Issue link: https://www.e-digitaleditions.com/i/1327492
January/February/March 2021 I 43 The most likely way to preserve the SR4 plant when migrating to 400G is to use BD4.2 BiDi. It increases the lane rate and halves the number of wavelengths compared to SWDM4 400G, which uses two wavelengths at 50G and four plus four MPOs (4 lanes, 8 fibers). APPLICATIONS DRIVING FIBER DEPLOYMENTS WITHIN THE NETWORK After looking at technology drivers and changes in optical fiber and transceiver technology, it is important to look at the applications that are driving fiber deployment, many of which are related to 5G. The data center is probably the market segment that has changed the most. When looking at historical models of the data center space, it used a traditional, three tier approach. There were a few fiber connections between the core switches and then perhaps some out to the aggregation switches. The rest of the data center was predominantly copper. More current data center models, such as leaf-spine architectures and East-West traffic, have vastly increased the number of physical connections due to the need for more redundancy and lower latencies. This type of traffic will only intensify with 5G. Increased East-West traffic has led to a 180-degree change in data center design. Rather than mostly copper with a few optical fiber backbones, today's data centers are predominantly optical fiber with little copper within the server cabinets or for band network management. The data center landscape is again changing. Instead of the current model where a small number of centralized "mega" data centers are hosting applications, the trend is now reversing toward more of a distributed architecture using smaller micro or edge data centers. This is needed to accomplish certain criteria and objectives, such as the lower latency needed in upcoming 5G networks. FIGURE 6: Data centers are the brain of a smart community. 4G Macro 4G 5G 5G Macro 5G Small Cell 5G Small Cell SERVER 5G NETWORK SMS SMS Internet Internet HD, 3D, Ultra video Vehicles, Home Appliances Speed 1Gb/Second Speed 20Gb/Second Latency 10 ms Latency <1 ms 1000 connections/Km 2 1 million connections/Km 2 Video 4G 5G With 4G, latency is about 80 milliseconds or longer. The objective for 5G is less than five milliseconds. Con- sider autonomous vehicles with the current 4G system. If a signal is sent to a macro tower that is 10, 15, or 20 miles away, by the time the response returns, that vehicle will have moved several feet. Because there will be data centers much closer to the edge devices with 5G, latency will be lower and the car would have moved inches rather than feet. In order for this to happen, many more data centers will need to be added near those edge devices, and there will be a lot more optical fiber deployment in the outside plant to connect all the edge data centers back to the central hubs. In fact, until those edge data centers are in place, there will be no true 5G. Instead, companies are deploying a lot of 4G radios and antennas and increasing their capacity. Users do notice an increase in speed, but it is still 4G.