What are the categories of 800G optical modules?

800G optical modules have entered mass production this year. Thanks to the explosion of AI technologies such as ChatGPT, the market demand for 800G optical modules has further increased. Here we have compiled information about 800G optical modules for your reference.

800G=8*100G=4*200G, therefore, according to the single channel rate, it can be divided into two categories, namely single channel 100G and 200G. The corresponding architecture is shown in the figure below.

Single-channel 100G optical modules can be implemented quickly, while 200G has higher requirements for optical devices. Since the maximum rate supported by the current electrical interface is 112GbpsPAM4, for single-channel 200G, a gearbox is required for conversion.

What are the categories of 800G optical modules?

For multi-mode, there are two main standards for 800G optical modules, corresponding to transmission distances less than 100m.

1) 800GSR8

It uses a VCSEL (vertical cavity surface emitting laser) solution with a wavelength of 850nm and a single-channel rate of 100GbpsPAM4, requiring 16 optical fibers. This can be seen as an upgraded version of 400GSR4, with the number of channels doubled. The optical interface is MPO-16 or 2 rows of MPO-12, as shown in the figure below.

2) 800GSR4.2

This solution uses 850nm/910nm wavelengths, bidirectional transmission, and uses the DeMux in the module to split the two wavelengths. The single channel rate is 100GbpsPAM4, which requires 8 optical fibers. Compared with SR8, the number of optical fibers in this solution is reduced by half. Its block diagram is shown below:

Its optical fiber interface is shown in the figure below, which adopts MPO-12 interface.

For single-mode, there are multiple standards for 800G optical modules.

1) 800GDR8, 800G2xDR4 and 800GPSM8

The internal architecture of these three standards is similar, including 8 Tx and 8 Rx, with a single channel rate of 100Gbps and requiring 16 optical fibers.

The transmission distance of PSM8 is 100m, and the transmission distance of DR8 and 2*DR4 is 500m. The optical interface of 2xDR4 is 2 MPO-12, as shown in the figure below, which can be interconnected with 400GDR4 optical module to facilitate data center upgrades. The optical interface of PSM8 and DR8 is MPO-16.

2) 800G2xFR4 and 2xLR4

The internal structure of these two standards is similar, including 4 wavelengths, and the single channel rate is 100Gbps. The number of optical fibers is reduced through Mux, and 4 optical fibers are required, as shown in the figure below.

These two solutions are upgrades of 400GFR4 and LR4 optical modules, using CWDM4 wavelengths of 1271/1291/1311/1331nm. 2xFR4 supports a transmission distance of 2km, and 2xLR4 supports a transmission distance of 10km. Its optical interface uses dual CS or dual LC interfaces.

3) 800GFR4

This solution uses four wavelengths with a single channel rate of 200 Gbps and requires two optical fibers to support a transmission distance of 2 km, as shown in the figure below.

It uses a duplex LC optical interface, as shown in the figure below.

4) 800GFR8

This solution uses 8 wavelengths, each with a rate of 100 Gbps, and requires two optical fibers to support a transmission distance of 2 km, as shown in the figure below. The 8 wavelength channels are 1271/1291/1311/1331/1351/1371/1391/1411 nm.

Both QSFP-DD and OSFP can support 800G, and the comparison between the two is shown in the figure below. For the 800 optical module, QSFP-DD has made some supplementary updates, namely QSFP-DD800.

The main differences between the two are:

1) Size: OSFP is slightly larger

QSFP-DD and OSFP size comparison

2) Power consumption: OSFP’s power consumption is slightly higher than QSFP-DD

3) Compatibility: QSFP-DD is perfectly compatible with QSFP28 and QSFP+, while OSFP is not.

The single-mode 800G optical modules currently in mass production mainly use the EML (high-speed electro-absorption modulated laser) solution. Can silicon photonic solutions gain a foothold in the market? It is still unknown, mainly depending on cost and power consumption. For single-wavelength 200G solutions, EML or thin-film lithium niobate are two possible technical routes.