Thursday 24 September, 2020 |

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.

A Simple Application of 10GBase-T Transceiver in Copper Network

Besides fiber optic cables, 10G Ethernet SFP+ transceivers can transfer data over copper cables, like twin-axial cabling or twisted pair cabling. This kind of SFP+ transceiver is equipped with a RJ-45 connector on one side, as the below figure shows. It is called 10GBase-T SFP+ transceiver. With cat6, cat6a or cat7 copper cables, 10GBase-T SFP+ transceiver could make a link length up to 30 meters.

Why SFP+ 10GBase-T transceiver?

Since optic fiber could make transmit faster and further and build a complete network system, why SFP+ 10GBase-T transceiver is needed? This is a key question encountered by 10GBase-T SFP+ transceiver. As a star member of 10G SFP+ transceiver family, 10GBase-T SFP+ transceiver is popular for a wide range of applications in copper-based infrastructure of network system. When connecting 10G modules to copper networks, 10GBase-T SFP+ transceiver can directly connect into the copper networks, while the other 10G SFP+ transceivers using optic fibers need to connect with media converter to realize this connection. Let me show you this application with a good example.

A Specific Application

Sometimes, due to the consideration of cost savings, there are some devices equipped with RJ-45 port still working in 10G Ethernet standard in many data centers, workstation, or servers network. For these devices, the only way to connect them to a host switch is using the RJ-45 port over a cat6a or cat7 copper cable. But what if this host switch has no RJ-45 port but only SFP+ slots? There are two solutions answering this question.

The first solution is using a SFP+ 10GBase-SR transceiver, a fiber patch cord with duplex LC port, a media converter and finally a cat6a copper cable connecting to the endpoint.

Like the table shown above, the second solution is very simple. Just a SFP+ 10GBase-T transceiver and a cat6, cat6a or cat7 copper cable are enough. No optical fiber and no media converter mean lower cost.

Now note the point in this application. First, you do have a endpoint with RJ-45 port. Second, you have a host switch equipped with SFP+ slots but no RJ-45 port. Third, you don’t want to dissipate neither of them and hope put them together to build a network. Then, being the cable system within 30 meters is under application. So SFP+ 10GBase-T transceiver is a good and advisable choice.

10Gtek provides the 100% compatible SFP+ 10GBase-T transceiver with many switch vendors such as Cisco, HP, Juniper, Arista, Brocade and etc. Since it has the interoperability for a ranges of brands, 10Gtek SFP+ 10GBase-T transceiver certainly will run well in this kind of application.

Understand 10G SFP+ Transceiver From the Perspective of Connecting Cable Types

SFP+ transceiver is very popular in many data center and enterprise servers network application. As we all known, 10G SFP+ transceivers have a big branch family. Different SFP+ transceivers can provide a wide variety of connectivity options. There are several approaches for us to understand 10G SFP+ transceivers family. For example, with the compliance to different 10G Ethernet standard, we can classify transceivers as 10GBase-SR, 10GBase-LR, 10GBase-ER, 10GBase-ZR etc. Or viewing from the port type, we can see the difference between the SFP+ transceiver configured with duplex LC connector or a RJ-45 connector. But there is another approach we can understand and distinguish SFP+ transceivers. And That is waht I am going to talk about: the Connecting Cable Types.

1.Copper Cable

10GBase-T SFP+ is a transceiver configured with a RJ-45 port, which means that it uses copper cable to provide connections of 10G transmission speed. Cat 6, cat 6a or cat 7 copper cable is required in this situation. As for the transmission distance, it only supports a link length of up to 30 meters. 10GBase-T SFP+ transceiver is a suitable one for very short distances and offer a cost-effective way to connect within racks and across adjacent racks.

2.Multi-mode fiber

10GBase-SR SFP+ is the transceiver using multi-mode fiber to transfer data in SFP+ family. It is using 850nm wavelength. 10GBaase-SR transceiver supports a link length of 26m on standard Fiber Distributed Data Interface (FDDI)-grade multi-mode fiber. Using OM3 multi-mode fiber, up to 300m link lengths are possible. Using OM4 multi-mode, up to 400m link lengths are possible.

3.Both single-mode fiber & multi-mode fiber available

10GBase-LX4 and 10GBase-LRM transceiver is using both single-mode fiber and multi-mode fiber to transfer data. 10GBase-LX4 transceiver uses CWDM technology to divide 12.5 GB/s data streams into four 3.125 GB/s data streams that are propagated in optical fibers. And due to the 8B/10B encoding, the effective data flow is 10 GB/s. But 10GBase-LX4 transceiver has the disadvantages of high cost and much power consumption. Therefore,it has a very narrow market. 10GBase-LRM transceiver is a replacement of 10GBASE-LX4 transceiver, allowing distances up to 220 meters. It supports link lengths of 220m on standard Fiber Distributed Data Interface (FDDI) grade Multi-mode Fiber. There’s one thing to notice. To make sure that specifications are met over FDDI-grade, OM1 and OM2 fibers, the transceiver should be coupled through a mode conditioning patch cord. No mode conditioning patch cord is required for applications over OM3 or OM4. Besides, using standard single-mode fiber, 10GBase-LRM module also can support a link length of 300m. In general, multi-mode fiber connecting is the most application scenario for 10GBase-LRM transceiver.

4.Single-mode fiber

There are three basic kinds of transceivers using single-mode fibers to transfer data in SFP+ family: 10GBase-LR, 10GBase-ER, 10GBase-ZR. With carrying different wavelength, every transceiver can reach up different distances. For example, 10GBase-LR transceiver can support a link length of up to 10 kilometers. 10GBase-ER transceiver can support a link length of up to 40 kilometers. 10GBase-ZR transceiver can support a link length of up to 80 kilometers. Due to a superior transmission range and usually a long length of optic fiber cable, using these three transceivers means much higher cost. So these three kinds of transceivers are the better option where budget is not a constraint, or when the demand for long cable system.

Conclusion

From the perspective of connecting cable types, we will have a more clear image of 10G SFP+ transceiver. In fact, we can easily draw the conclusion: different cable types constrain the transmission distance of the 10G SFP+ transceiver. The range of transmission distance is an important consideration factor of selecting SFP+ transceivers.

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