Oki Develops High-Sensitive and Low-Power Consumption
Limiting Amplifier IC for 10Gb/s Optical Communication Systems

Oki began sample shipment of the ICs at the end of June, and it expects to market them on a large scale beginning in September of this year. The company expects to sell 5,000 units per month.

The new ICs will be available in two packaging options: as a bare die (model KGA4217L) and in a 24-pin ceramic quad flat pack (QFP) (KGL4217L).

"The demand for high-bandwidth communications systems is rising more than ever, because exchanges of voice, text, and images are becoming more common," says Tamotsu Kimura, GaAs products manager at the Components Division of Oki. "The key devices that enable such systems, with speeds in the range of 10 Gb/s, are high-speed semiconductor ICs that provide stable operations with low consumption of power."

The newly developed IC detects 1s and 0s from noisy electrical signals in the data stream and reproduces the data pulses at 10 Gb/s. The electrical signals are converted from optical signals by using a photo-director and a transimpedance amplifier.

The new IC provides a best-in-class input-voltage swing of only 35 mV peak-to-peak at a 10-Gb/s data rate. This is possible because the gate-electrode dimensions are as small as 0.18 microns, due to the structure of the metal semiconductor field-effect transistor (MESFET) of the IC. In this structure, an active layer is formed by ion implantation within a gallium arsenide (GaAs) substrate. A gate electrode, which is a refractory metal, is then patterned on top of the active layer.

Further, the chip, by using a direct coupled FET logic (DCFL) inverter-amplifier circuit, can operate at a low power-supply of only 2 volts, lower than previously possible. This low-power supply voltage enables the chip to run at only 0.25 W.

Specifications:

• Power-supply voltage: 2V
• Power dissipation: 0.25W
• Input-voltage swing: 35mVpp
• Output-voltage swing: 0.6V

Notes:

• Gb : gigabit = 1 billion bits
• Wavelength division multiplexing(WDM):
  A method of increasing the transmission capacity by transmitting multiple signals at different wavelengths on a single optical fiber. Research aiming to multiplex around 100 different wavelengths on the same fiber is now underway.
• Metal-semiconductor field-effect transistor (MESFET):
  A type of field-effect transistor (FET) in which the channel is formed directly beneath a metal gate, which itself is in intimate contact with the semiconductor.
• Direct-coupled FET logic (DCFL):
  One of the basic types of logic circuits used in compound semiconductor devices. Its structure consists of load elements connected directly to grounded-source switching FETs. It is effective for low-voltage operation and greater integration of circuits.

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. With more than 20,000 employees worldwide, Oki Electric provides customers with top-notch products and technologies for telecommunication systems, information systems and electronic devices through its corporate slogan "Oki, Network Solutions for a Global Society." Oki's all manufacturing facilities are ISO9001 and ISO14001 certified.