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In a post-deadline paper at the Optical Fiber Communication/National Fiber Optic Engineers Conference (OFC/NFOEC 2008) in San Diego, CA, USA (26-28 February), Tokyo-based Hitachi Ltd and spin-off Opnext Inc of Eatontown, NJ, USA announced the first wide temperature range operation of a 1310nm 25Gb/s EA-DFB (electro-absorption modulator with integrated distributed feedback laser) for 100 Gigabit Ethernet 10km single-mode fiber (SMF) applications.

A study by the IEEE HSSG (High Speed Study Group) showed that, by 2010, the bandwidth required in core networking will be best satisfied by 100Gb/s interfaces. Also, bandwidth needs are expected to double every 18 months, resulting in demand for multi-port 100Gb/s systems. A 10km SMF (single mode fiber) 100Gb/s Ethernet specification is being discussed in the IEEE 802.3ba taskforce. For this application, 1310nm four-channel x 25Gb/s WDM (wavelength division multiplexing) transmission is the most attractive technology, say the firms.

One of the technology challenges is to achieve 1310nm 25Gbit/s WDM optical devices. CWDM (course wavelength division multiplexing) technology is expected to be the most cost-effective solution due to the wide wavelength pitch, which enables 100% wavelength yield and either less strict or no temperature control.

Using high-speed device technology that has already been proven in 1550nm 40Gb/s EA-DFB lasers used commercially in 40Gb/s transceivers, Hitachi and Opnext have demonstrated EA-DFB lasers operating at 25Gb/s with wavelengths of 1290, 1310, 1330 and 1350nm.

Also, a wide operating temperature range of 0-85ºC was achieved by the use in the electro-absorption (EA) modulator section of aluminum-based material which has a temperature-tolerant band-gap structure that decreases the temperature-dependent performance of the modulator.

The firms say that the EA-DFB lasers demonstrate the technical feasibility of the CWDM grid, which achieves low-cost 100Gb/s optical transceiver modules with low power consumption and compact size. This is expected to accelerate the adoption of 100Gb/s interfaces in the network.

The 25Gb/s 1310nm CWDM EA-DFB lasers are based on Hitachi’s uncooled high-speed laser technology, which has already been demonstrated in previous uncooled 10Gb/s and cooled 40Gb/s EA-DFB lasers, says Masahiko Aoki of Hitachi’s Central Research Laboratories. “We believe that uncooled operation is the key to achieving small and low-cost 100GbE transceivers for local-area network (LAN) application,” he adds.

Opnext gives live demonstrations

Also at OFC, Opnext gave several live demonstrations, including the following:

• Opnext’s first live demonstration of 100Gb/s client-side technology, showing how 100 Gigabit Ethernet (100GbE) transmission can allow increased bandwidth of connections in the core networking area using a simple system configuration with less fiber and fewer optical modules per interface, while maintaining low power consumption and meeting cost constraints. This market is expected to grow strongly, supported by increased numbers of end users (as committed to by a number of ISPs), increased access rates and methods, and increased services targeted for end-users.

• A 43Gb/s tunable 5x7” 300-pin transponder module (the TRV7BA0) using phase shift keying and incorporating the SFI-5 interface for long-haul dense wavelength division multiplexing (DWDM) applications, enabling a transition from discrete components to an integrated solution for up to 43Gb/s line-side applications.

“These are exciting times for 100G and 40G advancements,” said Opnext’s president and CEO Harry Bosco. The technologies demonstrated at OFC/NFOEC 2008 are key elements to enabling these markets, he reckons.

See related items:

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Opnext launches first 640nm/150mW red laser; enters human-body light-measuring device market

Opnext expects revenue shortfall due to supply issues

Opnext passes half-million 10G transceiver shipment milestone

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