Fujitsu and HHI achieve optical amplitude noise reduction with high-speed optical switch

MARCH 6, 2008 -- 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 companies' ultra high-speed optical switch reduces optical noise without the need to convert optical signals into electrical signals.

MARCH 6, 2008 -- Fujitsu Laboratories Ltd. (search for Fujitsu Laboratories) 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 to reduce optical amplitude noise, which degrades the quality of optical signals when they are transmitted.

Employing this technology, the companies say they have successfully verified the suppression of optical amplitude noise using a 107-Gbit/sec phase modulated ultra high-speed signal. Furthermore, 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 OFC/NFOEC 2008 Conference, held in San Diego, CA, from February 24 to February 28.

In accordance with the rapid growth of broadband Internet, optical networks must be able to support high-speed transmission and the rapidly growing volume of data transmission. Because optical signals are more susceptible to optical amplitude noise as data transmission becomes faster and volumes greater, there are significant limits to achievable transmission distances. Thus, Fujitsu Laboratories and HHI believe research and development of new technologies to reduce optical amplitude noise is a necessity.

The conventional method for overcoming the optical amplitude noise problem involves converting the optical signals into electrical signals, electrically eliminating the noise impact, and then reconverting the signal back to an optical signal. However, for long-distance data transmission, this method requires higher power for optical signal amplification and conversion to electrical signals. Therefore, new technologies are required to enable networks that are more efficient and consume less power.

Fujitsu and HHI say the new technology they developed employs an ultra high-speed optical switch capable of processing optical signals in less than a picosecond. 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, say the companies.

By placing an ultra high-speed optical switch in the middle of an optical transmission link, even after data was transmitted across 320 km with a 107-Gbit/sec optical signal modulated by differential phase shift keying (search for ), the transmitted data essentially reproduced without changing the characteristics of the data prior to transmission, thereby verifying high-quality optical transmission through this test. It was also verified that using the switch makes it possible to roughly double the length of transmission distances.

In addition, the companies say that 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.

Fujitsu and HHI believe the new technology can be applied to optical regeneration, which is a key technology for next-generation ultra high-speed photonic networks. The companies confirm they will continue their research efforts to develop higher functionality in order to enable practical application of this new technology.


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