800G Optical Transceiver Module Form Factor

Currently, there are two types of 800G optical transceiver module form factors: QSFP-DD and OSFP.

The number of electrical lanes for QSFP-DD and OSFP is 8 for 400G and 800G, respectively. However, the transmission speed of the electrical signal per lane is 100G.

OSFP is considered to have an advantage in the form factor of 800G optical transceiver modules. The reason for this advantage is the heat dissipation and internal circuit implementation, which I introduced in the 400G article.

800G optical transmission standard

Table 2 below summarizes the 800G optical transmission standards.

This section explains table classification. First, the second line from the top is the standard that uses Multi-mode Fiber. Lines 3 to 6 are standards that use Single-mode fiber. Lines 3 to 6 are classified by maximum transmission distance. The third column from the left in the table is the standard that uses multi-core optical fiber. The 4th row is a standard that uses 2-core optical fiber.

The above standards are standardized by the following organizations:

・IEEE802.3 Ethernet Working Group of the Institute of Electrical and Electronics Engineers of America

・An organization promoting optical network technology (OIF) in which optical network equipment and related component vendors participate.

Four representative standards based on transmission distance

Typical optical transmission standards for 800G optical transceiver modules include (1) SR8 for short distances, (2) 800GBASE-DR8 for medium distances, (3) 2x400G DR4, and (4) 2x400G FR4.

(1) 800GBASE-SR8 for short distances

The 8 in SR8 indicates that the optical signal has 8 lanes. In other words, the optical signal consists of 100G x 8 lanes. We believe that the 800GBASE-SR8 (Figure 1) will be used for short-distance connections with a transmission distance of less than 100m.

Figure 1. 800GBASE-SR8 block diagram

(2) 800GBASE-DR8/800GBASE-DR8+, (3) 2x400G DR4, (4) 2x400G FR4 for medium range

Next, we will introduce optical transmission standards for medium distances with maximum transmission distances of 500m and 2km.

(2) 800GBASE-DR8/800GBASE-DR8+

First, we will introduce the optical transmission standards ``800GBASE-DR8'', which has a maximum transmission distance of 500m, and ``800GBASE-DR8+'', which has a maximum transmission distance of 2km.

 

The "8" in DR8/DR8+ also indicates that there are eight lanes of optical signals, resulting in a configuration of 100G x 8 lanes. Due to the difference in maximum transmission distance, the type of fiber used is different from SR8. However, the internal configuration is considered to be similar to 800GBASE-SR8. Regarding the optical connector, 800GBASE-SR8/DR8/800GBASE-DR8+ uses an MPO-16 connector as the optical connector. The MPO-16 connector is configured with 8 transmit lanes and 8 receive lanes, as shown in Figure 2.

Figure 2. MPO-16 connector diagram
* QSFP-DD MSA See more

　

Next, there are 2x400G DR4 and 2x400G FR4, which are medium-distance optical transmission standards that use the same multi-core optical fiber. The 800G optical signal standard includes two standards that use two existing 400G optical transmission standards: 2x400G DR4 and 2x400G FR4.

(3) 2x400G DR4

2x400G DR4 is an 800G optical transmission standard with a maximum transmission distance of 500m, using two sets of 400GBASE-DR4, which is a 400G optical transmission standard. Below is the block diagram of 2x400G DR4.

Figure 3. 2x400G DR4 block diagram

Again, there are 8 lanes for transmitting and receiving electrical signals. Of these 8 lanes of electrical signals, 4 lanes for transmission and 4 lanes for reception are used to combine them into one set. The parts grouped into one set are surrounded by the orange dotted line in the diagram. The area surrounded by this orange dotted line has the same configuration as 400GBASE-DR4. By thinking in the same way, the area surrounded by the green dotted line will have the same configuration as 400GBASE-DR4.

 

Thus, 2x400G DR4 is a standard that uses two pairs of the 400G optical transmission standard 400GBASE-DR4, which has a maximum transmission distance of 500m. 2x400G DR4 uses dual MPO-12 connectors as optical connectors. The dual MPO-12 connector is configured with two pairs of MPO-12 connectors, as shown in Figure 4.

Figure 4. Dual MPO-12 connector diagram
* QSFP-DD MSA See more

Breakout is also possible by using two optical transceiver modules with an optical transmission standard of 400GBASE-DR4, as shown in Figure 5 below.

Figure 5. 2x400G DR4 and 400GBASE-DR4 breakout example

(4) 2x400G FR4

2x400G FR4 is an 800G optical transmission standard with a maximum transmission distance of 2km, using two sets of 400GBASE-FR4, which is a 400G optical transmission standard. Below is the block diagram of 2x400G FR4.

Figure 6. 2x400G FR4 block diagram

Thinking in the same way as 2x400G DR4, the areas surrounded by orange dotted lines and green dotted lines in the diagram have the same configuration as 400GBASE-FR4.

Thus, 2x400G FR4 is a standard that uses two pairs of 400GBASE-FR4, a 400G optical transmission standard with a maximum transmission distance of 2km. 2x400G FR4 uses dual LC connectors as optical connectors. Dual LC connectors are configured with two pairs of LC connectors, as shown in Figure 7.

Figure 7. Dual LC connector diagram
* QSFP-DD MSA See more

Long-distance 800G LR and 800G ZR are also available.

There are also long-distance optical transmission standards with maximum transmission distances of 10km and 120km. These are currently being standardized by OIF, but it appears that the optical transmission standard will be 800G LR, which has a maximum transmission distance of 10 km without an optical amplifier, and 800G ZR, which has a maximum transmission distance of 120 km with an optical amplifier.

New optical transceiver module for 800G transmission: Linear-drive Pluggable Optics

For 800G, a new concept product called Linear Drive Optics = LPO is being considered. Specifically, it eliminates the DSP and CDR that perform signal processing and clock regeneration, and directly converts electrical and optical signals.

The biggest advantage is reduced power consumption. On the other hand, it will be disadvantageous in terms of signal quality, and it will be difficult to achieve long transmission distances.

We explained the transmission standards for 800G optical transceiver modules.

In this article, we have summarized the 800G optical transmission standards that have been confirmed or are expected to be standardized in the future.

In addition to 800LR and 800ZR, there are other optical transmission standards that are being standardized by IEEE P802.3 dj. According to the standard, the transmission speed per optical signal lane is 200Gbps. With optical signals having a transmission speed of 200Gbps per lane, it appears that the establishment of an 800G optical transmission standard with a 200Gx4 lane configuration and an even faster 1.6Tbps optical transmission standard are also in the works. We will also provide information on these as soon as they become available.

Macnica offers the Finisar Transceiver series from Coherent, a leading company in optical transceiver modules. Our experienced sales staff and technical staff dedicated to optical transceiver module products provide comprehensive support from customer consideration to installation and operation. If you are interested, please contact us using the form below.

This article is also often read