Apr 2 2008
Oki Electric Industry Co., Ltd. announced it is the world's first to achieve all optically regenerated transmission, which enables unlimited transmission of 160Gbps optical signals with single wavelength. To demonstrate the results of this project, OKI used an optical test-bed provided by the National Institute of Information and Communications Technology (NICT)'s Japan Gigabit Network II (JGN II)(1). The research that led to OKI's achievement was conducted as part of the "Research and Development on Lambda Utility Technology,” under the auspices of NICT.
“This result proves that we can now transmit data at 160Gbps data, a speed equivalent to transmitting four movies, approximately 8 hours of data, in a single second. This amount of data at this speed can be sent over distances greater than the length of Japan, which is about 3,000km, and in fact to the other side of the planet, which is about 20,000km,” said Takeshi Kamijo, General Manager of Corporate R&D Center at OKI. “160Gbps data transmission uses an ultra high-speed optical communication technology that is expected to be commercialized in 2010 or after. OKI will analyze the findings from the field trial and develop a commercial-level 160Gbps optical 3R Regenerator.”
In a conventional optical communication system, an optical amplifier is placed every 50 to 100 km to compensate for propagation loss. Because signal distortion and timing jitter accumulate during transmission, the faster the speed of transmission, the shorter the transmission range. Therefore, to achieve longer distance, optical signals are converted into electric signals before the transmission limit is reached and converted back into optical signals and re-transmitted after the signal processing is completed. However, the speed for batch signal processing is currently limited to 40Gbps. Therefore, technologies to efficiently regenerate optical signals without converting them to electric signals are required in order to achieve a transmission speed of over 100Gbps.
To do this, OKI developed an all-optical 3R Regenerator, which uses a specialized optical-repeater technology with functions for re-amplification, re-shaping to remove optical signal wave distortion, and re-timing to avoid timing jitter accumulation. With these advances, in theory, it is possible to achieve signal processing speeds of over 200Gbps.
OKI also developed a Polarization Mode Dispersion Compensator (PMDC) that adaptively mitigates the impact of the changes in transmission line characteristics that are unique to optical fiber. Polarization mode dispersion is a phenomenon whereby wave distortion increases in an oval-shaped fiber core. The dispersion value changes depending on the temperature or transmission environment. Because the faster the transmission speed, the more sensitive it is to such changes, a PMDC is indispensable for transmission systems operating at over 40Gbps. OKI's newly developed PMDC adopts a design to fully leverage the optical 3R Regenerator.
In the field trial using this equipment, in principle, OKI proved there was hardly any limit to transmission distance. Though 40Gbps and 80Gbps transmission using all-optical 3R Regenerators has been done in the past, OKI is the first in the world to conduct a field trial using 160Gbps optical signal regenerators.
By evaluating the performance of all-optical 3R regenerators while changing the regenerator spacing, OKI achieved a maximum regenerator spacing of 380km, which is equivalent to transmitting at 160Gbps between Tokyo and Osaka with just one optical 3R regenerator.
The findings from this trial were reported at the general conference held by The Institute of Electronics, Information and Communication Engineers on March 20.
Note
(1) Optical test-bed provided by Japan Gigabit Network II (JGN II)
Working together with JGN II, NICT provides a next generation optical network R&D environment to manufactures and institutions who do not have their own environment.