GBIC, SFP, SFP+, SFP28, QSFP, QSFP+, QSFP28 are all packaging methods for optical transceiver, they are different transmission rates and are the main ways to distinguish optical modules. Among them, SFP, SFP+, SFP28 have the same size, and QSFP+, QSFP28 have the same size. These methods are the main types of optical modules for DAC Cable and AOC cable, and are widely used in data centers, AI intelligence, telecommunications, big data, cloud computing and other occasions.
What is GBIC?
GBIC (Gigabit Bit Rate Interface Converter)
Until 2000, GBIC was the most popular optical module package and the most widely used form of Gigabit modules. GBIC is an interface device that converts Gigabit electrical signals into optical signals. GBIC is designed to be hot-swappable.
GBIC modules are divided into two categories: one is GBIC modules are used in cascade to achieve common connections with other switches; the second is GBIC modules dedicated to stacking to achieve redundant connections with other switches.
What is SFP?
SFP, short for Small Form-factor Pluggable, is a small hot pluggable optical transceiver. SFP is half the size of GBIC module and can be configured with more than twice the number of ports in the same panel. Functionally, the two are not much different and both support hot-swappable. This design greatly increases the port density of network equipment. The transmission rates of SFP packaged optical modules are 155M, 1.25G, 2.5G, etc. The interface type is mainly LC interface, which is generally used in SONET/SDH network, 100M/1000M Ethernet and other low-speed transmission applications. The maximum bandwidth supported by SFP is 4Gbps.
What is SFP+?
SFP+ is an enhanced version of SFP. Its appearance and size are the same as SFP. Its transmission rates are 6G, 8G, 10G, etc. It supports 8Gbit/s Fiber Channel, 10G Ethernet and optical transmission network standard OTU2. In addition, SFP+ direct-connect cables (i.e. SFP+ DAC high-speed cables and AOC active optical cables) can connect two SFP+ ports without adding additional optical modules and cables (network cables or fiber jumpers). It is a good choice for two adjacent short-distance networks. It is a good choice for directly connecting two close switches. The packaging type includes 6G/8G FC optical modules, 10G optical modules, 10G electrical port modules, 10G DAC high-speed cables and 10G AOC active optical cables, which are mainly used in 10GBASE-SR Ethernet links in data centers.
What is SFP28?
SFP28 is an enhanced version of SFP+. It has the same size as SFP+, but can support a single-channel 25Gb/s transmission rate. SFP28 provides an efficient solution for 10G-25G-100G network upgrades to meet the growing needs of next-generation data center networks.
What is QSFP?
QSFP Quad Small Form-factor Pluggable, is a four-channel small pluggable optical module with four independent full-duplex transceiver channels. It was originally designed to replace single-channel SFP with high-density optical modules, and QSFP is only 30% larger than the standard SFP module. The device supports rates from 100Mbps to 10Gbps and, like SFP, has digital diagnostics to monitor link performance.
QSFP was developed for high-density applications. The four-channel pluggable interface of QSFP achieves a transmission rate of 40Gbps. It is used as a fiber optic solution that outperforms the 4-channel CX4 interface in terms of speed and density.
What is QSFP+?
QSFP+ is an upgraded version of QSFP. QSFP can support 4-way transmission at the same time, and the data rate of each channel is 1Gbit/s. However, QSFP+ is different from QSFP in that the data rate of each channel is 10Gbit/s. It supports 4×10Gbit/s transmission channels, and can reach a transmission rate of 40Gbps through 4 channels. Compared with SFP+, the transmission rate of QSFP+ optical module can be up to four times that of SFP+ optical module. QSFP+ optical module can be directly used for 40G network deployment, which can effectively save costs while increasing port density.
What is QSFP28?
QSFP28 is designed to meet the needs of 100G applications through four high-speed differential signal channels, with a transmission rate of 25Gbp/s for each channel. Through four channels, a 100Gbps transmission rate can be achieved, which can meet the application requirements of 100G Ethernet (4×25Gbps) and EDR InfiniBand.
From the above explanation, the main distinction is based on the speed and the number of built-in devices:
| Packaging method | Transmission rate | Number of built-in optical devices |
| SFP | <3G | 1 laser and 1 detector |
| SFP+ | 6G-16G | 1 laser and 1 detector |
| SFP28 | 25G/32G | 1 laser and 1 detector |
| QSFP+ | 40G/56G | 4-channel laser array, 4-channel detector array |
| QSFP28 | 100G | 4-channel laser array, 4-channel detector array |
Differences of different packaging
From above detail explanation, you must know the what SFP, SFP+, SFP28, QSFP+, and QSFP28 are, so following will introduce the specific similarities and differences between them.
SFP vs. SFP+:
| Size | The size and appearance of SFP and SFP+ modules are basically the same |
| Transmission rate | SFP can transmit up to 4Gbit/s, and SFP+ can transmit up to 10Gbit/s. |
| Transmission standard | SFP is based on the SFF-8472 protocol, while SFP+ is based on the SFF-8431 and SFF-8432 protocols. |
| Compatibility | You can use SFP modules on the SFP+ port of the switch, but the rate will be reduced to 1Gbit/s. However, SFP+ modules cannot be used in SFP slots, otherwise the port or module may be damaged. |
SFP+ vs SFP28
| Size | SFP28 is an upgraded version of SFP+, but SFP+ and SFP28 have the same size. |
| Transmission rate | The transmission rate of SFP+ is 10Gbit/s, and the transmission rate of SFP28 is 25Gbit/s. |
| Compatibility | If the SFP+ optical module is inserted into the SFP28 port, the link transmission rate is 10Gbit/s, and vice versa. |
| Cable | SFP28 direct-attached copper cable has higher bandwidth and lower loss than SFP+ direct-attached copper cable. |
QSFP+ vs QSFP28
| Size | QSFP+ and QSFP28 are the same size and both have 4 integrated transmit and receive channels |
| Transmission rate | QSFP+ modules support 40Gbit/s single channel rate, and QSFP28 modules support 100Gbit/s transmission rate. |
| Compatibility | QSFP28 modules cannot be used for 10G branch links, but if the switch with QSFP28 ports supports QSFP+ modules, QSFP+ modules can be inserted into QSFP28 ports to achieve 4×10G branch links. |
| Cable | QSFP+ and QSFP28 both have the same DAC/AOC high-speed cable, but the rates are different. QSFP+ DAC/AOC supports 4×10Gbit/s transmission rate. QSFP28 DAC/AOC supports 4×25Gbit/s or 2×50Gbit/s. |
SFP28 vs QSFP28
| Size | SFP28 and QSFP28 differ in size and protocol standards. |
| Transmission rate | SFP28 modules support 25 Gb/s on a single channel, QSFP28 modules support 100Gbit/s transmission rate. |
| Compatibility | They can both be used in 100G networks, but SFP28 is used as a QSFP28 to SFP28 breakout cable like below image. |
Conclusion
From above similarity and differences between SFP and SFP+, SFP28 and SFP+, QSFP+ and QSFP28 optical transceivers, we know that though some of them have similar size and appearance, their working speeds are different. Furthermore, the main driving force of the development of optical transceivers is to achieve higher bandwidth with smaller size. QSFP28 and QSFP+ have the same size but higher bandwidth, which proves this point. And next artile will introduce 3 types package for 400G optical transceivers.
