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Electronic Engineering Times
October 11, 1999, Issue: 1082
Section: Semiconductors
Whizzy switches, transceivers due for optical gear
Loring Wirbel
CHICAGO - To meet the increasing complexity of optical cross-connect and add-drop mux functions in very high-bandwidth backbones, semiconductor suppliers stepped up to the plate at the recent National Fiber Optic Engineers Conference with higher-density switches for equipment backplanes and lower-cost transceivers. The conference played host to product introductions from Conexant Systems Inc., Giga North America Inc., Vitesse Semiconductor Corp. and other players in the high-speed silicon and GaAs fields.
Giga, which showed some of the earliest 10-Gbit mux/demux products last winter, is fleshing out most functions up to the optical/electrical interface, including transimpedance amp, driver and forward-error-correction (FEC) circuits, and retimers. In the FEC camp, it is moving from silicon bipolar processes, used in the 10.66-Gbit GD16558/559 devices sampling this fall, to silicon germanium 12.2- to 12.8-Gbit devices, the GD16748/749s.
Receiver blocks that integrate clock/data recovery and mux/demux functions already are available in speeds between 10 and 12.5 Gbits/second, said product marketing manager Wendy Bell. Moving into new function blocks, such as transimpedance amp and autogain control functions, gives Giga an end-to-end play up to the fiber-optic transceiver. The TIA/AGC devices are offered in analog differential (GD19906) and analog single-ended (GD19906) versions.
Because of the growing importance of internal retiming of high-speed signals, Giga also demonstrated its GD14526 retiming device at the conference, a chip integrating 4:2 mux and bang-bang phase detector in a 40-pin package that uses the company's Flexguide transmission-line technology. The 14526 can be tuned in a range of 1,200 to 1,500 Mbits/s.
Vitesse, which introduced its first 10-Gbit TIA recently, focused primarily on OC-48 (2.5-Gbit) switching and retiming functions for the show, debuting three crosspoint switches: the 17 x 17 VSC834, the 34 x 34 VSC835 and the 64 x 65 VSC836. All three operate up to 2.7 Gbits/s to handle OC-48 channels with built-in FEC overhead. Vitesse also launched a quad-channel retimer device, the VSC8124, which can retime Sonet signals inside an optical transport device without having to meet full Sonet jitter specs.
Simon Keeton, product-marketing engineer, said all three switches work with the Clos-style crosspoint architectures found in many optical transmission systems. The large crosspoints can be used in the backplane and interface directly to Vitesse's 2 x 2 switches, the VSC830s, which can be used in individual line cards. The advantage in offering high and low densities, said telecom marketing director Greg Borodaty, is that for every large crosspoint switch sold, Vitesse can sell many 2 x 2 VSC830s to populate the line cards. Typical power dissipation goes from 8 watts for the 17 x 17 switch to 25 W for the 64 x 65 switch, though Vitesse is developing lower-power options for planned larger switches.
The VSC8124 retimer is intended for dense wave-division multiplexing matrices, telecom switch cores and optical cross-connect cores. The retimer can tolerate up to 260 ps of peak-to-peak jitter. It can lock onto a local clock in less than 80 ns and monitor four channels at once. The 100-pin device dissipates a maximum 3 W.
Eye on Conexant
As Vitesse eyes its future 68 x 68 switch, it faces unexpected competition from Conexant, a new player in large Sonet backbones. Conexant has quietly been developing mixed-signal optical interface devices from the former Rockwell Semiconductor facility in Newbury Park, Calif., but the launch of the CXS6803 68 x 68 crosspoint switch signals its initial foray into large-matrix switches.
The OC-48 switch supports FEC at up to 3.2 Gbits/s. Achim Hill, business director for the Icon (integrated circuits for optical networks) group at Conexant, said the company not only plans a range of crosspoint switches but will also offer a full suite of transceivers, preamps, clock/data recovery, laser driver and mux/demux chips.
The CXS6803 is a differential, 3-Gbit/s BiCMOS switch that generates 7-ps root mean square jitter, allowing it to be used in large cascaded matrices. The chip offers multicast and broadcast capabilities and has an on-board pseudorandom generator transmitter and receiver. Conexant said it plans to offer 16 x 16 switches for 10-Gbit networks, as well.
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