With the rising demands for bandwidth from fast-growing cloud services and data centers, all network components are continuing to keep pace with the trend to meet the expectations of the end users. While the connectors are moving from LC to MTP type, the optical transceivers are also progressing in line with the emerging trends. 100G transceiver market is booming and will be more popular in the near future. In 2013, Cisco announced its proprietary 100G transceiver called CPAK. The CPAK transceiver has been able to offer something interesting to 100G technology buyers. But what makes CPAK transceiver different from other 100G transceiver? Let’s unveil its mystery.

What Is CPAK Transceiver?

CPAK transceiver was launched in the market later than CFP2. Its appearance is similar to the CFP2 optical transceiver, but the interface uses the IEEE standard to support compatibility with other interfaces, so as to make them well suit for connections in service provider data center, enterprise and edge networks. This kind of 100G transceiver has generally 82 pins on its electrical interface (40 pins on the top row and 42 on the bottom row), and there is a duplex SC or 12-fiber /24-fiber MPO/MTP connector on its optical interface. CPAK 100GBASE optical module can be plugged into the CPAK ports of Cisco switches and routers. To offer a flexible selection, 100G CPAK modules accommodate a variety of distance and fiber type requirements, so you can choose the model in line with your requirements.

What Makes CPAK Transceiver Different in 100G Networks?

To face the exploding demand of network bandwidth, there are many options for 100G modules, like CFP, CFP2, CFP4, QSFP28, CPAK. So the competition among 100G optical transceivers remains fierce. Under this condition, what makes 100G CPAK module different from other 100G transceiver modules? And what are the benefits of CPAK transceiver? The most difference is that CPAK transceiver is the first 100G optical module using CMOS photonics which bring extremely efficient low-power optical circuits, and it is Cisco propriety. Besides, CPAK optical transceiver incorporates IEEE standard interfaces available in several different types: 100GBASE-SR10, 100GBASE-ER4L, 100GBASE-LR4, 10x10G-ERL, 10x10GBASE-LR, etc. Generally, different 100G module types can communicate with each other under the same standard and the same speed rate. For example, 100GBASE-LR4 whether from CFP/CFP2/CFP4 or CPAK will be inter-operate.

100G Transceiver Comparison: CPAK vs. CFP/CFP2/CFP4 vs. QSFP28

Currently, there are many different 100G transceiver options with a range of form factors, including CFP, CXP, CPAK, CFP2, CFP4, and QSFP28. The following makes a 100G module comparison: CPAK vs. CFP/CFP2/CFP4 vs. QSFP28.

Size - The CPAK transceivers are less than one third the size of CFP modules. In comparison with CFP2 modules, CPAK optical transceivers are 20% smaller. However, it is larger than CFP4 and QSFP28. Until now, the large size does not meet the needs of high-density data centers, so the small form factors (QSFP28) are becoming more and more popular.

Electrical Connection - The optical connection of all 100G form factors can support both 10 x 10Gbps and 4 x 25Gbps variants. But for electrical connection, CPAK and CFP2 optical transceiver can support 10 x 10Gbps and 4 x 25Gbps mode for an aggregate of 100Gbps data rate. CFP module realizes internet speed by using 10 x 10Gbps in each direction (RX/TX), while CFP4 and QSFP28 support 4 x 25Gbps.

Distance - 100GBASE-SR4 CPAK module supports link lengths of up to 70m (100m) over OM3 (OM4) multimode fiber with MPO connectors; CPAK 100GBASE-ER4 Lite and CPAK 10x10GBASE-ERL module support link lengths up to about 25 km over standard SMF. On the other hand, QSFP28-100G-SR4 operates at multimode fiber for a distance of 100m; QSFP-100G-ER4L-S can support a much longer distance of 25 - 40km reach over SMF.

Power Consumption - CPAK module consumes 40% less power than CFP2 and 70% less power than CFP form factors. But it is a little higher than CFP4 and QSFP28.

Price - Since CPAK transceiver is Cisco proprietary module, the compatible 100G CPAK modules are not available from third-party vendors. So the price is very high in the market. On the contrary, 100G QSFP28 module price will continue to drop according to forecast of optical transceiver market. Take FS.COM compatible QSFP 100G SR4 as an example, it is only $199 with free shipping.

Among the various 100G transceivers, most of switch vendors could choose the QSFP28 transceivers. Because of its lower power consumption and higher density, it has become the mainstream form of 100G optical transceiver. More details about 100G QSFP28 transceiver, please read the article Decoding 100G QSFP28 Fiber Optic Transceiver.

The Influence and Future of CPAK Transceiver

CPAK transceiver represents a significant advancement in optical networking. With its unique feature of having CMOS photonics technology, the most benefit lies in the fact that it delivers exceptionally high port density and front panel bandwidth. As of now, Cisco and its compatible vendors have designed switches with CPAK ports. Under this situation, this kind of 100G module could be more likely to stand out among other form factors in the near future. But in such a fierce market environment, it is hard to say whether CPAK will be a hot star in 100G transceiver market. So far, the biggest challenge to win the market comes from QSFP28 transceivers that have delivered fabulous results in developing 100G networks. If it wants to capture the 100G transceiver market, it has to maintain a steady speed in terms of development and compatibility. More information about optical transceiver market, please refer to Global Optical Transceiver Market: Striding to 200G and 400G.

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