As we all know, 100G is the future trend of network development. For the 100G optical transceivers market, the demand for 100G CFP optical transceivers in the telecom market in 2017 has increased by several times in the past year, and the follow-up demand for 100G optical transceiver solutions will also continue to increase. Before deciding to design a product or purchasing a 100G optical transceiver, you should understand the type and characteristics of the 100G optical transceivers to be able to make better judgments and choices. Here we will provide a comprehensive introduction about 100G optical transceivers for all of you.
100G Standard Introduction
100G interface standards include: SR4 (Short Reach), SR10, LR4 (Long Reach), ER4, ZR4; Among them, all the standard electrical signals are 1010G, For LR4 and ER4, the external optical signal is 425G. In addition, SR4 and SR10 are mainly used for short-distance transmission. The transmission distance does not exceed 100M. LR4, ER4 and CR4 are mainly used for long-distance transmission. LR4 transmission distance support 10KM, ER4 support 40KM. ZR4 supports 80KM.
100G Optical Transceiver Types
At present, the mainstream 100G optical transceiver models introduced on the market mainly include: CXP optical transceiver, CFP/CFP2/CFP4 optical transceiver and QSFP28 optical transceiver.
CXP:
C for CXP represents 12 in hexadecimal, because CXP is a 12 full-duplex channel module with 12 * 10G transceivers. CXP is simple to implement, support hot-pluggable and has a smaller form factor than CFP. It supports 100GBASE-SR10 of the short-distance transmission. Under SR10 standard, it can interflow with CFP, CFP2, CFP4, and QSFP28 optical transceivers.
CFP Series (CFP / CFP2 / CFP4):
The C of 100G CFP optical transceiver stands for the number 100 (centum). It is a form factor pluggable optical transceiver, the volume is very large. CFP2 and CFP4 optical transceivers are smaller and smaller, CFP2 size is the half of the CFP half and the size of the CFP4 optical transceiver is one-half of the CFP2, supporting 40G / 100G. CFP4 optical transceiver width and power consumption has been greatly improved. The compact size is more suitable for high-density 100G Ethernet.
Note: CFP4 does not support the SR10 standard.
QSFP28 (Quad Small Form-factor Pluggable)
The 100G QSFP28 is implemented with 4 * 25 Gbps channels. In addition, the QSFP28 optical transceiver has an upgraded electrical interface that supports signals up to 28G and achieves the highest possible rate of 4 × 28 Gbit / s. 100G QSFP28 form factor sizes are smaller than the CFP4 optical transceiver, you can switch with high port density. Currently, there are four kinds of popular QSFP28 optical transceivers in the market based on different form factors: 100G QSFP28 CWDM4, 100G QSFP28 PSM4, 100G QSFP28 SR4 and 100G QSFP28 LR4. As the QSFP28 technology matures, the cost of the QSFP28 optical transceiver decreases, prompting the QSFP28 optical transceiver to become more and more popular.
CPAK:
The 100G form factor interface is introduced by Cisco, currently supporting 100GBASE-SR10, 100GBASE-SR4, and 100GBASE-LR4.
Types of 100G Optical Transceiver Connectors
Common connector types are: SC / LC / MPO and so on. The traditional 10G interface often use SC / LC connectors in the form of dual-core interconnect single-income hair. LC connector and SC connector are similar, but the LC connector is smaller than the SC.
MPO connector is a multiple fiber push-on / push-off all-in-one adapter. In simple terms, it is the use of parallel technology, the number of transponders in a box and the final combination of multiple optical fibers. MPO is divided into MPO12 and MPO24;
MPO 12 is 12 cores with 4 receivers and 4 transmissions, using 12 optical fibers, there are 4 idle, so the standard is SR4 / LR4.
The MPO 24 is a 24-core, 12-wire, 12-wire, 24-wire optical fiber soldered into 12-core arrays, one for transmit and one for receive. Take CFP as an example, in each array, the middle 10 * 10G optical fiber is used to transmit traffic, while the two optical fibers at both ends are idle. A total of four of the two arrays are idle, so the format is SR10. CXP module is 12 transmit and 12 receive, there is no idle line.
Take QSFP28 as an example, if the module inside uses splitters and multiplexers to 4 way 28g data modulated onto a fiber, the external transceiver is a single pay-single LC interface, so for long-distance can save fiber. This kind of optical fiber transmission technology with multiple optical fibers is called wavelength division multiplexing (WDM). Generally, short-distance uses MPO type, long-distance uses LC interface type for saving fiber.
How to Interoperate for Different 100G Optical Transceivers
The same type of 100G modules can communicate with each other. For example: CXP can interoperate with CXP; CFP-SR10 can interoperate with CFP-SR10. Different 100G module types can communicate with each other under the same standard and the same interface type. For example, CFP / CFP2 / CFP4 can communicate with the QSFP28 in the same signal system and the same interface type. For example, CFP2-LR4 with the duplex LC interface can interoperate with QSFP28-LR4 when the interface is duplex LC.
CXP module can interoperate with CFP / CFP2 / CFP4 / QSFP28 optical transceiver only when SR10 is adopted. When CXP and CFP2-SR10 are interoperated, the CXCPs must be screened out 1, 12, 13 and 24 at the edge of the CXP. Because CXP is 12 channels, CFP2 is 10 channels.
Conclusion
From the development trend, QSFP28 optical transceiver and CFP series optical transceiver are 100G network hot solutions, and the use of CXP will be less and less. The following table summarizes the commonly-used 100G optical transceiver types.
| Types | Standard | The Largest Transmission Distance | Connector | Channel | Wavelength | Fiber Types |
| CXP | SR10 | 100m | MPO24 | 12*10G | 850nm | MMF |
| CFP/CFP2/CFP4 |
(CFP4 doesn’t support SR10)
LR4
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