Not so distant from now, the world communication as it is nowadays was really a dream 20 years ago, when no one imagined to have smart homes or even video chats, let alone IOT or IOV. However, 5G makes it all possible, makes it all real.
The new power of 5G is a result of the technical synergy of successive inventions which connected the world to Internet in no time.
OPTICAL TRANSMISSION IN THE CORE
No wonder we can now find the optical transmission in the core of the 5G network, given its huge potential speed, low latency and interface immunity.
Here, I would like to focus on the Optical Transmission development and constrains, starting from the previous decade where SDH and traditional DWDM layer 1 networks were dominating the optical networks for a long time, supporting only TDM, ATM, EOS & P2P Ethernet services in rates which didn’t exceed 10G/s as Max.
Source: https://primex.com/how-point-to-point-and-passive-optical-fiber-networks-are-different/
DWDM ALL IN ONE
DWDM benefited a lot in improving the network by sparing the fiber used between stations, decreasing the number of needed OLA NEs and facilitating protection alternatives. However, at the same time, there was a waste of resources in the traditional DWDM network, with misuse in its limited channels with no smart protection schemes. That was a big constraint for the development of services, as the maximum rate in the core DWDM was not more than 10Gb/s, while in the access network normal costumers did not get more than 100Mb/s.
Source: https://www.packetlight.com/applications/dwdm-cwdm-connectivity
STEPS TO OVERCOME SPEED CONSTRAINTS
The first move was towards using Packet switching instead of circuit switching, allowing for more resilient systems to emerge. That supported rates starting from 64kb/s upward to unlimited rates, with QoS and sophisticated protection mechanisms depending on routing protocols aware of network topology changes in order to calculate the paths and reroute the traffic.
The second step was finding a system which could utilize the DWDM networks in the core layer. That was OTN - with its great potential electrical and optical service grooming - along with ASON protection capabilities (in the access layer, EPON / GPON was newly added).
The next step focused on raising the rate of signal sent using a pair of optical fiber in the core network, that was using new Modulation methods like QPSK, QAM and their sub-kinds. For example, QPSK uses four points on the constellation diagram that double the data rate compared with a BPSK system, while maintaining the same bandwidth of the signal but halving the bandwidth needed. However, that wasn’t enough to meet the continuous need for saving the spectrum. The ePDM+QPSK modulation was the solution, as it decreased the needed spectrum bandwidth to a quarter of the transmitted signal and allowed 100Gb/s to be sent over only 28G.
And at last, the coherent detection system, along with smaller channel spacing in the optical band to get to more than 600G/channel allowed for great world connectivity with a totally optical network at a very limited delay.
In the sum of all, we find that the development of the E2E optical network paved the way to the 5G on-time services with minimum latency and very high speed. Not only in the core network, but also to customer premises like NG-PON2.
In our network, we chose to build our future-proof, totally optical network based on the Huawei OSN9800 in the core and Huawei OSN1800 Enhanced in the branches. With this big step forward we feel the future closer.
