard band.
- the device used in the optical OFDM communication system for example, the individual difference of the characteristics of the photodiode, the optical modulator, the driver amplifier, the preamplifier, etc., the characteristic change due to the environmental change such as temperature, and the time-dependent change can be avoided.
- This has the effect of reducing the influence of inter-subcarrier interference generated by photoelectric conversion, and is widely applicable in general.
- the functional block diagram of the distortion generation part of the transmission signal processing part inside the transmitter which shows 1st Embodiment. 1 is a configuration diagram of an optical OFDM communication system using an optical modulator.
- the schematic diagram of the optical spectrum of an optical OFDM signal The schematic diagram of the spectrum of a baseband OFDM signal.
- FIG. 3 is a signal point distribution diagram of transmission / reception signals on the IQ plane (in the case of the first embodiment).
- the signal point distribution map of the transmission / reception signal on the IQ plane in the case of the second embodiment).
- subcarrier modulation is assumed to be 4-QAM, but this embodiment is not limited to this, and can be applied to any subcarrier modulation scheme.
- the number of subcarriers is N (N is an integer).
- FIG. 3 shows a configuration diagram of an optical OFDM communication system.
- the optical OFDM communication system includes, for example, a transmitter (optical transmitter) 1, an optical fiber 5, and a receiver (optical receiver) 6.
- the transmitter 1 includes, for example, a transmission signal processing unit 100, a driver amplifier 2, a laser 3, and an optical modulator 4.
- the transmitter 1 may include an input terminal 9.
- the receiver 6 includes, for example, a photodiode 7, a preamplifier 8, and a reception signal processing unit 200.
- the receiver 6 may include an output terminal 10.
- the transmitter 1 and the receiver 6 are connected via an optical fiber 5.
- the transmitter 1 may include a direct modulation semiconductor laser 20 and an optical filter 30 as shown in FIG. 4 instead of the laser 3 and the optical modulator 4, for example.
- the driver amplifier 2, the laser 3, and the optical modulator 4 may be referred to as a transmission unit.
- FIG. 1 is a configuration diagram of a transmission signal processing unit 100 according to the first embodiment.
- the transmission signal processing unit 100 includes, for example, a serial-parallel conversion unit (S / P) 110, a subcarrier modulation unit 120, an inverse FFT unit (inverse Fourier transform unit) 130, and a parallel-serial conversion unit (P / S). ) 140, a cyclic prefix insertion unit (CPI) 150, a digital-analog conversion unit (D / A conversion unit) 160, a distortion generation unit 170, and a subtraction unit 300.
- Data to be originally communicated is converted into 2N parallel data by the serial-parallel converter 110.
- the subcarrier modulation unit 120 modulates N subcarriers using the parallel data.
- the input signal is converted to time-axis data by the inverse FFT unit 130 and converted to serial data by the parallel-serial conversion unit 140.
- the serial data is inserted with a cyclic prefix by the cyclic prefix insertion unit 150, passes through the D / A conversion unit 160, and is sent to the drive amplifier 2 as an analog signal.
- This signal is amplified by the driver amplifier 2 shown in FIG. 3, and is then output from the transmitter 1 to the optical fiber 5 as an optical OFDM signal using the laser light from the laser 3 as a carrier by the optical modulator 4.
- the optical OFDM signal enters the receiver 6 through the optical fiber 5 serving as a transmission path.
- this electric signal is amplified by the preamplifier 8, demodulated by the reception signal processing unit 200, and taken out from the output terminal 10 as serial data.
- the configuration of received signal processing section 200 is the same as the configuration shown in FIG. 6, for example, and a normal OFDM signal processing configuration can be used.
- FIG. 2 shows a configuration diagram of the distortion generation unit 170 of the present embodiment.
- the distortion generation unit 170 includes, for example, an inverse FFT unit 171, a parallel-serial conversion unit (P / S) 172, a square calculation unit 173, a serial-parallel conversion unit (S / P) 174, and an FFT unit (Fourier).
- the input signal is converted into a time-axis signal by the inverse FFT unit 171 and converted into serial data by the parallel-serial conversion unit 172.
- This is basically the baseband OFDM signal itself.
- a received electric signal including inter-subcarrier interference can be generated by taking an absolute value of this signal and performing a square calculation with a square calculation unit 173 having the same effect as the photoelectric conversion of the photodiode.
- the absolute value is taken because the baseband OFDM signal is generally a complex number.
- This signal is converted into parallel data by the serial-parallel converter 174, and this signal is decomposed into subcarriers by the FFT unit 175.
- the result of evaluating the effect of this embodiment by simulation is shown below.
- the simulation was performed using the following parameters. That is, the number of subcarriers was 128, the modulation of each subcarrier was 4-QAM, the number of symbols was 256, and two independent PN15-stage pseudo-random signals were used.
- the magnitude of distortion due to inter-subcarrier interference was evaluated by EVM (Error Vector Magnitude).
- EVM Error Vector Magnitude
- FIG. 15 summarizes the simulation results.
- FIG. 15 represents the signal point arrangement of the subcarriers of the transmission / reception signal on the IQ plane.
- the signal point arrangement of the transmission signal in this case represents the signal point arrangement of the data to be originally communicated, and when this appears as the signal point arrangement of the received signal, the ideal communication without any distortion can be realized. is there.
- the signal point arrangement when this signal is received by the direct detection reception method is displayed in FIG. 15 as a reception signal when there is no distortion generator. From this table, it can be seen that signal points are spread and distributed on the IQ plane due to intersubcarrier interference caused by photoelectric conversion in direct detection. The EVM of this received signal was calculated to be 17.6%.
- the signal point arrangement of the transmission signal is a signal (d k ) after subtracting the distortion generated by the distortion generator, and is very different from the signal point arrangement of the signal to be originally communicated.
- the signal point constellation of a signal obtained by receiving this signal with a receiver of the direct detection reception system has a small signal point spread as shown in the received signal with the distortion generation unit in FIG.
- the EVM was actually calculated, it decreased to 6.6%, and the effect of the present embodiment could be confirmed quantitatively.
- FIG. 7 is a configuration diagram of the transmission signal processing unit 100 of the transmitter 1 according to the second embodiment.
- the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.
- the overall configuration of the system is the same as that of the first embodiment.
- the transmission signal processing unit 100 further includes a distortion generation unit 170 ′ and a subtraction unit 310.
- the distortion generator 170 used in the first embodiment is used twice (distortion generators 170 and 170 ′ in FIG. 7).
- the distortion generators 170 and 170 ′ can use the same configuration. This generates a residual distortion of inter-subcarrier interference (corresponding to the term
- the generated distortion component is further subtracted from the output signal of the subtracting unit 300 by the subtracting unit 310, and the signal is transmitted as an optical OFDM signal.
- the receiver has the same configuration as the conventional optical OFDM communication receiver 6 shown in FIG. As can be seen from the signal point arrangement of the received signal with the distortion generator in FIG. 15, residual distortion may remain even if the distortion generator 170 is used. Therefore, the residual distortion is further generated by the distortion generation unit 170 ′ and subtracted from the output signal of the subtraction unit 300 to further reduce the residual distortion at the time of reception.
- FIG. 16 shows the result of verifying the effect of the present embodiment by simulation.
- the column without the distortion generator is the signal point arrangement on the IQ plane of the transmission signal and the reception signal when the conventional optical OFDM communication system is used, which is the distortion generation of FIG. 15 of the first embodiment. It is the same as the case of no part.
- the signal point arrangement of the transmission signal and the reception signal when this embodiment is used is shown in a column with two distortion generation units.
- the distortion due to the interference between the sub-carriers is clearly reduced, and the EVM value can be reduced from 17.6% to 3.8%.
- the EVM is 6.6% in the system using one distortion generation unit, but is 3 in the system using two distortion generation units. It has improved to 8%. Therefore, the effect of this embodiment has been verified.
- the present embodiment has a feature that distortion due to inter-subcarrier interference can be further reduced than in the first embodiment.
- the distortion generator 170 is used twice. However, the distortion generator 170 may be used as many times as the distortion component is small.
- FIG. 13 is a configuration diagram of a transmission signal processing unit according to the third embodiment.
- the transmission signal processing unit 100 according to the third embodiment includes, for example, a serial-parallel conversion unit (S / P) 110, a subcarrier modulation unit 120, an inverse FFT unit 130, and a parallel-serial conversion unit (P / P).
- S) 140 a serial-parallel conversion unit (S / P) 110, a subcarrier modulation unit 120, an inverse FFT unit 130, and a parallel-serial conversion unit (P / P).
- S) 140 a serial-parallel conversion unit (S / P) 110, a subcarrier modulation unit 120, an inverse FFT unit 130, and a parallel-serial conversion unit (P / P).
- S) 140 a serial-parallel conversion unit (S / P) 110, a subcarrier modulation unit 120, an inverse FFT unit 130, and a parallel-serial conversion unit (P
- FIG. 14 is a configuration diagram of the predistortion unit 180 in the present embodiment.
- the predistortion unit 180 includes, for example, a distortion generation unit 170 and a subtraction unit 320.
- the transmission signal processing unit 100 inside the transmitter 1 converts data to be originally communicated into parallel data by the serial-parallel conversion unit 110, and the subcarrier modulation unit 120 modulates the subcarrier with these parallel data.
- Each modulated subcarrier signal passes through the 2: 1 switch 181 and is input to the predistortion unit 180.
- the predistortion unit 180 divides the input signal into two and inputs one to the distortion generation unit 170.
- the distortion generation unit 170 has the same configuration as that shown in FIG.
- the predistortion unit 180 subtracts the distortion component ⁇ k, which is the output signal of the distortion generation unit 170, from the input signal divided into two by the subtraction unit 320 and outputs the result.
- the output signal of the predistortion unit 180 passes through the 2: 1 switch 182, is guided to the inverse FFT unit 130, is converted into time axis data by the inverse FFT unit 130, and is output as serial data by the parallel-serial conversion unit 140. Is done.
- a cyclic prefix is added to this signal by the CPI unit 150, and this digital data is converted to an analog signal by the D / A unit 160 and sent to the driver amplifier. From this point on, data restoration from the optical receiver is the same as in the other embodiments.
- the residual distortion can be reduced by using the predistortion unit 180 a plurality of times.
- a case where the predistortion unit 180 is used twice will be described.
- each step is as follows. First, there is a step of guiding each symbol to the distortion generation unit 180.
- the 2: 1 switch 181 is set to guide the modulation unit output to the input of the predistortion unit 180 by the control signal from the switch control unit 190.
- the predistortion unit 180 subtracts the distortion component ( ⁇ k) generated by photoelectric conversion from the signal (ck) to be originally communicated.
- a signal (ck ⁇ k) is output.
- the 1: 2 switch 182 guides this signal (ck ⁇ k) to the 2: 1 switch 181 by the control signal from the switch control unit 190, and the 2: 1 switch 181 inputs this signal to the predistortion unit 180. Is set to lead again.
- the predistortion unit 180 calculates a distortion component generated by photoelectric conversion using the input signal (ck ⁇ k), and outputs a signal obtained by subtracting it.
- the signal that has passed through the predistortion unit 180 in this way passes through the 1: 2 switch 182 controlled by the control signal from the switch control unit 190 in the next step, and is guided to the inverse FFT unit 130 and the subsequent steps. .
- the signal subtracted by the distortion by the predistortion unit 180 is transmitted twice.
- the distortion is generated three times or more, and a plurality of distortion components ⁇ 1k, ⁇ 2k,... Are sequentially subtracted from the subcarrier signal output from the modulation unit 120.
- the timing of each step is determined by the SW control unit 190 by generating a distortion component by a predetermined number of times distortion generating unit 170 and subtracting by the subtracting unit 320 in accordance with the symbol clock (or an integral multiple thereof). It can be controlled to repeat.
- This embodiment has a feature that the configuration of the signal processing unit is simpler than that of the second embodiment, and the circuit scale does not increase even when the distortion generation unit is used a plurality of times.
- the present invention can be used, for example, in an optical OFDM communication system that performs photoelectric conversion and direct detection on the receiving side.
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Optical Communication System (AREA)
Abstract
Description
第一の手法は、例えば非特許文献1に示されているガードバンド方式である。この方式で生成したベースバンドOFDM信号のスペクトルの模式図とこの信号を直接検波受信した場合に発生する受信電気信号のスペクトルの模式図を、それぞれ図10(a)と(b)に示す。この方式では、本来通信する信号が乗せられたサブキャリア信号を信号帯域Bだけ、直流から離しガードバンドを設ける。これを光OFDM信号に変換して送信し、直接検波する。この場合、サブキャリア間干渉(ICI)は直流から信号帯域Bの間に発生し、本来通信しようとしていたデータが乗っているサブキャリアとは周波数が異なり干渉を起こさない。
A.J.Lowery、L.Du、and J.Armstrong、「Orthogonal Frequency Division Multiplexing for Adaptive Dispersion Compensation in Long Haul WDM Systems」、OFC2006、Postdeadline Papers、PDP39、2006 W.Peng、X.Wu、and V.R.Arbab、et al、「Experimental Demonstration of a Coherently Modulated and Directly Detected Optical OFDM Systems Using an RF-Tone Insertion」、OFC2008、OMU2、2008 W.Peng、X.Wu、V.R.Arbab、et al、「Experimental Demonstration of 340km SSMF Transmission Using a Virtual Single Sideband OFDM Signal that Employs Carrier Suppressed and Iterative Detection Techniques」、OFC2008、OMU1、2008
本発明は、例えばこの歪成分δkを送信器内部の歪生成回路で発生させ、本来送りたい情報信号ckから引き算して送ることによってこの歪成分を小さく抑えるものである。
この歪んだ信号(d1、d2)を用いて光OFDM通信を行う。この場合の光OFDM信号は次式で表される。すなわち、
光送信器が、ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、光ファイバを介して光信号で送信し、
光受信器が、該光ファイバを伝播した光信号をフォトダイオードで光電変換して直接検波受信し、各サブキャリア信号を復調して元のディジタルデータを再生する光OFDM通信システムにおける前記光送信器であって、
ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、変調されたサブキャリア信号を出力する変調部と、
該サブキャリア信号を逆FFT演算してベースバンドOFDM信号を生成し、該ベースバンドOFDM信号の絶対値を二乗演算してサブキャリア間干渉による歪成分を生成する歪生成部と、
前記変調部から出力されたサブキャリア信号から前記歪生成部で生成された歪成分を差し引いて送信信号を求める減算部と、
歪成分が差し引かれた該送信信号を逆FFT演算して時間軸の信号に変換する逆FFT部と、
前記逆FFT部で変換された送信信号に基づく光信号を前記光ファイバを介して前記光受信器に送信する送信部と
を備えた前記光送信器が提供される。
前記減算部の出力から前記第2の歪生成部で生成された第2の歪成分を差し引いて送信信号を求める第3の減算部と
をさらに備え、
前記逆FFT部は、前記歪成分及び前記第2の歪成分が差し引かれた送信信号を逆FFT演算して時間軸の信号に変換する。
光送信器が、ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、光ファイバを介して光信号で送信し、
光受信器が、該光ファイバを伝播した光信号をフォトダイオードで光電変換して直接検波受信し、各サブキャリア信号を復調して元のディジタルデータを再生する光OFDM通信システムにおける前記光送信器であって、
ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、変調されたサブキャリア信号を出力する変調部と、
サブキャリア間干渉による歪成分を差引いた送信信号を生成するプリディストーション部と、
該送信信号を逆FFT演算してベースバンドOFDM信号を生成する逆FFT部と、
前記逆FFT部で生成されたベースバンドOFDM信号に基づく光信号を前記光ファイバを介して前記光受信器に送信する送信部と、
前記変調部の出力か前記プリディストーション部の出力かどちらか一方を選択して前記プリディストーション部の入力に導く第一のスイッチと、
前記プリディストーション部の出力を、前記逆FFT部か、前記プリディストーション部の入力かどちらか一方に選択して導く第二のスイッチと、
前記第一及び第二のスイッチを切り替えるスイッチ制御部と
を備え、
前記プリディストーション部は、前記第一のスイッチを介して入力された信号を、該信号の絶対値を二乗演算して前記歪成分を生成する歪生成部に導き、前記プリディストーション部の入力信号から歪生成部の出力を差し引き新たな送信信号を生成する前記光送信器が提供される。
ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、光ファイバを介して光信号で送信する光送信器と、
該光ファイバを伝播した光信号をフォトダイオードで光電変換して直接検波受信し、各サブキャリア信号を復調して元のディジタルデータを再生する光受信器と
を備え、
前記光送信器は、
ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、変調されたサブキャリア信号を出力する変調部と、
該サブキャリア信号を逆FFT演算してベースバンドOFDM信号を生成し、該ベースバンドOFDM信号の絶対値を二乗演算してサブキャリア間干渉による歪成分を生成する歪生成部と、
前記変調部から出力されたサブキャリア信号から前記歪生成部で生成された歪成分を差し引いて送信信号を求める減算部と、
歪成分が差し引かれた該送信信号を逆FFT演算して時間軸の信号に変換する逆FFT部と、
前記逆FFT部で変換された送信信号に基づく光信号を前記光ファイバを介して前記光受信器に送信する送信部と
を有する光OFDM通信システムが提供される。
前記減算部で求められた送信信号を逆FFT演算してベースバンドOFDM信号を生成し、該ベースバンドOFDM信号の絶対値を二乗演算して、該送信信号のサブキャリア間干渉による第2の歪成分を生成する第2の歪生成部と、
前記減算部の出力から前記第2の歪生成部で生成された第2の歪成分を差し引いて送信信号を求める第3の減算部と
をさらに備え、
前記逆FFT部は、前記歪成分及び前記第2の歪成分が差し引かれた送信信号を逆FFT演算して時間軸の信号に変換する。
ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、光ファイバを介して光信号で送信する光送信器と、
該光ファイバを伝播した光信号をフォトダイオードで光電変換して直接検波受信し、各サブキャリア信号を復調して元のディジタルデータを再生する光受信器とを備え、
前記光送信器は、
ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、変調されたサブキャリア信号を出力する変調部と、
サブキャリア間干渉による歪成分を差引いた送信信号を生成するプリディストーション部と、
該送信信号を逆FFT演算してベースバンドOFDM信号を生成する逆FFT部と、
前記逆FFT部で生成されたベースバンドOFDM信号に基づく光信号を前記光ファイバを介して前記光受信器に送信する送信部と、
前記変調部の出力か前記プリディストーション部の出力かどちらか一方を選択して前記プリディストーション部の入力に導く第一のスイッチと、
前記プリディストーション部の出力を、前記逆FFT部か、前記プリディストーション部の入力かどちらか一方に選択して導く第二のスイッチと、
前記第一及び第二のスイッチを切り替えるスイッチ制御部と
を備え、
前記プリディストーション部は、前記第一のスイッチを介して入力された信号を、該信号の絶対値を二乗演算して前記歪成分を生成する歪生成部に導き、前記プリディストーション部の入力信号から歪生成部の出力を差し引き新たな送信信号を生成する光OFDM通信システムが提供される。
1.第1の実施の形態
図1等を参照して第1の実施の形態を説明する。ここでは説明のためサブキャリアの変調は4-QAMと仮定するが、本実施の形態はこれに制限されるものではなく、任意のサブキャリア変調方式に対して適用可能である。またサブキャリアの本数はN本(Nは整数)とする。
光OFDM通信システムは、例えば、送信器(光送信器)1と、光ファイバ5と、受信器(光受信器)6とを備える。送信器1は、例えば、送信信号処理部100と、ドライバアンプ2と、レーザ3と、光変調器4とを有する。送信器1は、入力端子9を備えてもよい。受信器6は、例えば、フォトダイオード7と、プリアンプ8と、受信信号処理部200とを有する。受信器6は、出力端子10を備えてもよい。送信器1と受信器6は、光ファイバ5を介して接続される。なお、送信器1は、例えば、レーザ3及び光変調器4に変えて図4に示すように直接変調用半導体レーザ20及び光フィルタ30を備えてもよい。なお、本実施の形態において、ドライバアンプ2、レーザ3及び光変調器4を送信部と称することがある。
送信信号処理部100は、例えば、シリアル-パラレル変換部(S/P)110と、サブキャリア変調部120と、逆FFT部(逆フーリエ変換部)130と、パラレル-シリアル変換部(P/S)140と、サイクリックプリフィックス挿入部(CPI)150と、ディジタル-アナログ変換部(D/A変換部)160と、歪生成部170と、減算部300とを備える。
本来通信すべきデータは、シリアル-パラレル変換部110で2N個のパラレルデータに変換される。サブキャリア変調部120は、このパラレルデータを用いてN本のサブキャリアに変調をかける。この変調されたサブキャリア(ck、k=1、2、・・・N)は3分割され、そのうち2つは歪生成部170の入力信号となる。残りは、減算部300で歪生成部170の出力信号(δk、k=1、2、・・・N)が引き算され、その結果(dk、k=1、2、・・・N)が逆FFT部130に入力される。入力された信号は、逆FFT部130で時間軸のデータに変換され、パラレルーシリアル変換部140でシリアルデータに変換される。このシリアルデータはサイクリックプリフィックス挿入部150でサイクリックプリフィックスが挿入され、D/A変換部160を通過してアナログ信号としてドライブアンプ2へ送出される。
歪生成部170は、例えば、逆FFT部171と、パラレルーシリアル変換部(P/S)172と、二乗演算部173と、シリアル-パラレル変換部(S/P)174と、FFT部(フーリエ変換部)175と、減算部176とを備える。
図15はI-Q平面における送受信信号のサブキャリアの信号点配置を表している。歪生成部なしの場合は、本実施の形態を適用しない通常の光OFDM通信の場合の信号点配置を表している。この場合の送信信号の信号点配置は、本来通信すべきデータの信号点配置を表しており、これが受信信号の信号点配置として現れる場合がまったく歪の無い理想的な通信が実現できた場合である。この信号を直接検波受信方式で受信した場合の信号点配置が、歪生成部なしの場合の受信信号として図15に表示されている。この表から直接検波における光電変換によるサブキャリア間干渉によって信号点がI-Q平面上に拡散して分布するのが分かる。この受信信号のEVMを計算すると17.6%となった。
本実施の形態では、例えば、サブキャリア間干渉による歪をディジタル信号処理で生成できるという特長がある。
第2の実施の形態を図7等を参照して説明する。図7は第2の実施の形態における送信器1の送信信号処理部100の構成図を示す。第1の実施の形態と同様の構成については同じ符号を付し、説明を省略する。なお、システムの全体構成は第1の実施の形態と同様である。
第3の実施の形態を図13と図14等を参照して説明する。システムの全体構成は第1の実施の形態と同様である。第1の実施の形態と同様の構成については同じ符号を付し、説明を省略する。
第3の実施の形態の送信信号処理部100は、例えば、シリアル-パラレル変換部(S/P)110と、サブキャリア変調部120と、逆FFT部130と、パラレル-シリアル変換部(P/S)140と、サイクリックプリフィックス挿入部(CPI)150と、ディジタル-アナログ変換部(D/A変換部)160と、プリディストーション部180と、サブキャリアに対応した2:1スイッチ(第一のスイッチ)181及び1:2スイッチ(第二のスイッチ)182と、スイッチ制御部190とを備える。
プリディストーション部180は、例えば、歪生成部170と、減算部320とを備える。
送信器1の内部の送信信号処理部100では、本来通信するデータをシリアル-パラレル変換部110によってパラレルデータに変換し、サブキャリア変調部120では、サブキャリアをこれらのパラレルデータで変調する。変調された各サブキャリア信号は、2:1スイッチ181を通過してプリディストーション部180に入力する。プリディストーション部180は、その入力信号を2分割し一方を歪生成部170に入力させる。歪生成部170は図2と同じ構成をしており、その入力信号から歪成分δkを生成して出力する。プリディストーション部180は先ほど2分割したその入力信号から、歪生成部170の出力信号である歪成分δkを減算部320で引き算し、出力する。プリディストーション部180の出力信号は、2:1スイッチ182を通過して逆FFT部130に導かれ、逆FFT部130によって時間軸のデータに変換され、パラレル-シリアル変換部140でシリアルデータとして出力される。この信号にCPI部150でサイクリックプリフィクスが付加されこのディジタルデータはD/A部160でアナログ信号に変換されてドライバアンプに送られる。これ以降光受信器からのデータの復元までは他の実施の形態と同じである。
本実施の形態では、第2の実施の形態と比較して信号処理部の構成がシンプルになっており、また歪生成部を複数回使う場合でも回路規模は増大しない、という特長がある。
Claims (11)
- 光送信器が、ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、光ファイバを介して光信号で送信し、
光受信器が、該光ファイバを伝播した光信号をフォトダイオードで光電変換して直接検波受信し、各サブキャリア信号を復調して元のディジタルデータを再生する光OFDM通信システムにおける前記光送信器であって、
ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、変調されたサブキャリア信号を出力する変調部と、
該サブキャリア信号を逆FFT演算してベースバンドOFDM信号を生成し、該ベースバンドOFDM信号の絶対値を二乗演算してサブキャリア間干渉による歪成分を生成する歪生成部と、
前記変調部から出力されたサブキャリア信号から前記歪生成部で生成された歪成分を差し引いて送信信号を求める減算部と、
歪成分が差し引かれた該送信信号を逆FFT演算して時間軸の信号に変換する逆FFT部と、
前記逆FFT部で変換された送信信号に基づく光信号を前記光ファイバを介して前記光受信器に送信する送信部と
を備えた前記光送信器。 - 前記歪生成部は、
前記変調部からのサブキャリア信号を逆FFT演算してベースバンドOFDM信号を求める第2の逆FFT部と、
該ベースバンドOFDM信号の絶対値を二乗演算する二乗演算部と、
前記二乗演算部での演算結果をFFT演算してサブキャリア毎の信号に変換するFFT部と、
前記FFT部で変換された信号から、前記変調部からのサブキャリア信号を差し引いて歪信号を求める第2の減算部と
を有する請求項1に記載の光送信器。 - 前記歪生成部は、
前記第2の逆FFT部で変換されたベースバンドOFDM信号をシリアル信号に変換して前記二乗演算部に出力するパラレル-シリアル変換部と、
前記二乗演算部での演算結果をパラレル信号に変換して前記FFT演算部に出力するシリアル-パラレル変換部と
をさらに有する請求項2に記載の光送信器。 - 前記減算部で求められた送信信号を逆FFT演算してベースバンドOFDM信号を生成し、該ベースバンドOFDM信号の絶対値を二乗演算して、該送信信号のサブキャリア間干渉による第2の歪成分を生成する第2の歪生成部と、
前記減算部の出力から前記第2の歪生成部で生成された第2の歪成分を差し引いて送信信号を求める第3の減算部と
をさらに備え、
前記逆FFT部は、前記歪成分及び前記第2の歪成分が差し引かれた送信信号を逆FFT演算して時間軸の信号に変換する請求項1に記載の光送信器。 - 光送信器が、ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、光ファイバを介して光信号で送信し、
光受信器が、該光ファイバを伝播した光信号をフォトダイオードで光電変換して直接検波受信し、各サブキャリア信号を復調して元のディジタルデータを再生する光OFDM通信システムにおける前記光送信器であって、
ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、変調されたサブキャリア信号を出力する変調部と、
サブキャリア間干渉による歪成分を差引いた送信信号を生成するプリディストーション部と、
該送信信号を逆FFT演算してベースバンドOFDM信号を生成する逆FFT部と、
前記逆FFT部で生成されたベースバンドOFDM信号に基づく光信号を前記光ファイバを介して前記光受信器に送信する送信部と、
前記変調部の出力か前記プリディストーション部の出力かどちらか一方を選択して前記プリディストーション部の入力に導く第一のスイッチと、
前記プリディストーション部の出力を、前記逆FFT部か、前記プリディストーション部の入力かどちらか一方に選択して導く第二のスイッチと、
前記第一及び第二のスイッチを切り替えるスイッチ制御部と
を備え、
前記プリディストーション部は、前記第一のスイッチを介して入力された信号を、該信号の絶対値を二乗演算して前記歪成分を生成する歪生成部に導き、前記プリディストーション部の入力信号から歪生成部の出力を差し引き新たな送信信号を生成する前記光送信器。 - 前記スイッチ制御部は、シンボル時間に基づき、
はじめに前記第一のスイッチを、前記変調部からの信号が前記プリディストーション部に導かれるように設定し、
次に、前記プリディストーション部を通過した信号が前記第二のスイッチと第一のスイッチによって予め定められた回数だけ前記プリディストーション部を通過するように設定し、
さらに、予め定められた回数だけ前記プリディストーション部を通過した信号が、前記逆FFT部に導かれるように前記第二のスイッチを設定する、請求項5に記載の光送信器。 - 前記プリディストーション部は、その入力信号からその歪成分を差し引いた信号を出力し、再度この出力信号が前記プリディストーション部に入力されることによって、歪成分を差し引いた信号から第二の歪成分をさらに差し引き、
前記スイッチ制御部は、前記第二のスイッチを切り替えて、第二の歪成分が差し引かれた該プリディストーション部の出力を前記FFT部に導く請求項5に記載の光送信器。 - 前記プリディストーション部は、その入力信号に基づき前記歪生成部で出力される歪成分をその入力信号から減算部で差し引いて出力することを特徴とする、請求項5に記載の光送信器。
- ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、光ファイバを介して光信号で送信する光送信器と、
該光ファイバを伝播した光信号をフォトダイオードで光電変換して直接検波受信し、各サブキャリア信号を復調して元のディジタルデータを再生する光受信器と
を備え、
前記光送信器は、
ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、変調されたサブキャリア信号を出力する変調部と、
該サブキャリア信号を逆FFT演算してベースバンドOFDM信号を生成し、該ベースバンドOFDM信号の絶対値を二乗演算してサブキャリア間干渉による歪成分を生成する歪生成部と、
前記変調部から出力されたサブキャリア信号から前記歪生成部で生成された歪成分を差し引いて送信信号を求める減算部と、
歪成分が差し引かれた該送信信号を逆FFT演算して時間軸の信号に変換する逆FFT部と、
前記逆FFT部で変換された送信信号に基づく光信号を前記光ファイバを介して前記光受信器に送信する送信部と
を有する光OFDM通信システム。 - 前記減算部で求められた送信信号を逆FFT演算してベースバンドOFDM信号を生成し、該ベースバンドOFDM信号の絶対値を二乗演算して、該送信信号のサブキャリア間干渉による第2の歪成分を生成する第2の歪生成部と、
前記減算部の出力から前記第2の歪生成部で生成された第2の歪成分を差し引いて送信信号を求める第3の減算部と
をさらに備え、
前記逆FFT部は、前記歪成分及び前記第2の歪成分が差し引かれた送信信号を逆FFT演算して時間軸の信号に変換する請求項9に記載の光OFDM通信システム。 - ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、光ファイバを介して光信号で送信する光送信器と、
該光ファイバを伝播した光信号をフォトダイオードで光電変換して直接検波受信し、各サブキャリア信号を復調して元のディジタルデータを再生する光受信器とを備え、
前記光送信器は、
ディジタルデータをシンボル時間にわたって互いに直交する複数のサブキャリアにマッピングして変調し、変調されたサブキャリア信号を出力する変調部と、
サブキャリア間干渉による歪成分を差引いた送信信号を生成するプリディストーション部と、
該送信信号を逆FFT演算してベースバンドOFDM信号を生成する逆FFT部と、
前記逆FFT部で生成されたベースバンドOFDM信号に基づく光信号を前記光ファイバを介して前記光受信器に送信する送信部と、
前記変調部の出力か前記プリディストーション部の出力かどちらか一方を選択して前記プリディストーション部の入力に導く第一のスイッチと、
前記プリディストーション部の出力を、前記逆FFT部か、前記プリディストーション部の入力かどちらか一方に選択して導く第二のスイッチと、
前記第一及び第二のスイッチを切り替えるスイッチ制御部と
を備え、
前記プリディストーション部は、前記第一のスイッチを介して入力された信号を、該信号の絶対値を二乗演算して前記歪成分を生成する歪生成部に導き、前記プリディストーション部の入力信号から歪生成部の出力を差し引き新たな送信信号を生成する光OFDM通信システム。
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2010544038A JP5058343B2 (ja) | 2008-12-22 | 2009-12-18 | 光送信器及び光ofdm通信システム |
US13/140,355 US8467687B2 (en) | 2008-12-22 | 2009-12-18 | Optical transmitter and optical OFDM communication system |
EP09834791A EP2381605A1 (en) | 2008-12-22 | 2009-12-18 | Optical transmitter and optical ofdm communication system |
CN200980151925.3A CN102265540B (zh) | 2008-12-22 | 2009-12-18 | 光发送器以及光ofdm通信系统 |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2008-326034 | 2008-12-22 | ||
JP2008326034 | 2008-12-22 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2010073990A1 true WO2010073990A1 (ja) | 2010-07-01 |
Family
ID=42287600
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2009/071139 WO2010073990A1 (ja) | 2008-12-22 | 2009-12-18 | 光送信器及び光ofdm通信システム |
Country Status (5)
Country | Link |
---|---|
US (1) | US8467687B2 (ja) |
EP (1) | EP2381605A1 (ja) |
JP (1) | JP5058343B2 (ja) |
CN (1) | CN102265540B (ja) |
WO (1) | WO2010073990A1 (ja) |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2011124798A (ja) * | 2009-12-10 | 2011-06-23 | Planners Land Co Ltd | 可視光通信送信装置 |
US8111993B2 (en) | 2005-10-12 | 2012-02-07 | Ofidium Pty Ltd. | Methods and apparatus for optical transmission of digital signals |
US8112001B2 (en) | 2006-12-20 | 2012-02-07 | Ofidium Pty, Ltd. | Non-linearity compensation in an optical transmission |
JP2012049735A (ja) * | 2010-08-25 | 2012-03-08 | Nippon Hoso Kyokai <Nhk> | デジタル信号の送信装置 |
WO2012073308A1 (ja) * | 2010-11-29 | 2012-06-07 | 株式会社日立製作所 | 光通信システム、光送信器及びトランスポンダ |
WO2012104982A1 (ja) * | 2011-01-31 | 2012-08-09 | 富士通株式会社 | 光送信器および光信号送信方法 |
JP2016524387A (ja) * | 2013-05-16 | 2016-08-12 | ゼットティーイー(ユーエスエー)インコーポレーテッド | ハーフサイクル化直交周波数分割多重送信及び受信 |
CN115001576A (zh) * | 2022-05-20 | 2022-09-02 | 复旦大学 | 基于可见光通信系统的micro-LED预失真方法、系统、存储介质及智能终端 |
Families Citing this family (35)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102005030299B4 (de) * | 2005-06-24 | 2010-08-12 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Dynamisches datenratenadaptives Signalverarbeitungsverfahren in einem drahtlosen Infarot-Datenübertragungssystem |
JP5058343B2 (ja) * | 2008-12-22 | 2012-10-24 | 株式会社日立製作所 | 光送信器及び光ofdm通信システム |
US8787767B2 (en) * | 2012-02-03 | 2014-07-22 | Raytheon Company | High-speed low-jitter communication system |
US9455788B2 (en) | 2014-02-10 | 2016-09-27 | Ciena Corporation | Hitless modulation scheme change systems and methods in optical networks |
US10257596B2 (en) | 2012-02-13 | 2019-04-09 | Ciena Corporation | Systems and methods for managing excess optical capacity and margin in optical networks |
US9258190B2 (en) | 2014-02-10 | 2016-02-09 | Ciena Corporation | Systems and methods for managing excess optical capacity and margin in optical networks |
CN102780669B (zh) * | 2012-06-11 | 2015-04-22 | 北京邮电大学 | 全光ofdm信号光层网络编码的实现方法和装置 |
CN104769875B (zh) * | 2012-06-20 | 2018-07-06 | 安华高科技通用Ip(新加坡)公司 | 采用正交频分复用的高频谱效率传输 |
US10014975B2 (en) * | 2012-09-28 | 2018-07-03 | Infinera Corporation | Channel carrying multiple digital subcarriers |
US9014555B2 (en) | 2012-10-26 | 2015-04-21 | Industrial Technology Research Institute | Method and device for receiving optical signals |
EP2733879B1 (en) * | 2012-11-16 | 2018-06-20 | ADVA Optical Networking SE | Method and device for transmitting an optical digital WDM signal over an optical transmission link or a passive optical network |
WO2016121341A1 (ja) * | 2015-01-28 | 2016-08-04 | 日本電気株式会社 | 光送信器、光通信システム、および光通信方法 |
EP3301878B1 (en) * | 2015-06-25 | 2020-04-22 | Huawei Technologies Co., Ltd. | Data transmission method and device based on orthogonal frequency-division-multiplexing technique |
CN107294597B (zh) * | 2016-03-31 | 2019-11-08 | 富士通株式会社 | 光发射机和光接收机的频率响应特性的测量装置及方法 |
US9831947B2 (en) | 2016-04-20 | 2017-11-28 | Ciena Corporation | Margin determination systems and methods in optical networks |
US10601520B2 (en) | 2018-02-07 | 2020-03-24 | Infinera Corporation | Clock recovery for digital subcarriers for optical networks |
US11368228B2 (en) | 2018-04-13 | 2022-06-21 | Infinera Corporation | Apparatuses and methods for digital subcarrier parameter modifications for optical communication networks |
US11095389B2 (en) | 2018-07-12 | 2021-08-17 | Infiriera Corporation | Subcarrier based data center network architecture |
US10587339B1 (en) | 2018-11-27 | 2020-03-10 | Ciena Corporation | Systems and methods for achieving best effort home route capacity on protection paths during optical restoration |
US11258528B2 (en) | 2019-09-22 | 2022-02-22 | Infinera Corporation | Frequency division multiple access optical subcarriers |
US11075694B2 (en) | 2019-03-04 | 2021-07-27 | Infinera Corporation | Frequency division multiple access optical subcarriers |
US11336369B2 (en) | 2019-03-22 | 2022-05-17 | Infinera Corporation | Framework for handling signal integrity using ASE in optical networks |
US10965439B2 (en) | 2019-04-19 | 2021-03-30 | Infinera Corporation | Synchronization for subcarrier communication |
US11838105B2 (en) | 2019-05-07 | 2023-12-05 | Infinera Corporation | Bidirectional optical communications |
US11088764B2 (en) | 2019-05-14 | 2021-08-10 | Infinera Corporation | Out-of-band communication channel for sub-carrier-based optical communication systems |
US11489613B2 (en) | 2019-05-14 | 2022-11-01 | Infinera Corporation | Out-of-band communication channel for subcarrier-based optical communication systems |
US11239935B2 (en) | 2019-05-14 | 2022-02-01 | Infinera Corporation | Out-of-band communication channel for subcarrier-based optical communication systems |
US11190291B2 (en) | 2019-05-14 | 2021-11-30 | Infinera Corporation | Out-of-band communication channel for subcarrier-based optical communication systems |
US11476966B2 (en) | 2019-05-14 | 2022-10-18 | Infinera Corporation | Out-of-band communication channel for subcarrier-based optical communication systems |
US11296812B2 (en) | 2019-05-14 | 2022-04-05 | Infinera Corporation | Out-of-band communication channel for subcarrier-based optical communication systems |
US11297005B2 (en) | 2019-09-05 | 2022-04-05 | Infiriera Corporation | Dynamically switching queueing schemes for network switches |
EP4042607A1 (en) | 2019-10-10 | 2022-08-17 | Infinera Corporation | Network switches systems for optical communications networks |
US20210111802A1 (en) | 2019-10-10 | 2021-04-15 | Infinera Corporation | Hub-leaf laser synchronization |
AU2020364088A1 (en) | 2019-10-10 | 2022-05-12 | Infinera Corporation | Optical subcarrier dual-path protection and restoration for optical communications networks |
US11329722B2 (en) | 2020-03-27 | 2022-05-10 | Relative Dynamics Incorporated | Optical terminals |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH1051416A (ja) * | 1996-08-02 | 1998-02-20 | Matsushita Electric Ind Co Ltd | 伝送装置 |
JP2003530729A (ja) * | 1999-05-24 | 2003-10-14 | コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ | 変調及び伝送の奇数次の歪みを予め補償する光通信 |
JP2008206064A (ja) * | 2007-02-22 | 2008-09-04 | Kddi Corp | 光伝送装置及び方法 |
Family Cites Families (19)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001041387A1 (en) * | 1999-11-27 | 2001-06-07 | Deutsche Telekom Ag | Method for co-channel interference cancelation in a multicarrier communication system |
DE60003954T2 (de) * | 2000-02-24 | 2004-05-27 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Vorrichtung zur reduzierung von nachbarkanalstörungen durch vorlinearisierung und vorverzerrung |
US7307569B2 (en) * | 2001-03-29 | 2007-12-11 | Quellan, Inc. | Increasing data throughput in optical fiber transmission systems |
CN1212735C (zh) * | 2002-06-07 | 2005-07-27 | 三星电子株式会社 | 正交频分复用多载波调制数字广播信号的方法及发送器 |
US7180368B2 (en) * | 2002-11-14 | 2007-02-20 | Hitachi Kokusai Electric Inc. | Distortion compensation circuit, distortion compensation signal generating method, and power amplifier |
JP4505238B2 (ja) * | 2004-02-25 | 2010-07-21 | 株式会社日立国際電気 | 歪補償回路 |
US7580630B2 (en) * | 2004-06-07 | 2009-08-25 | Nortel Networks Limited | Spectral shaping for optical OFDM transmission |
US7539125B2 (en) * | 2005-10-14 | 2009-05-26 | Via Technologies, Inc. | Method and circuit for frequency offset estimation in frequency domain in the orthogonal frequency division multiplexing baseband receiver for IEEE 802.11A/G wireless LAN standard |
US7623796B2 (en) * | 2006-02-27 | 2009-11-24 | Alcatel-Lucent Usa Inc. | Data-aided multi-symbol phase estimation for optical differential multilevel phase-shift keying signals |
US7639754B2 (en) * | 2006-03-29 | 2009-12-29 | Posdata Co., Ltd. | Method of detecting a frame boundary of a received signal in digital communication system and apparatus of enabling the method |
US8112001B2 (en) * | 2006-12-20 | 2012-02-07 | Ofidium Pty, Ltd. | Non-linearity compensation in an optical transmission |
US7796898B2 (en) * | 2007-01-29 | 2010-09-14 | Ofidium Pty Ltd. | Methods and apparatus for generation and transmission of optical signals |
EP2247012B1 (en) * | 2008-02-22 | 2012-08-29 | Nippon Telegraph And Telephone Corporation | Optical OFDM receiver, subcarrier separation circuit, subcarrier separation method and system |
US8204377B2 (en) * | 2008-10-23 | 2012-06-19 | Alcatel Lucent | System, method and apparatus for joint self phase modulation compensation for coherent optical polarization-division-multiplexed orthogonal-frequency division-multiplexing systems |
US8233809B2 (en) * | 2008-10-28 | 2012-07-31 | Nec Laboratories America, Inc. | Polarization independent frequency domain equalization (FDE) for chromatic dispersion (CD) compensation in PolMux coherent systems |
JP5058343B2 (ja) * | 2008-12-22 | 2012-10-24 | 株式会社日立製作所 | 光送信器及び光ofdm通信システム |
TWI360984B (en) * | 2009-03-25 | 2012-03-21 | Ind Tech Res Inst | Method for receiving an optical ofdm signal and re |
US8218979B2 (en) * | 2009-06-30 | 2012-07-10 | Alcatel Lucent | System, method and apparatus for coherent optical OFDM |
US8873971B2 (en) * | 2010-10-11 | 2014-10-28 | Nec Laboratories America, Inc. | Nonlinear compensation using an enhanced backpropagation method with subbanding |
-
2009
- 2009-12-18 JP JP2010544038A patent/JP5058343B2/ja not_active Expired - Fee Related
- 2009-12-18 EP EP09834791A patent/EP2381605A1/en not_active Withdrawn
- 2009-12-18 US US13/140,355 patent/US8467687B2/en not_active Expired - Fee Related
- 2009-12-18 WO PCT/JP2009/071139 patent/WO2010073990A1/ja active Application Filing
- 2009-12-18 CN CN200980151925.3A patent/CN102265540B/zh not_active Expired - Fee Related
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH1051416A (ja) * | 1996-08-02 | 1998-02-20 | Matsushita Electric Ind Co Ltd | 伝送装置 |
JP2003530729A (ja) * | 1999-05-24 | 2003-10-14 | コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ | 変調及び伝送の奇数次の歪みを予め補償する光通信 |
JP2008206064A (ja) * | 2007-02-22 | 2008-09-04 | Kddi Corp | 光伝送装置及び方法 |
Non-Patent Citations (4)
Title |
---|
A. J. LOWERY, L. DU, J. ARMSTRONG: "Orthogonal frequency division multiplexing for adaptive dispersion compensation in long haul WDM systems", OFC2006, 2006 |
W. PENG, X. WU, V. R. ARBAB ET AL.: "Experimental demonstration of 340 km SSMF transmission using a virtual single sideband OFDM signal that employs carrier suppressed and iterative detection techniques", OFC 2008, 2008 |
W. PENG, X. WU, V. R. ARBAB ET AL.: "Experimental demonstration of a coherently modulated and directly directed optical OFDM systems using an RF-tone insertion", OFC2008, 2008 |
WEI-REN PENG ET AL.: "Experimental Demonstration of 340 km SSMF Transmission Using a Virtual Single Sideband OFDM Signal that Employs Carrier Suppressed and Iterative Detection Techniques", OFC/NFOEC 2008, February 2008 (2008-02-01), XP031391514 * |
Cited By (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8111993B2 (en) | 2005-10-12 | 2012-02-07 | Ofidium Pty Ltd. | Methods and apparatus for optical transmission of digital signals |
US8112001B2 (en) | 2006-12-20 | 2012-02-07 | Ofidium Pty, Ltd. | Non-linearity compensation in an optical transmission |
JP2011124798A (ja) * | 2009-12-10 | 2011-06-23 | Planners Land Co Ltd | 可視光通信送信装置 |
JP2012049735A (ja) * | 2010-08-25 | 2012-03-08 | Nippon Hoso Kyokai <Nhk> | デジタル信号の送信装置 |
CN103229439A (zh) * | 2010-11-29 | 2013-07-31 | 株式会社日立制作所 | 光通信系统、光发送器及转发器 |
WO2012073308A1 (ja) * | 2010-11-29 | 2012-06-07 | 株式会社日立製作所 | 光通信システム、光送信器及びトランスポンダ |
JP5583788B2 (ja) * | 2010-11-29 | 2014-09-03 | 株式会社日立製作所 | 光通信システム、光送信器及びトランスポンダ |
US9048953B2 (en) | 2010-11-29 | 2015-06-02 | Hitachi, Ltd. | Optical communication system, optical transmitter, and transponder |
WO2012104982A1 (ja) * | 2011-01-31 | 2012-08-09 | 富士通株式会社 | 光送信器および光信号送信方法 |
US9356689B2 (en) | 2011-01-31 | 2016-05-31 | Fujitsu Limited | Optical transmitter and optical signal transmission method |
JP2016524387A (ja) * | 2013-05-16 | 2016-08-12 | ゼットティーイー(ユーエスエー)インコーポレーテッド | ハーフサイクル化直交周波数分割多重送信及び受信 |
CN115001576A (zh) * | 2022-05-20 | 2022-09-02 | 复旦大学 | 基于可见光通信系统的micro-LED预失真方法、系统、存储介质及智能终端 |
CN115001576B (zh) * | 2022-05-20 | 2023-08-15 | 复旦大学 | 基于可见光通信系统的micro-LED预失真方法、系统、存储介质及智能终端 |
Also Published As
Publication number | Publication date |
---|---|
US20110249978A1 (en) | 2011-10-13 |
US8467687B2 (en) | 2013-06-18 |
CN102265540B (zh) | 2015-01-14 |
JPWO2010073990A1 (ja) | 2012-06-14 |
JP5058343B2 (ja) | 2012-10-24 |
EP2381605A1 (en) | 2011-10-26 |
CN102265540A (zh) | 2011-11-30 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP5058343B2 (ja) | 光送信器及び光ofdm通信システム | |
Bo et al. | Toward practical Kramers-Kronig receiver: Resampling, performance, and implementation | |
JP5404925B2 (ja) | 光通信システム、光受信器、光トランスポンダ、波長多重光通信システム、波長多重受信装置及び波長多重光トランスポンダ | |
JP5296226B2 (ja) | 光通信システム、光送信器、光受信器及び光トランスポンダ | |
Pan et al. | Inter-channel crosstalk cancellation for Nyquist-WDM superchannel applications | |
US8718160B2 (en) | Multi-carrrier optical communication method and system based on DAPSK | |
JP2017517925A (ja) | 光ファイバ通信における非線形補償の方法 | |
CN102687475A (zh) | 用于在光学网络部件中处理数据的方法以及光学网络部件 | |
US10014954B2 (en) | Imaging cancellation in high-speed intensity modulation and direct detection system with dual single sideband modulation | |
WO2011113097A2 (en) | Method and apparatus for fiber non-linearity mitigation | |
JP2010041706A (ja) | 光直交周波数分割多重信号の位相変調方法及び装置 | |
Li et al. | Simplified DSP-based signal–signal beat interference mitigation technique for direct detection OFDM | |
Wu et al. | Training symbol assisted in-band OSNR monitoring technique for PDM-CO-OFDM system | |
WO2014155775A1 (ja) | 信号処理装置、光通信システム、及び信号処理方法 | |
Qiu et al. | OFDM-PON optical fiber access technologies | |
Hussin et al. | Performance analysis of RF-pilot phase noise compensation techniques in coherent optical OFDM systems | |
Bernhard et al. | Multicarrier transmission using Hadamard transform for optical communications | |
Torres-Zugaide et al. | Hammerstein-based equalizer for nonlinear compensation in coherent OFDM long-reach PONs | |
JP6116001B2 (ja) | 光送信装置及び光受信装置 | |
Zhang et al. | Demonstration of 24-Gb/s carrier-less amplitude and phase modulation (CAP) 64QAM radio-over-fiber system over 40-GHz Mm-wave fiber-wireless transmission | |
Zhang et al. | A new beat interference cancellation receiver with 3× 3 optical coupler for the SSB-OOFDM signal with reduced guard band | |
An et al. | Experimental Demonstration of Single-wavelength, Single-polarization 102-Gb/s DMT Signal Transmission over 105-km Single-span SMF in an IM-DD System | |
London et al. | Analysis of nonlinearity of Mach-Zehnder modulator in coherent optical OFDM in the presence of PAPR | |
Sato et al. | Transmission of 200G PM-16QAM Subcarriers with Reduction of Penalty from Linear Crosstalk Using Super-Nyquist Filtering and Low Complexity MMSE | |
Ye et al. | Capacity improvement by adaptive bit-loading and Volterra filtering in a DML-based IM/DD system |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
WWE | Wipo information: entry into national phase |
Ref document number: 200980151925.3 Country of ref document: CN |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 09834791 Country of ref document: EP Kind code of ref document: A1 |
|
ENP | Entry into the national phase |
Ref document number: 2010544038 Country of ref document: JP Kind code of ref document: A |
|
WWE | Wipo information: entry into national phase |
Ref document number: 13140355 Country of ref document: US |
|
REEP | Request for entry into the european phase |
Ref document number: 2009834791 Country of ref document: EP |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2009834791 Country of ref document: EP |
|
NENP | Non-entry into the national phase |
Ref country code: DE |