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Oki Succeeds in Developing the World's Smallest Microlens for Optical Communications Components

- Enabling Mass-Production of Optical Components for Metro and Access Networks at Lower Costs -

Tokyo, Japan, December 10, 2002 -- Oki Electric Industry Co., Ltd. (TSE: 6703) today announced that the company has succeeded in developing the world's smallest silicon-based microlens, allowing for mass-production of high-performance optical components at low cost for the metro and access-network markets. This microlens improves the performance of optical components, as it can be used for surface-mount technology (SMT), a popular method for the mass-production of low-end optical components at low cost. The cost of the microlens itself is also reduced by more than ten fold, as it is produced using LSI fabrication technology.

"Because it enables production in volume of high-performance optical components at very low cost, I believe that this microlens and its associated technology will meet growing optical market requirements, in particular those of the metro and access network markets, where many network carriers are presenting severe competition. This will help in the deployment of broadband access," said Harushige Sugimoto, General Manager of the Corporate Research and Development Center at Oki Electric.

Oki employs silicon diffractive optical elements (DOE) for the microlens, as silicon is transparent at the wavelengths of 1.3-µm and 1.55-µm used for mid- to long-distance optical communications. Combining conventional LSI mass-production technology and deep etching technology now popular in micromachine fabrication, Oki has succeeded in reducing the diameter of the microlens to 125-µm, identical to that of an optical fiber.

This enables the microlens to be used in the conventional SMT process for optical components. The SMT process uses a silicon substrate featuring a V-shaped groove for the optical fiber attachment; a laser diode chip is mounted on the top surface of the substrate using alignment marks. This structure allows for fully automated assembly of optical components enabling low-cost mass-production.

Until now, however, virtually no lens has been available for use in the SMT process, and only a small portion of the light from the laser diode could be coupled into the optical fiber. The microlens developed by Oki shares the same V-shaped groove as the optical fiber, enabling the microlens to be automatically aligned between the laser diode and the optical fiber.

The coupling efficiency of the microlens reaches -3.0 dB for a fiber output power, comparable to that achieved by conventional lenses. Therefore, the microlens is expected to expand the applications of SMT optical components from conventional low-end uses to the higher-performance applications required for metro and access networks.

These microlenses generate collimating optical beams by inserting two of them in the same V-shaped groove. Any functional elements required the metro and access networks, such as isolators and filters, can be placed between these lenses; the silicon V-groove substrate thus may serve as a universal platform for various applications of more advanced optical components at low cost.

Oki plans to offer microlens samples in December 2002. The company will begin commercial shipment of this product in 2003, targeting various applications including those involving the use of high-performance, small, low-cost optical components required for the metro- and access-network optical communications markets and for the high-speed data network market.

Outline Chart of the Developed Technology

A silicon-based microlens with its diameter of 125-µm and an example of its usage

Glossary

- Surface mount technology (SMT):
A packaging technology used for the mass-production of optical components at low cost. Automated flip-chip bonding machines are used for passive placement of optical devices (such as laser diodes, microlenses, and optical fibers) on silicon V-groove platforms. The optical fiber is aligned with the precisely etched V-groove. The corresponding laser diode is placed on the same platform through visual recognition of the alignment marks on the silicon substrate.

- Diffractive optical element (DOE):
A miniaturized Fresnel lens fabricated on substrates using photolithography and etching techniques commonly employed in the silicon LSI industry.

- Silicon V-groove substrate:
An optical platform featuring a V-groove, which accurately aligns and fixes the optical fiber. The V-groove is precisely etched using silicon LSI technology to enable passive alignment of conventional optical fibers with sub-micron accuracy.

- Isolator
A device that effectively passes optical signals in one direction and blocks them in the opposite direction. This device is commonly used in mid- to long-range optical communications to stabilize laser diode performance by eliminating feed back light.

- Filter:
A device that transmits an optical signal of a certain wavelength, blocking signals of other wavelength. This device is used in wavelength division multiplexing (WDM) systems to combine or split different wavelength signals.

Notes:
  • Names of companies and products are trademarks or registered trademarks of the respective companies.

About Oki Electric Industry Co., Ltd.
Founded more than a century ago in 1881, Oki Electric Industry Co., Ltd. is Japan's first telecommunications manufacturer, headquartered in Tokyo, Japan. Oki Electric provides customers with top-quality products, technologies and solutions for telecommunications systems, information systems and electronic devices through its corporate vision, "Oki, Network Solutions for a Global Society."



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