Fujitsu, Fujitsu Laboratories, and Fujitsu Research and Development Center in China have developed a digital signal processing algorithm that compensates for waveform distortion in optical fiber transmission signals over long-distance transmission systems exceeding several hundred kilometers. It is reported that the circuit scale and power consumption can be reduced by approximately 85% compared to conventional technologies, and by about 50% compared to Fujitsu's previous technologies.
According to Fujitsu, this technology enables communication service providers to offer long-distance transmission systems with a unit wavelength exceeding 100 Gbit/s to their backbone transmission networks and networks connecting large data centers, with a smaller scale and lower power consumption.
Part of this research was implemented as part of the "General Link Technology Development" project commissioned by the National Institute of Information and Communications Technology (NICT) in Japan. Technical details were announced at the ECOC2011 (37th European Conference and Exhibition on Optical Communication) held in Geneva, Switzerland, on September 18, 2011.
When ultra-high-speed signals exceeding 100 Gbit/s are transmitted over optical fibers for distances greater than several hundred kilometers, waveform distortion occurs due to nonlinear optical effects, making it difficult to accurately receive the signals. Therefore, the industry has been researching nonlinear compensation technology that utilizes receivers to compensate for signal distortion and restore orderly waveforms.
However, when packaging nonlinear compensation technology with the original methods, semiconductor integrated circuits required a circuit scale of over 100 million gates, making it challenging to implement using semiconductor technology from before 2020. Fujitsu developed an independent technology in September 2010 that significantly reduced circuit scale compared to the original, with practical application expected by 2015. This technology has now been improved.
According to Fujitsu, the newly developed signal processing algorithm can reduce the number of circuit segments required for processing to about one-seventh of that of conventional technologies (about one-half of Fujitsu's previous technology) while maintaining the original distortion compensation performance.
First, the signal distortion was analyzed using mathematical expressions, identifying distortion components that the original technology overlooked. The expressions were then modified to include these distortion components. By organizing these expressions, an efficient method was developed to achieve high-precision compensation with a small-scale circuit. By adding this compensation circuit to the technology announced in September 2010, the overall circuit scale and number of segments were reduced while maintaining the original distortion compensation performance.
Applying this technology to a 112 Gbit/s transmission experiment over 1500 km revealed that the signal quality obtained with 20 circuit segments under the original technology could be achieved with just 3 circuit segments using this new technology. By reducing the circuit scale, power consumption can be significantly decreased. Additionally, when using the same number of circuit segments as the original technology, higher signal quality can be achieved, with the potential to extend transmission distances.
Fujitsu plans to equip the developed technology in long-distance optical communication systems exceeding 100 Gbit/s, aiming for practical application by 2015. Furthermore, it is also prepared for applications in high-capacity short-distance transmission used within data centers and access networks.