Electronic Design

New ICs Turn Passive Optical Networks Into Reality

The ultimate home or office broadband connection consists of optical fiber. While it has been too expensive for local loop connections, fiber's cost is beginning to drop. Recent developments have provided new components that make it possible to implement a fully passive optical network (PON) at very low cost.

Japan already has optical fiber to the home (FTTH). U.S. carriers like Bell South, SBC, and Verizon are testing and experimenting with these promising new networks. With inexpensive fiber and the wide availability of optical transceiver modules already in place, all that's needed are the circuits that make the PON work.

Motorola's MC92701 broadband-PON (BPON) layer termination device, which fully complies with the ITU-T G.983 specification, fills that void. It's designed to work with the company's flexible PowerQUICC communications processors to create the Optical Network Termination (ONT) devices for the home or the Optical Network Unit (ONU) devices for the office/business end of a BPON.

The ONT and ONU boxes communicate with the Optical Line Termination (OLT) unit that's at the carrier's central office. With the MC92701/PowerQUICC combination, vendors can quickly create a product similar to a cable box to make the BPON work.

The BPON's beauty and low cost are inherent in its fully passive nature. No expensive optical-electrical-optical (OEO) conversions like those in other optical networks are necessary. A single passive splitter lets the carrier build a BPON with up to 32 nodes at distances up to 20 km. The MC92701 implements a system based upon the ATM that's capable of 155 or 622 Mbits/s downstream using 1555- or 1490-nm lasers or 155 Mbits/s upstream with a 1310-nm laser. The resulting network makes other older broadband connections look like what they are—last century's technology.

The chip supports dynamic bandwidth assignment (DBA) used to achieve quality-of-service (QoS) control and peak bandwidth allocation. The chip also handles all ATM cell processing. Both the clock and data recovery (CDR) unit and the clock phase-locked loop are on-chip, and they operate with an external 19.44-MHz crystal. A seamless interface to the PowerQUICC is provided.

OEMs can easily pick features and characteristics based on their choice of PowerQUICC processor. Interfaces to 10/100 Ethernet, 24-line POTS, HPNA, USB, and PCMCIA are available. Some models of PowerQUICC, such as the MPC885, also have built-in security features.

The MC92701 is scheduled for production during the first quarter of 2004. Contact your local Motorola sales representative for pricing information.

Motorola Inc.

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TAGS: Components
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