CN108667512B - A kind of dispersion estimation method and device that heterodyne is relevant - Google Patents
A kind of dispersion estimation method and device that heterodyne is relevant Download PDFInfo
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- CN108667512B CN108667512B CN201710219552.5A CN201710219552A CN108667512B CN 108667512 B CN108667512 B CN 108667512B CN 201710219552 A CN201710219552 A CN 201710219552A CN 108667512 B CN108667512 B CN 108667512B
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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
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
- H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
- H04B10/0795—Performance monitoring; Measurement of transmission parameters
- H04B10/07951—Monitoring or measuring chromatic dispersion or PMD
Abstract
A kind of dispersion estimation method and device that heterodyne is relevant, belongs to high speed optical communication technical field.A kind of device of dispersive estimates includes first processing units, the second processing unit, time domain cross-correlated signal peak search element and dispersion computing unit；A kind of dispersion estimation method in optical fiber telecommunications system includes: that the tested channel optical signal after S1 transmits optical fiber link carries out branch, optics smear, balance detection and low-pass filtering, obtains the different beat signal of two-way；S2 calculates the conjugate product of the Fourier transformation of two-way beat signal in S1, then does inverse Fourier transform and obtain time domain cross-correlated signal；S3 time domain cross-correlated signal peak search element searches for the peak position of time domain cross-correlated signal in S2, obtains the correspondence time of peak position；S4 is calculated in S1 according to the correspondence time of peak position by the dispersion values of light signal.The present invention can rapidly and accurately measure the dispersion of optical fiber link and measurement range is wide, measurement error is low is also applicable in more modulation.
Description
Technical field
The present invention relates to dispersion estimation methods and device that a kind of heterodyne is concerned with, belong to high speed optical communication technical field.
Background technique
In recent years, as the rapid development in the fields such as mobile Internet, cloud computing, big data, Internet of Things is so that data flow
Explosive growth is presented in amount.The rapid growth of data traffic to the transmission capacity of existing optical fiber telecommunications system and optical-fiber network,
Transmission range, system complexity and reliability are put forward higher requirements.In high speed long-distance optical fiber communication system, the color of optical fiber
The crosstalk for causing the broadening of optical time domain cross-correlated signal peak value to will lead to intersymbol is dissipated, so that the bit error rate of system increases, limitation system
The transmission capacity of system.Therefore the dispersion of high speed optical fiber communication link is quickly and accurately measured and is monitored and is particularly important.
Existing Fiber Dispersion Monitoring method mainly includes the dispersive estimates method based on RF pilot tone, vestigial sideband filter method,
Scanning search Dispersion Method etc..
Dispersive estimates method based on RF pilot tone is to be inserted into radio frequency pilot signal in transmitting terminal, since fibre-optical dispersion is following thereon
The opposite phase offset of symbol can occur after optical fiber link transmits for band signal, when phase difference is (2k+1) π, lower sideband
Electric signal power after optical detection is minimum.The prison of optical fiber link dispersion is realized by analysis RF power spectrum in slowly decreasing fibers point
It surveys.The disadvantage is that pilot tone need to be inserted into transmitting terminal.
Optical signal is carried out the filtering of upper and lower sideband using bandpass filter by vestigial sideband filter method respectively, passes through detection
The delay inequalitys of two vestigial sideband (vsb) signals or phase difference calculate the dispersion of optical fiber.Vestigial sideband filter method be not necessarily to transmitter into
Row change, high sensitivity can distinguish the positive and negative of dispersion, while not by the shadow of polarization mode dispersion, nonlinear birefringence and chirp
It rings.But the bandwidth of its bandpass filter is equal to the bit rate of signal, opaque to signal rate.
The method of scanning search dispersion is the signal for unknown dispersion, and certain dispersion step-length is arranged and is scanned；It is right
In each dispersion values, go out a functional value relevant to dispersion using designed cost function calculation, by comparing all
Calculated functional value finds extreme value therein (maximum value or minimum value), to find actual dispersion values, completes dispersion
Estimation.The disadvantage is that calculation amount is too big.
Summary of the invention
The purpose of the present invention is to solve the computationally intensive and measurements of dispersion real-time measurement in existing High-speed Optical Fiber Link
The low technological deficiency of precision proposes a kind of dispersion estimation method and device that heterodyne is relevant.
Specifically, a kind of relevant dispersion estimation method and device of heterodyne of the present invention includes in a kind of optical fiber telecommunications system
The method of dispersive estimates and a kind of device of dispersive estimates；
Wherein, a kind of device of dispersive estimates, the abbreviation present apparatus mainly include first processing units, the second processing unit,
Time domain cross-correlated signal peak search element and dispersion computing unit；
Wherein, all modules of the present apparatus are respectively positioned in receiving end；
The connection relationship of each module is as follows in the present apparatus:
First processing units connect the second processing unit；The second processing unit connects time domain cross-correlated signal peak value searching list
Member；Time domain cross-correlated signal peak search element connects dispersion computing unit；
The function of each module is as follows in the present apparatus:
First processing units are completed by the function based on light signal branch, optical frequency mixing, balance detection, low-pass filtering；
The second processing unit complete receive first processing units obtained by signal, Fourier transformation, calculate conjugate product again into
The function of row inverse Fourier transform；
Time domain cross-correlated signal peak search element complete receive second unit obtained by signal and carry out peak value searching and
Calculate the function that peak position corresponds to the time；
Dispersion computing unit is completed to receive time domain cross-correlated signal peak search element output signal and calculates tested light letter
The function of number dispersion values；
A kind of dispersion estimation method in optical fiber telecommunications system, comprising the following steps:
S1: receiving end optical fiber link is transmitted after tested channel optical signal carry out branch, optics smear, balance detection
And low-pass filtering, obtain the different beat signal of two-way；
Specifically:
S1.1 first processing units will be divided into two paths of signals with light power divider by light signal；
Wherein, it is tested the optical signal of channel, referred to as by light signal, symbol rate is denoted as RS；
The S1.1 two paths of signals exported and two centre frequencies are respectively f by S1.2c+fLAnd fc-fRLocal oscillation signal carry out
Optics smear；
Wherein, fcFor the centre frequency of optical signal carrier, the sum of the frequency departure of two local oscillators, i.e. fL+fRSize can divide
It Deng Yu not be by light signal symbol rate RSBe more than or equal to 1 integral multiple；
Two paths of signals of the S1.3 after S1.2 optics smear obtains two after balanced detector and low-pass filter again
The different beat signal in road；
S2: the conjugate product of the Fourier transformation of the two-way difference beat signal of step S1 output is calculated, then conjugation is multiplied
Product carries out inverse Fourier transform and obtains time domain cross-correlated signal；Specifically:
The different beat signal of the two-way that S2.1 exports step S1 carries out Fourier transformation respectively and obtains two-way beat frequency letter
Number spectral density；
Wherein, the spectral density of two-way beat signal is denoted as F respectivelyL(f) and FR(f)；
S2.2 calculates separately the conjugate product of the spectral density of two beat signals of step S2.1 output again；
Wherein, the conjugate product of the spectral density of two-way beat signal can pass through F* L(f)FR(f) it calculates, gained is denoted as
PLR(f), F can also be passed throughL(f)F* R(f) gained is denoted as PRL(f)；Calculated especially by formula (1):
PLR(f)=F* L(f)FR(f) or PRL(f)=FL(f)F* R(f) (1)
Wherein, subscript * indicates that conjugation calculates；
S2.3 does inverse Fourier transform to the S2.2 conjugate product exported and is converted to time domain cross-correlated signal；
Resulting time domain cross-correlated signal, is denoted as RLR(τ) or RRL(τ)；
S3: the peak position of time domain cross-correlated signal peak search element search step S2 output time-domain cross-correlated signal,
Obtain the correspondence time of peak position；
That is time domain cross-correlated signal peak search element time domain cross-correlated signal R that described the second processing unit is obtainedLR
(τ) or RRL(τ) is scanned for, and finds position of the peak value in the time domain cross-correlated signal, it is corresponding that peak position is calculated
Time；
Wherein, the peak position corresponding time, it is denoted as T；
S4: it is calculated in step S1 according to the correspondence time of the peak position of S3 output by the dispersion values of light signal；
Wherein, dispersion values are calculated especially by following formula (2):
Wherein, c indicates that vacuum light speed, λ are the wavelength of optical signal, and Dz is dispersion values；
So far, from step S1 to step S4, the method that completes the dispersive estimates in a kind of optical fiber telecommunications system.
Beneficial effect
The present invention is based on the dispersion estimation methods of heterodyne coherent reception, compared with existing dispersion estimation method, have such as
It is lower the utility model has the advantages that
1. the dispersion that the method for the invention can quickly and accurately measure optical fiber link；
2. the method for the invention has the characteristics that measurement range is wide and measurement error is low；
3. the method for the invention is suitable for more modulation format, including QPSK, 16QAM, 64QAM etc.；
4. the method for the invention has robustness to optical signal to noise ratio (OSNR), laser linewidth and nonlinear effect；
5. the dispersion measurement device structure that the method for the invention is relied on is simple, be easily integrated and without to transmitter into
Row changes.
Detailed description of the invention
Fig. 1 is dispersion estimation method in a kind of heterodyne of the present invention relevant dispersion estimation method and device and embodiment 1
Flow diagram；
Fig. 2 is a kind of dispersive estimates device of the relevant dispersion estimation method and device and embodiment 1 of heterodyne of the present invention
Structural schematic diagram；
Fig. 3 is a kind of the relevant of the relevant dispersion estimation method and device and the dispersive estimates of embodiment 2 of heterodyne of the invention
Beat frequency receiver block diagram；
Fig. 4 is optical time domain cross-correlation letter in a kind of heterodyne of the present invention relevant dispersion estimation method and device and embodiment 2
Number peak value is after the transmission of 1000km optical fiber, through handling obtained peak position figure；
Fig. 5 is optical time domain cross-correlation letter in a kind of heterodyne of the present invention relevant dispersion estimation method and device and embodiment 2
Number peak value is after the transmission of different length optical fiber, the dispersion values and error of estimation.
Specific embodiment
For aforementioned and the object, technical solutions and advantages of the present invention of the invention are more clearly understood, saying below
Bright book will combine the attached drawing in the embodiment of the present invention, and technical solution in the embodiment of the present invention is further elaborated, is saying
In bright book and attached drawing, only certain exemplary embodiments of this invention is specifically disclosed, showing wherein can be using principle of the invention
Some embodiments, it will thus be appreciated that the present invention is not limited to described embodiments, on the contrary, the present invention is appended including falling into
Power.Based on the embodiments of the present invention, obtained by those of ordinary skill in the art without making creative efforts
Other embodiments shall fall within the protection scope of the present invention.
Embodiment 1
The present embodiment dispersion estimation method and device relevant based on a kind of heterodyne of the present invention illustrate specifically in conjunction with attached drawing
A kind of method of dispersive estimates proposed by the invention.Fig. 1 is a kind of side of dispersive estimates described in the present invention and the present embodiment
The flow diagram of method.
As seen from Figure 1, specific implementation step includes:
Step S101: two paths of signals and two centre frequencies will be divided by light signal with luminous-power distributor in receiving end
Different local oscillation signals carries out relevant beat reception, and the different electric signal of two-way is obtained after balance detection；
Specifically, the two paths of signals local oscillation signal different from two centre frequencies carry out relevant beat reception be with two in
Frequency of heart is respectively fc+fLAnd fc-fRLocal oscillation signal carry out optics smear.Two paths of signals after optics smear is visited through overbalance
Analog-to-digital conversion is carried out after surveying device, low-pass filter, the sample frequency of analog-to-digital conversion is fS.Be converted to the different digital signal of two-way
YL[n] and YR[n].Wherein fcFor the centre frequency for being tested optical signal carrier, the sum of centre frequency deviation of two local oscillation signals fL
+fREqual to by light signal symbol rate RSIntegral multiple, i.e., one times, twice, three times or four times etc., it may be assumed that
(fL+fR)∈{RS,2RS,3RS,4RS}；
Step S102: Fourier transformation is carried out to two path signal and obtains their spectral density, calculates two path signal
The conjugate product of spectral density, when finally doing inverse Fourier transform to the conjugate product of two path signal spectral density and obtaining one
Domain cross-correlated signal；
Specifically: the two ways of digital signals Y for obtaining step S101L[n] and YR[n] does Digital Signal Processing, specific practice
For to digital signal YL[n] and YR[n] carries out Fast Fourier Transform (FFT), then does conjugate multiplication, finally carries out fast Fourier transforma
Get time domain cross-correlated signal sequence R [n] in return, calculation is as follows:
IFFT{conj[FFT{YL[n]}]*FFT{YR[n]}}
Wherein, conj [] is to take conjugation, and FFT { } is Fast Fourier Transform (FFT), and IFFT { } is that fast Fourier is inverse
Transformation.
Step S103: the time domain cross-correlated signal peak that above-mentioned time domain cross-correlated signal determines the time domain cross-correlated signal is searched for
It is worth position, the time domain cross-correlated signal peak position is corresponding with by the dispersion values of light signal；
Specifically: the time domain cross-correlated signal sequence R [n] that search is obtained by step S102 Digital Signal Processing looks for the sequence
The sequence number m of peak position in column is T according to the peak position calculating peak value corresponding time.Calculation formula are as follows:
Wherein, fSFor sample frequency.
Step S104: it according to the time domain cross-correlated signal peak position, is calculated by the dispersion values of light signal；
The corresponding time T of peak position obtained especially by step S103, determines the dispersion values of optical fiber link.Formula is
Wherein, c indicates that vacuum light speed, λ are the wavelength of optical signal, and Dz is dispersion values.
Fig. 2 is the structural schematic diagram of the dispersive estimates device of the embodiment of the present invention, from figure 2 it can be seen that the device 200
It include: that first processing units 201, the second processing unit 202, time domain cross-correlated signal peak search element 203 and dispersion calculate
Unit 204.
First processing units 201: two paths of signals will be divided into light power divider by light signal in receiving end, with two
Centre frequency is fc+fLAnd fc-fRLocal oscillation signal carry out optics smear, obtain two-way using balance detection, low-pass filter
Different beat signal u1(t) and u2(t).And the difference f of two local oscillation signal centre frequenciesL+fRSize need meet { fL+fR|
Rs,2RS,3RS... condition, wherein RSFor by light signal symbol rate.
The second processing unit 202: the two-way beat signal u that the first processing units are obtained1(t) and u2(t) located
Reason, obtains a time domain cross-correlated signal R (τ), and processing method is as follows,
Mode one:
Mode two:
Wherein,For Fourier transformation,For inverse Fourier transform,To be taken after Fourier transformation altogether
Yoke.
Time domain cross-correlated signal peak search element 203: the time domain that the unit obtains described the second processing unit is mutual
OFF signal R (τ) is scanned for, and finds position of the peak value in the time domain cross-correlated signal, it is corresponding that peak position is calculated
Time is T.
Dispersion computing unit 204: the peak position pair obtained according to the time domain cross-correlated signal peak search element 203
The time T answered is calculated, and determines that, by the dispersion values of light signal, calculation formula is as follows:
Wherein, c indicates that vacuum light speed, λ are the wavelength of optical signal, and Dz is dispersion values.
Embodiment 2
The present embodiment 2 elaborates the relevant of device described in a kind of heterodyne of the present invention relevant dispersion estimation method and device
The principle of beat frequency receiver.It as shown in Fig. 3, is the principle of the relevant beat frequency receiver of device of the present invention.
Shown in Fig. 3, two paths of signals is divided into after luminous-power distributor by light signal, respectively with two centre frequencies
For fc+fLAnd fc-fRLocal oscillation signal optics smear is carried out in two 90 ° of frequency mixers, it may be assumed that 90 ° of 1 Hes of Hybrid in Fig. 3
90 ° of Hybrid_2 are input to LPF, i.e. low-pass filter then using balanced detector, using ADC, i.e. simulation numeral
Converter inputs in digital signal processor DSP and carries out Digital Signal Processing, calculates by the dispersion values of light signal.
With reference to the accompanying drawing and simulation example, optical fiber link dispersion estimation method proposed by the present invention is done and is further explained
It states.
Coherent fiber communication system is built in VPI, in the light that transmitting terminal sends 25G baud rate, modulation format is 16QAM
Signal carries out Digital Signal Processing in receiving end after light coherent reception and digital-to-analogue conversion and estimates after optical fiber link transmits
Count the dispersion values of optical fiber link.Wherein the abbe number of optical fiber is 16ps/nm/km, chromatic dispersion gradient 80s/m3, and launched power is
The line width of 0dBm, optical signal to noise ratio 15dB, local oscillator laser take 100KHz.
As shown in figure 3, two-way will be divided by light signal with two centre frequencies with luminous-power distributor in receiving end being
fc+fLAnd fc-fRLocal oscillation signal carry out optics smear, be converted to two-way by balance detection, the laggard line number mould of low-pass filtering
Beat frequency digital signal, and then Digital Signal Processing is carried out, processing mode is as follows
IFFT{conj[FFT{YL[n]}]*FFT{YR[n]}}
Wherein, conj [] is to take conjugation, and FFT { } is Fast Fourier Transform (FFT), and IFFT { } is that fast Fourier is inverse
Transformation.Two ways of digital signals obtains a signal sequence relevant to dispersion after processing, if Fig. 4 is that optical signal passes through 1000km
After optical fiber transmission, the signal sequence relevant to dispersion that is handled with method proposed by the present invention.Wherein horizontal axis represents the time,
The longitudinal axis is that timing signal sequence normalizes amplitude, as, comprising a peak value, position and the dispersion values of peak value have in Fig. 4 signal sequence
One-to-one relationship can estimate dispersion by the peak value.The peak position of the signal sequence relevant to dispersion is searched for,
The corresponding time 1/F of peak value is calculated, is further determined that by the dispersion values of light signal.Fig. 5 is that signal transmits 100km in optical fiber
To 1000km it is corresponding it is tired integrate dispersion values as 1600ps/nm to 16000ps/nm in the case where using the method for the present invention measurement color
It dissipates as a result, wherein X-axis is actual dispersion values, left Y-axis is the dispersion values estimated with the method for the present invention, and right Y-axis is dispersion
Measurement error.Real CD (ps/nm) is the true dispersion values of signal in figure, and Estimated CD (ps/nm) is the dispersion of estimation
Value, Error CD (ps/nm) represent dispersive estimates error, as shown in figure 5, the true dispersion values when signal arrive for 1600ps/nm
The worst error of 16000ps/nm dispersive estimates is no more than 20ps/nm.It can be seen that by the result of Fig. 5, this method can be measured accurately
The dispersion values of different optical fiber two-way.
The above description is merely a specific embodiment, but scope of protection of the present invention is not limited thereto, for
Those skilled in the art, in the case where not departing from spirit and claims of the present invention range, thought according to the present invention
It is all within the scope of the present invention that various variants and modifications are made to the present invention with principle.
Claims (1)
1. a kind of relevant dispersion estimation method of heterodyne, it is characterised in that: the dispersive estimates device of support, including the first processing are single
Member, the second processing unit, time domain cross-correlated signal peak search element and dispersion computing unit；
Wherein, all units of the dispersive estimates device are respectively positioned in receiving end；
The connection relationship of each unit is as follows in the dispersive estimates device:
First processing units connect the second processing unit；The second processing unit connects time domain cross-correlated signal peak search element；
Time domain cross-correlated signal peak search element connects dispersion computing unit；
The relevant dispersion estimation method of the heterodyne, comprising the following steps:
S1: receiving end optical fiber link is transmitted after tested channel optical signal carry out branch, optics smear, balance detection and
Low-pass filtering obtains the different beat signal of two-way, specifically:
S1.1 first processing units will be divided into two paths of signals with light power divider by light signal；
Wherein, it is tested the optical signal of channel, referred to as by light signal, symbol rate is denoted as RS；
The S1.1 two paths of signals exported and two centre frequencies are respectively f by S1.2c+fLAnd fc-fRLocal oscillation signal carry out optics
Smear；
Wherein, fcFor the centre frequency of optical signal carrier, the sum of the frequency departure of two local oscillators, i.e. fL+fRSize be equal to it is tested
Optical signal symbol rate RSBe more than or equal to 1 integral multiple；
Two paths of signals of the S1.3 after S1.2 optics smear obtains two-way not again after balanced detector and low-pass filter
Same beat signal；
S2: calculate step S1 output two-way difference beat signal Fourier transformation conjugate product, then to conjugate product into
Row inverse Fourier transform obtains time domain cross-correlated signal, specifically:
The different beat signal of the two-way that S2.1 exports step S1 carries out Fourier transformation respectively and obtains two-way beat signal
Spectral density；
Wherein, the spectral density of two-way beat signal is denoted as F respectivelyL(f) and FR(f)；
S2.2 calculates separately the conjugate product of the spectral density of two beat signals of step S2.1 output again；
Wherein, the conjugate product of the spectral density of two-way beat signal can pass through F* L(f)FR(f) it calculates, gained is denoted as PLR
(f), F can also be passed throughL(f)F* R(f) gained is denoted as PRL(f)；Calculated especially by formula (1):
PLR(f)=F* L(f)FR(f) or PRL(f)=FL(f)F* R(f) (1)
Wherein, subscript * indicates that conjugation calculates；
S2.3 does inverse Fourier transform to the S2.2 conjugate product exported and is converted to time domain cross-correlated signal；
Resulting time domain cross-correlated signal, is denoted as RLR(τ) or RRL(τ)；S3: time domain cross-correlated signal peak search element search step
The peak position of rapid S2 output time-domain cross-correlated signal, obtains the correspondence time of peak position, specifically:
The time domain cross-correlated signal R that time domain cross-correlated signal peak search element obtains described the second processing unitLR(τ) or RRL
(τ) is scanned for, and finds position of the peak value in the time domain cross-correlated signal, the peak position corresponding time is calculated；
Wherein, the peak position corresponding time, it is denoted as T；
S4: it is calculated in step S1 according to the correspondence time of the peak position of S3 output by the dispersion values of light signal；
Wherein, dispersion values are calculated especially by following formula (2):
Wherein, c indicates that vacuum light speed, λ are the wavelength of optical signal, and Dz is dispersion values.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101795167A (en) * | 2010-01-27 | 2010-08-04 | 中国人民解放军理工大学 | High-precision time-delay precompensation optical fiber timing method |
| WO2013113378A1 (en) * | 2012-02-01 | 2013-08-08 | Huawei Technologies Co., Ltd. | Method for estimating a chromatic dispersion of a received optical signal |
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| CN101795167A (en) * | 2010-01-27 | 2010-08-04 | 中国人民解放军理工大学 | High-precision time-delay precompensation optical fiber timing method |
| WO2013113378A1 (en) * | 2012-02-01 | 2013-08-08 | Huawei Technologies Co., Ltd. | Method for estimating a chromatic dispersion of a received optical signal |
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