Gb / s EA modulator Kiyoshi Nagai Hiroshi Wada

The colossal increase in data communications traffic over recent years, with an expanding Internet population and a steady advance from transmission of simple text, to images, to animated images, has created demands for expanded capacity in optical communications systems. The amount of data carried by a single fibre can be increased by raising the signal transmission speed, or adopting wavelength division multiplexing to use a plurality of transmission wavelengths, and capacity enhancement initiatives combining both of these approaches are also being developed. Increases in transmission speed from 2.5 Gb/s to 10 Gb/s have been achieved on the back of accelerated performance in electronic and optical devices, and a 10 Gb/s optical communications system has already been released as a product for practical application. In recent years, high-speed devices with 40 Gb/s capability have been gradually reaching the stage of practical implementation, and developers have been working in real earnest on 40 Gb/s fibre-optic communications systems suitable for in-field use. A key element in achieving 40 Gb/s system performance is the optical modulator used to convert the electrical signals to optical signals. The EA modulator, which is a semiconductor device, has the advantages of compactness and easy integration with other optical devices, such as semiconductor lasers. Much is expected of this type of modulator, and below, we look at the 40 Gb/s EA modulator1) that has been developed by Oki.