COL Cover Story: Efficient upstream data transmission by joint scheme of dispersion compensation and electro-modulation
At: 2017/2/8 16:30:00 by admin

With the worldwide applications of emerging multi-mediaservices and mobile fronthaul, the user’s bandwidth demand is constantly increasing.So the passive optical network (PON) with 100 Gb/s system capacity supporting25 Gb/s data rate per wavelength is actively discussed and studied. In order toachieve 25 Gb/s data rate per wavelength for upstream signals, modulationformats, optical devices and the technical solutions supporting burst-modetransmission while overcoming accumulated chromatic dispersion become the mainfactors to be considered. How to achieve better performance with reduced systemcost is a critical problem for 100 Gb/s PON in upstream links.

 

A scheme of partial chromatic dispersion compensation combinedwith advanced modulation formats is proposed to solve the above-mentioned problemsby Professor Lilin Yi’s group, from State Key Laboratory of Advanced OpticalCommunication Systems and Networks, Shanghai Jiao Tong University. By employinglow cost optical devices, upstream 0-40 km transmission of 25 Gb/s per wavelengthhas been achieved. The research result is reported in ChineseOptics Letters Volume 15, No. 2, 2017 (Honglin Ji, et al., Upstream Dispersion Management of 25 Gb/s Duobinary and PAM-4 Signals to Support 0-40 kmDifferential Reach).

 

In order to achieve 25 Gb/s data rate per wavelength forupstream signals, they use 10 GHz electro-modulation laser (EML) basedelectrical duo-binary (EDB) and quaternary level pulse amplitude modulation(PAM-4) format with optical dispersion compensation (ODC) in optical lineterminal (OLT) side. To overcome the accumulated chromatic dispersion whileconsidering the positive and negative dispersion tolerance of EDB or PAM-4, partialdispersion compensation method is employed to support 0-40 km differentialreach. And the EDB-based modulation scheme achieves the highest uplink powerbudget of 39.5 dB so far. Therefore, EML based EDB format in ONU side combinedwith ODC in OLT will be an attractive solution for the upstream datatransmission in symmetric 100 G-PONs.

 

Professor Weisheng Hu from the research group believesthat the proposed partial dispersion compensation method combined with advancedmodulation formats can achieve higher transmission data rate, higher powerbudget with low cost, which will facilitate the 100G-PON standardization and deployment.

 

The following works will mainly focus on the deepanalysis of the system performance and the system stability in the long-termmeasurement.


Graphic descriptionFigure a shows the eye diagrams of the transmitted NRZ and PAM-4 signal. Figure bshows the picture of the experimental set up. Figure c shows the eye diagramsof the received Duobinary and PAM-4 signal. Figure d shows a schematic ofpassive optical network.


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