WO2018040041A1 - 一种信号调制和解调的方法、装置及系统 - Google Patents

一种信号调制和解调的方法、装置及系统 Download PDF

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Publication number
WO2018040041A1
WO2018040041A1 PCT/CN2016/097721 CN2016097721W WO2018040041A1 WO 2018040041 A1 WO2018040041 A1 WO 2018040041A1 CN 2016097721 W CN2016097721 W CN 2016097721W WO 2018040041 A1 WO2018040041 A1 WO 2018040041A1
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Prior art keywords
signal
filter
pam
optical
modulation
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PCT/CN2016/097721
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English (en)
French (fr)
Inventor
左天健
张亮
周恩波
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华为技术有限公司
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Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Priority to PCT/CN2016/097721 priority Critical patent/WO2018040041A1/zh
Priority to CN201680088392.9A priority patent/CN109565487B/zh
Priority to EP16914607.3A priority patent/EP3496350B1/en
Publication of WO2018040041A1 publication Critical patent/WO2018040041A1/zh
Priority to US16/287,920 priority patent/US10608742B2/en

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    • 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
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2589—Bidirectional transmission
    • 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
    • H04B10/54—Intensity modulation
    • H04B10/541—Digital intensity or amplitude modulation
    • 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
    • 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
    • H04B10/524—Pulse modulation

Definitions

  • the present invention relates to the field of signal processing technologies, and in particular, to a method, device and system for signal modulation and demodulation.
  • the Pulse Amplitude Modulation Four Level is a high-order modulation format with twice the spectral efficiency of Non-Return-to-Zero (NRZ).
  • PAM4 has been included in the IEEE802.3bj study.
  • the PAM4 modulation format has also received widespread attention.
  • the specific process of PAM4 modulation and demodulation includes: using a PAM4 encoder to transmit two 2-level NRZ signals at the transmitting end. Encoded into a 4-level PAM signal, the transmitter converts the PAM signal into a PAM optical signal and uses an electro-optic modulator to optically modulate the PAM optical signal, and transmits the optical signal obtained by the optical modulation, and the receiving end adopts a receiver. The optical signal is converted into an electrical signal, which is then converted into a 2-way 2-level NRZ signal by a PAM4 decoder.
  • the capacitor is filtered out, CS * and C * S are carrier beat signals, which will generate the information to be received, and SS * is the Signal-Signal Beat Interference (SSBI).
  • SSBI Signal-Signal Beat Interference
  • the PAM optical signal is modulated at the QUAD point of the modulation curve of the electro-optic modulator (which can be referred to in FIG. 4 below), that is, when performing optical modulation, the electro-optic modulator is
  • the bias voltage is set to H ⁇ V pi +V pi /2 (H is a positive integer, negative integer or 0), so that the receiver will generate SSBI after converting the optical signal into an electrical signal, since SSBI itself will generate useful signals.
  • V pi is the output optical power of the electro-optic modulator that changes from a maximum value to a minimum value or a minimum value in any period on the modulation curve of the electro-optic modulator
  • the value of the bias voltage changes to the maximum value.
  • the modulation curve is the independent variable as the bias voltage.
  • the dependent variable is the curve corresponding to the output optical power. When the bias voltage is 0, the output optical power is the largest.
  • Embodiments of the present invention provide a method, apparatus, and system for signal modulation and demodulation to eliminate SSBI generated in a prior art modulation and demodulation method.
  • a method for signal modulation is provided, which is applied to an IMDD system, the method comprising: a transmitting end performing PAM encoding on an input signal to obtain a PAM signal; and a transmitting end electrically modulating a PAM signal by using a first filter; The electrically modulated PAM signal is converted into an analog signal; the transmitting end uses an electro-optic modulator to optically modulate the analog signal to obtain an optical signal.
  • the bias voltage of the electro-optic modulator is M+V pi , and V pi is the modulation of the electro-optic modulator.
  • the output optical power of the electro-optic modulator changes from the maximum value to the minimum value or the change value of the bias voltage from the minimum value to the maximum value in any one cycle on the curve.
  • the modulation curve is the independent variable as the bias voltage, and the dependent variable is The curve corresponding to the function of the output optical power, M is the value of the bias voltage when the output optical power is maximum; the transmitting end transmits the optical signal.
  • the first aspect provides a method for modulating an analog signal by setting a bias voltage of the electro-optic modulator to M+V pi , that is, modulating the analog signal at a NULL point of a modulation curve of the electro-optic modulator, at this time, the optical carrier
  • the power is approximately 0, and the transmitted useful signal is included in the SSBI, which is equivalent to eliminating the influence of SS * on system performance, that is, eliminating the impact of SSBI on system performance.
  • the absolute value of the difference between the function value of the convolution of the shaping function included in the first filter and the shaping function included in the second filter at the sampling moment is The value is in a first preset range
  • the second filter is a filter for receiving an electrical signal obtained by converting the received optical signal by the receiving end of the optical signal transmitted by the transmitting end to perform electrical demodulation.
  • This possible implementation enables the receiving end to better restore the signal sent by the transmitting end.
  • the first filter and the second filter are both CAP filters.
  • the period of the virtual carrier of the first filter and the second filter is greater than or equal to T b
  • T b is the period of the input signal.
  • This possible implementation can improve spectral efficiency.
  • the DC and 0 of the electrically modulated PAM signal are The absolute value of the difference is within the third predetermined range.
  • This possible implementation can make the power of the optical carrier closer to zero.
  • a method for signal demodulation is provided, which is applied to an IMDD system, the method comprising: receiving a light signal at a receiving end, and converting the optical signal into an electrical signal, wherein a power of the optical carrier in the optical signal is different from 0 The absolute value of the value is in the second preset range; the receiving end uses the second filter to electrically demodulate the electrical signal; the receiving end performs PAM decoding on the electrically demodulated electrical signal to obtain the restored input signal.
  • the electrical signal is obtained by converting the optical signal sent by the transmitting end, because the absolute value of the difference between the power of the optical carrier and the zero in the optical signal is within the second preset range, therefore, the electrical signal Only SS * is included, that is, the transmitted useful signal is included in SS * , and SS * is the signal that the receiving end needs to receive. Therefore, SSBI is no longer interference, which eliminates the impact of SSBI on system performance.
  • the shaping function included in the second filter and the shaping function included in the first filter are convoluted at the sampling time, and the absolute value of the difference between the function value and the value of 1
  • the cutoff frequency of the second filter is between one and two times the frequency of the virtual electrical carrier of the second filter, and the frequency of the virtual electrical carrier of the second filter is greater than or equal to two One-fold the baud rate of the input signal
  • the first filter is a filter that optically modulates the signal obtained by the PAM encoding of the input signal at the transmitting end of the transmitted optical signal.
  • This possible implementation enables the receiving end to better restore the signal sent by the transmitting end.
  • the first filter and the second filter are both CAP filters.
  • the period of the virtual carrier of the first filter and the second filter is greater than or equal to T b , T b is the period of the input signal.
  • This possible implementation can improve spectral efficiency.
  • a signal modulation apparatus for use in an IMDD system, the apparatus comprising: a PAM encoder, a first filter, a DAC, and an electro-optic modulator sequentially connected; and a PAM encoder for inputting the input signal
  • the bias voltage of the electro-optic modulator is M+V pi
  • V pi is the output optical power of the electro-optic modulator changes from the maximum value to the minimum value in any period on the modulation curve of the electro-optic modulator
  • the change value of the bias voltage when the minimum value changes to the maximum value, the modulation curve is the independent variable as the bias voltage, the dependent variable is the curve corresponding to the function of the output optical power, and M is the value of the bias voltage when the output optical power is maximum.
  • the various devices in the device provided by the third aspect are used to implement the method provided by the first aspect. Therefore, the beneficial effects of the device can be seen in the beneficial effects of the method provided by the first aspect, and details are not described herein again.
  • the apparatus further includes: an optical carrier coupled to the electro-optic modulator for providing the electro-optic modulator with input light that optically modulates the analog signal.
  • the convolution function of the shaping function included in the first filter and the shaping function included in the second filter is The absolute value of the difference between the function value of the sampling instant and the value of 1 is within a first preset range
  • the second filter is an electrical signal obtained by converting the received optical signal by the receiving end of the optical signal transmitted by the receiving transmitting end. Electrically demodulated filter.
  • This possible implementation enables the signal demodulating device to better restore the signal transmitted by the signal modulated device.
  • the first filter and the second filter are both CAP filters.
  • the period of the virtual carrier of the first filter and the second filter is greater than or equal to T b
  • T b is the period of the input signal.
  • This possible implementation can improve spectral efficiency.
  • the first possible implementation manner of the third aspect, or any one of the fourth possible implementation manners, in the fifth possible implementation manner, after the electrical modulation is within a third predetermined range.
  • This possible implementation can make the power of the optical carrier closer to zero.
  • a signal demodulation device for use in an IMDD system, comprising: a receiver connected in sequence, a second filter, and a PAM decoder; and a receiver for receiving an optical signal and converting the optical signal For an electrical signal, the absolute value of the difference between the power of the optical carrier in the optical signal and 0 is within a second predetermined range; a second filter for electrically demodulating the electrical signal; and a PAM decoder for The electrically demodulated electrical signal is PAM decoded to obtain a restored input signal.
  • the device provided in the fourth aspect is used to implement the method provided in the second aspect. Therefore, the beneficial effects of the device can be seen in the beneficial effects of the method provided in the second aspect, and details are not described herein again.
  • the shaping function included in the second filter and the shaping function included in the first filter are convoluted at the sampling time, and the absolute value of the difference between the function value and the value of 1
  • the cutoff frequency of the second filter is between one and two times the frequency of the virtual electrical carrier of the second filter, and the frequency of the virtual electrical carrier of the second filter is greater than or equal to two One-fold the baud rate of the input signal
  • the first filter is a filter that optically modulates the signal obtained by the PAM encoding of the input signal at the transmitting end of the transmitted optical signal.
  • This possible implementation enables the signal demodulating device to better restore the signal transmitted by the signal modulated device.
  • the first filter and the second filter are both CAP filters.
  • the period of the virtual carrier of the first filter and the second filter is greater than or equal to T b , T b is the period of the input signal.
  • This possible implementation can improve spectral efficiency.
  • a system for signal modulation and demodulation comprising: any one of the signal modulation apparatus provided by the third aspect and any one of the signal demodulation apparatuses provided by the fourth aspect.
  • the apparatus for signal modulation included in the system provided by the fifth aspect is the apparatus provided by the third aspect, and the apparatus for signal demodulation is the apparatus provided by the fourth aspect. Therefore, the beneficial effects of the system can be referred to the third aspect and the fourth aspect. The beneficial effects of the provided device will not be described here.
  • FIG. 1 is a schematic diagram of a system composition for implementing a PAM4 modulation and demodulation method in the prior art
  • FIG. 2 is an interaction flowchart of a method for signal modulation and demodulation according to an embodiment of the present invention
  • FIG. 3 is a schematic diagram of a principle of performing optical modulation by an electro-optic modulator according to an embodiment of the present invention
  • FIG. 4 is a schematic diagram of a modulation curve of an electro-optic modulator according to an embodiment of the present invention.
  • FIG. 5 is a schematic diagram of a frequency spectrum of multiple signals according to an embodiment of the present invention.
  • FIG. 6 is a schematic diagram of the composition of a device for signal modulation according to an embodiment of the present invention.
  • FIG. 7 is a schematic structural diagram of another apparatus for signal modulation according to an embodiment of the present disclosure.
  • FIG. 8 is a schematic structural diagram of a device for demodulating a signal according to an embodiment of the present invention.
  • FIG. 9 is a schematic structural diagram of a system for signal modulation and demodulation according to an embodiment of the present invention.
  • the "first” and “second” in the first filter and the second filter in this embodiment may be any filter, which is not specifically mentioned here, just to distinguish the difference between the two filters, the same reason
  • the “first”, “second”, and “third” in the first preset range, the second preset range, and the third preset range are also merely for distinguishing the differences of the three preset ranges.
  • the embodiment of the invention provides a method for signal modulation and demodulation, which is applied to an IMDD system. As shown in FIG. 2, the method includes:
  • the transmitting end performs PAM encoding on the input signal to obtain a PAM signal.
  • the sending end of the embodiment of the present invention may be a network device, and may be a base station, a router, or a switch.
  • the input signal may be an NRZ signal or a PAM signal.
  • the PAM signal before the PAM encoding and the PAM signal after the PAM encoding may be different numbers of PAM signals, and the PAM signal may specifically It is a 4-level, 8-level or 16-level PAM signal.
  • step 201 a method in the prior art may be used.
  • the PAM4 encoder may be used to encode two 2-level NRZ signals into one PAM4 signal.
  • the transmitting end electrically modulates the PAM signal by using a first filter.
  • the convolution of the shaping function included in the first filter and the shaping function included in the second filter is at a first preset range, and the absolute value of the difference between the function value and the sampling time at the sampling time is within a first preset range.
  • the second filter is a filter that receives an electrical signal obtained by converting a received optical signal by a receiving end of the optical signal sent by the transmitting end to perform electrical demodulation.
  • the convolution of the shaping function included in the first filter and the shaping function included in the second filter has a function value equal to 1 at the sampling instant.
  • the optional and preferred method enables the receiving end to better restore the signal sent by the transmitting end.
  • the receiving end to better restore the signal sent by the transmitting end.
  • the first filter and the second filter may both be Carrierless Amplitude Phase Modulation (CAP) filters.
  • CAP Carrierless Amplitude Phase Modulation
  • a period of the virtual carrier of the first filter and the second filter is greater than or equal to T b , and T b is a period of the input signal.
  • the spectral efficiency can be improved.
  • the period of the virtual carrier of the first filter and the second filter is equal to T b .
  • the transmitting end converts the electrically modulated PAM signal into an analog signal.
  • the transmitting end optically modulates the analog signal by using an electro-optic modulator to obtain an optical signal.
  • the bias voltage of the electro-optic modulator is M+V pi
  • V pi is an electro-optic modulator in any period on the modulation curve of the electro-optic modulator.
  • the output optical power changes from the maximum value to the minimum value or the change value of the bias voltage when the value changes from the minimum value to the maximum value.
  • the modulation curve is the independent variable as the bias voltage, and the dependent variable is the curve corresponding to the function of the output optical power. The value of the bias voltage at which the output optical power is maximum.
  • the electro-optic modulator may be a Mach-Zehnder electro-optic modulator (MZM).
  • MZM Mach-Zehnder electro-optic modulator
  • the optical signal obtained by optically modulating the analog signal at the transmitting end is (C+S).
  • the operation of the electro-optic modulator is mainly based on the electro-optic effect, as shown in FIG. 3, the specific method is to first divide the input light into branches, and respectively enter the two optical branches of the electro-optic modulator, in each An electrode is added to the optical branch, and the electrode changes the phase of the light on the optical branch.
  • the voltage difference between the electrodes of the two optical branches is M+V pi , the phases of the light on the two optical branches are opposite.
  • the output end of the combined output light obtained by the interference of the light on the two optical branches is approximately 0, that is, the power of the optical carrier is approximately zero.
  • the bias voltage of the electro-optic modulator refers to the difference between the voltages applied to the electrodes on the two optical branches of the electro-optic modulator.
  • the output optical power of the electro-optic modulator refers to the power of the output optical carrier of the electro-optic modulator, and the electro-optic
  • the modulation curve of the modulator refers to the curve of the independent variable as the bias voltage and the dependent variable as a function of the output optical power. According to the design of the electro-optic modulator itself, the curve can be sinusoidal, cosine or a certain phase different from the sinusoid.
  • the value of the curve, M can be determined from the modulation curve of the electro-optic modulator.
  • the curve is a cosine curve as an example, and the curve can be specifically seen in FIG. 4.
  • the output optical power of the electro-optic modulator periodically changes according to the cosine law as the bias voltage changes, and V pi refers to
  • the output optical power of the electro-optic modulator is a change value of the bias voltage during the change period of the output optical power of the electro-optic modulator from the maximum value to the minimum value or the minimum value to the maximum value. In this case, when When the value of the bias voltage is HV pi +V pi /2, the output optical power of the electro-optic modulator is half of the maximum output optical power of the electro-optic modulator.
  • the point on the curve is the QUAD point, and the value of the bias voltage.
  • the point on the curve is NULL, and the value of H can be a positive integer, a negative integer, and 0.
  • the bias voltage of the electro-optic modulator will be set between -30V and +30V, and V pi is generally 4V, then the value of H It can be set to -4, -3, -2, -1, 0, 1, 2, and 3.
  • the specific value of H can be determined according to the actual application scenario. limited.
  • the transmitting end sends an optical signal.
  • the receiving end receives the optical signal, and converts the optical signal into an electrical signal, where an absolute value of a difference between a power of the optical carrier and the zero in the optical signal is within a second preset range.
  • the receiving end of the embodiment of the present invention is a network device that can communicate with the sending end, and specifically can be a base station, a router, or a switch.
  • the second preset range is the allowable error range.
  • the bias voltage of the electro-optic modulator is M+V pi , the difference between the power of the optical carrier and 0 is within a second predetermined range.
  • the absolute value of the difference between the direct current and the zero of the signal electrically modulated by the first filter to the PAM signal is within a third predetermined range, preferably, The DC of the signal electrically modulated by the first filter is 0, and the first preset range and the third preset range are allowed error ranges. In this case, the power of the optical carrier can be made closer to 0. .
  • the receiving end electrically demodulates the electrical signal by using a second filter.
  • the shaping function included in the second filter and the shaping function included in the first filter are convoluted at the sampling moment, and the absolute value of the difference between the function value and the 1 is within a first preset range, and the second filtering
  • the cutoff frequency of the device is between one and two times the frequency of the virtual electrical carrier of the second filter, and the frequency of the virtual electrical carrier of the second filter is greater than or equal to one-half the baud rate of the input signal.
  • the optional method can enable the receiving end to better restore the signal sent by the transmitting end.
  • the receiving end can enable the receiving end to better restore the signal sent by the transmitting end.
  • the useful signal received by the receiving end is in (CS * + C * S)
  • the useful signal can be directly decoded, but in the embodiment of the present invention, the useful signal received by the receiving end is In SS * , a filter is needed to electrically demodulate the useful signal in SS * , and then decode to obtain a useful signal.
  • the receiving end performs PAM decoding on the electrically demodulated electrical signal to obtain a restored input signal.
  • the PAM signal is denoted as A k
  • DC is a k f (t) of the direct current
  • a k is modulated via a first electrical filter is a CAP a k f (t)
  • a k f ( t) The signal after passing through the DC blocking capacitor is A k f(t)-DC.
  • the signal after the receiving end converts the received optical signal into an electrical signal is (A k f(t)-DC 2 )
  • the signal obtained by electrically demodulating (A k f(t)-DC) 2 by the second CAP filter is
  • ⁇ c is the frequency of the virtual electric carrier of the second CAP filter, and the first item in the above calculation result Because the frequency is too large, it will be filtered by the receiver or the second CAP filter.
  • the fourth DC ⁇ g match (t- ⁇ )d ⁇ is DC, which will be filtered by the DC blocking capacitor in the receiver.
  • FIG. 5 shows A k , A k f(t) and The spectrum of the spectrum, as can be seen from Figure 5, the DC of A k f(t) is equal to 0, A k and The spectrum diagram is similar. It can be seen that the receiving end converts the received optical signal into an electrical signal and electrically modulates it with a second CAP filter, and the PAM signal is relatively accurately restored.
  • the carrier to signal power ratio (CSPR) calculation method of the PAM optical signal is: Wherein, P c is the power of the optical carrier, and P s is the power of the optical signal.
  • the power of the optical carrier accounts for more than half of the sum of the power of the optical carrier and the optical signal, that is, the value of CSPR is greater than two. One of the points.
  • the power of the optical carrier is 0. Therefore, the value of the CSPR is the smallest (ie, 0), so that all the power can be used to transmit a useful signal (ie, an optical signal), and thus, Improve system performance. And, at the same optical signal noise ratio (OSNR) (OSNR) When N is noise), since P c decreases, P s increases, which can improve the actual signal-to-noise ratio (SNR).
  • OSNR optical signal noise ratio
  • SNR signal-to-noise ratio
  • the method provided by the embodiment of the invention modulates the analog signal by setting the bias voltage of the electro-optic modulator to M+V pi , that is, modulating the analog signal to the NULL point of the modulation curve of the electro-optic modulator.
  • the optical carrier The power is approximately 0, and the transmitted useful signal is included in the SSBI, which is equivalent to eliminating the impact of SS * on system performance, ie eliminating the impact of SSBI on system performance.
  • the embodiment of the present invention further provides a device 60 for signal modulation, which is applied to an IMDD system.
  • the device 60 includes: a PAM encoder 601, a first filter 602, and a digital-to-analog converter (Digital). To analog converter (referred to as DAC) 603 and electro-optic modulator 604;
  • DAC digital-to-analog converter
  • electro-optic modulator 604 electro-optic modulator
  • the PAM encoder 601 is configured to perform PAM encoding on the input signal to obtain a PAM signal.
  • the first filter 602 is configured to electrically modulate the PAM signal
  • the DAC 603 is configured to convert the electrically modulated PAM signal into an analog signal
  • the electro-optic modulator 604 is configured to optically modulate the analog signal to obtain an optical signal, and send the optical signal
  • the bias voltage of the electro-optic modulator 604 is M+V pi
  • the V pi is a variation value of the bias voltage when the output optical power of the electro-optic modulator changes from a maximum value to a minimum value or a minimum value to a maximum value in any one cycle on a modulation curve of the electro-optic modulator
  • the modulation The curve is that the argument is the bias voltage, the dependent variable is a curve corresponding to the function of the output optical power, and M is the value of the bias voltage when the output optical power is maximum.
  • the PAM encoder 601, the first filter 602, and the DAC 603 can be integrated in the same digital signal processing (DSP).
  • DSP digital signal processing
  • the device 60 further includes: an optical carrier 605 connected to the electro-optic modulator 604, configured to provide the electro-optic modulator 604 with input light for optically modulating the analog signal. .
  • the convolution of the shaping function included in the first filter 602 and the shaping function included in the second filter is the absolute value of the difference between the function value of the sampling moment and the first predetermined range.
  • the second filter is a filter that receives an electrical signal obtained by converting a received optical signal by a receiving end of the optical signal sent by the transmitting end to perform electrical demodulation.
  • the first filter 602 and the second filter are both CAP filters.
  • a period of the virtual carrier of the first filter 602 and the second filter is greater than or equal to T b , and T b is a period of the input signal.
  • the embodiment of the present invention further provides a device 80 for signal demodulation, which is applied to an IMDD system.
  • the device 80 includes: a receiver 801, a second filter 802, and a PAM decoder 803 connected in sequence;
  • the receiver 801 is configured to receive an optical signal, and convert the optical signal into an electrical signal, where an absolute value of a difference between a power of the optical carrier and an optical signal in the optical signal is within a second preset range;
  • the second filter 802 is configured to perform electrical demodulation on the electrical signal
  • the PAM decoder 803 is configured to perform PAM decoding on the electrically demodulated electrical signal to obtain the restored input signal.
  • the second filter 802 and the PAM decoder 803 can be integrated in the same DSP.
  • the shaping function of the second filter 802 and the shaping function included in the first filter are respectively within a first preset range, and the absolute value of the difference between the function value and the sampling time at the sampling time is
  • the cutoff frequency of the second filter 802 is between one and two times the frequency of the virtual electrical carrier of the second filter 802, and the frequency of the virtual electrical carrier of the second filter 802 is greater than or equal to two.
  • One-fold times the baud rate of the input signal, and the first filter is a filter that transmits a signal obtained by PAM encoding the input signal by a transmitting end of the optical signal.
  • the first filter and the second filter 802 are both CAP filters.
  • the period of the virtual carrier of the first filter and the second filter 802 is greater than or equal to T b , and T b is a period of the input signal.
  • the various devices in the device 80 provided by the embodiments of the present invention are used to implement the foregoing method. Therefore, the beneficial effects of the device 80 can be seen in the beneficial effects of the foregoing method, and details are not described herein again.
  • the embodiment of the invention further provides a system for signal modulation and demodulation, comprising: any one of the signal modulation devices provided by the above embodiments and any device for demodulating the signal.
  • the system may include a device 60 for signal modulation as shown in FIG. 6 and a device 80 for signal demodulation as shown in FIG. 8. It should be noted that not shown in FIG. Signal processing.
  • the device for signal modulation included in the system is the device 60, and the device for demodulating the signal is the device 80. Therefore, the beneficial effects of the system can be seen in the beneficial effects of the device 60 and the device 80, and details are not described herein.
  • the disclosed apparatus and method may be implemented in other manners.
  • the device implementation described above The example is merely illustrative.
  • the division of the module is only a logical function division, and the actual implementation may have another division manner, for example, multiple modules or components may be combined or integrated into another system, or Some features can be ignored or not executed.
  • each functional module in each embodiment of the present application may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.
  • the above integrated modules can be implemented in the form of hardware or in the form of software functional modules.

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Abstract

本发明实施例公开了一种信号调制和解调的方法、装置及系统，涉及信号处理技术领域，用于消除现有技术中的调制和解调的方法中产生的SSBI。该方法包括：发送端将输入信号进行PAM编码得到PAM信号；发送端采用第一滤波器对PAM信号进行电调制；发送端将电调制后的PAM信号转换为模拟信号；发送端采用电光调制器对模拟信号进行光调制得到光信号并发送该光信号；接收端接收光信号，并将光信号转换为电信号；接收端采用第二滤波器对电信号进行电解调；接收端对电解调后的电信号进行PAM解码，得到还原后的输入信号。该方法可以用于对光通信中的输入信号进行调制和解调。

Description

一种信号调制和解调的方法、装置及系统 技术领域
本发明涉及信号处理技术领域，尤其涉及一种信号调制和解调的方法、装置及系统。
背景技术
4电平脉冲幅度调制(Pulse Amplitude Modulation four level，简称PAM4)是一种高阶调制格式，其频谱效率是不归零码(Non-Return-to-Zero，简称NRZ)的两倍。在背板互连中，PAM4已经被纳入IEEE802.3bj的研究。在下一代100G以太网中，PAM4调制格式也受到广泛的关注。
如图1所示，在强度调制和直接检测(Intensity Modulation and direct detection，简称IMDD)系统中，PAM4调制解调的具体过程包括：在发送端采用PAM4编码器将2路2电平的NRZ信号编码成一路4电平的PAM信号，发射机将PAM信号转换为PAM光信号并采用电光调制器对PAM光信号进行光调制，并发送经过光调制后得到的光信号，接收端采用接收机将光信号转换成电信号，再通过一个PAM4解码器把电信号转换成2路2电平NRZ信号。
具体的，若将PAM光信号记为S，将光载波记为C，则发射机光调制后得到的光信号为(C+S)，接收端采用接收机将光信号转换成电信号的过程为：(C+S)(C*+S*)＝CC*+(CS*+C*S)+SS*，其中，CC*为载波自拍，会产生直流，从而被接收机中的隔直电容过滤掉，CS*和C*S为载波拍信号，会产生需要接收的信息，SS*为信号自拍干扰(Signal–Signal Beat Interference，简称SSBI)。
在上述PAM4调制解调的过程中，在电光调制器的调制曲线的 QUAD点(可参加下文中图4中的标注)对PAM光信号进行调制，即在进行光调制时，将电光调制器的偏置电压设置为H·Vpi+Vpi/2(H为正整数、负整数或0)，从而使得接收机将光信号转换为电信号后会产生SSBI，由于SSBI本身会对有用信号产生干扰，因此，产生的SSBI会影响IMDD系统的性能，其中，Vpi为电光调制器的调制曲线上的任意一个周期内电光调制器的输出光功率由最大值变化到最小值或由最小值变化到最大值时偏置电压的变化值，调制曲线为自变量为偏置电压，因变量为输出光功率的函数对应的曲线，当偏置电压为0时，输出光功率最大。
发明内容
本发明的实施例提供了一种信号调制和解调的方法、装置及系统，用以消除现有技术中的调制和解调的方法中产生的SSBI。
为达到上述目的，本发明的实施例采用如下技术方案：
第一方面，提供了一种信号调制的方法，应用于IMDD系统，该方法包括：发送端将输入信号进行PAM编码得到PAM信号；发送端采用第一滤波器对PAM信号进行电调制；发送端将电调制后的PAM信号转换为模拟信号；发送端采用电光调制器对模拟信号进行光调制，得到光信号，电光调制器的偏置电压为M+Vpi，Vpi为电光调制器的调制曲线上的任意一个周期内电光调制器的输出光功率由最大值变化到最小值或由最小值变化到最大值时偏置电压的变化值，调制曲线为自变量为偏置电压，因变量为输出光功率的函数对应的曲线，M为输出光功率最大时偏置电压的值；发送端发送光信号。
第一方面提供的方法，通过将电光调制器的偏置电压设置为M+Vpi后对模拟信号进行调制，即将模拟信号调制在电光调制器的调制曲线的NULL点，此时，光载波的功率近似为0，传输的有用 信号包含在SSBI中，也就等于消除了SS*对系统性能的影响，即消除了SSBI对系统性能的影响。
结合第一方面，在第一种可能的实现方式中，第一滤波器中包含的整形函数与第二滤波器中包含的整形函数的卷积在采样时刻的函数值与1的差值的绝对值在第一预设范围内，第二滤波器为接收发送端发送的光信号的接收端对接收到的光信号进行转换后得到的电信号进行电解调的滤波器。
该种可能的实现方式能够使得接收端更好的将发送端发送的信号还原。
结合第一方面的第一种可能的实现方式，在第二种可能的实现方式中，第一滤波器和第二滤波器均为CAP滤波器。
结合第一方面的第一种可能的实现方式或第二种可能的实现方式，在第三种可能的实现方式中，第一滤波器和第二滤波器的虚拟载波的周期大于或等于Tb，Tb为输入信号的周期。
该种可能的实现方式能够提高频谱效率。
结合第一方面、第一方面的第一种可能的实现方式至第三种可能的实现方式中的任一种，在第四种可能的实现方式中，电调制后的PAM信号的直流与0的差值的绝对值在第三预设范围内。
该种可能的实现方式，可以使得光载波的功率更加的接近0。
第二方面，提供了一种信号解调的方法，应用于IMDD系统，该方法包括：接收端接收光信号，并将光信号转换为电信号，光信号中的光载波的功率与0的差值的绝对值在第二预设范围内；接收端采用第二滤波器对电信号进行电解调；接收端对电解调后的电信号进行PAM解码，得到还原后的输入信号。
第二方面提供的方法，通过对发送端发送的光信号进行转换得 到电信号，由于光信号中的光载波的功率与0的差值的绝对值在第二预设范围内，因此，电信号中仅包括SS*，即传输的有用信号包含在SS*中，SS*就是接收端需要接收的信号，因此，SSBI也就不再是干扰，消除了SSBI对系统性能的影响。
结合第二方面，在第一种可能的实现方式中，第二滤波器包含的整形函数与第一滤波器中包含的整形函数的卷积在采样时刻的函数值与1的差值的绝对值在第一预设范围内，第二滤波器的截止频率在第二滤波器的虚拟电载波的频率的一倍至两倍之间，第二滤波器的虚拟电载波的频率大于或等于二分之一倍的输入信号的波特率，第一滤波器为发送光信号的发送端对输入信号经过PAM编码后得到的信号进行电调制的滤波器。
该种可能的实现方式能够使得接收端更好的将发送端发送的信号还原。
结合第二方面的第一种可能的实现方式，在第二种可能的实现方式中，第一滤波器和第二滤波器均为CAP滤波器。
结合第二方面的第一种可能的实现方式或第二种可能的实现方式，在第三种可能的实现方式中，第一滤波器和第二滤波器的虚拟载波的周期大于或等于Tb，Tb为输入信号的周期。
该种可能的实现方式能够提高频谱效率。
第三方面，提供了一种信号调制的装置，应用于IMDD系统，该装置包括：依次连接的PAM编码器、第一滤波器、DAC和电光调制器；PAM编码器，用于将输入信号进行PAM编码得到PAM信号；第一滤波器，用于对PAM信号进行电调制；DAC，用于将电调制后的PAM信号转换为模拟信号；电光调制器，用于对模拟信号进行光调制得到光信号，并发送光信号，电光调制器的偏置电压为M+Vpi， Vpi为电光调制器的调制曲线上的任意一个周期内电光调制器的输出光功率由最大值变化到最小值或由最小值变化到最大值时偏置电压的变化值，调制曲线为自变量为偏置电压，因变量为输出光功率的函数对应的曲线，M为输出光功率最大时偏置电压的值。
第三方面提供的装置中的各个器件用于实现第一方面提供的方法，因此，该装置的有益效果可以参见第一方面提供的方法的有益效果，在此不再赘述。
结合第三方面，在第一种可能的实现方式中，该装置还包括：与电光调制器连接的光载波器，用于为电光调制器提供对模拟信号进行光调制的输入光。
结合第三方面或第三方面的第一种可能的实现方式，在第二种可能的实现方式中，第一滤波器中包含的整形函数与第二滤波器中包含的整形函数的卷积在采样时刻的函数值与1的差值的绝对值在第一预设范围内，第二滤波器为接收发送端发送的光信号的接收端对接收到的光信号进行转换后得到的电信号进行电解调的滤波器。
该种可能的实现方式能够使得信号解调的装置更好的将信号调制的装置发送的信号还原。
结合第三方面的第二种可能的实现方式，在第三种可能的实现方式中，第一滤波器和第二滤波器均为CAP滤波器。
结合第三方面的第二种可能的实现方式或第三种可能的实现方式，在第四种可能的实现方式中，第一滤波器和第二滤波器的虚拟载波的周期大于或等于Tb，Tb为输入信号的周期。
该种可能的实现方式能够提高频谱效率。
结合第三方面、第三方面的第一种可能的实现方式至第四种可能的实现方式中的任一种，在第五种可能的实现方式中，电调制后 的PAM信号的直流与0的差值的绝对值在第三预设范围内。
该种可能的实现方式，可以使得光载波的功率更加的接近0。
第四方面，提供了一种信号解调的装置，应用于IMDD系统，包括：依次连接的接收机、第二滤波器和PAM解码器；接收机，用于接收光信号，并将光信号转换为电信号，光信号中的光载波的功率与0的差值的绝对值在第二预设范围内；第二滤波器，用于对电信号进行电解调；PAM解码器，用于对电解调后的电信号进行PAM解码，得到还原后的输入信号。
第四方面提供的装置中的各个器件用于实现第二方面提供的方法，因此，该装置的有益效果可以参见第二方面提供的方法的有益效果，在此不再赘述。
结合第四方面，在第一种可能的实现方式中，第二滤波器包含的整形函数与第一滤波器中包含的整形函数的卷积在采样时刻的函数值与1的差值的绝对值在第一预设范围内，第二滤波器的截止频率在第二滤波器的虚拟电载波的频率的一倍至两倍之间，第二滤波器的虚拟电载波的频率大于或等于二分之一倍的输入信号的波特率，第一滤波器为发送光信号的发送端对输入信号经过PAM编码后得到的信号进行电调制的滤波器。
该种可能的实现方式能够使得信号解调的装置更好的将信号调制的装置发送的信号还原。
结合第四方面的第一种可能的实现方式，在第二种可能的实现方式中，第一滤波器和第二滤波器均为CAP滤波器。
结合第四方面的第一种可能的实现方式或第二种可能的实现方式，在第三种可能的实现方式中，第一滤波器和第二滤波器的虚拟载波的周期大于或等于Tb，Tb为输入信号的周期。
该种可能的实现方式能够提高频谱效率。
第五方面，提供了一种信号调制和解调的系统，包括：第三方面提供的任意一种信号调制的装置和第四方面提供的任意一种信号解调的装置。
第五方面提供的系统中包括的信号调制的装置为第三方面提供的装置，信号解调的装置为第四方面提供的装置，因此，该系统的有益效果可以参见第三方面和第四方面提供的装置的有益效果，在此不再赘述。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为现有技术中的一种实现PAM4调制解调方法的系统组成示意图；
图2为本发明实施例提供的一种信号调制和解调的方法的交互流程图；
图3为本发明实施例提供的一种电光调制器进行光调制的原理示意图；
图4为本发明实施例提供的一种电光调制器的调制曲线的示意图；
图5为本发明实施例提供的多个信号的频谱示意图；
图6为本发明实施例提供的一种信号调制的装置的组成示意 图；
图7为本发明实施例提供的又一种信号调制的装置的组成示意图；
图8为本发明实施例提供的一种信号解调的装置的组成示意图；
图9为本发明实施例提供的一种信号调制和解调的系统的组成示意图。
具体实施方式
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行详细地描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。
本实施例中的第一滤波器和第二滤波器中的“第一”和“第二”可以为任一滤波器，此处并非特指，仅仅为了区分两个滤波器的不同，同理，第一预设范围、第二预设范围和第三预设范围中的“第一”、“第二”和“第三”也仅仅为了区分三个预设范围的不同。
本发明实施例提供了一种信号调制和解调的方法，应用于IMDD系统，如图2所示，该方法包括：
201、发送端将输入信号进行PAM编码得到PAM信号。
本发明实施例的发送端可以为网络设备，具体可以为基站、路由器或交换机等。
其中，输入信号可以为NRZ信号，也可以为PAM信号，当输入信号为PAM信号时，PAM编码前的PAM信号和PAM编码后的PAM信号可以为不同数目电平的PAM信号，PAM信号具体可以为4电平、8电平或16电平PAM信号等。
步骤201在具体实现时可以采用现有技术中的方法，例如，当PAM信号为PAM4时，可以采用PAM4编码器将2路2电平的NRZ信号编码成一路PAM4信号。
202、发送端采用第一滤波器对PAM信号进行电调制。
可选的，所述第一滤波器中包含的整形函数与第二滤波器中包含的整形函数的卷积在采样时刻的函数值与1的差值的绝对值在第一预设范围内，所述第二滤波器为接收所述发送端发送的所述光信号的接收端对接收到的光信号进行转换后得到的电信号进行电解调的滤波器。优选的，第一滤波器中包含的整形函数与第二滤波器中包含的整形函数的卷积在采样时刻的函数值等于1。
该可选及优选的方法能够使得接收端更好的将发送端发送的信号还原，具体可参见下述实施例中关于图5的描述。
其中，第一滤波器和第二滤波器均可以为无载波幅度相位调制(Carrierless Amplitude Phase modulation，简称CAP)滤波器。
可选的，所述第一滤波器和所述第二滤波器的虚拟载波的周期大于或等于Tb，Tb为所述输入信号的周期。该情况下，可以提高频谱效率，优选的，第一滤波器和第二滤波器的虚拟载波的周期等于Tb。
203、发送端将电调制后的PAM信号转换为模拟信号。
204、发送端采用电光调制器对模拟信号进行光调制，得到光信号，电光调制器的偏置电压为M+Vpi，Vpi为电光调制器的调制曲线上的任意一个周期内电光调制器的输出光功率由最大值变化到最小值或由最小值变化到最大值时偏置电压的变化值，调制曲线为自变量为偏置电压，因变量为输出光功率的函数对应的曲线，M为输出光功率最大时偏置电压的值。
具体的，电光调制器可以为马赫-曾德尔电光调制器(Mach-Zehnder electro-optic Modulator，简称MZM)。
具体的，若将模拟信号记为S，光载波记为C，则发送端对模拟信号进行光调制后得到的光信号为(C+S)。
具体的，电光调制器的工作主要是基于电光效应进行的，如图3所示，具体的做法是，首先将输入光分为支路，分别进入电光调制器的两个光支路，在每个光支路上加有电极，电极会改变光支路上的光的相位，当两个光支路的电极上的电压差为M+Vpi时，两个光支路上的光的相位相反，在输出端将两个光支路上的光进行干涉后得到的合并后输出的输出光的功率近似为0，即光载波的功率近似为0。
电光调制器的偏置电压是指电光调制器的两个光支路上所加电极上的电压的差值，电光调制器的输出光功率是指电光调制器的输出光载波的功率的大小，电光调制器的调制曲线是指自变量为偏置电压，因变量为输出光功率的函数的曲线，根据电光调制器本身的设计，该曲线可以为正弦曲线、余弦曲线或与正弦曲线相差一定相位的曲线，M的值可以根据电光调制器的调制曲线进行确定。
本发明实施例中以该曲线为余弦曲线为例进行说明，则该曲线具体可参见图4，电光调制器的输出光功率随着偏置电压的变化按余弦规律周期性变化，Vpi是指电光调制器的输出光功率在一个变化周期内，电光调制器的输出光功率从最大值变化到最小值或由最小值变化到最大值的过程中偏置电压的变化值，该情况下，当偏置电压的值为HVpi+Vpi/2时，电光调制器的输出光功率为电光调制器的最大输出光功率的一半，此时曲线上的点为QUAD点，当偏置电压的值为M+Vpi、且M＝2HVpi时，电光调制器的输出光功率近似为0，此时曲线上的点为NULL点，H的值可以为正整数、负整数和0。
若电光调制器的调制曲线为余弦曲线，则M＝2HVpi，一般情况下，电光调制器的偏置电压会被设置在-30V至+30V之间，Vpi一般为4V，则H的值可以设置为-4、-3、-2、-1、0、1、2和3，此处仅仅为举例说明，H的具体值可以根据实际的应用场景确定，本发明实施例对此不作具体限定。
205、发送端发送光信号。
206、接收端接收光信号，并将光信号转换为电信号，所述光信号中的光载波的功率与0的差值的绝对值在第二预设范围内。
本发明实施例的接收端为可以与发送端进行通信的网络设备，具体可以为基站、路由器或交换机等。
第二预设范围为允许的误差范围。电光调制器的偏置电压为M+Vpi时，光载波的功率与0之间的差值在第二预设范围内。
接收端将光信号转换为电信号的过程为：(C+S)(C*+S*)＝CC*+(CS*+C*S)+SS*，C*为C的共轭，S*为S的共轭，其中，由于电光调制器的偏置电压为M+Vpi时，在电光调制器的调制曲线的NULL点对模拟信号进行调制，由于电光调制器的调制曲线的NULL点光载波的功率近似为0，即C＝0，则(C+S)(C*+S*)＝CC*+(CS*+C*S)+SS*＝SS*，即传输的有用信号包含在SS*中，SS*就是接收端需要接收的信号，因此，SSBI也就不再是干扰，消除了SSBI对系统性能的影响。
具体的，采用第一滤波器对PAM信号进行电调制后的信号(即下文中的Akf(t))的直流与0的差值的绝对值在第三预设范围内，优选的，采用第一滤波器对PAM信号进行电调制后的信号的直流为0，第一预设范围和第三预设范围为允许的误差范围，该情况下，可以使得光载波的功率更加的接近0。
207、接收端采用第二滤波器对电信号进行电解调。
可选的，第二滤波器包含的整形函数与第一滤波器中包含的整形函数的卷积在采样时刻的函数值与1的差值的绝对值在第一预设范围内，第二滤波器的截止频率在第二滤波器的虚拟电载波的频率的一倍至两倍之间，第二滤波器的虚拟电载波的频率大于或等于二分之一倍的输入信号的波特率。
该可选的方法能够使得接收端更好的将发送端发送的信号还原，具体可参见下述实施例中关于图5的描述。
在现有技术中，由于接收端接收到的有用信号在(CS*+C*S)中，因此，可以直接解码获取有用信号，而本发明实施例中，由于接收端接收到的有用信号在SS*中，需要采用滤波器将SS*中的有用信号电解调出来，再进行解码获取有用信号。
208、接收端对电解调后的电信号进行PAM解码，得到还原后的输入信号。
以下对本发明的技术方案的原理进行示例性的描述，将PAM信号记为Ak，第一CAP滤波器为f(t)＝g(t)2cos(ωcτ)，第二CAP滤波器为h(t)＝gmatch(t)，DC是Akf(t)的直流，则Ak经过第一CAP滤波器进行电调制后的信号为Akf(t)，Akf(t)经过隔直流电容后的信号为Akf(t)-DC，根据步骤206的分析，接收端将接收到的光信号转换为电信号后的信号为(Akf(t)-DC)2，采用第二CAP滤波器对(Akf(t)-DC)2进行电解调后的信号为
Figure PCTCN2016097721-appb-000001
Figure PCTCN2016097721-appb-000002
在上述计算结果中，ωc即第二CAP滤波器的虚拟电载波的频率， 上述计算结果中的第一项
Figure PCTCN2016097721-appb-000003
由于频率太大，会被接收机或第二CAP滤波器滤掉，第四项DC∫gmatch(t-τ)dτ是直流，会被接收机中的隔直电容滤掉，在设计时可以令Akf(t)的直流等于0，则DC等于0，则第三项AkDC∫g(τ)gmatch(t-τ)cos(ωcτ)dτ等于0，第一CAP滤波器中包含的整形函数为g(t)2，第二CAP滤波器中包含的整形函数为gmatch(t)，在本发明实施例中，
Figure PCTCN2016097721-appb-000004
在采样时刻等于1，因此第二项在采样时刻等于Ak 2。
具体的，图5中示出了Ak、Akf(t)及
Figure PCTCN2016097721-appb-000005
的频谱图，从图5中可以看出Akf(t)的直流等于0，Ak与
Figure PCTCN2016097721-appb-000006
的频谱图类似，由此可见，接收端在将接收到的光信号转换为电信号并采用第二CAP滤波器进行电调制后，比较准确地还原出了PAM信号。
在IMDD系统中，PAM光信号的载波信号功率比(Carrier to Signal Power Ratio，简称CSPR)的计算方法为：
Figure PCTCN2016097721-appb-000007
其中，Pc为光载波的功率，Ps为光信号的功率，现有技术中，光载波的功率占了光载波和光信号的功率之和的一半以上，也就是说，CSPR的值大于二分之一。
本发明实施例提供的方法中，光载波的功率为0，因此，CSPR的值为最小(即0)，这样可以使得全部的功率都用于传输有用的信号(即光信号)，因此，可以提高系统的性能。并且，在同一光信噪比(Optical Signal Noise Ratio，简称OSNR)(
Figure PCTCN2016097721-appb-000008
N为噪声)下，由于Pc减小，因此，Ps增大，这样可以提高实际的信噪比(Signal Noise Ratio，简称SNR)
Figure PCTCN2016097721-appb-000009
本发明实施例提供的方法，通过将电光调制器的偏置电压设置 为M+Vpi后对模拟信号进行调制，即将模拟信号调制在电光调制器的调制曲线的NULL点，此时，光载波的功率近似为0，传输的有用信号包含在SSBI中，也就等于消除了SS*对系统性能的影响，即消除了SSBI对系统性能的影响。
本发明实施例还提供了一种信号调制的装置60，应用于IMDD系统，如图6所示，装置60包括：依次连接的PAM编码器601、第一滤波器602、数字模拟转换器(Digital to analog converter，简称DAC)603和电光调制器604；
所述PAM编码器601，用于将输入信号进行PAM编码得到PAM信号；
所述第一滤波器602，用于对所述PAM信号进行电调制；
所述DAC603，用于将电调制后的PAM信号转换为模拟信号；
所述电光调制器604，用于对所述模拟信号进行光调制得到光信号，并发送所述光信号，所述电光调制器604的偏置电压为M+Vpi，所述Vpi为所述电光调制器的调制曲线上的任意一个周期内所述电光调制器的输出光功率由最大值变化到最小值或由最小值变化到最大值时所述偏置电压的变化值，所述调制曲线为自变量为所述偏置电压，因变量为所述输出光功率的函数对应的曲线，M为所述输出光功率最大时所述偏置电压的值。
其中，PAM编码器601、第一滤波器602和DAC603可以集成在同一个数字信号处理(Digital Signal Processing，简称DSP)中。
可选的，如图7所示，装置60还包括：与所述电光调制器604连接的光载波器605，用于为所述电光调制器604提供对所述模拟信号进行光调制的输入光。
可选的，所述第一滤波器602中包含的整形函数与第二滤波器中包含的整形函数的卷积在采样时刻的函数值与1的差值的绝对值在第一预设范围内，所述第二滤波器为接收所述发送端发送的所述光信号的接收端对接收到的光信号进行转换后得到的电信号进行电解调的滤波器。
可选的，所述第一滤波器602和所述第二滤波器均为CAP滤波器。
可选的，所述第一滤波器602和所述第二滤波器的虚拟载波的周期大于或等于Tb，Tb为所述输入信号的周期。
本发明实施例提供的装置60中的各个器件用于实现上述方法，因此，装置60的有益效果可以参见上述方法部分的有益效果，在此不再赘述。
本发明实施例还提供了一种信号解调的装置80，应用于IMDD系统，如图8所示，装置80包括：依次连接的接收机801、第二滤波器802和PAM解码器803；
所述接收机801，用于接收光信号，并将所述光信号转换为电信号，所述光信号中的光载波的功率与0的差值的绝对值在第二预设范围内；
所述第二滤波器802，用于对所述电信号进行电解调；
所述PAM解码器803，用于对电解调后的所述电信号进行PAM解码，得到还原后的所述输入信号。
其中，第二滤波器802和PAM解码器803可以集成在同一个DSP中。
可选的，所述第二滤波器802包含的整形函数与第一滤波器中包含的整形函数的卷积在采样时刻的函数值与1的差值的绝对值在第一预设范围内，所述第二滤波器802的截止频率在所述第二滤波器802的虚拟电载波的频率的一倍至两倍之间，所述第二滤波器802的虚拟电载波的频率大于或等于二分之一倍的所述输入信号的波特率，所述第一滤波器为发送所述光信号的发送端对所述输入信号经过PAM编码后得到的信号进行电调制的滤波器。
可选的，所述第一滤波器和所述第二滤波器802均为CAP滤波器。
可选的，所述第一滤波器和所述第二滤波器802的虚拟载波的周期大于或等于Tb，Tb为所述输入信号的周期。
本发明实施例提供的装置80中的各个器件用于实现上述方法，因此，装置80的有益效果可以参见上述方法部分的有益效果，在此不再赘述。
另外，在图6、图7以及图8中还示出了信号的处理过程。
本发明实施例还提供了一种信号调制和解调的系统，包括：上述实施例提供的任意一种信号调制的装置和任意一种信号解调的装置。示例性的，如图9所示，该系统可以包括如图6所示的信号调制的装置60和如图8所示的信号解调的装置80，需要说明的是，图9中未示出信号的处理过程。该系统中包括的信号调制的装置为装置60，信号解调的装置为装置80，因此，该系统的有益效果可以参见装置60和装置80的有益效果，在此不再赘述
在本申请所提供的几个实施例中，应该理解到，所揭露的装置和方法，可以通过其它的方式实现。例如，以上所描述的装置实施 例仅仅是示意性的，例如，所述模块的划分，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式，例如多个模块或组件可以结合或者可以集成到另一个系统，或一些特征可以忽略，或不执行。
另外，在本申请各个实施例中的各功能模块可以集成在一个处理模块中，也可以是各个模块单独物理存在，也可以两个或两个以上模块集成在一个模块中。上述集成的模块既可以采用硬件的形式实现，也可以采用软件功能模块的形式实现。
以上所述，以上实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的精神和范围。

Claims (18)

  1. 一种信号调制的方法，其特征在于，应用于强度调制和直接检测IMDD系统，所述方法包括：
    发送端将输入信号进行脉冲幅度调制PAM编码得到PAM信号；
    所述发送端采用第一滤波器对所述PAM信号进行电调制；
    所述发送端将电调制后的PAM信号转换为模拟信号；
    所述发送端采用电光调制器对所述模拟信号进行光调制，得到光信号，所述电光调制器的偏置电压为M+Vpi，所述Vpi为所述电光调制器的调制曲线上的任意一个周期内所述电光调制器的输出光功率由最大值变化到最小值或由最小值变化到最大值时所述偏置电压的变化值，所述调制曲线为自变量为所述偏置电压，因变量为所述输出光功率的函数对应的曲线，M为所述输出光功率最大时所述偏置电压的值；
    所述发送端发送所述光信号。
  2. 根据权利要求1所述的方法，其特征在于，所述第一滤波器中包含的整形函数与第二滤波器中包含的整形函数的卷积在采样时刻的函数值与1的差值的绝对值在第一预设范围内，所述第二滤波器为接收所述发送端发送的所述光信号的接收端对接收到的光信号进行转换后得到的电信号进行电解调的滤波器。
  3. 根据权利要求2所述的方法，其特征在于，所述第一滤波器和所述第二滤波器均为无载波幅度相位调制CAP滤波器。
  4. 根据权利要求2或3所述的方法，其特征在于，所述第一滤波器和所述第二滤波器的虚拟载波的周期大于或等于Tb，Tb为所述输入信号的周期。
  5. 一种信号解调的方法，其特征在于，应用于强度调制和直接检测IMDD系统，包括：
    接收端接收光信号，并将所述光信号转换为电信号，所述光信号 中的光载波的功率与0的差值的绝对值在第二预设范围内；
    所述接收端采用第二滤波器对所述电信号进行电解调；
    所述接收端对电解调后的所述电信号进行脉冲幅度调制PAM解码，得到还原后的所述输入信号。
  6. 根据权利要求5所述的方法，其特征在于，所述第二滤波器包含的整形函数与第一滤波器中包含的整形函数的卷积在采样时刻的函数值与1的差值的绝对值在第一预设范围内，所述第二滤波器的截止频率在所述第二滤波器的虚拟电载波的频率的一倍至两倍之间，所述第二滤波器的虚拟电载波的频率大于或等于二分之一倍的所述输入信号的波特率，所述第一滤波器为发送所述光信号的发送端对所述输入信号经过PAM编码后得到的信号进行电调制的滤波器。
  7. 根据权利要求6所述的方法，其特征在于，所述第一滤波器和所述第二滤波器均为无载波幅度相位调制CAP滤波器。
  8. 根据权利要求6或7所述的方法，其特征在于，所述第一滤波器和所述第二滤波器的虚拟载波的周期大于或等于Tb，Tb为所述输入信号的周期。
  9. 一种信号调制的装置，其特征在于，应用于强度调制和直接检测IMDD系统，所述装置包括：依次连接的脉冲幅度调制PAM编码器、第一滤波器、数字模拟转换器DAC和电光调制器；所述PAM编码器，用于将输入信号进行PAM编码得到PAM信号；
    所述第一滤波器，用于对所述PAM信号进行电调制；
    所述DAC，用于将电调制后的PAM信号转换为模拟信号；
    所述电光调制器，用于对所述模拟信号进行光调制得到光信号，并发送所述光信号，所述电光调制器的偏置电压为M+Vpi，所述Vpi为所述电光调制器的调制曲线上的任意一个周期内所述电光调制器的输出光功率由最大值变化到最小值或由最小值变化到最大值时所述偏置电压的变化值，所述调制曲线为自变量为所述偏置电压，因变 量为所述输出光功率的函数对应的曲线，M为所述输出光功率最大时所述偏置电压的值。
  10. 根据权利要求9所述的装置，其特征在于，所述装置还包括：
    与所述电光调制器连接的光载波器，用于为所述电光调制器提供对所述模拟信号进行光调制的输入光。
  11. 根据权利要求9或10所述的装置，其特征在于，所述第一滤波器中包含的整形函数与第二滤波器中包含的整形函数的卷积在采样时刻的函数值与1的差值的绝对值在第一预设范围内，所述第二滤波器为接收所述发送端发送的所述光信号的接收端对接收到的光信号进行转换后得到的电信号进行电解调的滤波器。
  12. 根据权利要求11所述的装置，其特征在于，所述第一滤波器和所述第二滤波器均为无载波幅度相位调制CAP滤波器。
  13. 根据权利要求11或12所述的装置，其特征在于，所述第一滤波器和所述第二滤波器的虚拟载波的周期大于或等于Tb，Tb为所述输入信号的周期。
  14. 一种信号解调的装置，其特征在于，应用于强度调制和直接检测IMDD系统，包括：依次连接的接收机、第二滤波器和脉冲幅度调制PAM解码器；
    所述接收机，用于接收光信号，并将所述光信号转换为电信号，所述光信号中的光载波的功率与0的差值的绝对值在第二预设范围内；
    所述第二滤波器，用于对所述电信号进行电解调；
    所述PAM解码器，用于对电解调后的所述电信号进行PAM解码，得到还原后的所述输入信号。
  15. 根据权利要求14所述的装置，其特征在于，所述第二滤波器包含的整形函数与第一滤波器中包含的整形函数的卷积在采样时刻的函数值与1的差值的绝对值在第一预设范围内，所述第二滤波器 的截止频率在所述第二滤波器的虚拟电载波的频率的一倍至两倍之间，所述第二滤波器的虚拟电载波的频率大于或等于二分之一倍的所述输入信号的波特率，所述第一滤波器为发送所述光信号的发送端对所述输入信号经过PAM编码后得到的信号进行电调制的滤波器。
  16. 根据权利要求15所述的装置，其特征在于，所述第一滤波器和所述第二滤波器均为无载波幅度相位调制CAP滤波器。
  17. 根据权利要求15或16所述的装置，其特征在于，所述第一滤波器和所述第二滤波器的虚拟载波的周期大于或等于Tb，Tb为所述输入信号的周期。
  18. 一种信号调制和解调的系统，其特征在于，包括：权利要求9-13任一项所述的信号调制的装置和权利要求14-17任一项所述的信号解调的装置。
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