Mitsubishi develops fast 16-way optical switch

Engineers at Mitsubishi Electric have developed a 16-way optical cross-connect switch for use in metropolitan area fibre networks that they say is capable of operating faster than similar products from other companies.

Mitsubishi Electric's new switch, which was demonstrated at the company's research and development centre, could connect and disconnect fibre paths in less than one millisecond or around one-tenth the time of components currently in use, a manager of the company's opto-electronics team, Tatsuo Hatta, said.

At the heart of the device is a component called a Bascule optical switch. This consists of a small square polymer sheet into which a 16-by-16 waveguide grid has been scored. Directly below each point where the waveguides cross is a 0.3 -millimetre diameter ball - the same type as that used in a ballpoint pen - and beneath that is a piezo-actuator. When the actuator is switched off the ball is at rest and light passes directly through the junction, but when energised the actuator pushes the ball up so it impacts the polymer. This creates a break in the waveguide and light then takes a 90-degree turn. In this way light from any of 16 input fibres can be switched to any of 16 output fibres.

The Bascule switch had several advantages over competing technologies being pushed for use in such optical cross-connect systems, said Hatta.

Compared to micro-electrical-mechanical systems (MEMS) type switches, which bounce light off small mirrors, the new component is about 10 times faster and has less signal loss.

Against thermo-optical effect switches the speed was also faster and the power consumption was much less, he said. The first product samples based on the 16-way switch and a previously developed eight-way switch should be available by September, the company said.

Mass production was planned within the coming 12 months, Hatta said.

The company will first target the metropolitan area optical network market, which is expected to expand as broadband communication systems become more pervasive.

Already that move is on in the company's home market.

At the end of 2003 there were just under 900,000 subscribers to fibre-to-the-home Internet services in Japan compared with 10.2 million digital subscriber line (DSL) and 2.5 million cable Internet subscribers, according to figures from Japan's Ministry of Public Management, Home Affairs, Posts and Telecommunications (MPHPT).

Mitsubishi Electric had 14 domestic and seven overseas patents pending on the technology, it said.