Japan races toward 40 Gb/s
Anticipating the needs of the market, Japanese electronics companies are moving quickly toward the development of components and transmission systems for 40 Gb/s (OC-768). "In the near future, when 40-Gb/s and 80-wavelength systems are successfully combined, just one fiber would be sufficient to connect all the household telephones in Japan," says Shinzo Suzaki of Fujikura (Tokyo, Japan).
Fujikura is but one of many Japanese companies working on this technology. "For 40-Gb/s systems, management of chromatic dispersion and polarization mode dispersion (PMD) are most important," says Suzaki. "We are focusing and developing our products to meet those needs."
Companies like Asahi Glass (Tokyo, Japan), Hitachi (Tokyo, Japan), Mitsubishi Electric (Tokyo, Japan), NEC Corporation (Tokyo, Japan), NTT (Tokyo, Japan), Sumitomo Electric (Osaka, Japan), Toshiba (Tokyo, Japan), Yokogawa Electric (Tokyo, Japan), and a few others see a coming market for OC-768 in the United States, and they want to be in on the ground floor. Mitsubishi, for example, announced a 40-Gb/s electro-absorption modulator that would soon be on the market, according to Takashi Sugihara. The multi-quantum-well (MQW) modulator was grown on a semi-insulating substrate to reduce its parasitic capacitance. Mitsubishi estimates the device's lifetime at more than 17 million hours.
Yokogawa has used hetrojunction bipolar transistors to develop telecommunications logic integrated circuits [ICs] and a driver IC for optical communications laser diodes. The devices respond at speeds of up to 50 Gb/s. Yokogawa says they are compatible with OC-768 40-Gb/s WDM optical communication networks.
NEC Corp. (Tokyo, Japan) has a 40 Gb/s multiplexer ready to go. In September it will start delivering the product which is designed for metropolitan-area data-centric networks. It uses four channels of 10 Gb/s optical signals coarse wavelength-division multiplexing (WDM) to yield an aggregate 40-Gb/s data rate. NEC says coarse WDM is very cost-effective compared with the dense WDM technology used in backbone networks.
KDDI's Otani says his company is almost ready to market 40 Gb/s optical 3R regenerators, which will help address transmission performance issues such as dispersion and PMD in WDM networks.
Efficiency becomes an important factor to consider with the oncoming 40 Gb/s rush. "Carriers are suffering from decreasing income and will use money for what is most cost effective," Otani says. "So if new WDM terminal equipment can be applicable to both 10 Gb/s and 40 Gb/s, we will purchase that equipment instead of those that cannot handle 40 Gb/s. That way, we can start 40-Gb/s service whenever we like, and we don't have to operate all channels at 40 Gb/s, just some of them. Others will operate at 10 Gb/s or 2.5 Gb/s, depending on the service."
