19 March 2010


Opnext partners with Mobius to develop low-power quad CMOS ADC for 127Gb/s PM-QPSK modulation

Optical module and component maker Opnext Inc of Fremont, CA, USA claims that it has solved one of the major challenges of delivering a polarization multiplexed quadrature phase shift keying (PM-QPSK) coherent receiver.

In collaboration with Mobius Semiconductor of Irvine, CA (a privately held firm specializing in high-performance mixed-signal products for next-generation communications and networking standards), the firm has developed a low-power quad CMOS analog-to-digital converter (ADC), designed for use in a 127Gb/s PM-QPSK modulation scheme.

Opnext verified the digital signal processing (DSP) and forward error correction (FEC) algorithms on its real-time 100G coherent platform (announced on 9 March). Mobius uses DSP-assisted mixed-signal calibration techniques to develop multi-gigasample data converters, making possible integrated transceivers with significantly reduced cost, power and form factor.

Mobius says that its calibration technology is naturally aligned with CMOS scaling. The Opnext–Mobius ADC will be integrated with the DSP and FEC into a single PM-QPSK receiver chip using a standard CMOS process, eliminating numerous high-speed interconnects between the ADC, DSP and the FEC. It also includes continuous digital background self-calibration and synchronization, eliminating the need for external calibration signals. The receiver is hence immune to process, voltage and temperature variations, allowing reliable performance over a broad range of operating conditions. The ADC will use a BGA (ball grid array) package enabling volume SMT manufacturing, consistent with Opnext's current 32Gb/s mux.

“Opnext previously announced the mux and last week it demonstrated its DSP prototype,” says Karen Liu, principal analyst at market research firm Ovum. “With this ADC, Opnext will have control of all the critical chips for its MSA [multi-source agreement] transponder: a reliable merchant supply of the transponder is essential for the 100G market to move quickly toward a robust supply chain,” she adds. Mobius’ CMOS-based technology is portable over different foundries and processes.

Opnext says that it continues to employ selective vertical integration on components like the ADC, with the goal of delivering the lowest-cost and highest-performance 100Gb/s Optical Internetworking Forum (OIF) MSA-compliant solution to its OEM partners.

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