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Hitachi and Opnext Achieve 43Gbit/s Transmission over 10km Optical Fiber

Hitachi, Ltd. and Opnext, Inc. today announce the development of its next generation semiconductor laser for 40 Gbit/s optical transmission. The new uncooled optical modulator integrated laser which does not require temperature control, has provided the world's first successful 10km single mode fiber transmission with a transmission speed of 43Gbit/s. This transmission was achieved during a test trial within a wide temperature range from 25°C to 85°C.

“This accomplishment is an important development in achieving energy-efficient, low-cost 40Gbit/s ultra-high-speed optical transceivers,” said Dr. Masahiro Aoki, department manager, Nanoelectronics Research Department, Central Research Laboratory, Hitachi, Ltd. “Uncooled lasers are a key component, as they contribute to the handling of larger data volumes, as well as, the lowering of costs in optical transmission equipment which will be required with further developments in an IT-oriented society.”

The recent explosion of high-speed Internet connection and related services is expected to drive the demand for even faster communication speeds, doubling every eighteen months. Accompanying this increase in communication traffic has been a surge in the power required by optical communications equipment. It is predicted that by 2010, the core network will require the equivalent power of ten nuclear power plants. In this age where reducing CO2 emissions is a critical issue, not only achieving high-speeds data transmission but also reducing the power consumption of optical communication equipment is in high demand. By using an uncooled laser and eliminating the need for temperature control, 10 to 20 percent power can be conserved. Thus, an optical transceiver can greatly contribute to energy-efficient ultra-high-speed optical fiber networks.

This technology will be presented at the 34th European Conference on Optical Communication (ECOC 2008) to be held from 21st to 25th September in Brussels, Belgium, by Hitachi and Opnext Japan, a subsidiary of the US company, Opnext, Inc.

Features of the prototype uncooled laser light source are as follows:

(1) 43Gbit/s, 10km-transmission using an 1300 nm range EA modulator integrated laser Electro-absorption (EA) modulators are a type of external modulator. Using EA modulation techniques results in less degradation of the signal waveform, thus enabling higher-speed longer-distance optical transmission, compared to directly modulated lasers. Hitachi and Opnext have been working on the development of EA modulator monolithically integrated semiconductor lasers, and past cooperation has resulted in a product capable of 40Gbit/s high-speed transmission. However, the operating wavelength of this product is 1550nm, and the transmission distance limited to 2km due to fiber dispersion. To overcome this limitation, research was conducted to develop a 40Gbit/s high-speed modulator structure which is capable of operating within a wavelength of 1300nm. This would ensure less fiber dispersion and enable 10km long-distance transmission.

(2) Use of temperature tolerant InGaAlAs (indium gallium aluminum arsenide) material in the EA modulator

In the newly developed laser light source, InGaAlAs, a temperature tolerant material was used in the EA modulator to expand the operational temperature range. Further, a semiconductor process was developed for this material to achieve a monolithically integrated modulator and laser structure similar to the conventional 1550nm device.

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