Fujitsu and HHI Achieve Optical Amplitude Noise Reduction Using Ultra High-Speed Optical Switch

Kawasaki, Japan and Berlin, March 06, 2008

Fujitsu Laboratories Ltd. and Fraunhofer Institute for Telecommunications, Heinrich Hertz Institut(HHI) today announced the development of an ultra high-speed optical switch that uses nonlinear optical fiber⁽¹⁾ to reduce optical amplitude noise⁽²⁾, which degrades the quality of optical signals when they are transmitted. Employing this technology, suppression of optical amplitude noise using a 107 gigabit per second (Gbps) phase modulated ultra high-speed signal was successfully verified. In addition, in a data transmission test across 320 km, it was verified that data quality after transmission could be received with roughly the equivalent of its quality prior to transmission.

Details of the new technology were presented at the Optical Fiber Communication Conference and Exposition (OFC) and the National Fiber Optic Engineers Conference (NFOEC) 2008 held in San Diego from February 24 to February 28.

Background

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.

Technological Challenges

In order 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.

Overview of the New Technology

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⁽³⁾. By controlling the power gain of the optical parametric amplification effect⁽⁴⁾ 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.

Results

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 320 kilometers with a 107Gbps optical signal modulated by differential phase shift keying(DPSK)⁽⁵⁾ 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.

Future Developments

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.

Fujitsu and HHI will continue their research efforts to develop higher functionality in order to enable practical application of this new technology.