Bandwidth, Density and “Lanes”

Each laser is capable of its own bandwidth (depending on several factors) and this defines the lane speed. For example, a given laser may be capable of 100 Gigabits/second (Gb/s) or 200Gb/s. You might also have 4 or 8 lanes such that 4x100Gb/s or 8x200Gb/s will give you 400Gb/s or 1.6Tb/s Transceivers. In 2024, over 20 million 400Gb/s and 800Gb/s transceivers were delivered to customers. However. the industry is changing as a result of the Artificial Intelligence (AI) drive for ever greater bandwidth, with 1.6Tb/s transceivers entering the marketplace in 2025. These are 8 lanes of 200Gb/s each. Ultimately they leave the transceiver by coupling to a pluggable fibre which contains a linear array of 8 fibres (Figure 6)

Figure 6: 8 Channel fibre array unit. Note fibres are held in place by “V-grooves” which give the name “V-groove array or VGA (not to be confused with Video Graphics Array).

Reaching higher bandwidth will require either increasing the bandwidth per lane or adding more lanes and both of these pathways are receiving attention. As 8 lane arrays (Figure 7a) are approaching the physical limitations of the transceiver, it does not currently seem likely that a liner 16 lane array will be developed (Figure 7b). This “beachfront” real estate (linear in one plane and limited by the neighbours) is a concept that also occurs in chip i/o too.

The current industry trend is to find solutions to allow us to exploit “ocean depth” by stacking an 8-channel on top of another 8-channel (Figure 7c). It should be possible for the reader to imagine the possibilities if the density can increase through ocean depth architectures. For example, the 4 stack VGA depicted in Figure 7d would represent a transmission bandwidth of 6.4 Tb/s, far beyond the industry targets for this decade.

Figure 7:  Various configurations of V groove Array.

a) Standard 8 Channel linear VGA (dominant as of 2025).
b) Potential 16 Channel linear VGA.
c) 16 Channel “Stacked” VGA
d) 4-layer, 32 channel VGA.