Beijing Jinkun Technology Co., Ltd. www.jonkon.com.cn

Abstract:We compared broadband in our experimentFBGCompared with traditional dispersion compensation fiber DCF at 525KM 40 ×10GPerformance in DWDM system. Here is a proposal to adoptFBGOptimization configuration plan for compensation.
introduction:
In recent years, chirpingFiber Bragg Grating (FBG)It has been identified as a feasible solution to reduce dispersion effects [1-3].FBGThe main advantages of compensation methods include low insertion loss, low nonlinear effects, and small size. Typically,FBGThe application of dispersion compensation was mainly limited to systems with fewer channels in the past, because it is very difficult to splice large grating chains together while maintaining low insertion loss. Multi channel chirping based on superstructure sampling gratingFBGThe emergence of FBG has eliminated the application limitations of FBG and improved its application inDWDMThe practical and effective application in the system has paved the way. broadbandFBGThe possible application areas of this technology are emerging urban and short-range area network applications, covering a distance of up to 500km. Currently, there are few studies on dispersion compensation within this distance rangetechnologyEvaluation report.
In this article, we compared fiber optic andFBGBased on dispersion compensationtechnologyAnalyzed 40 100G intervals10GTransmission performance of 525km SSMF channel. evaluatedFBGThe characteristics of several different system configurations of dispersion compensation modules were compared with typical DCF schemes. The results indicate that compared to DCF short-range applications, by extensively eliminating intermediate stage amplifiers,FBGCan provide dispersion compensation performance of *. However, deploying hybrid single-stage amplifiers and intermediate stage amplifiers may effectively achieve * system cost-effectiveness.

Experimental Configuration
We evaluate it through the configuration shown in Figure 1FBGThe performance. The terminal includes 40 C-band channels with 100GHz intervals, and the transmission line consists of 7 segments of 75km optical fiber. Each fiber segment contains a variable attenuator to balance losses. specifictestThe configuration is as follows:

(i) Distributed Mid Stage Compensation
This configuration allows for direct comparisonFBGAnd DCFtechnologyThe figure indicates the DCF module and its effective SSMF compensation length. Then six 84km DCFs were replaced with equivalent FBGs, while maintaining a constant intermediate loss.
(ii) Distributed single-stage compensation
The insertion loss of FBG is 2.3 ± 0.5dB, while the insertion loss of DCF is 8.1 ± 0.5dB. In order to utilize the low loss characteristics of FBG,FBGMoved to the starting position of each span, the intermediate amplifier is replaced by a single segment amplifier with the same gain, which reduces the noise figure of each EDFA by 1dB
(iii) Aggregate intermediate stage compensation)
The increase in 3dB cross segment loss (ii) requires higher output power to maintain the same OSNR. To avoid thisproblemWe evaluated the placement of all terminalsFBGThe performance of the dispersion compensator in this configuration includes compensation devices for 273km and 252km dispersion in the RX and TX amplifiers, respectively. Figure 2 shows that the residual dispersion of DCF and FBG dispersion compensation schemes is very close. Our goal is to overcompensate by 0.2ps (nm. km), which allows for compensation of SPM in transmission.

Figure 3 shows the results of four different configurations, with Q2 being the average of all wavelengths, displaying the overall performance trend, as expected, in the middle segmentFBGCompensation configuration and the use of DCF have a similar trend in addressing the nonlinearity caused by transmission fibershigh powerBefore roll off, the Q value and transmission power of these two situations are almost linearly related. It can be seen that due to the significant nonlinear effects in DCF, distributedFBGThe performance degradation occurred much later than DCF.
whenFBGPlaced before the span (configuration ii), due to the lower optical power of the incident transmission fiber, we see a better linear relationship between performance and power. Due to the fact that the attenuation of the line at 5 out of 7 spans is 3DB higher than the other two spans, performance deteriorates. However, due to the improvement of the noise index by single-stage amplification, this degradation can be offset. It can be seen that increasing the emitted light power can improve performance, but this is usually not an economically efficient way.
In the latter case, whenFBGIt is concentrated in the middle of two terminal amplifiers (configuration iii) and has good performance at low transmission optical power. This method combines the low noise and low span attenuation of a single-stage amplification system to improve performance. We see that the transmission power of this configuration allows for a reduction of 4dB compared to using traditional DCF, at a cost of only 0.5dBQ. Figure 4 shows this*FBGConfigure the receiving spectrum, OSNR, and eye diagram. This indicates that at higher channel transmission power, the eye diagram closes, and at this time, distributed dispersion compensation has better performance.

Conclusion
Compared DCF and multi-channel chirpFBGFour configurations in 4010GThe transmission performance of SSFM at 525 kilometers is similar to that of DCF and FBG in distributed dispersion compensation. Adding FBG in the transmission span is feasible because FBG has low insertion loss, allowing for the use of cheaper, low-noise index, single-stage amplifiers. But the reduced amplification noise is not enough to offset the cost caused by increased span attenuation. turnFBGConcentrating in the middle of the terminal amplifier and using primary amplification elsewhere can achieve a balanced trade-off between amplifier cost, performance, and transmission power.

Beijing Jinkun Technology Co., Ltd. www.jonkon.com.cn