OKI develops asymmetric PON system

MARCH 27, 2009 -- The telecom manufacturer's system uses hybrid optical time-division multiplexing and optical code-division multiplexing.

MARCH 27, 2009 -- OKI Electric Industry (search Lightwave for OKI Electric Industry) reports it has succeeded in developing the world's first 160-Gbps ultrahigh-speed, optical next-generation access (NGA) asymmetric PON system using hybrid optical time-division multiplexing (OTDM) and optical code-division multiplexing (OCDM). 160 Gbps is equivalent to sending six channels of uncompressed ultrahigh-definition video or 33 channels of high-definition video per second. Transmitting signals at a speed of 160 Gbps on a single optical fiber downstream means that superhigh-resolution and high-quality video delivery service that requires data greater than 1 GB, such as movie distribution and telemedicine, can be offered.

The research that led to OKI's achievement was conducted as part of "Research and development for ultra high-speed optical NGA Asymmetric PON system," under the auspices of NICT's "Basic Technology Promotion System for Private Sectors Program." The research was presented during OFC/NFOEC 2009, March 24-26, in san Diego, CA.

The mainstream optical access systems used by carriers today are GEPON (1.25 Gbps) in Japan and GPON in the U.S. and Europe (2.5 Gbps), which are used mainly to transmit data and video. In such optical access systems, the communication capacity per user when 16 users are connected is limited to 78 to 156 Mbps.

OKI says the ultrahigh-speed NGA asymmetric PON system significantly increases the communication capacity compared to conventional optical access systems. The system achieves 128x greater capacity than that of GEPON systems and 64x greater capacity than GPON systems. This means that with 16 users, telecom carriers can offer a 10-Gbps communication capacity for each user, enabling high-resolution and high-quality video delivery service.

"With this system, OKI will contribute a valuable tool to industries that need to transmit high-quality videos, such as the movie and telemedicine industries, and plan to help rejuvenate the communication environment in local areas," says Takeshi Kamijoh, general manager of the Corporate R&D Center at OKI. "With the market needs in mind, we will continue to make efforts to develop smaller and more stable equipment and continually improve the quality for optical access system over 100 Gbps."

An optical line terminal (OLT) is the main equipment for this system. After encoding the 10-Gbps signals using a 16-chip code, and optically multiplexing them into a 25-ps TDM slot, the developers quadrupled the signal with wavelength to output a multiplexed signal of 10 Gbps x 16 channels. OKI then transmitted this 160-Gbps signal over 20 km (reportedly the longest in an optical access system), divided the signal with a 1x16 splitter, extracted the signals from the optical network unit (ONU) that decodes with sign preference, and finally succeeded in decoding a 10-Gbps signal.

Though OKI multiplexed one code in a single TDM slot for this experiment, the system can multiplex up to four codes in a single slot, thus transmitting 4x the data (10 Gbps x 64 channels = 640 Gbps). To use the wavelength resources more effectively, a structure of 4 coding signals x 4 slots x 1 wavelength can also be achieved.


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