CN102724151A - Communication system, communication method, multichannel adaptive equalizer and OFDM (orthogonal frequency division multiplexing) signal demultiplexing method - Google Patents

Abstract

The invention discloses a communication system, a communication method, a multichannel adaptive equalizer and an OFDM (orthogonal frequency division multiplexing) signal demultiplexing method. The OFDM signal demultiplexing method includes the steps: receiving OFDM optical signals multiplexed by N-channel optical subcarrier waves, demodulating the OFDM optical signals by respectively using series intrinsic light different in angular frequency so as to obtain corresponding OFDM electrical signals; and after adjacent frequency band signals except for baseband signals are subjected to attenuation of a low-pass filter, sampling the OFDM electrical signals in each channel so as to obtain corresponding OFDM electrical signal sampling values, and then reducing data carried by the corresponding optical subcarrier waves in each channel by using a multichannel balance matrix to multiply by the N-channel OFDM electrical signal sampling values. The OFDM signal demultiplexing method has the advantages that a receiving end does not require strict match of sampling time of signal demodulation in each channel, sampling rate is determined by modulating signal rate carried by single optical carrier wave, ADC (analog-to-digital converter) bottleneck restriction can be bypassed, and the method is applicable to the high-speed optical communication system.

Description

The method of communication system, communication means and multi-channel adaptive equalizer and ofdm signal demultiplexing

Technical field

The present invention relates to communication system, be specifically related to the method for communication system, communication means and multi-channel adaptive equalizer and ofdm signal demultiplexing.

Background technology

Optical communication mainly contains Time Division Multiplexing and two kinds of technology paths of wavelength division multiplexing (WDM) to high speed development.Time division multiplexing is that various signals is interweaved in the different time section, along same Channel Transmission, again the signal extraction in each time period is come out to be reduced into primary signal at receiving terminal; At present; Adopt coherent optical communication technology and palarization multiplexing QPSK (QPSK) modulation, can realize the transmission rate of single wavelength 100G, still; It is the analog to digital converter of tens G that this scheme requires to adopt sample rate at receiving terminal; Because this is near the limit of electronic device, therefore, the method that directly improves transmission rate can't be used for the TDM optical communication system of higher rate.The way of wavelength division multiplexing is, at transmitting terminal signal is divided into multichannel, is modulated to respectively on the light carrier of different frequency to transmit; Recover and carry out demultiplexing again at receiving terminal; Therefore, the processing speed of receiving terminal electronic device requires by each road signal rate decision, and is relatively low.So WDM is the main direction of high speed optical communication development.

But traditional wavelength-division multiplex system requires that the protection interval much larger than spectrum modulation signal is arranged between the different light carriers, so that optical filter separates it, thereby causes huge frequency spectrum waste.OFDM (Orthogonal Frequency Division Multiplexing has been proposed for this reason; OFDM) technology; WDM signal (hereinafter to be referred as ofdm signal) after adopting OFDM multiplexing is made up of mutually orthogonal a plurality of optical carriers of next-door neighbour; Because each light carrier is closely adjacent in the ofdm signal, is accustomed in the industry each light carrier is called subcarrier, the basic principle of OFDM is following:

If the transmission cycle of ofdm signal is T; Then the interval delta f between the different sub carrier is Δ f=1/T; So, receive signal r (t) and can be expressed as

wherein:

C _kBe the transmission data of k number of sub-carrier, f _k(t) expression k number of sub-carrier.

To receive signal r (t) and in a code-element period, do cross-correlation, then have with intrinsic light

${\∫}_0^{T}r\left(t\right)f_m\left(t\right)\mathrm{dt}={\mathrm{\δ}}_{\mathrm{km}}{C}_k---\left(1\right)$

δ when k=m _Km=1, δ when k ≠ m _Km=0.

Can find out from formula (1), even the different sub carrier spectrum overlapping still can be eliminated different interchannel crosstalking fully.Receive certain subcarrier signals, only need the light signal that receives is done cross-correlation with corresponding intrinsic light carrier in a code-element period, can propose the data-signal of sending out, and the crosstalking of other light carriers of cancellation.

Because it is with high costs that serial intrinsic light of generation and receiving optical signals are done cross-correlation; So the actual coherent light OFDM receive mode that generally adopts is; With an intrinsic optical modulator ofdm signal, use high-speed AD (analog to digital converter) that restituted signal is sampled again earlier, do DFT then.For example, suppose that the ofdm signal that receives has 128 number of sub-carrier, then need in a code-element period, carry out 128 times time domain sample, do 128 DFT again, obtain the entrained data-signal of each subcarrier.

Though OFDM adopts the parallel transmitting-receiving of N number of sub-carrier, also requires each symbol sample N time (N is a carrier number).So, use discrete fourier transform method to handle ofdm signal at present, its receiving velocity is the same with single carrier, still receives the restriction of ADC sampling rate.

Summary of the invention

To the defective that exists in the prior art, the object of the present invention is to provide a kind of method to the multiplexing optical carrier demultiplexing of employing OFDM, may further comprise the steps:

The OFDM light signal that reception is become by N road photon carrier multiplexing, multiplexing method is: photon carrier wave entrained data in k road are by modulation signal I _k+ jQ _kBeing modulated at angular frequency is Ω _C+ k Ω ₀K road photon carrier wave on, Ω _CBe the angular frequency of the 0 road photon carrier wave, Ω ₀=2 π Δ f, Δ f=1/T, T are the transmission cycle of OFDM light signal, k=0 .., N-1;

The serial intrinsic light that uses different angular frequencies respectively obtains the corresponding OFDM signal of telecommunication to the demodulation of said OFDM light signal; Demodulation method is: use angular frequency to be Ω _C+ m Ω ₀Intrinsic light demodulation obtains the m road OFDM signal of telecommunication to the OFDM light signal, each road OFDM signal of telecommunication is made up of a baseband signal and N-1 the band signal adjacent with this baseband signal, with intrinsic light Ω _C+ m Ω ₀The photon carrier down-conversion that frequency is identical is a baseband signal, with intrinsic light Ω _C+ m Ω ₀The photon carrier down-conversion that frequency is different is the nearby frequency bands signal adjacent with this baseband signal, m=0 .., N-1;

Each road OFDM signal of telecommunication is sampled behind the nearby frequency bands signal beyond its baseband signal of low pass filter decay respectively, obtains corresponding OFDM signal of telecommunication sampled value, and wherein, m road OFDM signal of telecommunication sampled value does

In the formula, I _m+ jQ _mAnd I _k+ jQ _kBe respectively m road photon carrier wave modulation signal and k road (modulation signal of photon carrier wave of k ≠ m), and; h _MmBe stack coefficient corresponding in the OFDM signal of telecommunication of m road with m road photon carrier wave, h _MkBe stack coefficient corresponding in the OFDM signal of telecommunication of m road with other subcarriers, h _MmAnd h _MkConstitute one N * N multichannel stack matrix, said multichannel stack inverse of a matrix matrix is the balanced matrix of multichannel of multichannel equilizer, and the matrix element of the balanced matrix of said multichannel is called equalizing coefficient, and said equalizing coefficient adopts gradient algorithm to calculate;

Multiply by said N road OFDM signal of telecommunication sampled value with the balanced matrix of said multichannel and restore the corresponding entrained data of each road photon carrier wave.

In the method for above-mentioned demultiplexing,

Be that m road frequency is Ω _C+ m Ω ₀The initial phase of intrinsic light;

θ _kIt is the initial phase of k road photon carrier wave;

t _mBe of the sampling instant of the m road OFDM signal of telecommunication in code element 0.

In the method for above-mentioned demultiplexing, the balanced matrix of said multichannel is following stack inverse of a matrix matrix:

$\left[\begin{array}{ccccc}{h}_{00}& ..& h_{0k}& ..& h_{0(N-1)}\\ ..& ..& ..& ..& ..\\ h_{m0}& ..& h_{\mathrm{mk}}& ..& h_{m(N-1)}\\ ..& ..& ..& ..& ..\\ h_{(N-1)0}& ..& h_{(N-1)k}& ..& h_{(N-1)(N-1)}\end{array}\right].$

In the method for above-mentioned demultiplexing, it is multiplexing that every way carrier signal of transmitting terminal adopts two polarization states to carry out respectively, and the balanced matrix of said multichannel is F=(HP) ^-1, wherein:

H is a multicarrier stack matrix,

$H=\left[\begin{array}{cccccccc}{h}_{00}^x& 0& ..& h_{0k}^x& 0& ..& h_{0(N-1)}^x& 0\\ 0& h_{00}^y& ..& 0& h_{0k}^y& ..& 0& h_{0(N-1)}^y\\ ..& ..& ..& ..& ..& ..& ..& ..\\ h_{m0}^x& 0& ..& h_{\mathrm{mk}}^x& 0& ..& h_{m(N-1)}^x& 0\\ 0& {\mathrm{<figure-callout\; id="0x"\; label="h\; m"\; filenames="HSA00000734555800011.png"\; state="\{\{state\}\}">h</figure-callout>}}_m^0& ..& 0& h_{\mathrm{mk}}^y& ..& 0& h_{m(N-1)}^y\\ ..& ..& ..& ..& ..& ..& ..& ..\\ h_{(N-1)0}^x& 0& ..& h_{(N-1)k}^x& 0& ..& h_{(N-1)(N-1)}^x& 0\\ 0& h_{(N-1)0}^y& ..& 0& h_{(N-1)k}^y& ..& 0& h_{(N-1)(N-1)}^y\end{array}\right];$

P is a Jones matrix, $P=\left[\begin{array}{cccccccc}{A}_0& {\mathrm{<figure-callout\; id="0"\; label="B"\; filenames="HSA00000734555800011.png"\; state="\{\{state\}\}">B</figure-callout>}}_0& ..& 0& 0& ..& 0& 0\\ C_0& {\mathrm{<figure-callout\; id="0"\; label="D"\; filenames="HSA00000734555800011.png"\; state="\{\{state\}\}">D</figure-callout>}}_0& ..& 0& 0& ..& 0& 0\\ ..& ..& ..& ..& ..& ..& ..& ..\\ 0& 0& ..& A_m& B_m& ..& 0& 0\\ 0& 0& ..& C_m& D_m& ..& 0& 0\\ ..& ..& ..& ..& ..& ..& ..& ..\\ 0& 0& ..& 0& 0& ..& A_{N-1}& B_{N-1}\\ 0& 0& ..& 0& 0& ..& C_{N-1}& D_{N-1}\end{array}\right];$

X and y represent two polarization states, the variation of the A in the Jones matrix, B, C, D expression signal polarization state.

In the method for above-mentioned demultiplexing; Adopt the mode that combines with time-domain equalizer to reduce the unit impulse response of the OFDM signal of telecommunication; The length of said time-domain equalizer is 2L-1 tap; Be about to 2L-1 sample value and multiply by linear, additive summation behind the time domain equalization coefficient, the L value determines by signal impulse response length in time domain, in conjunction with the balanced expression formula of the multichannel equilizer of time-domain equalizer is:

${\mathrm{Eout}}_g^x\left(n\right)=\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{xx}}\left(l\right)\left[{\mathrm{Ein}}_m^x(n-l)\right]+\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{xy}}\left(l\right)\left[{\mathrm{Ein}}_m^y(n-l)\right],$

${\mathrm{Eout}}_g^y\left(n\right)=\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{yx}}\left(l\right)\left[{\mathrm{Ein}}_m^x(n-l)\right]+\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{yy}}\left(l\right)\left[{\mathrm{Ein}}_m^y(n-l)\right],$

Wherein, N representes n code-element period; G representes the data sequence number of multichannel equilizer output; L is the tap sequence number of time-domain equalizer; M representes the passage sequence number of multichannel equilizer input; The sampled value of corresponding m road ofdm signal, the mode that equalizing coefficient

and

adopt gradient method to upgrade automatically converges to automatically and satisfies on the filter factor of offsetting ICI and ISI.

In the method for above-mentioned demultiplexing, updating steps is following automatically for equalizing coefficient and

:

(1) initialization:

works as m=k; works as m=k, and its residual value all is 0;

(2) use gradient algorithm to upgrade, and confirm as and converge to ε automatically ²Minimum value the time value, more new formula is following:

$F_{\mathrm{gm}}^{\mathrm{xx}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{xx}}(l,n)-\mathrm{\&mu;}\frac{\&PartialD;{{\mathrm{\&epsiv;}}_x}^2}{\&PartialD;F_{\mathrm{gm}}^{\mathrm{xx}}(l,n)};$

$F_{\mathrm{gm}}^{\mathrm{xy}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{xy}}(l,n)-\mathrm{\&mu;}\frac{\&PartialD;{{\mathrm{\&epsiv;}}_x}^2}{\&PartialD;F_{\mathrm{gm}}^{\mathrm{xy}}(l,n)};$

$F_{\mathrm{gm}}^{\mathrm{yx}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{yx}}(l,n)-\mathrm{\&mu;}\frac{\&PartialD;{{\mathrm{\&epsiv;}}_y}^2}{\&PartialD;F_{\mathrm{gm}}^{\mathrm{yx}}(l,n)};$

$F_{\mathrm{gm}}^{\mathrm{yy}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{yy}}(l,n)-\mathrm{\&mu;}\frac{\&PartialD;{{\mathrm{\&epsiv;}}_y}^2}{\&PartialD;F_{\mathrm{gm}}^{\mathrm{yy}}(l,n)};$

In the formula: ε representes error, ε ²Corresponding ICI of minimum value and ISI minimum value, n representes to upgrade preceding coefficient value, the coefficient value after n+1 representes more, μ representes a fractional increments.

In the method for above-mentioned demultiplexing, error ε adopts the training sequence method to obtain,

${\mathrm{\&epsiv;}}_g^x=d_g^x\left(n\right)-{\mathrm{Eout}}_g^x\left(n\right);$

${\mathrm{\&epsiv;}}_g^y=d_g^y\left(n\right)-{\mathrm{Eout}}_g^y\left(n\right).$

In the method for above-mentioned demultiplexing, error ε adopts blind estimating method to obtain,

${\mathrm{\&epsiv;}}_g^x=1-{\mathrm{Eout}}_g^x\left(n\right){\left[{\mathrm{Eout}}_g^x\left(n\right)\right]}^{*};$

${\mathrm{\&epsiv;}}_g^y=1-{\mathrm{Eout}}_g^y\left(n\right){\left[{\mathrm{Eout}}_g^y\left(n\right)\right]}^{*}.$

The present invention also provides a kind of ofdm signal Deplexing apparatus; Comprise down-conversion device, low pass filter, acquisition module and digital signal processing module that intrinsic light source, multicarrier generation module, 90 degree frequency mixers and balanced reciver constitute, said intrinsic light source produces intrinsic light Ω _C, Ω _CAngular frequency for the intrinsic light source; Said multicarrier generation module is according to said intrinsic light Ω _CProducing angular frequency behind the shift frequency respectively is Ω _C+ m Ω ₀Serial intrinsic light, Ω ₀=2 π Δ f, Δ f=1/T, T are the transmission cycle of OFDM light signal, m representes m road intrinsic light, m=0 .., N-1; The down-conversion device of said 90 degree frequency mixers and balanced reciver formations respectively with said serial intrinsic light with the OFDM light signal demodulation that N road photon carrier multiplexing becomes, obtain the corresponding N road OFDM signal of telecommunication; Said low pass filter is respectively to each signal beyond its baseband signal of road OFDM signal of telecommunication decay; Said acquisition module is gathered each road OFDM signal of telecommunication respectively, obtains corresponding OFDM signal of telecommunication sampled value; Said digital signal processing module restores the corresponding entrained data of each road photon carrier wave with the balanced matrix multiple of said multichannel respectively to N road OFDM signal of telecommunication sampled value.

In said apparatus; The time-domain equalizer that also comprises the unit impulse response that is used to reduce the OFDM signal of telecommunication; The length of said time-domain equalizer is 2L-1 tap; Be about to 2L-1 sample value and multiply by linear, additive summation behind the time domain equalization coefficient, the L value determines by signal impulse response length in time domain, in conjunction with the balanced expression formula of the multichannel equilizer device of time domain equalization is:

${\mathrm{Eout}}_g^x\left(n\right)=\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{xx}}\left(l\right)\left[{\mathrm{Ein}}_m^x(n-l)\right]+\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{xy}}\left(l\right)\left[{\mathrm{Ein}}_m^y(n-l)\right],$

${\mathrm{Eout}}_g^y\left(n\right)=\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{yx}}\left(l\right)\left[{\mathrm{Ein}}_m^x(n-l)\right]+\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{yy}}\left(l\right)\left[{\mathrm{Ein}}_m^y(n-l)\right],$

Wherein, N representes n code-element period; G representes the data sequence number of multichannel equilizer output; Modulating data corresponding to the g light carrier that calculates; L is the tap sequence number of time-domain equalizer; M representes the passage sequence number of multichannel equilizer input; The sampled value of corresponding m road ofdm signal, the mode that equalizing coefficient

and

adopt gradient method to upgrade automatically converges to automatically and satisfies on the filter factor of offsetting ICI and ISI.

The present invention also provides a kind of communication system, comprises transmitting terminal and receiving terminal, and said receiving terminal is provided with above-mentioned Deplexing apparatus.

The present invention also provides a kind of communication means; Transmitting terminal in communication system; Modulate data on N the orthogonal sub-carriers; And then each orthogonal sub-carriers is closed ripple send to the receiving terminal of communication system through optical fiber, at receiving terminal, adopt and above-mentionedly carry out demultiplexing to the method that adopts the multiplexing optical carrier demultiplexing of OFDM.

The present invention; Do not adopt common fourier transform method that the OFDM light signal is carried out demultiplexing; But utilize the special characteristic of each subcarrier mutually orthogonal (being that the intercarrier frequency interval equals chip rate) in the light ofdm signal; Derive linear superposition and the stack coefficient constant characteristics of the sampled value of the OFDM signal of telecommunication for each sub-carrier modulation data, adopt the balanced method of multi-channel adaptive that synergistic effect is carried out inverse operation, demultiplexing OFDM light signal is also eliminated ICI (interchannel interference).The present invention also can combine the time domain equalization technology to reduce the unit impulse response of sub-carrier signal simultaneously, promptly eliminates ICI (interchannel interference) and ISI (symbol interference) simultaneously.

The multi-channel adaptive equilibrium acceptance method of ofdm signal of the present invention is easy to practicality, and its advantage is:

(1) to receive light with different intrinsic optical modulators after, to each road restituted signal parallel sampling, sample rate is with modulation signal speed to determine by single light carrier with ADC, the bottleneck that can walk around ADC limits.

(2) transmitting terminal need be IFFT.

(3) do not receive the influence of receiving terminal and transmitting terminal light source frequency difference.

(4) at receiving terminal and do not require the strictness coupling in the sampling time of each road restituted signal, the sampling ADC of also not being strict with each road restituted signal quantizes gain and equates.

Description of drawings

Fig. 1 communication system principle schematic provided by the invention;

The demodulation part sketch map of ofdm signal Deplexing apparatus among Fig. 2 the present invention (is example with a passage);

The signal processing sketch map of ofdm signal Deplexing apparatus among Fig. 3 the present invention.

Embodiment

OFDM light signal described in the present invention is meant the multichannel photon carrier wave of a series of mutually orthogonal (up-conversions), and each road photon carrier wave carries corresponding high-speed data respectively, and the described OFDM signal of telecommunication is meant that by angular frequency be Ω _C+ m Ω ₀Intrinsic light the signal of telecommunication that OFDM light signal demodulation (down-conversion) is obtained, each road OFDM signal of telecommunication is made up of a baseband signal and N-1 the band signal adjacent with this baseband signal, with intrinsic light Ω _C+ m Ω ₀The photon carrier down-conversion that frequency is identical is a baseband signal, with intrinsic light Ω _C+ m Ω ₀The photon carrier down-conversion that frequency is different is the nearby frequency bands signal adjacent with this baseband signal, m=0 .., N-1.

Innovative point of the present invention is: and do not adopt Fourier transform commonly used that the OFDM light signal is carried out demultiplexing; But utilize the special characteristic of each the photon carrier wave mutually orthogonal (being that the intercarrier frequency interval equals chip rate) in the OFDM light signal; The OFDM signal of telecommunication sampled value of deriving after the sampling is the linear superposition and the constant characteristics of stack coefficient of each photon carrier modulation data; Adopt the balanced method of multi-channel adaptive that synergistic effect is carried out inverse operation; Thereby restore the entrained data of each road photon carrier wave, and combine the time domain equalization technology to reduce the unit impulse response of the OFDM signal of telecommunication, eliminate ICI (interchannel interference) and ISI (symbol interference) simultaneously.For this reason, the invention provides the method for a kind of communication system, communication means and multi-channel adaptive equalizer and ofdm signal demultiplexing, the present invention is done further explain below in conjunction with accompanying drawing.

As shown in Figure 1, communication means provided by the invention adopts known in the industry IQ modulation technique to modulate data on the photon carrier wave of N quadrature (this process is also referred to as up-conversion process) and closes ripple through Optical Fiber Transmission at transmitting terminal; At receiving terminal; The OFDM light signal that uses a series of mutually orthogonal intrinsic optical modulators to receive obtains the N road OFDM signal of telecommunication; Each road OFDM signal of telecommunication is sampled respectively behind the nearby frequency bands signal beyond the baseband signal in the OFDM signal of telecommunication of this road of low pass filter decay respectively again; Then sampled result is utilized the entrained data of multi-channel adaptive equalizer each photon carrier wave of reduction, and compensate the channel impairments that CD (chromatic dispersion), PMD (polarization mode dispersion) etc. cause simultaneously.Digital processing is undertaken by the DSP module, and the DSP module can be FPGA, also can be custom-designed dsp chip, but top two kinds of elements below being not limited to.

Specifically:

A. at the transmitting terminal of communication system, the mode of the known in the industry IQ modulation technique of The data with up-conversion modulated data on the photon carrier wave of N quadrature, and then each photon carrier wave is closed behind the ripple receiving terminal that sends to communication system through optical fiber.Modulator approach is: photon carrier wave entrained data in k road are by modulation signal I _k+ jQ _kBeing modulated at angular frequency is Ω _C+ k Ω ₀K road photon carrier wave on, Ω _CBe the angular frequency of the 0 road photon carrier wave, Ω ₀=2 π Δ f, Δ f=1/T, T are the transmission cycle of OFDM light signal, k=0 .., N-1.

At receiving terminal, the mode that adopts down-conversion obtains the corresponding OFDM signal of telecommunication with the OFDM light signal demodulation that receives; Demodulation method is: use angular frequency to be Ω _C+ m Ω ₀Intrinsic light demodulation obtains the m road OFDM signal of telecommunication to the OFDM light signal, each road OFDM signal of telecommunication is made up of a baseband signal and N-1 the band signal adjacent with this baseband signal, with intrinsic light Ω _C+ m Ω ₀The photon carrier down-conversion that frequency is identical is a baseband signal, with intrinsic light Ω _C+ m Ω ₀The photon carrier down-conversion that frequency is different is the band signal adjacent with baseband signal, m=0, and .., N-1, the frequency of the down-conversion of the receive path corresponding with the m road OFDM signal of telecommunication is f _C+ m Δ f, then frequency is f _CThe photon carrier signal of+m Δ f is down converted to the base band in the OFDM signal of telecommunication of m road, and the both sides that the signal of other frequencies is down converted to the base band in the OFDM signal of telecommunication of m road form the nearby frequency bands signal, like this, through down-conversion, obtains the N road OFDM signal of telecommunication.

Among Fig. 1, the modulation of transmitting terminal representes with a mathematic(al) representation that with signal times what reality was corresponding is the IQ modulation, generally realizes through both arms MZ interferometer.The separating of receiving terminal called signal times and represented that with a mathematic(al) representation corresponding is the IQ demodulation, realized by the ofdm signal Deplexing apparatus, and the concrete structure of ofdm signal Deplexing apparatus will further be introduced afterwards in detail.

B. each road OFDM signal of telecommunication is passed through low pass filter respectively, decling phase is answered the adjacent signals beyond the baseband signal.

C. through the ADC acquisition module each road OFDM signal of telecommunication is sampled, each cycle data once sampling or secondary, the N road OFDM signal of telecommunication sampled value that obtains, each road OFDM signal of telecommunication sampled value is the linear superposition of N road photon carrier wave institute adjusting data.

D. at digital signal processing module, utilize the balanced matrix of multichannel to multiply by each road OFDM signal of telecommunication sampled value and restore the entrained data of each photon carrier wave in the OFDM light signal, concrete grammar will further be introduced afterwards in detail.

Fig. 2 shows the demodulation part sketch map of ofdm signal Deplexing apparatus; This sketch map only illustrates with a passage; As shown in Figure 2, ofdm signal Deplexing apparatus provided by the invention comprises: intrinsic light source, multicarrier generation device, optical filter, polarization beam apparatus, the demodulating equipment, low pass filter, acquisition module and the digital signal processing module that are made up of 90 degree frequency mixers and balanced reciver.The intrinsic light source is a laser, and sending frequency is the intrinsic light of fC, and is respectively f through multicarrier generation device (frequency is the modulation signal shift frequency of Δ f) generation carrier frequency _C, f _C+ Δ f, f _C+ 2 Δ f ..., f _C+ (N-1) the serial intrinsic light of Δ f, leaching m the required frequency of passage down-conversion through optical filter again is f _CThe intrinsic light of+m Δ f, the demodulating equipment that is made up of 90 degree frequency mixers and balanced recivers obtains the corresponding N road OFDM signal of telecommunication to the demodulation of OFDM light signal.Acquisition module is sampled to each road OFDM signal of telecommunication, the N road OFDM signal of telecommunication sampled value that obtains, and digital signal processing module utilizes the balanced matrix of multichannel to multiply by each road OFDM signal of telecommunication sampled value and restores the entrained data of each photon carrier wave in the OFDM light signal.The multicarrier generation device adopts known frequency shift technique to realize, and the dispersion compensation among Fig. 2 adopts known technology in the industry, repeats no more at this.

Below in conjunction with operation principle and reasoning process to provided by the invention to the method that adopts the multiplexing optical carrier demultiplexing of OFDM, carry out detailed explanation.

At the transmitting terminal of communication system, N road photon carrier multiplexing becomes the OFDM light signal, and modulator approach is not given unnecessary details at this as previously mentioned at present.

The carrier frequency of N road photon carrier wave is respectively f _C, f _C+ Δ f, f _C+ 2 Δ f ..., f _C+ (N-1) Δ f, so the expression formula of OFDM light signal is:

(I ₀+jQ ₀)exp[jΩ _Ct+θ ₀]+..+( _IK+jQ _K)exp[jΩ _Ct+j(K)Ω ₀t+θ _k]+..+

(2)

(I _N-1+jQ _N-1)exp[jΩ _Ct+j(N-1)Ω ₀t+θ _N-1]

I _k+ jQ _kBe the modulation signal of k road photon carrier wave, θ _kBe the initial phase of k road photon carrier wave, Ω _CBe the angular frequency of the 0 road photon carrier wave, Ω ₀=2 π Δ f, Δ f=1/T, T are the transmission cycle of OFDM light signal, k=0 .., N-1.

At receiving terminal, use the serial intrinsic light of different angular frequencies respectively, in a code-element period,, obtain the corresponding OFDM signal of telecommunication to the demodulation of said OFDM light signal, the concrete practice is: use angular frequency to be Ω _C+ m Ω ₀The m road OFDM signal of telecommunication that obtains after to the demodulation of OFDM light signal of intrinsic light, the m road OFDM signal of telecommunication is expressed as:

formula (3)

Wherein:

is the initial phase of m road intrinsic light; M=0; .., N-1.

Each road OFDM signal of telecommunication still is made up of the N sub-carrier signals; Comprise a baseband signal and N-1 the nearby frequency bands signal adjacent with this baseband signal; But which photon carrier wave is determined by demodulation intrinsic light frequency to corresponding base band by shift frequency; For example: baseband signal and nearby frequency bands signal in the OFDM signal of telecommunication of m road are obtained by following mode, with Ω _C+ m Ω ₀The photon carrier signal that the intrinsic light frequency is identical (being k=m) will down-convert to the baseband signal in the OFDM signal of telecommunication of m road, with Ω _C+ m Ω ₀The photon carrier signal that the intrinsic light frequency is different (be k ≠ m) will down-convert to the m road OFDM signal of telecommunication in the band signal adjacent with baseband signal.

Each road OFDM signal of telecommunication is sampled behind the nearby frequency bands signal beyond its baseband signal of low pass filter decay respectively, obtains corresponding OFDM signal of telecommunication sampled value, and the sampling instant of establishing the m road OFDM signal of telecommunication is t _m, then the sampled value of the m road OFDM signal of telecommunication is:

${\mathrm{Ein}}_m=(I_m+{\mathrm{jQ}}_m)h_{\mathrm{mm}}+\underset{k\&NotEqual;m}{\overset{N-1}{\mathrm{\&Sigma;}}}(I_k+j{Q}_k)h_{\mathrm{mk}}---\left(4\right)$

First expression in the formula (4) is modulated to the data on the photon carrier wave of m road, and second from crosstalking h _MmBe constant, represent the stack coefficient of corresponding m road photon carrier wave in the OFDM signal of telecommunication of m road, h _MkBe the stack coefficient of corresponding other road photon carrier waves in the OFDM signal of telecommunication of m road, visible, sampled value E _InmMust receive and close on crosstalking of photon carrier wave.

The stack coefficient h _MmAnd h _MkIn, the corresponding m of first m road OFDM signal of telecommunication in the subscript, the corresponding k of the k in subscript road photon carrier wave, when k=m, h _MkCan directly be written as h _Mm, I _m+ jQ _mAnd I _k+ jQ _kBe respectively the modulation signal of m road photon carrier wave and the modulation signal of k road photon carrier wave.

The stack coefficient h _MmAnd h _MkConstitute one N * N matrix; Be called multichannel stack matrix; Multichannel stack inverse of a matrix matrix is called the balanced matrix of multichannel, multiply by N road sampled value with the balanced matrix of multichannel and then can recover the data that are modulated on the photon carrier wave of N road, and the matrix element of the balanced matrix of multichannel is called the equalizing coefficient of multichannel equilizer; The equalizing coefficient of multichannel equilizer can not record the stack coefficient earlier, and directly calculates with gradient algorithm.

Supposing the sampling instant in code element 0, is t to the OFDM signal of telecommunication sampling instant of m road _m,, be t to the sampling instant of the m road OFDM signal of telecommunication then in the sampling instant of code element n _m+ nT, so in the sampling instant of code element n:

formula (7)

In the formula (7),

The stack coefficient of expression code element n,

The stack coefficient of expression code element 0, visible, h _MkIt also is constant.Then each element of multichannel stack matrix keeps constant in different code elements, sampled data is implemented linear equalization eliminates interchannel and crosstalks so can correspondence try to achieve the balanced matrix of multichannel.

Like this, N the linear superposition that OFDM signal of telecommunication sampled value all is the entrained modulating data of N road photon carrier wave that sampling obtains can be expressed as:

$\left[\begin{array}{c}{\mathrm{<figure-callout\; id="0"\; label="Ein"\; filenames="HSA00000734555800011.png"\; state="\{\{state\}\}">Ein</figure-callout>}}_0\\ ..\\ {\mathrm{Ein}}_m\\ ..\\ {\mathrm{Ein}}_{N-1}\end{array}\right]=\left[\begin{array}{ccccc}{h}_{00}& ..& h_{0k}& ..& h_{0(N-1)}\\ ..& ..& ..& ..& ..\\ {\mathrm{<figure-callout\; id="0"\; label="h\; m"\; filenames="HSA00000734555800011.png"\; state="\{\{state\}\}">h</figure-callout>}}_m& ..& h_{\mathrm{mk}}& ..& h_{m(N-1)}\\ ..& ..& ..& ..& ..\\ h_{(N-1)0}& ..& h_{(N-1)k}& ..& h_{(N-1)(N-1)}\end{array}\right]\&CenterDot;\left[\begin{array}{c}{I}_0+\mathrm{<figure-callout\; id="0"\; label="j\; Q"\; filenames="HSA00000734555800011.png"\; state="\{\{state\}\}">j</figure-callout>}{Q}_{}{}_0\\ ..\\ I_k+j{Q}_k\\ ..\\ I_{n-1}+{\mathrm{jQ}}_{N-1}\end{array}\right]---\left(8\right)$

Visible according to formula 8, can solve the entrained data of N road photon carrier signal by N sampled value, briefly be exactly that formula (8) inverse matrix that each side multiply by H gets final product.Because the OFDM signal of telecommunication is made up of baseband signal, the nearby frequency bands signal adjacent with base band; The OFDM signal of telecommunication is behind low pass filter, and the nearby frequency bands signal will be attenuated, therefore; In the stack matrix; Corresponding to the absolute value of the stack coefficient of the nearby frequency bands stack coefficient much smaller than baseband signal, above-mentioned relation uses mathematical expression to be ABS (h _MmABS (the h of)＞＞ _Mk), m ≠ k, the difference of k and m is big more, its coefficient h _MkMore little, such matrix determinant can not be 0, therefore can have inverse matrix all the time.

Owing in optical communication, generally adopt polarization multiplexing; Every road photon carrier wave is made up of the light carrier of two independent polarization states; Like this; Need distinguish modulating data and produce the OFDM light signal of palarization multiplexing at transmitting terminal, the change of polarization state will take place in the polarization signal light of both direction after Optical Fiber Transmission, and it changes available original polarization state and multiply by Jones matrix $\left[\begin{array}{cc}{A}_m& B_m\\ C_m& D_m\end{array}\right]$ Expression, so behind the consideration palarization multiplexing, the 2N road OFDM signal of telecommunication that obtains after the sampling can be expressed as with matrix multiple:

$\left[\begin{array}{c}{\mathrm{<figure-callout\; id="0x"\; label="Ein"\; filenames="HSA00000734555800011.png"\; state="\{\{state\}\}">Ein</figure-callout>}}_0^x\\ {\mathrm{Ein}}_0^y\\ ..\\ {\mathrm{Ein}}_m^x\\ {\mathrm{Ein}}_m^y\\ ..\\ {\mathrm{Ein}}_{N-1}^x\\ {\mathrm{Ein}}_{N-1}^y\\ \end{array}\right]=\left[\begin{array}{ccccccccc}{h}_{00}^x& 0& ..& h_{0k}^x& 0& ..& h_{0(N-1)}^x& 0& \\ 0& h_{00}^y& ..& 0& h_{0k}^y& ..& 0& h_{0(N-1)}^y& \\ ..& ..& ..& ..& ..& ..& ..& ..& \\ {\mathrm{<figure-callout\; id="0x"\; label="h\; m"\; filenames="HSA00000734555800011.png"\; state="\{\{state\}\}">h</figure-callout>}}_m^0& 0& ..& h_{\mathrm{mk}}^x& 0& ..& h_{m(N-1)}^x& 0& \\ 0& {\mathrm{<figure-callout\; id="0x"\; label="h\; m"\; filenames="HSA00000734555800011.png"\; state="\{\{state\}\}">h</figure-callout>}}_m^0& ..& 0& h_{\mathrm{mk}}^y& ..& 0& h_{m(N-1)}^y& \\ ..& ..& ..& ..& ..& ..& ..& ..& \\ h_{(N-1)0}^x& 0& ..& h_{(N-1)k}^x& 0& ..& h_{(N-1)(N-1)}^x& 0& \\ 0& h_{(N-1)0}^y& ..& 0& h_{(N-1)k}^y& ..& 0& h_{(N-1)(N-1)}^y& \\ & & & & & & & & \end{array}\right]\&CenterDot;$

$\left[\begin{array}{cccccccc}{A}_0& {\mathrm{<figure-callout\; id="0"\; label="B"\; filenames="HSA00000734555800011.png"\; state="\{\{state\}\}">B</figure-callout>}}_0& ..& 0& 0& ..& 0& 0\\ C_0& {\mathrm{<figure-callout\; id="0"\; label="D"\; filenames="HSA00000734555800011.png"\; state="\{\{state\}\}">D</figure-callout>}}_0& ..& 0& 0& ..& 0& 0\\ ..& ..& ..& ..& ..& ..& ..& ..\\ 0& 0& ..& A_m& B_m& ..& 0& 0\\ 0& 0& ..& C_m& D_m& ..& 0& 0\\ ..& ..& ..& ..& ..& ..& ..& ..\\ 0& 0& ..& 0& 0& ..& A_{N-1}& B_{N-1}\\ 0& 0& ..& 0& 0& ..& C_{N-1}& D_{N-1}\end{array}\right]\&CenterDot;\left[\begin{array}{c}{I}_0^x+\mathrm{<figure-callout\; id="0x"\; label="j\; Q"\; filenames="HSA00000734555800011.png"\; state="\{\{state\}\}">j</figure-callout>}{Q}_{}^{}{}_0^x\\ I_0^y+j{Q}_0^y\\ ..\\ I_k^x+j{Q}_k^x\\ I_k^y+j{Q}_k^x\\ ..\\ I_{N-1}^x+j{Q}_{N-1}^x\\ I_{N-1}^y+j{Q}_{N-1}^y\end{array}\right]$ Formula (9)

First matrix is H in the definition (9), corresponding to the signal filtering of receiving terminal and the stack coefficient after the sampling; Defining second matrix is P, corresponding to the variation of polarization state in the signal transmission, so a demand goes out its inverse matrix F=(HP) ^-1, and multiply by the OFDM signal of telecommunication sampled value that obtains of sampling and promptly can restore by the entrained data of OFDM light signal.

As everyone knows; In the communication system because dispersion interaction; The unit impulse response of optical carrier possibly continue a plurality of bauds; So when the design multichannel equilizer; For recovering signal better; Also need combine the time-domain equalizer technology; Further improve the accuracy of reduction of data, be about to sampled result

and import as the described equalizer of balanced formula (10) (11), obtain corresponding data with .

The length of getting time-domain equalizer is 2L-1 tap, multiply by the linear superposition behind the time domain equalization coefficient corresponding to the sampled value of the code element of 2L-1 in the time domain.Consider and handle 2L-1 code element, a N light carrier, two polarizations simultaneously, export 2N result, therefore, balanced calculating is difficult to use matrix notation, so provide the balanced expression formula of ofdm signal Deplexing apparatus with the form of adding up:

${\mathrm{Eout}}_g^x\left(n\right)=\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{xx}}\left(l\right)\left[{\mathrm{Ein}}_m^x(n-l)\right]+\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{xy}}\left(l\right)\left[{\mathrm{Ein}}_m^y(n-l)\right]---\left(10\right)$

${\mathrm{Eout}}_g^y\left(n\right)=\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{yx}}\left(l\right)\left[{\mathrm{Ein}}_m^x(n-l)\right]+\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{yy}}\left(l\right)\left[{\mathrm{Ein}}_m^y(n-l)\right]---\left(11\right)$

In formula (10), (11); N representes n code-element period; G representes the data sequence number of multichannel equilizer output; L is the tap sequence number of time-domain equalizer; M representes the passage sequence number of multichannel equilizer input; The sampled value of corresponding m road ofdm signal,

and

is equalizing coefficient.

Introduce value how to confirm above-mentioned each equalizing coefficient below so that the equalizing coefficient of equalizer satisfies the requirement of offsetting ICI and ISI.

Because the gradual character of channel; Add filter parameter that each road OFDM signal of telecommunication of receiving terminal passed through and the sampling instant of ADC and be difficult to coupling; Each matrix element of stack matrix is difficult to actual measurement, thus be difficult to obtain above-mentioned equalizing coefficient with the method for inverting, but the mode that adopts gradient method to upgrade automatically restrains automatically; Equalizing coefficient is converged on the correct equalizing coefficient automatically, and specific practice is:

(1) initialization equalizing coefficient:

When m=k,

its residual value all is 0.

(2) use gradient algorithm to upgrade, equalizing coefficient converges to ε automatically ²Value during for minimum value, more new formula is following:

$F_{\mathrm{gm}}^{\mathrm{xx}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{xx}}(l,n)-\mathrm{\&mu;}\frac{\&PartialD;{{\mathrm{\&epsiv;}}_x}^2}{\&PartialD;F_{\mathrm{gm}}^{\mathrm{xx}}(l,n)}---\left(12\right);$

$F_{\mathrm{gm}}^{\mathrm{xy}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{xy}}(l,n)-\mathrm{\&mu;}\frac{\&PartialD;{{\mathrm{\&epsiv;}}_x}^2}{\&PartialD;F_{\mathrm{gm}}^{\mathrm{xy}}(l,n)}---\left(13\right);$

$F_{\mathrm{gm}}^{\mathrm{yx}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{yx}}(l,n)-\mathrm{\&mu;}\frac{\&PartialD;{{\mathrm{\&epsiv;}}_y}^2}{\&PartialD;F_{\mathrm{gm}}^{\mathrm{yx}}(l,n)}---\left(14\right);$

$F_{\mathrm{gm}}^{\mathrm{yy}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{yy}}(l,n)-\mathrm{\&mu;}\frac{\&PartialD;{{\mathrm{\&epsiv;}}_y}^2}{\&PartialD;F_{\mathrm{gm}}^{\mathrm{yy}}(l,n)}---\left(15\right);$

In the formula: ε representes error, ε ²Corresponding ICI of minimum value and ISI minimum value, n representes to upgrade preceding equalizing coefficient value, the equalizing coefficient value after n+1 representes more, μ representes a fractional increments.

(3) can adopt training sequence or two kinds of method errors of calculation of blind estimation ε.

CMA (constant modulo n arithmetic) is a kind of blind algorithm for estimating commonly used, if transmission is the QPSK signal, then just in time satisfies constant mould condition.

This moment, the error expression was:

${\mathrm{\&epsiv;}}_g^x=1-{\mathrm{Eout}}_g^x\left(n\right){\left[{\mathrm{Eout}}_g^x\left(n\right)\right]}^{*}$

${\mathrm{\&epsiv;}}_g^y=1-{\mathrm{Eout}}_g^y\left(n\right){\left[{\mathrm{Eout}}_g^y\left(n\right)\right]}^{*}---\left(16\right)$

In conjunction with (16) formula and (12)～(15) formula, can obtain

$F_{\mathrm{gm}}^{\mathrm{xx}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{xx}}(l,n)+4\mathrm{\&mu;}{\mathrm{\&epsiv;}}_g^x{\mathrm{Eout}}_g^x\left(n\right){\left[{\mathrm{Ein}}_g^x(n-l)\right]}^{*}---\left(17\right)$

$F_{\mathrm{gm}}^{\mathrm{xy}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{xy}}(l,n)+4\mathrm{\&mu;}{\mathrm{\&epsiv;}}_g^x{\mathrm{Eout}}_g^x\left(n\right){\left[{\mathrm{Ein}}_m^y(n-l)\right]}^{*}---\left(18\right)$

$F_{\mathrm{gm}}^{\mathrm{yx}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{yx}}(l,n)+4\mathrm{\&mu;}{\mathrm{\&epsiv;}}_g^y{\mathrm{Eout}}_g^y\left(n\right){\left[{\mathrm{Ein}}_m^x(n-l)\right]}^{*}---\left(19\right)$

$F_{\mathrm{gm}}^{\mathrm{yy}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{yy}}(l,n)+4\mathrm{\&mu;}{\mathrm{\&epsiv;}}_g^y{\mathrm{Eout}}_g^y\left(n\right){\left[{\mathrm{Ein}}_m^y(n-l)\right]}^{*}---\left(20\right)$

If the employing training sequence finds corresponding training sequence bits postpone, establishing correct reception value is d _xWith d _y, then the error expression does

${\mathrm{\&epsiv;}}_g^x=d_g^x\left(n\right)-{\mathrm{Eout}}_g^x\left(n\right)---\left(21\right)$

${\mathrm{\&epsiv;}}_g^y=d_g^y\left(n\right)-{\mathrm{Eout}}_g^y\left(n\right)---\left(22\right)$

Substitution (12)～(15) also can obtain using the equalizing coefficient of training sequence method more new-type.

Top adaptive equalization is that the multichannel equilibrium is merged with time domain equalization.Also can divide two stages of treatment with time domain equalization in the reality, release more new formula of its equalizing coefficient the multichannel equilibrium.In this case, in a single day the coefficient of multichannel equilizer is obtained, and can be changed to fixed value.

In addition, in the demodulating process of reality, the intrinsic light of receiving terminal with send light and have frequency difference δ f, the surface sees that (7) formula will no longer set up.But among the present invention, intrinsic light is that a laser shift frequency K Δ f produces, and its frequency is f _C+ δ f, f _C+ Δ f+ δ f, f _C+ 2 Δ f+ δ f ..., f _C+ (N-1) Δ f+ δ f.So to all channels, sending light all is δ f with receiving the optical frequency difference, its influence can be regarded all restituted signal I as _k+ jQ _kMultiply by a multiple parameter exp (j2 π δ fnT), do not influence the elimination of inter-channel crosstalk, additional complex vector can be eliminated in subsequent treatment.

When not having frequency difference or after frequency difference compensated, h in theory _MkBe constant.But,, can be expressed as t to m optical carrier sampling instant at the sampling time of code element m because there is the jitter phenomenon in the actual samples clock _m+ nT+ δ t _mSo (7) formula becomes

Observation type (23) can find out, when abs (K-m)＞＞1, and h _MkCan not be approximately constant.So, can be earlier after the demodulation with in the low pass filter decay restituted signal apart from intrinsic carrier wave carrier wave institute band signal far away, reduce its influence to the result.Another benefit that low pass filter brings is, F when abs (K-m)＞＞1 _MkNumerical value is less so that can ignore.The equalizer that adopt on the historical facts or anecdotes border can only be offset the influence that closes on carrier wave, greatly simplifies than formula (10), (11) formula.

The present invention utilizes the linear superposition of the sampled result of the OFDM signal of telecommunication for all photon carrier wave institute tonal signals, and the constant characteristics of stack coefficient; Through sampling respectively at N passage; Obtain N sampled value, this N sampled value is all the linear superposition that data are sent on the N road, but the stack coefficient is different.Through similar mode of separating linear equation calculate each photon carrier wave with data.

The present invention is not limited to above-mentioned preferred forms, and anyone should learn the structural change of under enlightenment of the present invention, making, and every have identical or close technical scheme with the present invention, all falls within protection scope of the present invention.

Claims (12)

1. to the method that adopts the multiplexing optical carrier demultiplexing of OFDM, it is characterized in that, may further comprise the steps:

The OFDM light signal that reception is become by N road photon carrier multiplexing, multiplexing method is: photon carrier wave entrained data in k road are by modulation signal I _k+ jQ _kBeing modulated at angular frequency is Ω _C+ k Ω ₀K road photon carrier wave on, Ω _CBe the angular frequency of the 0 road photon carrier wave, Ω ₀=2 π Δ f, Δ f=1/T, T are the transmission cycle of OFDM light signal, k=0 .., N-1;

The serial intrinsic light that uses different angular frequencies respectively obtains the corresponding OFDM signal of telecommunication to the demodulation of said OFDM light signal; Demodulation method is: use angular frequency to be Ω _C+ m Ω ₀Intrinsic light demodulation obtains the m road OFDM signal of telecommunication to the OFDM light signal, each road OFDM signal of telecommunication is made up of a baseband signal and N-1 the band signal adjacent with this baseband signal, with intrinsic light Ω _C+ m Ω ₀The photon carrier down-conversion that frequency is identical is a baseband signal, with intrinsic light Ω _C+ m Ω ₀The photon carrier down-conversion that frequency is different is the nearby frequency bands signal adjacent with this baseband signal, m=0 .., N-1;

Each road OFDM signal of telecommunication is sampled behind the nearby frequency bands signal beyond its baseband signal of low pass filter decay respectively, obtains corresponding OFDM signal of telecommunication sampled value, and wherein, m road OFDM signal of telecommunication sampled value does

In the formula, I _m+ jQ _mAnd I _k+ jQ _kBe respectively the modulation signal and the k road of m road photon carrier wave, k ≠ m, the modulation signal of photon carrier wave, and; h _MmBe stack coefficient corresponding in the OFDM signal of telecommunication of m road with m road photon carrier wave, h _MkBe stack coefficient corresponding in the OFDM signal of telecommunication of m road with other subcarriers, h _MmAnd h _MkConstitute one N * N multichannel stack matrix, said multichannel stack inverse of a matrix matrix is the balanced matrix of multichannel of multichannel equilizer, and the matrix element of the balanced matrix of said multichannel is called equalizing coefficient, and said equalizing coefficient adopts gradient algorithm to calculate;

Multiply by said N road OFDM signal of telecommunication sampled value with the balanced matrix of said multichannel and restore the corresponding entrained data of each road photon carrier wave.

2. the method to the multiplexing optical carrier demultiplexing of employing OFDM as claimed in claim 1 is characterized in that,

Be that m road frequency is Ω _C+ m Ω ₀The initial phase of intrinsic light;

θ _kIt is the initial phase of k road photon carrier wave;

t _mBe of the sampling instant of the m road OFDM signal of telecommunication in code element 0.

3. the method to the multiplexing optical carrier demultiplexing of employing OFDM as claimed in claim 2 is characterized in that, the balanced matrix of said multichannel is following stack inverse of a matrix matrix:

$\left[\begin{array}{ccccc}{h}_{00}& ..& h_{0k}& ..& h_{0(N-1)}\\ ..& ..& ..& ..& ..\\ h_{m0}& ..& h_{\mathrm{mk}}& ..& h_{m(N-1)}\\ ..& ..& ..& ..& ..\\ h_{(N-1)0}& ..& h_{(N-1)k}& ..& h_{(N-1)(N-1)}\end{array}\right].$

4. the method to the multiplexing optical carrier demultiplexing of employing OFDM as claimed in claim 2 is characterized in that it is multiplexing that every way carrier signal of transmitting terminal adopts two polarization states to carry out respectively, and the balanced matrix of said multichannel is F=(HP) ^-1, wherein:

H is a multicarrier stack matrix,

$H=\left[\begin{array}{cccccccc}{h}_{00}^x& 0& ..& h_{0k}^x& 0& ..& h_{0(N-1)}^x& 0\\ 0& h_{00}^y& ..& 0& h_{0k}^y& ..& 0& h_{0(N-1)}^y\\ ..& ..& ..& ..& ..& ..& ..& ..\\ h_{m0}^x& 0& ..& h_{\mathrm{mk}}^x& 0& ..& h_{m(N-1)}^x& 0\\ 0& h_{m0}^x& ..& 0& h_{\mathrm{mk}}^y& ..& 0& h_{m(N-1)}^y\\ ..& ..& ..& ..& ..& ..& ..& ..\\ h_{(N-1)0}^x& 0& ..& h_{(N-1)k}^x& 0& ..& h_{(N-1)(N-1)}^x& 0\\ 0& h_{(N-1)0}^y& ..& 0& h_{(N-1)k}^y& ..& 0& h_{(N-1)(N-1)}^y\end{array}\right];$

P is a Jones matrix, $P=\left[\begin{array}{cccccccc}{A}_0& B_0& ..& 0& 0& ..& 0& 0\\ C_0& D_0& ..& 0& 0& ..& 0& 0\\ ..& ..& ..& ..& ..& ..& ..& ..\\ 0& 0& ..& A_m& B_m& ..& 0& 0\\ 0& 0& ..& C_m& D_m& ..& 0& 0\\ ..& ..& ..& ..& ..& ..& ..& ..\\ 0& 0& ..& 0& 0& ..& A_{N-1}& B_{N-1}\\ 0& 0& ..& 0& 0& ..& C_{N-1}& D_{N-1}\end{array}\right];$

X and y represent two polarization states, the variation of the A in the Jones matrix, B, C, D expression signal polarization state.

5. as claimed in claim 4 to the method that adopts the multiplexing optical carrier demultiplexing of OFDM; It is characterized in that; Adopt the mode that combines with time-domain equalizer to reduce the unit impulse response of the OFDM signal of telecommunication, the length of said time-domain equalizer is 2L-1 tap, and linear, additive was sued for peace after soon 2L-1 sample value multiply by the time domain equalization coefficient; The L value is by signal impulse response length decision in time domain, in conjunction with the balanced expression formula of the multichannel equilizer of time-domain equalizer is:

${\mathrm{Eout}}_g^x\left(n\right)=\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{xx}}\left(l\right)\left[{\mathrm{Ein}}_m^x(n-l)\right]+\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{xy}}\left(l\right)\left[{\mathrm{Ein}}_m^y(n-l)\right],$

${\mathrm{Eout}}_g^y\left(n\right)=\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{yx}}\left(l\right)\left[{\mathrm{Ein}}_m^x(n-l)\right]+\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{yy}}\left(l\right)\left[{\mathrm{Ein}}_m^y(n-l)\right],$

Wherein, N representes n code-element period; G representes the data sequence number of multichannel equilizer output; L is the tap sequence number of time-domain equalizer; M representes the passage sequence number of multichannel equilizer input; The sampled value of corresponding m road ofdm signal, the mode that equalizing coefficient

and

adopt gradient method to upgrade automatically converges to automatically and satisfies on the filter factor of offsetting ICI and ISI.

6. as claimed in claim 5 to the method that adopts the multiplexing optical carrier demultiplexing of OFDM; It is characterized in that updating steps is following automatically for equalizing coefficient

and :

(1) initialization:

works as m=k;

works as m=k, and its residual value all is 0;

(2) use gradient algorithm to upgrade, and confirm as and converge to ε automatically ²Minimum value the time value, more new formula is following:

$F_{\mathrm{gm}}^{\mathrm{xx}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{xx}}(l,n)-\mathrm{\&mu;}\frac{\&PartialD;{{\mathrm{\&epsiv;}}_x}^2}{\&PartialD;F_{\mathrm{gm}}^{\mathrm{xx}}(l,n)};$

$F_{\mathrm{gm}}^{\mathrm{xy}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{xy}}(l,n)-\mathrm{\&mu;}\frac{\&PartialD;{{\mathrm{\&epsiv;}}_x}^2}{\&PartialD;F_{\mathrm{gm}}^{\mathrm{xy}}(l,n)};$

$F_{\mathrm{gm}}^{\mathrm{yx}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{yx}}(l,n)-\mathrm{\&mu;}\frac{\&PartialD;{{\mathrm{\&epsiv;}}_y}^2}{\&PartialD;F_{\mathrm{gm}}^{\mathrm{yx}}(l,n)};$

$F_{\mathrm{gm}}^{\mathrm{yy}}(l,n+1)=F_{\mathrm{gm}}^{\mathrm{yy}}(l,n)-\mathrm{\&mu;}\frac{\&PartialD;{{\mathrm{\&epsiv;}}_y}^2}{\&PartialD;F_{\mathrm{gm}}^{\mathrm{yy}}(l,n)};$

In the formula: ε representes error, ε ²Corresponding ICI of minimum value and ISI minimum value, n representes to upgrade preceding coefficient value, the coefficient value after n+1 representes more, μ representes a fractional increments.

7. the method to the multiplexing optical carrier demultiplexing of employing OFDM as claimed in claim 6 is characterized in that error ε adopts the training sequence method to obtain,

${\mathrm{\&epsiv;}}_g^x=d_g^x\left(n\right)-{\mathrm{Eout}}_g^x\left(n\right);$

${\mathrm{\&epsiv;}}_g^y=d_g^y\left(n\right)-{\mathrm{Eout}}_g^y\left(n\right).$

8. the method to the multiplexing optical carrier demultiplexing of employing OFDM as claimed in claim 6 is characterized in that error ε adopts blind estimating method to obtain,

${\mathrm{\&epsiv;}}_g^x=1-{\mathrm{Eout}}_g^x\left(n\right){\left[{\mathrm{Eout}}_g^x\left(n\right)\right]}^{*};$

${\mathrm{\&epsiv;}}_g^y=1-{\mathrm{Eout}}_g^y\left(n\right){\left[{\mathrm{Eout}}_g^y\left(n\right)\right]}^{*}.$

9.OFDM the signal Deplexing apparatus is characterized in that, comprising:

The intrinsic light source produces intrinsic light Ω _C, Ω _CAngular frequency for the intrinsic light source;

The multicarrier generation module is according to said intrinsic light Ω _CProducing angular frequency behind the shift frequency respectively is Ω _C+ m Ω ₀Serial intrinsic light, Ω ₀=2 π Δ f, Δ f=1/T, T are the transmission cycle of OFDM light signal, m representes m road intrinsic light, m=0 .., N-1;

The down-conversion device that 90 degree frequency mixers and balanced reciver constitute with the OFDM light signal demodulation of said serial intrinsic light with N road photon carrier multiplexing one-tenth, obtains the corresponding N road OFDM signal of telecommunication respectively;

Low pass filter is respectively to each signal beyond its baseband signal of road OFDM signal of telecommunication decay;

Acquisition module is gathered each road OFDM signal of telecommunication respectively, obtains corresponding OFDM signal of telecommunication sampled value;

Digital signal processing module restores the corresponding entrained data of each road photon carrier wave with the balanced matrix multiple of the described multichannel of claim 1 respectively to N road OFDM signal of telecommunication sampled value.

10. device as claimed in claim 9; It is characterized in that; Also comprise the time-domain equalizer of the unit impulse response that is used to reduce the OFDM signal of telecommunication, the length of said time-domain equalizer is 2L-1 tap, and linear, additive is sued for peace after being about to 2L-1 sample value and multiply by the time domain equalization coefficient; The L value is by signal impulse response length decision in time domain, in conjunction with the balanced expression formula of the multichannel equilizer device of time domain equalization is:

${\mathrm{Eout}}_g^x\left(n\right)=\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{xx}}\left(l\right)\left[{\mathrm{Ein}}_m^x(n-l)\right]+\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{xy}}\left(l\right)\left[{\mathrm{Ein}}_m^y(n-l)\right],$

${\mathrm{Eout}}_g^y\left(n\right)=\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{yx}}\left(l\right)\left[{\mathrm{Ein}}_m^x(n-l)\right]+\underset{l=-L+1}{\overset{L-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{F}_{\mathrm{gm}}^{\mathrm{yy}}\left(l\right)\left[{\mathrm{Ein}}_m^y(n-l)\right],$

Wherein, N representes n code-element period; G representes the data sequence number of multichannel equilizer output; Modulating data corresponding to the g light carrier that calculates; L is the tap sequence number of time-domain equalizer; M representes the passage sequence number of multichannel equilizer input; The sampled value of corresponding m road ofdm signal, the mode that equalizing coefficient

and adopt gradient method to upgrade automatically converges to automatically and satisfies on the filter factor of offsetting ICI and ISI.

11. communication system comprises transmitting terminal and receiving terminal, it is characterized in that, said receiving terminal is provided with Deplexing apparatus as claimed in claim 9.

12. communication means at the transmitting terminal of communication system, modulates data on N the orthogonal sub-carriers; And then each orthogonal sub-carriers closed ripple sends to communication system through optical fiber receiving terminal; It is characterized in that,, adopt the method for claim 1 to carry out demultiplexing at receiving terminal.

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