Avago's latest optical engine targets active optical cables

Avago Technologies has unveiled its first family of active optical cables for use in the data centre and for high performance computing.

The company has developed an optical engine for use in the active optical cables (AOCs). Known as the Atlas 75x, the optical engine reduces the power consumption and cost of the AOC to better compete with direct-attach copper cables. 

“Some 99 percent of [active optical cable] applications are 20m or less”

Sharon Hall, Avago

"This is a price-elastic market," says Sharon Hall, product line manager for embedded optics at Avago Technologies. "A 20 percent price premium over a copper solution, then it starts to get interesting."

The AOC family comprises a 10 Gigabit-per-second (Gbps) single channel SFP+ and two QSFP+ cables - a 4x10Gbps QSFP+ and a QSFP+-to-four SFP+. The SFP+ AOC is used for 10 Gigabit Ethernet, 8 Gigabit Fibre Channel and Infiniband applications. The QSFP+ is used for 4-channel Infiniband, serial-attached SCSI (SAS) storage while the QSFP-to-four-SFP+ is required for server applications.

There are also three 12-channel CXP AOC products: 10-channel and 12-channel cables with each channel at 10Gbps; and a 12-channel CXP, each at 12.5Gbps. The devices supports the 100GBASE-SR10 100 Gigabit Ethernet and 12-channel Infiniband standards.

The 12-channel 12.5Gbps CXP product is used typically for proprietary applications such as chassis-to-chassis links where greater bandwidth is required, says Avago. 

The SFP+ and QSFP+ products have a reach of 20m whereas competing AOC products achieve 100m. “Some 99 percent of applications are 20m or less,” says Hall.

The SFP+ and QSFP+ AOC products use the Atlas 75x optical engine. The CXP cable uses Avago’s existing Atlas 77x MicroPod engine and has a reach of 100m. 

The Atlas 75x duplex 10Gbps engine reduces the power consumption by adopting a CMOS-based VCSEL driver instead of a silicon germanium one.  “With CMOS you do not get the same level of performance as silicon germanium and that impacts the reach,” says Hall. “This is why the MicroPod is more geared for the high-end solutions.” 

The result of using the Atlas 75x is an SFP+ AOC with a power consumption of 270mW compared to 200mW of a passive direct-attach copper cable. However, the SFP+ AOC has a lower bit error rate (1x10-15 vs. 1x10-12), a reach of up to 20m compared to the copper cable’s 7m and is only a quarter of the weight.

The SFP+ AOC does have a lower power consumption compared to active direct-attach cable, which consumes 400-800mW and has a reach of 15m.

Avago says that up to a 30m reach is possible using the Atlas 75x optical engine. Meanwhile, samples of the AOCs are available now.