5G bandwidth demands and transceiver options
The main driving force for fiber deployment in the 80s, when cellular and fiber infrastructures were simultaneously deploying for the first time, is the same as now--scaling consumer bandwidth demand. As 5G mobile devices replace obsolete generations of cellular technology, consumer demands are expected to continue growing in leaps and bounds.
As demand escalates, so too must the supply to meet it. The 5G project proposition is a two-fold approach of creating a cellular platform capable of delivering 10 Gbps to mobile devices (4K and 8K video streaming needs) and supporting a dramatic increase in the quantity of simultaneous devices that can be connected to that network (needed in support of IoT enablement).
Correlated to the 5G prediction and response plan (especially the video applications) are stringent latency requirements able to avoid exceeding 1 ms. As if bringing today into the future of wireless connectivity wasn't enough, 5G networks are also anticipated to be significantly more energy efficient than its predecessors.
Backhaul & midhaul: no unexpected disruptions
It's widely accepted that this type of platform can only be successfully achieved with current and upcoming technologies by utilizing fiberization. Cellular fiber infrastructure was utilized only periodically in the past, and when it was, it was primarily to interface between cell sites and mobile switching centers (MSCs) over a mobile backhaul network. Predating mobile 3G, fiber was rarely used as copper-based TDM worked well enough.
The backhaul will be tactically modified through adoption of 5G technologies. The anticipation is that carriers will more widely choose packet-based transport over fiber, however few may retain limited use of copper and radio transmission methods. The preferred choice in the backhaul is fiber, however challenges ranging from environmental or regulatory to time-to-market may necessitate other methods. Most significantly, fiberization of the fronthaul and midhaul portions of the cellular network infrastructure is progressing swiftly.
Optical backhaul and midhaul networks frequently use SMF transport, though that backhaul infrastructure follows what is being used in metro and regional wireline networks. These networks perform quite similarly:
- Backhaul infrastructure often needs to reach up to hundreds of kilometers. Modern longhaul backhaul links utilize 100G CFP modules (both inclusive and exclusive of an EDFA). Whereas for the 5G backhaul, reaches typically extend to only tens of kilometers, offering broader transceiver options to choose from.
- 100G QSFP28 options are commonly selected with preference to ER models for 20-40 km ranges. Regarding backhaul/midhaul use cases, QSFP form factors are selected in contrast to CFP due to a large delta of power levels needed to operate – the former consumes less than 4w, while the latter is nearly 30w.
- Optical backhaul is carefully and cautiously creeping towards he next generation, with 200G QSFP56 modules intended for backhaul/midhaul applications hitting the market. 400G will then undoubtedly trail close behind 200G in market adoption.
Fronthaul: 25G enters the stage
Here the fiber connects up the remote radio heads (RRUs) and the baseband units (BBUs). The growing interest in the fronthaul is attributed to new C-RAN architectures for 5G infrastructure, with high bandwidth and speeds needed. This requirement presents new opportunities for fiber optic deployments, as these opportunities are not just relevant to 10G and 100G, but also 25G data rates. The fronthaul costs for the 5G service providers are substantial amounts, but these transceiver/optical costs are reasonable since C-RANs minimize site deployment costs, power consumption, and maintenance expenses.
5G service providers are gravitating towards 10G fronthaul transceiver selections because they are inexpensive options. The 10G module commonly deployed in this market is a DWDM SFP, reaching up to 40 km as an ER and 70 km as a ZR. When these speeds aren't quite enough, 100G transceivers may offer a higher data rate alternative, though 25G options more frequently appearing as a more optimal solution.
There are a few different reasons driving the growing adoption of 25G optics in the 5G ecosystem. For select fronthaul applications, 100G is excessive (specifications far exceeding need with related cost increases), while 10G doesn’t offer quite enough bandwidth despite it's lower price point. The advantages of 25G in mobile are many, with a leading benefit that 25G is cheaper to deploy--a lower cost achieved through use of an SFP format (SFP28) unlike the QSFP28 transceivers used for 100G.
What role do third-party optics play in 5G deployment?
With all of the hype and excitement surrounding the 5G movement, it is new to market, and in turn, is risky to deploy. Keeping infrastructure costs as low as possible certainly helps mitigate that risk, which is where third-party transceiver supplier benefits are best served. With the risks of 5G and service providers looking to upgrade but at reduced cost, they can leverage their currentinfrastructure by using WDM (CWDM) transceiver options available via third party suppliers.
With 5G at such an early stage of deployment, no one really knows for sure what the infrastructure “should” look like in any given geography. This is another reason to keep costs low; some transceivers may actually end up being thrown away as infrastructure designs are streamlined for optimal efficiency as technology matures. Conversely, some may require expedited expansion to meet further surprises in demand. Third-party transceiver firms generally carry a positive historical reputation for quickly dispatching fully compatible transceivers to customers rapidly.
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