Commercial reflective electro-absorption modulator lets customers passively uplink at 10 Gbit/s

July 9, 2008--A commercial reflective electro-absorption modulator (R-EAM), the first such product of its kind, has been announced by CIP Technologies (Ipswich, England). The device provides a simple and low-cost way of extending two-way high-speed fiber-optic networks to the consumer world, allowing customers to uplink at speeds to 10 Gbit/s. The reason for the simplicity is that all laser light sources, even for customer uplinking, are contained back at the central facility.

The absorption of the R-EAM changes with applied electric field, a result of the quantum confined Stark effect acting within the multi-quantum-well structure. The rear facet of the indium phosphide chip has a high-reflectivity coating to return the incoming laser light along the same path back to the input fiber. "Think of it operating as a shutter in front of a mirror," says David Smith, chief technical officer at CIP. The very short (less than 1 mm) optical path within the device reduces bandwidth-limiting signal distortion.

The R-EAM can generate useful modulation over a 32 nm band centered on the 1550 nm C band. A complete network consists of many "seed" lasers at the central facility, each with a slightly different wavelength, with an arrayed waveguide grating (AWG) combining their light to be sent long-distance over a single fiber. In the customers' neighborhood, an AWG splitter/combiner sends each wavelength to and from a different customer, and then back over the single fiber. At the central facility, and AWG splitter and optical receivers collect the signals from the customers.

A second major application for R-EAMs is in wireless networks, where the devices make it possible to extend the coverage of a wireless access point with a network of remote antennas. For example, a single fiber-optic cable could easily support 32 antennas operating on different wavelengths, providing a low-cost means of extending the coverage of short-range, high-data-rate wireless technologies around a building or plant. Because of the passive way in which R-EAMs operate, the cost of remote nodes in this application could be extremely small, as in their simplest form they can be fabricated with just a R-EAM and a simple antenna and operate without any need for local power. Because the R-EAM will also operate as a photodiode, these passive nodes can provide both uplink and downlink capabilities.

Smith notes that CIP Technologies plans to extend the modulation bandwidth of its R-EAMs to 40 Gbit/s and beyond.


John Wallace

Most Popular Articles


Click here to have your products listed in the Laser Focus World Buyers Guide.

Article Archive

View Laser Focus World past articles now.

Social Activity

  •  
  •  
  •  
  •  
  •  
Copyright © 2007-2014. PennWell Corporation, Tulsa, OK. All Rights Reserved.PRIVACY POLICY | TERMS AND CONDITIONS