CN1913397A - Dispersion real-time monitoring method applied in DWDM high speed transmission system - Google Patents

Abstract

This invention provides a method for monitoring fiber dispersion timely in the high speed DWDM system, which applies a method that a monitor signal occupies a channel independently while the original network topological structure is not changed to avoid influence of digital signals in the traditional method to monitor signals, which can monitor the dispersion volume of each channel accurately and carry out dynamic optical routing on the optical path to provide a very good management plan to dispersion to the intelligent optical network wide of the next generation.

Description

A kind of dispersion real-time monitoring method that is applied in the DWDM high speed transmission system

Affiliated technical field

The invention belongs to technical field of optical fiber communication, it is particularly related to the technology of dispersion management aspect in dense wave division multipurpose DWDM (the Dense WavelengthDivision Multiplexing) system.

Background technology

Signal is to be carried by different frequency contents and different mode composition in optical fiber, and these different frequency contents have different propagation velocitys with pattern during by same substance, thereby cause chromatic dispersion.Also can go to understand from the angle of waveform broadening in time, i.e. light pulse be during passing through spread fiber, and its waveform broadening has taken place in time and caused that signal distortion causes distortion, and this phenomenon just is called chromatic dispersion.From the nineties in 19th century, the Internet networks development impels data communication service rapidly to increase, the client to the optical fiber communication capacity require increasing.And one of the approach that improves channel capacity at present is to improve single-channel transmission rate, but because in the optical fiber telecommunications system, the width of light pulse is by the transmission rate decision of system, and transmission rate is big more, system is just more little to the tolerance limit of chromatic dispersion, thus easier generation intersymbol interference; Another approach that improves channel capacity is exactly multiplexing (WDM) that carries out multi-wavelength.But continuous development along with wavelength division multiplexed network, especially the application of EDFA image intensifer, repeater span is more and more longer, the CHROMATIC DISPERSION IN FIBER OPTICS parameter is subjected to the influence of factors such as natural environment, weather easily, this is for the ultrahigh speed trunk transmission system of 40Gbit/s, and its tolerance limit to chromatic dispersion has only 60ps/nm.Traditional fixedly dispersion compensation schemes can't be carried out accurate dispersion compensation, and transmission signals will produce the insufferable error rate of system.For this reason, use chromatic dispersion monitoring technology flexible and high performance-price ratio is monitored actual data signal and is realized that dynamic dispersion compensation is very necessary.

Method of measurement that some are traditional such as impulse time delay method (time domain method), group delay phase shift method (are seen document 1:B.Costa, etc. " Measurement of Chromatic Dispersion in Single mode fiber by incoherent Sources ", CSELT.), need obtain measuring-signal and reference signal simultaneously asks its relative time delay poor then, these methods are used more extensive in short-range closed loop, but are difficult to accomplish this point in the optical fiber telecommunications system of reality.A lot of for this reason data and document are being done a large amount of theoretical researches and simulation analysis to optical fiber dispersion aspect the monitoring in real time.Comprising the power monitoring method of monotony frequency (with reference to 2:Takushima Y, Kikuchi K.A novel method for optical fibre dispersion measurement and itsapplication to in-service monitor.Optical Communication, 2001.ECOC ' 01.27th EuropeanConference on.2001,9 (3): 276-277), sideband phase modulated method is (with reference to 3:Dimmick T.E, Rossi G, Blumenthal D.J, Optical dispersion monitoring technique using double sideband subcarriers.IEEEPhoton.Technol.Lett., 2003,12 (7): 900-902) etc.But in these monitoring methods, monitor signal is subjected to the influence of the digital signal in the same channel easily, is difficult to fiber optic transmission system is carried out accurate chromatic dispersion monitoring.

In dwdm system, all do not carry out the conversion of photoelectricity light in order to carry out the dynamic routing in the light territory at each node, just must know the dispersion measure after each optical channel is through several sections optical fiber, but because monitor signal and data-signal following two problems can occur when transmitting simultaneously in same channel:

(1) monitor signal can not correctly carry out the monitoring of chromatic dispersion owing to the interference of data-signal;

(2) data-signal can not correctly transmit information owing to the interference of monitor signal.

Therefore, the way that monitor signal and data-signal is placed on a channel can not be applied in the actual communication systems.In order to monitor the chromatic dispersion of long-distance optical fiber exactly, just the nonlinear effect in digital signal, the optical fiber and all may must be had influence on our factor of needed monitoring variable and be reduced to minimum.

Summary of the invention

The object of the present invention is to provide a kind of method of monitoring chromatic dispersion in real time in dwdm system.Can in long-distance, at a high speed main line network, can monitor out the dispersion measure of each channel of system accurately by this method.In order to describe content of the present invention easily, at first some technical terms are defined:

Tone signal: sinusoidal monitor signal;

Supervisory channel: be used for the light wave transmissions passage of chromatic dispersion monitoring, the centre wavelength of this passage is λ ₀

Data channel: be used for the light wave transmissions passage of transfer of data, it comprises n passage, and the centre wavelength of i passage is λ _i(i=1,2 ... n);

Dispersion parameters and chromatic dispersion gradient: be the characterisitic parameter of optical fiber, can from the optical fiber parameter tables of data that producer provides, obtain;

Tone signal phase modulated method (document G.Meslener, " Chromatic dispersion induced distortion ofmodulated monochromatic light employing direct detection ", Quantum Electronics of IEEE Journal, 1984, vol.20, pp1208-1216,): at first use a single-tone monitor signal that light carrier is carried out phase modulated, light signal after the modulation is coupled in one section optical fiber, terminal at optical fiber extracts this monitor signal filtration by opto-electronic conversion, carry out the detection of power in electric territory, there are following formula relation in its power and optical fiber dispersion

$P\left(\mathrm{\&Omega;}\right)=\frac{1}{2}{\left\{{4i}_0\right[J_0\left(A\right)J_1\left(A\right)\sin \frac{{\mathrm{\&Omega;}}^2{{\mathrm{\&lambda;}}_0}^2{D}_{{\mathrm{\&lambda;}}_0}\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="A20051002090600071.png"\; state="\{\{state\}\}">L</figure-callout>}}{4\mathrm{\&pi;c}}+J_1\left(A\right)J_2\left(A\right)\sin \frac{{3\mathrm{\&Omega;}}^2{{\mathrm{\&lambda;}}_0}^2{D}_{{\mathrm{\&lambda;}}_0}\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="A20051002090600071.png"\; state="\{\{state\}\}">L</figure-callout>}}{4\mathrm{\&pi;c}}\left]\right\}}^2$

In the formula, the power at P (Ω) expression modulation angular frequency Ω place, J _mBe m rank Bessel function, A is modulation depth (also being phase-modulation index), and Ω is the angular frequency of single-tone monitor signal, i ₀Be the average light electric current at receiver end place, c is the light velocity in the vacuum, λ ₀Be supervisory channel light wave centre frequency, D _{λ 0}Be dispersion parameters, L is the length of optical fiber, D _{λ 0}L is the optical fiber dispersion amount.

The invention provides the optical fiber dispersion method of real-time in a kind of DWDM of being applied in high speed transmission system, it may further comprise the steps, as shown in Figure 1:

The light signal of the light signal of step 1, supervisory channel 1 and data channel 2 utilizes optical add/drop multiplexer (OADM) 3 to be coupled in the optical fiber 4;

Step 2, signal after coupling are transmitted in optical fiber 4, and multistage uses the signal of 5 pairs of decay of image intensifer to amplify, and arrive chromatic dispersion monitoring modular 6 at last;

Step 3, in chromatic dispersion monitoring modular 6, the light signal of supervisory channel extracts from optical fiber by optical filter, after opto-electronic conversion, utilizes power meter to detect the power of this single-tone monitor signal in electric territory;

Step 4, utilize the relation between the optical fiber dispersion value and the detected performance number of power meter in the tone signal phase modulated method, obtain the optical fiber dispersion amount D of supervisory channel in the optical fiber 4 _{λ 0}L;

Step 5, according to the chromatic dispersion gradient S of optical fiber 4, can calculate centre wavelength is λ _iThe optical fiber dispersion amount of data channel

$D_{{\mathrm{\&lambda;}}_i}L=D_{{\mathrm{\&lambda;}}_0}L[1+S({\mathrm{\&lambda;}}_i-{\mathrm{\&lambda;}}_0)];$

By above step, the dispersion measure that detects any fiber channel in the dwdm system that just can be real-time.

Need to prove: the tone signal phase modulated method that this paper provided can be monitored optical fiber dispersion in real time, utilize existing dynamic compensation technology, for example: temperature is coordinated chirped fiber grating, the tuning chirped fiber grating of stress etc., just can realize the optical fiber dispersion adaptive equalization.

Advantage of the present invention:

(1) owing to being monitor signal to be carried out phase modulated higher certainty of measurement is arranged, in the easier optical fiber long-haul transmission system that is applied to multi-wavelength than other chromatic dispersion monitoring methods.

(2) can in traditional optical transmission system,, add dispersing monitor at an easy rate as at the Receiver And Transmitter end.Can not change the intermediate configurations of original system like this, save cost of investment;

(3) can monitor the value of chromatic dispersion in system at an easy rate.Because the phase modulated method can obtain littler nonlinear effect by the specific strength modulation method, and less than the measuring condition of in time domain, monitoring the required harshness of impulse time delay difference;

(3) monitoring distance is long, can carry out the monitoring of chromatic dispersion in the scope of 450km.Traditional method all is short-range monitoring, has only hundreds of rice usually, and the method for list of references 2 is in the increase along with fiber lengths, and its radio-frequency power is what reduce, and this has higher requirement to extracting monitor signal;

(4) monitoring accuracy height.Even considered the influence of the factors such as nonlinear effect of optical fiber, the error of its monitoring is in 30km in the system of 10Gbit/s; In the 40Gbit/s system, in the scope of 400km, also can be good at carrying out the monitoring of chromatic dispersion.

(5) can be used in the actual fiber optic transmission system, can be applicable to dynamic light path, for follow-on intelligent all-optical network realizes that good dispersion management provides theoretical foundation by dispersion real-time monitoring in the network.

Accompanying drawing and description of drawings:

Fig. 1 multi-channel optical node system carries out the block diagram of chromatic dispersion monitoring

Wherein, the 1st, supervisory channel, the 2nd, data channel, the 3rd, optical add/drop multiplexer OADM (optical Add/DropMultiplexers), the 4th, dispersive optical fiber, the 5th, fiber amplifier, the 6th, optical fiber dispersion monitoring modular.

The relation curve of optical fiber error length and optical fiber physical length in Fig. 2 16 channels, 10G and the 40G system

Wherein, abscissa is the transmission length of optical fiber; Ordinate is the fiber lengths that monitors and the error between the actual fiber length.Wherein dotted line is represented the measure error of 10Gbit/s transmission system.The great talent 13km of its error at the 500km place.Solid line is represented the measure error of 40Gbit/s transmission system.The maximum 15.8km of its error at the 500km place, but error does not all exceed ± 2km in the scope in 400km, does not exceed the dispersion tolerance distance of 40Gbit/s transmission system.

Embodiment:

We have carried out the emulation of the dwdm system of n=16 channel.Supervisory channel centre wavelength is 1558.58nm in the emulation, and 16 channel center wavelength intervals are 0.8nm.Consider the nonlinear effect of optical fiber, the frequency of carrying out the monitor signal of phase modulated is 2.5GHz.Transmission Fibers is a G.652 optical fiber of standard single mode, and repeater span is 50km.The gain of image intensifer is 10dB, and the optical filter centre wavelength of supervisory channel is 1558.58nm, and three dB bandwidth is 40GHz.The monitor value of monitor signal process 500km standard single-mode fiber transmission and the error curve between the calculated value are as shown in Figure 2.From the result as can be known: in 10Gbit/s and the 40Gbit/s system in the maximum respectively measure error that 12.8km and 15.3km are arranged of 500km.In the fiber optic transmission system of 10Gbit/s, can realize the interior chromatic dispersion monitoring of scope of 500km.In the 40Gbit/s system, can in 450km, carry out the accurate monitoring of chromatic dispersion.As can be seen, it is long that the method for this paper has monitoring distance from example, the monitoring accuracy height, and method realizes advantages such as easy, can be widely used in two-forty, the long-distance optical fiber communication system.

Claims (1)

1, a kind of optical fiber dispersion method of real-time that is applied in the DWDM high speed transmission system is characterized in that may further comprise the steps:

The light signal of the light signal of step 1, supervisory channel 1 and data channel 2 utilizes optical add/drop multiplexer (OADM) 3 to be coupled in the optical fiber 4;

Step 2, signal after coupling are transmitted in optical fiber 4, and multistage uses the signal of 5 pairs of decay of image intensifer to amplify, and arrive chromatic dispersion monitoring modular 6 at last;

Step 3, in chromatic dispersion monitoring modular 6, the light signal of supervisory channel extracts from optical fiber by optical filter, after opto-electronic conversion, utilizes power meter to detect the power of this single-tone monitor signal in electric territory;

Step 4, utilize the relation between the optical fiber dispersion value and the detected performance number of power meter in the tone signal phase modulated method, obtain the optical fiber dispersion amount D of supervisory channel in the optical fiber 4 _{λ 0}L;

Step 5, according to the chromatic dispersion gradient S of optical fiber 4, can calculate centre wavelength is λ _iThe optical fiber dispersion amount of data channel

$D_{{\mathrm{\&lambda;}}_i}L=D_{{\mathrm{\&lambda;}}_0}L[1+S({\mathrm{\&lambda;}}_i-{\mathrm{\&lambda;}}_0)].$

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