400G optical modules of various types, you need to look this up!

With the rapid development of mobile Internet, cloud computing, large data technology, the transport network between the need for higher data rate port, in order to meet the market needs, emerged 400G optical module, the optical module mainly 400G introduction.
400G Introduction:
100G = 25G . 4, present mainly 100G NRZ encoding scheme implemented in the form of a four-channel, single channel rate of 25G. CWDM4 center wavelength is four, the four channels can be seen as broad sense. Will increase to 100G 400G, if still in the form of four channels, each channel rate needs to be increased to 100G, even with the PAM4 encoding, modulation rate single channel also needs to achieve 50G, that there are still some challenges in the current. If the form of an 8-channel, single channel rate of 50G, using PAM4 coding, 100G single channel rate and the requirements, just as 25G. In comparison, the lower the difficulty channel scheme 8 can be achieved increases, but need PAM4 scheme. PAM4 scheme for signal generation, detection and so made new demands.
400G products:
. 1, the optical module CFP8
CFP8 CFP4 is an extension of, the channel number is increased to 8 channels, will also increase the size, of 40 102 9.5 mm ^. 3. With the parallel signals 16 to 25G to work quickly to market and application 400G products. But the high cost, the need to use the laser 16 to 25G, or using PLC splitter to reduce the number of lasers, the splitter LOSS too high, resulting in a direct transmit power of the laser is relatively large, so the cost will be high. Higher power consumption, a panel interface density is too low, larger size.

2, OSFP light module
OSFP English name is Octal Small Formfactor Pluggable, Octal referring 8, octal meaning, which means the direct use of electrical signals 56G, 856GbE, but the 56GbE signal is formed by the DML laser 25G in the PAM4 modulation. The criteria for the new interface standard, is not compatible with existing optoelectronic interface. The structure diagram below, OSFP own radiator, a size of 100.4 22.58 13 is ^. 3 mm, a lot of power consumption is relatively low compared CFP8 small, only 15W maximum, but more than QSFP-DD slightly larger size, thus requiring more large area of PCB, and the PCB need to mechanical structure Hosting cage, 1RU front panel.

Which is different from the electrical pin interface QSFP-DD, each having a vertical row, as shown below:

. 3, the optical module QSFP-DD
QSFP-DD wherein Q means a "Quad", 4-way means, each of the QSFP56 a. 4 56Gbe, 200G signal is formed; refers to a DD "Double Density", there are two parallel QSFP56, 2 200G 400Gbe signal generation, stands Quad Small form Factor Pluggable-Double Density , which is a program for expanding QSFP will 4 the original channel interface line increases, the channel becomes 8. Smaller than OSFP, can be compatible with existing and 100GbE QSFP28 40GbE QSFP interfaces, the original QSFP28 module can still be used, simply to insert a module, so that a smooth upgrade.

With the addition of four channels, the upper and lower surfaces of the electrically pin interface increases a row, as shown in FIG. The following figure on the left of a row of pins is the newly added pad pin.

4, COBO optical module
COBO is "consortium for on board optics" for short, is placed in direct reflective module PCB board, are no longer restricted to limit the density of the front panel of the interface, while the heat dissipation problem can be multiplexed between the PCB heat sink is strong greatly eased. This small module size, and should not further reduce the size of the space, but because it is not hot-swappable, once a module fails, the entire board needs anti-business stopped, only after removing the board, very inconvenient.

FIG comparison scale 400G optical module:

the size, power and cost of these three terms, QSFP-DD and COBO more promising in the future application of the data center 400G.