Avanex and SHF announce breakthrough in 40Gb/s duobinary signal generation for commercial applications

News
04/02/2005

Avanex Corporation (Nasdaq: AVNX) and SHF Communication Technologies AG today announced the joint development of a 40 Gb/s duobinary modulator-driver assembly, a significant milestone toward field-applicable 40 Gb/s transmission.

The new 40 Gb/s duobinary transmitter sub-assembly combines an optimized SHF driver amplifier (SHF 825F) and the Avanex PowerBit™ 40 Gb/s Intensity Modulator to enable at least five times longer transmission distances compared to the traditional intensity-modulated NRZ approach, and without dispersion compensation. It reduces the bandwidth requirements of electronics and modulators because of its higher spectral efficiency.

In addition to improved performance, the subassembly approach will simplify the manufacturing of line cards to reduce overall cost of ownership because manufacturers will not need to go through the costly process of matching the driver and modulator to obtain the required performance. Because of the less stringent technological demands on the electronics and modulator, the transmitter subassembly also can be manufactured with larger specification margins.

“This new duobinary modulator-driver assembly is a major breakthrough to support 40 Gb/s transmission rates,” Dr. Giovanni Barbarossa, Chief Technology Officer and Vice President, Product Development of Avanex, said. “It permits the 40 Gb/s optical signal to pass beyond 10 kilometers, exponentially multiplying the transmission reach without dispersion compensation. It also enables 40 Gb/s transmission in the 50 GHz ITU grid by using the existing 10 Gb/s optical infrastructure. This highly attractive modulation format outperforms the common 40 Gb/s NRZ transmission and illustrates Avanex's leadership in developing integrated solutions for next-generation networks.”

Dr. Michael Martin, Chief Technology Officer of SHF, added, "SHF’s experience in designing and manufacturing high-performance microwave assemblies results in an optical transmitter solution that combines superb electro-optic performance with low production cost. Such assemblies will facilitate the production of line cards for deployment of 40 Gb/s transmission systems and promise to be highly competitive with existing NRZ transmitter designs."

At 10 Gb/s, the well-known duobinary modulation format enables uncompensated transmission distances of 200 kilometers or more (over SMF fiber), corresponding to about 12 km at 40 Gb/s. By combining the specifically designed components, Avanex and SHF have succeeded in creating a building block that overcomes the electrical and optical challenges of 40 Gb/s duobinary signal generation. This assembly allows for more than 12 km uncompensated transmission.

The Avanex-SHF solution also addresses the tendency of duobinary transmission to be particularly jitter sensitive. By integrating a low pass Bessel filter into the driver amplifier, Avanex and SHF succeed in reducing the number of electrical transitions that could contribute to jitter generation, resulting in significantly improved optical signal quality.

The exceptionally low modulator drive voltage (Vpi) of less than 4 V and the specifically designed driver amplifier enable the "two-Vpi" modulator operation required to convert the duobinary electrical signal into a binary optical signal. The overall electro-optic bandwidth of approximately 13 GHz is sufficient to realize 42.8 Gb/s transmission. The spectral width of the optical signal is only about 13 GHz at –3dB, and 30 GHz at –10 dB respectively, and the 50 GHz bandwidth is below ‑40dB. The unique characteristics of this assembly lead to a Q-factor penalty of only 1dB after 150 ps/nm total dispersion (at 42.8 Gb/s), with 3 dB FEC margin or potentially 300 ps/nm dispersion tolerance.

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