Although 10G/40G has become the mainstream on telecommunication network market nowadays, service providers and enterprise data centers are still demanding higher data transmission speed to achieve higher level of performance and scalability, which explains why 100G Ethernet appeared on the scene. According to the statistics from market research company like IHS, 100G becomes a hit in the year of 2016. This post tends to give a brief overview of optical transceivers and cabling solutions for 100G Ethernet.
100 Gigabit Ethernet (100GbE) is the computer networking technology which was first defined by IEEE 802.3ba-2010 standard for transmitting Ethernet frames at rates of 100 gigabits per second. The 100G standards define numerous port types with different optical and electrical interfaces and different numbers of optical fiber strands per port. The mainly used 100G standards are showed in the following table.
Optical transceiver is considered to be a key component to ensure the flexibility and reliability of the whole system. The most commonly used 100G transceivers on the market are CFP, CFP2, CFP4 and QSFP28. The following part will introduce them in details.
CFP/CFP2/CFP4: The CFP (c form-factor pluggable) is a multi-source agreement (MSA) to produce a common form-factor for the transmission of high-speed digital signals. The “c” stands for the Latin letter C used to express the number 100 (centum), since the standard was primarily developed for 100 Gigabit Ethernet. The CFP transceiver can be used to support both single-mode fiber, multimode fiber and a variety of data rates, protocols, and link lengths. While the electrical connection of a CFP uses 10×10 Gbit/s lanes in each direction (RX, TX), the optical connection can support both 10×10 Gbit/s and 4×25 Gbit/s variants of 100Gbit/s interconnects. With the improvement in technology, higher-density and higher-performance CFP2 and CFP4 transceivers are needed. CFP2 and CFP4 has the similar electrical connection with the CFP, but they specify a form-factor of 1/2 and 1/4 respectively in size of the original specification. When you use these transceiver modules, you should note that they are not interchangeable, but they can be inter-operable at the optical interface with appropriate connectors. The image below shows CFP, CFP2 and CFP4 transceivers.
QSFP28: QSFP28 is a hot-pluggable, high-density transceiver available in single-mode and multimode versions to support data center, cloud networks, and high-performance computing networks applications. Just as the 40G QSFP+ is implemented with four 10Gbs lanes, the QSFP28 uses four 25 Gbs lanes for an aggregate data rate of 100Gbs. Typically, there are two versions of QSFP28 transceivers, 100GBase-SR4 QSFP28 for short distance data transmission and 100GBase-LR4 QSFP28 for long distance data transmission. The following picture shows these two types.
100G Direct Cabling Solutions: There are various 100G direct cabling solutions available on the market. You can choose the appropriate one according to the data transmission distance that you require. For 100G short direct cabling, we can use 100GBase-SR4 QSFP28 and 100G QSFP28 to QSFP28 cables. As we all know, 100GBase-SR4 QSFP28 can support the length of up to 70 m and 100 m over OM3 and OM4 12 fiber multimode MTP cable respectively, and 100G QSFP28 to QSFP28 passive direct attach cable can support up to 5 m, while the 100G QSFP28 to QSFP28 active direct attach cable can support up to 10 m. For 100G long direct cabling, 100GBase-LR4 transceivers (including 100GBase-LR4 QSFP28, CFP, CFP2 and CFP4) are good choices. All of them can achieve the link length of up to 10 km on single-mode LC patch cables. Here shows a Cisco QSFP-100G-CU3M passive direct attach copper cable.
100G Breakout Cabling Solution: 100G QSFP28 to 4SFP28 direct attach copper cable (shown in the following picture) is the commonly used cable type for 100G breakout cabling applications. This cable provides connectivity between system units with SFP28 port on one side and four different SFP28 ports on the other side, which enables higher port bandwidth, density and configurability at a low cost and reduces power requirement in data centers.