The 25G Ethernet is proposed standard for Ethernet connectivity in a data center environment, developed by IEEE 802.3 task force P802.3by. According to the IEEE standards, 25G Ethernet is now defined for both single-lane and four-lane versions of 25G, such as SFP28 25G transceivers (1×25 Gbps) and QSFP 28 100G transceivers (4×25 Gbps). This article will focus on 25G SFP28 transceiver.
The 25G SFP28 transceiver is a high performance module which supports 25G data rate for data communication applications. It has two types: SFP-25G-SR and SFP-25G-LR. The former one is designed to use a nominal wavelength of 850nm and can operate over OM3 fiber up to 70 meters and OM4 fiber up to 100 meters. It is suitable for short-range data communication and interconnect applications. While the latter one features a highly reliable 1310nm DFB transmitter and PIN photo-detector into duplex LC connector, providing links up to 10 kilometers over single mode fiber. It is designed for long-reach applications. Here is a figure of SFP-25G-SR for you.
Generally speaking, 25G SFP28 transceiver is usually used for 25G to 100G connectivity. This part will take 25G SFP28 SR transceiver for example.
Cabling Solution 1. From the figure below we can see that one 100G QSFP28 transceiver can be connected with four 25G SFP28 transceivers via the MTP LC fanout cable. This is the simplest cabling solution for 25G to 100G connectivity.
Cabling Solution 2. We can deploy the MTP/MPO breakout cassette to accomplish the optical link. As the following figure shows, one end of MTP trunk cable is plugged into the MTP/MPO mm connector interface of 100G QSFP28 transceiver, while the other end is plugged into the MTP port at the rear of the MTP/MPO breakout cassette. Then the LC ports in the front of the MTP cassette and four 25G SFP28 transceivers are connected by four duplex LC patch cables.
Cabling Solution 3. In addition to deploy MTP modular cassette, we can also use fiber enclosure containing MTP fiber adapter panel. In this way, the cabling can be flexible. Since the fiber enclosure can hold up to four MTP fiber adapter panels, the fiber density can be greatly improved. The cabling solution is shown in the following figure. From the left to the right, the 100G QSFP28 transceiver is connected with MPO adaptor on the MTP fiber adapter panel by MTP trunk cable. The MTP fiber adapter panel will be installed in the fiber enclosure. Then another MTP trunk cable connect the MPO adaptor on both MTP adapter panel and at the rear of the MTP cassette. Finally, the whole 25G to 100G connectivity is completed by the connection between duplex LC ports in the front of the MTP cassette and four 25G SFP28 transceivers, using four duplex LC patch cables.
Cabling Solution 4. We can replace the MTP cassette and four duplex LC patch cables with one MTP LC fanout cable. As the following figure shows, the MTP connect interface of the harness cable is plugged into the MPO adaptor on the MTP fiber adapter panel while the other end four duplex LC connector interfaces are plugged into four 25G SFP28 transceivers.
By using MTP components, 25G to 100G connectivity can be accomplished with high cost effectiveness. I hope after reading this article, you can have a better understanding of 25G SFP28 transceiver as well as 25G to 100G connectivity.