CN1266865C - Method for suppressing self-phase modulating effect in over long-distance optical transmission system - Google Patents
Method for suppressing self-phase modulating effect in over long-distance optical transmission system Download PDFInfo
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Abstract
The present invention relates to a method for restraining the effect of self phase modulation (SPM) in an extra long distance optical transmission system, which comprises the procedures: a dispersion compensated module is adopted in each link level to distributively and completely compensate dispersion, the position and the dispersion measure of the dispersion compensated module in each link level is adjusted, power input points of optical signals are taken as the reference points, the accumulated dispersion measure from a random reference point to a receiver is positive, and the tatal dispersion of the system is within the dispersion tolerance of the receiver, so that the reference point produces an SPM effect interacting with dispersion so as to compress the widened pulse. The present invention is suitable for a DWDM system and capable of flexibly controlling the accumulated total residual dispersion, the transmission distance is free from the limitation of linear dispersion, and the problems of the SPM effect of an entire C-BAND waveband in extra long distance transmission can be conveniently solved under the existing technical conditions of dispersion compensation without increasing any new device. Proved by emulation, simulation, experiments and the application test of an actual transmission system, the present invention can be reliably operated.
Description
Technical field
The invention belongs to extra long distance optical transport technology field, specifically is the method that suppresses in a kind of extra long distance optical transmission system from phase modulated (SPM) effect.
Background technology
In two-forty, over distance optical transmission system, adopted higher launched power to guarantee the Optical Signal To Noise Ratio (OSNR) of receiving terminal.Higher power causes the generation of SPM effect, and the front and back that make light pulse are along producing red shift and blue shift shown in Figure 1.The SPM effect is irreversible and can constantly be accumulated along with link, and the SPM effect of accumulation can cause the deterioration of systematic function.Therefore in high speed over distance optical transmission system, must adopt effective method to suppress the SPM effect.
The frequency distribution of light pulse is, high fdrequency component is preceding, low frequency component after, when in the anomalous dispersion district, transmitting, because the effect of positive dispersion, high fdrequency component is walked fast and low frequency component loses time, thereby makes pulse stretching.And from Fig. 1, can see that the just in time opposite and positive dispersion of the distribution of frequency chirp interacts pulse is compressed, thereby suppress the SPM effect.
The long haul optical transmission systems of now common high speed adopts two kinds of methods to reduce the SPM effect usually:
1, reduces launched power;
2, every grade of under-compensated method of fiber span utilizes a spot of positive dispersion to suppress the single-stage section of striding SPM effect, thereby reaches the purpose of the SPM effect that alleviates accumulative total.
Utilize and reduce the mode that launched power reduces the SPM effect, because the launched power reduction, thereby transmission range shortened.
Second kind of scheme all adopts the undercompensation technology to every grade of fiber span, remaining chromatic dispersion will constantly be accumulated, for long haul optical transmission systems, the chromatic dispersion of accumulation generally can not surpass the patient scope of system, and to the extra long distance optical transmission system, optical fiber link length is much larger than the linkage length of long haul optical transmission systems, the residual dispersion of accumulative total head and shoulders above the dispersion tolerance of system.The dispersion spectrum of this method correspondence as shown in Figure 2, visible final residual chromatic dispersion will be above the receiving margin of system.
In sum, existing two kinds are suppressed SPM effect method, are that cost reduces the SPM effect to sacrifice transmission range all, are not suitable for the extra long distance optical transmission system.
Summary of the invention
In view of the prior art above shortcomings, the invention provides the method that suppresses in a kind of extra long distance optical transmission system from phase modulated (SPM) effect, to improve the performance of extra long distance optical transmission system.
In the extra long distance optical transmission system, suppress method from phase modulated (SPM) effect, comprise: in every grade of link, adopt dispersion compensation module (DCM) that distributed full remuneration is carried out in chromatic dispersion, regulate position and the dispersion measure of dispersion compensation module in link, with the optical signal power input point is reference point, the accumulative total dispersion measure of arbitrary reference point before the receiver is all for just, the total dispersion of simultaneity factor is in the dispersion tolerance of receiver, SPM effect and chromatic dispersion that this reference point is produced interact, and compress broadened pulse.
The present invention adopts distributed dispersion compensation technology to suppress the SPM effect, in every grade of link, adopt dispersion compensation module (DCM) that full remuneration is carried out in chromatic dispersion, by regulating position and the dispersion measure of dispersion compensation module in link, SPM effect and chromatic dispersion are interacted, compress broadened pulse, improve the performance of system.Be suitable for dwdm system, can control total residual dispersion of accumulation flexibly, transmission range is not subjected to the restriction of linear dispersion; Have consequent compatibility, this technology also is applicable to long haul optical transmission systems simultaneously.
This technology is used simple and flexible, is applicable to the network of the various complexity in the actual engineering; This invention can solve the SPM effect problem of whole C-BAND wave band in the extra long distance transmission easily increasing any new unit under the existing dispersion compensation technical conditions.
SPM effect inhibition technology of the present invention is tested through emulation, simulation, and the application test of actual transmissions system, and is reliable, can suppress the SPM effect effectively.
Description of drawings
Fig. 1 represents the frequency chirp that the SPM effect produces;
Fig. 2 is the existing dispersion spectrum that suppresses the SPM effect;
Fig. 3 is the distributed Dispersion Compensation Systems structural representation of the present invention;
Fig. 4 connects the dispersion profile figure on road for an example of the present invention;
Fig. 5 is that the SPM of two kinds of dispersion compensation experiments suppresses the effect contrast figure.
Embodiment
Below in conjunction with accompanying drawing the inventive method is further analyzed explanation.
The present invention adopts the dispersion compensation technology of optimization, producing zone (the luminous power input of optical fiber) with the SPM effect is reference point, the chromatic dispersion that guarantees any one reference point accumulative total before the receiver is all for just, SPM effect and chromatic dispersion that this reference point is produced interact, compress broadened pulse, improve the performance of system.This technology is applicable to that any employing dispersion compensation module carries out the system of dispersion compensation.
A point-to-point optical transmission system as shown in Figure 3.Be a compensating unit with n fiber span in the link, total m compensating unit.DCM (dispersion compensation module) has an amplifier to compensate the power loss that DCM brings before, so can regard the image intensifer of DCM and its front as a functional unit altogether.Da, Db, Dc be respectively optical fiber dispersion in the DCM that enters the precompensation before the optical fiber, the compensation link DCM, regulate the DCM that enters the residual dispersion before the receiver.Optical signal power input point with i fiber span in j the dispersion compensation unit is a reference point, and the accumulative total dispersion measure before from this reference point to receiver satisfies (1) formula:
Dij＝Dc+(m-j)Db+(mn-jn-n-i)DfLf (1)
The total dispersion of simultaneity factor also must satisfy (2) formula:
D
On＞Dtotal=Da+Dc+mDb+mnDfLf＞D
Down(2)
Wherein, D
OnAnd D
DownBe respectively patient maximum chromatic dispersion and minimum dispersion of receiver.Dtotal represents that system is through the total dispersion value after the dispersion compensation; Df represents the CHROMATIC DISPERSION IN FIBER OPTICS coefficient, and Lf represents the length of optical fiber, DfLf=optical fiber dispersion coefficient * fiber lengths: represent one section CHROMATIC DISPERSION IN FIBER OPTICS.0≤i＜n，0≤j＜m。
Satisfied (1) formula, then play accumulative total chromatic dispersion before the receiver for just from reference point (the light signal input point of i fiber span of j dispersion compensation unit the), these positive dispersions and interact in the SPM effect that this reference point produces and can compress broadened light signal improve systematic function.
Satisfy (2) formula, then from the residual dispersion of transmitted from transmitter to receiver accumulative total within the patient dispersion range of receiver, make system not be subjected to the restriction of chromatic dispersion
Make dispersion compensation structure satisfy (1) and (2) formula, only need to regulate dispersion compensation module in link the position and the dispersion measure of dispersion compensation module just can realize.Position and the dispersion measure of described adjusting dispersion compensation module in link is to regulate the DCM that enters optical fiber precompensation before or compensate the DCM of optical fiber dispersion in the link or the DCM that adjusting enters receiver residual dispersion before.
The following method of bright this realization for instance:
Suppose m=10, n=1, Da=-DfLf/2, Db=-DfLf, Dc=-DfLf/2, D
On=DfLf/4, D
Down=-DfLf/4.
Can obtain a kind of dispersion profile figure as shown in Figure 4.Can see that from the residual dispersion coordinate system of Fig. 4 the residual dispersion of whole link is zero, be in the dispersion tolerance scope [D of receiver
Down～D
On] in, satisfied (2) formula.
The luminous power input of the 4th fiber span of picked at random is a reference point, and coordinate for referencial use (being relative surplus chromatic dispersion coordinate) can see that the relative surplus chromatic dispersion of the from the 4th to the 10th section of striding accumulative total is DfLf/2, has satisfied (1) formula.In fact, (power of 1～10 fiber span is gone into fine point) selects a point as the reference point arbitrarily from abscissa 0～9, and the relative surplus chromatic dispersion can both be satisfied (1) formula.
Dispersion compensation structure shown in Figure 3 is a distributed dispersion compensation structure.Can suppress the SPM effect effectively, the accumulative total residual dispersion that enters receiver simultaneously can not surpass the patient scope of system.This scheme compatibility the existing scheme of utilizing dispersion management to suppress the SPM effect.
Verify the feasibility of this technology by two kinds of dispersion compensation contrast experiments.With reference to Fig. 3, these two kinds of structures are respectively:
1、n＝1，m＝30，Da＝0，Db＝Dc＝-DfLf。Equal zero to the accumulation residual dispersion of receiver in any one SPM effect generation zone (luminous power injection place of optical fiber) of this structure.
2、n＝1，m＝30，Da＝Db＝Dc＝-DfLf。Any one SPM effect of this structure produces regional (luminous power injection place of optical fiber) and arrives the accumulation residual dispersion of receiver greater than zero.
Adopt Electroabsorption Modulated Laser, signal rate is 10Gb/s, individual channel is tested, two kinds of test results as shown in Figure 5:
Among Fig. 5, launched power causes receiver sensitivity to descend owing to Optical Signal To Noise Ratio is limited less than 2dBm the time, and when launched power greater than 2dBm the time, system no longer is subjected to the restriction of Optical Signal To Noise Ratio, and mainly is subjected to the influence of SPM effect.Can see, second kind of structure (curve of Fig. 5 bottom) to the inhibition effect of SPM effect than good many of first kind of structure (curve of Fig. 5 top).
Claims (4)
1, the method that suppresses self phase modulation in a kind of extra long distance optical transmission system, comprise: in every grade of link, adopt dispersion compensation module that distributed full remuneration is carried out in chromatic dispersion, increase or reduce the quantity of the dispersion compensation module of each chromatic dispersion compensation point in link, reaching with the optical signal power input point is reference point, the accumulative total dispersion measure of arbitrary reference point before the receiver is all for just, the total dispersion of simultaneity factor is in the dispersion tolerance of receiver, self phase modulation and chromatic dispersion that this reference point is produced interact, and compress broadened pulse.
2, according to the method for the described inhibition self phase modulation of claim 1, it is characterized in that: described increase or reduce the dispersion compensating number of blocks of each chromatic dispersion compensation point in the link is to increase or reduce to enter the dispersion compensation module that is used for precompensation before the optical fiber or be used to compensate the dispersion compensation module of link optical fiber dispersion or be used to change the dispersion compensation module that enters the residual dispersion before the receiver.
3, according to the method for the described inhibition self phase modulation of claim 1, it is characterized in that the accumulative total dispersion measure of the arbitrary reference point of described adjusting before the receiver all is that positive step is: have m compensating unit at one, each compensating unit comprises in the link of n fiber span, optical signal power input point with i fiber span in j the dispersion compensation unit is a reference point, and described reference point satisfies formula to the preceding accumulative total dispersion measure of receiver:
Dij＝Dc+(m-j)Db+(mn-jn+n-i)DfLf＞0
Wherein, Db, Dc are respectively the dispersion compensation module of optical fiber dispersion in the compensation link, the dispersion compensation module that adjusting enters the residual dispersion before the receiver; Dij represents that each reference point is to receiver accumulative total dispersion measure before; Df is the CHROMATIC DISPERSION IN FIBER OPTICS coefficient, and Lf is the length of optical fiber, 0≤i＜n, 0≤j＜m.
4, the method for the described inhibition self phase modulation of claim 1, it is characterized in that: the total dispersion of described system is between the maximum chromatic dispersion and minimum dispersion of receiver, have the link that m compensating unit, each compensating unit comprise n fiber span for one, the total dispersion amount of link satisfies formula:
On the D＞Dtotal=Da+Dc+mDb+mnDfDl＞D under
Wherein, be respectively patient maximum chromatic dispersion and minimum dispersion of receiver under the last and D of D; Dtotal represents that system is through the total dispersion value after the dispersion compensation; Da, Db, Dc be respectively optical fiber dispersion in the dispersion compensation module that enters the precompensation before the optical fiber, the compensation link dispersion compensation module, regulate the dispersion compensation module that enters the residual dispersion before the receiver, Df represents the CHROMATIC DISPERSION IN FIBER OPTICS coefficient, Lf represents the length of optical fiber, 0≤i＜n, 0≤j＜m.
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| CN102386968B (en) * | 2010-08-31 | 2015-07-15 | 富士通株式会社 | Self-phase modulation noise calculating device, removing device and optical coherent receiver |
| CN109412694A (en) * | 2017-08-17 | 2019-03-01 | 上海长弋通信技术有限公司 | A kind of 1550nm extra long distance DTV fibre-optic transmission system (FOTS) |
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