Fiber Optic Transceivers for 5G Networking Equipment
5G rollouts are on the horizon, with major telecom companies set to rollout limited network access in the US and Europe. Most folks pay attention to the wireless requirements in these networks, but local antennas will still need to be connected to the telephone network and the Internet with high bandwidth optical fibers or wireless backhaul connections.
All this requires fiber optic transceivers to support fiber networking equipment. Choosing the right transceiver for fiber networks depends on multiple factors, although in 5G the principal factors to consider are bandwidth, data rate, conversion loss, and fiber type. Before you can choose the correct fiber transceiver, the first step is to determine what type of fiber the network is using, or what type of fiber cable the application will require to achieve optimal speed and bandwidth.
Which Type of Fiber are You Using?
There are two main types of fiber cable, each of which is appropriate for different applications and will require different transceivers:
Multimode Fiber (MMF): this type of fiber can be used to transmit multiple channels simultaneously. Greater mode density leads to greater modal dispersion that accumulates over the distance of the fiber, thus these fibers are best used for short-run links, such as in MAN and LAN networks.
Single-mode Fiber (SMF): This fiber is designed for longer distances and will provide faster data transmission rates in a single channel with the correct transceivers. These fibers are often bundled in a single cable for massive data transmission over long distances.
Within SMF and MMF classes of fiber, there are different fiber types that provide different data rates and are rated for use over different distances under TIA/EIA standards for fiber optics. Your optical power budget will also determine the limit transceiver you can use for a given link length, and your output on the transmitting side may need to increase the output from your transmitting transceiver to compensate losses in a link.
Clearly, there are several important systems design points to consider, but the first important points to consider in a real network are link length and required data rate. Newer portions of fiber to support upcoming 5G rollouts require multi-Gbps data transmission over long distances to support connections between base stations and cell towers, and to provide fiber-to-the-home and fiber-to-the-premises.
Some municipalities are already installing dark fiber that is capable of up to 40 or 100 Gbps, and networking equipment to support these dark fiber networks will need to include transceivers to support these data rates. Ideal link lengths can range anywhere from hundreds of meters (MMF will be used here) up to be dozens of kilometers (SMF will be used here) in order to support existing cellular infrastructure. If you’re working with SMF fiber over long distances, expect to drop bundles of fiber and deploy scalable networking equipment that includes swappable transceivers with standard form factors. QSFP+ or CFP will be the dominant form factors, especially CFP as it already supports 40 and 100 Gbps systems.
Note that, in some cases, you can get away with using an SMF with a fiber optic transceiver designed for MMF as the core in an SMF fiber is about 20% the value required in the receiver. This provides easy coupling and the fiber will be insensitive to alignment, but this is not recommended and many not work over longer distances. In the ideal case, you should choose a transceiver that will support the data rates and fiber type you are using in your particular application.
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