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40Gbit/s optical networks DQPSK receiver is tiny

Posted: 12 Jan 2010 ?? ?Print Version ?Bookmark and Share

Keywords:DQPSK receiver? PLC? optical network?

DQPSK receiver

Fujitsu Optical Components Ltd (FOC) announced the development of a compact (45mm x 27mm x 8mm) integrated DQPSK receiver, which uses a balanced receiver and a delay line interferometer using Planar Lightwave Circuit (PLC) technology. The product is designed for use in 40Gbit/s transponders for 40Gbit/s optical networks, which are being widely adopted by telecommunications carriers worldwide.

The compact receiver will improve the miniaturization of 40Gbit/s transponders, thereby making it possible to manufacture environmental-friendly optical transmission equipment for 40Gbit/s optical networks.

In recent years, the global expansion of new services such as cloud computing and on-line streaming has brought about a dramatic increase in data communications. As the data transmission volume of communications networks rises, optical transmission equipment for 40Gbit/s backbone networks is being widely introduced. However, due to advances in transmission speed, the components that constitute these optical transmission equipments are growing both in size and complexity. Larger equipment results in the need for larger installation space. Meeting the demands of growing data communications while reducing environmental impact at the same time has become a major challenge for 40Gbit/s systems.

Until recently, generating digital signals of 1 and 0 by turning a light on and off had been the common method of intensity modulation for optical networks. However, responding to the growing needs for ultrahigh-speed and long-distance transmission, phase modulation has become the mainstream modulation method for 40Gbit/s optical networks. Phase modulation generates digital signals of 1 and 0 by changing the phase of light while allowing it to be in the on position.

DQPSK, one of the phase modulation formats, transmits 2 bits per symbol using four phases, thus increasing the spectral efficiency, and provides enhanced tolerance to both chromatic and polarization mode dispersions. In addition, DQPSK reduces the operating bandwidth of optical and electrical peripheral components that are used in 40Gbit/s optical transponders and/or transmission systems. However, there exists technical issues to overcome since the DQPSK optical modulator and receiver becomes bigger and complicated in structure.

FOC has succeeded in commercializing the most compact integrated 40Gbit/s DQPSK receiver. This receiver is used for 40Gbit/s optical transponders capable of handling DQPSK allowing the transponders to become more compact and lower cost.

A DQPSK receiver module requires two delay line interferometers, therefore, the module's size constraints become more obvious and the complexity of optical coupling increases, which makes it a challenging task to install a lot of optical elements by conventional method using free-space optics. FOC has overcome the technical difficulties by integrating the two delay line interferometers into a single compact chip by the PLC technology. Moreover, the PLC technology can reduce the manufacturing cost because PLC is manufactured by using the semiconductor wafer processes.

Also, a DQSPK receiver module requires integrating the PLC chip and the photo detectors with high efficiency optical coupling. To achieve the high efficiency optical coupling, the waveguide design of PLC chip is optimized and the elements are precisely mounted by micro-assembly technology. Hermetically sealed package is also used to achieve the high reliability. FOC applies the optimized high-speed circuit design and stable mass-production technology, which is already being used for FOC's existing products.

All DC terminals are located on both side walls separately from RF signal terminals. By integrating RF signal terminals on one flexible print circuit, enhanced connection and circuit board arrangements, as well as simplified working processes and manufacturing cost reductions, are achieved.

Sales of the receiver will begin February 1.

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