Data centers provide computing and storage resources for applications, data, and content. In order to achieve mutual communication——sharing data and content, providing redundant backup, data centers need to be interconnected. Data Center Interconnect (DCI) is realized to connect two or more data centers together by high rate optical devices.

DCI technology enables data to be transmitted across ultra-long distances, from inter-city and even transoceanic connections. Some large operators use DCI to connect their own data centers in their expanded enterprise infrastructure, and others connect to partners, cloud providers, or data center operators to simplify data, share resource or deal with disaster recovery needs. Submarine cables are applied to data centers connecting and Internet exchanges between countries and continents separated by oceans.

In current data center architecture, there are three modulation technologies based on NRZ, PAM4 and coherent. Among them, NRZ is mature and easy to manage. This article mainly explains DCI transmission solutions based on NRZ and ultra-long distance coherent DCI solutions.

N×10G NRZ transmission

Product details: client-side uses 10G SFP+ SR optical transceivers, 10G OEO client-side uses 10G SR optical transceivers to connect with client-side, line side uses 10G DWDM 80km optical transceivers to connect with AWG.

Notes: 10G OTU unit is composed of 10G optical transceivers and board cards. One channel 10G service is end-to-end connected. OTU board cards need 2pcs of client-side 10G SR and 2pcs of line side 10G DWDM.

N×40G NRZ Transmission

Product details: client-side uses 40G QSFP SR4 optical transceivers, OTU unit realizes the conversion of one 40GE service into four 10GE services, 4×10G Muxponder client-side uses 40G SR4 optical transceivers to connect with client-side, line side uses 10G DWDM 80km transceivers to connect with AWG.

Notes: system can transmit 10 channels of 40G services when using 40CH AWG. The OTU unit is composed of 40G optical transceivers, 10G optical transceivers and board cards. One 40G service is end-to-end connected, OTU board cards need 2pcs of client-side 40G QSFP SR4 and 8pcs of line side 10G DWDM.

N×25G NRZ Transmission

Product details: client-side uses 25G SFP28 SR optical transceivers, 25G OEO client-side uses 25G SR optical transceivers to connect with client-side, line side uses 25G DWDM 10km optical transceivers to connect with AWG.

Notes: For 25G system, the system residual dispersion is required to be controlled at ±100ps/nm. The 25G OTU unit is composed of 25G optical transceivers and board cards. One 25G service is end-to-end connected. OTU board cards need 2pcs of client-side 25G SFP28 SR and 2pcs of line-side 25G DWDM.

N×100G NRZ Transmission

Product details: client-side uses 100G QSFP28 SR4 optical transceivers, the OTU unit realizes the conversion of one 100GE service into four 25GE services, 4×25G Muxponder client-side uses 100G QSFP28 SR4 optical transceivers to connect with client-side, line side uses 25G DWDM 10km optical transceivers to connect with AWG.

Notes: system can transmit 10 channels of 100G services when using 40CH AWG. For 4×25G system, the system residual dispersion is required to be controlled at ±100ps/nm. The OTU unit is composed of 100G optical transceivers, 25G optical transceivers and board cards. One 100G service is end-to-end connected, OTU board cards need 2pcs of client-side 100G QSFP28 SR4 and 8pcs of line side 25G DWDM.

N×10/25/40/100G hybrid transmission

Product details: client-side uses 10G/25G/40G/100G optical transceivers, 100G OTU unit realizes the conversion of one 100GE service into four 25GE services, 4×25G Muxponder client-side uses 100G QSFP28 SR4 optical transceivers to connect with client-side, line side uses 25G DWDM 10km optical transceivers to connect with AWG. 40G realizes the conversion of one 40GE service into four 10GE services, 4×10G Muxponder client-side uses 40G QSFP SR4 optical transceivers to connect with client-side, line side uses 10G DWDM 10km optical transceivers to connect with AWG. Some 25G clients use 25G SFP28 SR optical transceivers, 25G OEO client-side uses 25G SR optical transceivers to connect with client-side, line side uses 25G DWDM 10km optical transceivers to connect with AWG. 10G OTU unit consists of 10G optical transceivers and board cards. One 10G service is end-to-end connected. OTU board cards need 2pcs of client-side 10G SR and 2pcs of line side 10G DWDM.

Notes: The system supports 10G/25G/40G/100G hybrid access, dispersion is used in accordance with 25G signal requirements, which meet other rate signal transmission requirements.

For ultra-long-distance DCI, the most effective transmission technology is coherent optical transmission. By establishing fast and reliable connections, physically independent data centers can easily share resources and balance workloads.

N×100/200G coherent transmission

Product details: client-side uses 100G QSFP28 SR4 optical transceivers. OTU unit realizes the conversion of one 100GE service into one 100G coherent optical signal or two 100GE services into one 200G coherent optical signal. 2×100 Muxponder client-side uses 100G QSFP28 SR4 to connect with client-side, line side uses 100/200G CFP2 DCO to connect with AWG. OTU unit is composed of 100G optical transceivers, 100G/200G coherent transceivers and board cards. One channel 100G service is end-to-end connected. OTU board cards need 2pcs of client-side 100G QSFP28 SR4 and 2pcs of 100G CFP2 DCO. Two channels service are end-to-end connected, OTU board cards need 4pcs of client-side 100G QSFP28 SR4 and 2pcs of 100G CFP2 DCO.

Notes: When 2×100G Muxponder board cards transmit a single 100GE service, line side uses 100G CFP2 DCO. When 2×100G Muxponder board cards transmit two 100GE services, line side uses 200G CFP2 DCO.

Coptolink has invested very much in new technology development, optical design, process reliability and automated production, has the goal to become a competitive and reliable supplier in data center products market. Coptolink can provide DCI with a full range of optical transceivers, passive MUX/DEMUX WDM devices and coherent transmission subsystems.

Coptolink has many years of experience in R&D and production of optical transceivers, complete reliable test system, analysis and improvement capabilities for reliability related issues at the equipment level, transceiver level and device level, all conform to international GR468, GR1221 and other general standards to ensure product reliability.