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PAM-4 PHY devices allow transmission rates of 40/50Gb/s

Posted: 19 Dec 2014     Print Version  Bookmark and Share

Keywords:Broadcom  direct attach cable  PHY  level pulse amplitude modulation 

Broadcom Corp. has unleashed what it boasts as the industry's first high speed 4-level pulse amplitude modulation (PAM-4) physical layer transceivers (PHYs). The PAM-4 PHYs allow transmission rates of 40/50Gb/s serially over multiple physical media including direct attach cables (DAC) and optical fibre, stated the company.

To support the rapid rise in video and data traffic, there is growing demand for higher speed and more bandwidth over currently deployed infrastructure. As a result, system OEMs are looking at ways to optimize 40/100GbE connectivity. Based on PAM-4 technology, Broadcom's BCM82040 and BCM82004 devices are the first in a line of 40/50/100GbE devices optimised to meet these requirements.

The 28nm BCM82040 and BCM82004 PHYs support higher data throughput over existing low bandwidth channels by transmitting more bits per symbol. PAM-4 enables the transmission of 40Gb/s at a baud rate of 20Gbaud, resulting in improved signal integrity while re-using existing channels for higher data throughput and enabling the use of lower cost cables and optics. The PAM4-line code in the PHYs require half the bandwidth of non-return-to-zero (NRZ) line code, resulting in higher throughput and lower total system cost and power consumption, added Broadcom.

Both devices are geared to transmit and receive 40/50G data over two pairs of media versus eight pairs of media using existing 4x10G quad small form-factor pluggable (QSFP) cables. For 40G optical applications, the BCM82040 reduces the number of optical components and optical fibres required by a factor of four, eliminating expensive components and further reducing cost and power.

Broadcom's PAM-4 PHYs are available in 7 x 7mm package fits within QSFP+ form factor, cable assembly and optics modules. The BCM82040 is optimised for transmitting 40/50Gb/s over optical fibre and the BCM82004 is optimised for transmitting 40/50Gb/s over direct attach cable (DAC). Both devices are sampling.

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