Broadcom unveils 40G/50G PAM-4 physical layer chip

Broadcom Corp. (NASDAQ: BRCM) has introduced what it claims is the industry's first high-speed four-level Pulse Amplitude Modulation (PAM-4) physical layer transceivers (PHYs). The new PAM-4 PHYs enable serial transmission rates of 40/50 Gbps over multiple physical media, including direct attach cables (DAC) and fiber-optic cable.

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 Gigabit Ethernet and 100 Gigabit Ethernet connectivity. PAM-4 technology has emerged as a popular choice for these applications (see the webinar "Verifying PAM4 Performance in 28G & 56G Designs").

Broadcom's BCM82040 and BCM82004 devices are the first in a line of 40/50/100GbE devices optimized to meet these requirements. Built on 28-nm semiconductor process technology, the BCM82040 and BCM82004 PHYs support higher data throughput over existing low-bandwidth channels by transmitting more bits per symbol.

PAM-4 coding enables the transmission of 40 Gbps data rate at a symbol (baud) rate of 20 Gbaud. Thus, the PAM4 line code in the new 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.

The device comes in two flavors. The BCM82040 is optimized for transmitting 40/50 Gbps over optical fiber and the BCM82004 is optimized for transmitting 40/50 Gbps over DACs. Broadcom's PAM-4 PHYs come in a 7x7-mm package that fits within the QSFP+ form factor cable assembly and optical modules.

Both PHYs are designed to transmit and receive 40/50G data over two pairs of media versus eight pairs of media using 4x10G QSFP-enabled cables. In 40G applications, the BCM82040 reduces the number of optical components and optical fibers required by a factor of four, compared to a 4x10G approach.

Both devices are now sampling.

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