Fujitsu develops amplifier to enable PON-based optical aggregation networks

Fujitsu Ltd. and Fujitsu Laboratories Ltd. say they have developed optical amplifier technology for PONs that would quadruple the number of splits and double reach. The development would enable the use of PON technology for optical aggregation applications.

While PONs are now a commonly accepted approach to deliver services to consumers and businesses, the fact that each PON will support only 32 end-user connections at a distance of approximately 20 km has prevented their consideration for aggregation requirements, Fujitsu says.

Fujitsu and Fujitsu Laboratories say their new amplifier technology can overcome these limitations, particularly in the upstream. The new burst-mode optical amplifier technology uses a semiconductor optical amplifier (SOA), an integrated SOA-array module fabrication technology, and an SOA chip fabrication technology that enables uncooled operation. The resulting PON amplifier will quadruple the split ratio in a PON and double the transmission distance between the central office equipment and the terminal equipment, the Fujitsu organizations assert.

The burst-mode amplifier would be placed in a remote node between the optical line terminal (OLT) in the central office and the optical network termination (ONT) at the customer’s site. The amplifier would remain in an “off” state until it detects an incoming upstream signal. The fact that the amplifier would not always be on reduces optical signal-to-noise ratio (OSNR) to the point where traffic from 128 ONTs could be amplified with the same OSNR as 32.

The manufacturing technology enables four SOAs to be integrated into a single module and uses a coupling scheme that couples four SOAs with four singlemode fibers. Meanwhile, the SOA chip fabrication process sees an aluminum composite material deployed in the active layer of the SOA. This process enables high gain, even at high temperatures, the Fujitsu units assert. The ability to operate without cooling reduces module volume to one-fifth, with one-sixth the power compared with a conventional cooled SOA module, they continue. The module operates at temperatures up to 85°C, which means it can be installed outdoors.

Research results derived by the Commissioned Research of National Institute of Information and Communications Technology (NICT) were applied to portion of the amplifier work, the Fujitsu groups acknowledge. The team presented its research in a paper last month at ECOC in Geneva.