Ultra high-speed optical switch enables optical amplitude noise reduction

Fujitsu Laboratories Ltd and Fraunhofer Institute for Telecommunications, Heinrich Hertz Institut (HHI) have developed an ultra high-speed optical switch that uses nonlinear optical fiber to reduce optical amplitude noise, which degrades the quality of optical signals when they are transmitted. Employing this technology, suppression of optical amplitude noise using a 107Gbps phase modulated ultra high-speed signal was successfully verified. In addition, data quality after test transmission across 320km could be received with roughly the equivalent of its quality prior to transmission.

In accordance with the rapid growth of broadband internet, there is a need for optical networks that are further efficient and capable of handling high-speed transmission and along with the rapid growth of data transmission volumes. Due to the fact that optical signals are more susceptible to optical amplitude noise as data transmission becomes faster and with greater data volume, there are significant limits to transmission distances that can be achieved. Thus, research and development of new technologies that can reduce optical amplitude noise is necessary.

To overcome the optical amplitude noise problem, a conventional solution has been to convert optical signals into electrical signals, electrically eliminate the noise impact, and then reconvert the signal back to an optical signal. However, for long-distance data transmission, this method requires much power for optical signal amplification and conversion to electrical signals. Therefore, there is demand for new technologies to enable networks that are more efficient and which consume less power.

The new technology developed by Fujitsu and HHI employs an ultra high-speed optical switch they developed that is capable of processing optical signals in less than a picosecond (one trillionth of a second). By controlling the power gain of the optical parametric amplification effect from the optical signals, raising it when signals are weak and lowering it when signals are strong, the switch reduces optical noise without the need to convert optical signals into electrical signals.

By placing an ultra high-speed optical switch employing this technology in the middle of an optical transmission link, even after data was transmitted across 320km with a 107Gbps optical signal modulated by differential phase shift keying (DPSK) data, the transmitted data essentially reproduced without change the characteristics of the data prior to transmission, thereby verifying high-quality optical transmission through this test. Compared to results when the switch is not employed, it was also verified that using the switch makes it possible to roughly double the length of transmission distances.

Furthermore, by optimizing the design of the nonlinear optical fiber, it is possible to cover much wider wavelength ranges than are currently used in optical transmissions, and handle optical signals in a variety of modulation formats.

It is anticipated that this new technology can be applied to optical regeneration, which is a key technology for next-generation ultra high-speed photonic networks.