OKI develops gain-coupled DFB lasers for practical use
(Technology News, 30 Mar 2007 )
Oki Electric Industry Co Ltd, telecommunications manufacturer from Japan, announced that it has developed a gain-coupled (GC-) DFB laser that is tolerant of optical reflection. By employing the GC-DFB laser, OKI succeeded in developing of optical isolator-free optical transmitter modules for practical applications, enabling lower cost, smaller size optical modules for use in long distance networks, such as FTTH.
Harushige Sugimoto, senior vice president and CTO at Oki Electric Industry, said, "The results we obtained from this technology confirm that it will contribute to achieving lower cost, isolator free optical subassembly modules. Because the manufacturing process of the GC-DFB laser is approximately equivalent to that of conventional index-coupled (IC-) DFB lasers, chip manufacturing costs are expected to be the same as well.” He further added, “We are developing samples for evaluation, planning to provide them to the market by June this year. In our long term plan, we are aiming to commercialize small and low cost components for optical communication using OKI’s original silicon lens technology."
For a normal FTTH light source, Fabry-Perot lasers that emit multiple modes are used for short distance transmission (up to 10km), while IC-DFB lasers that emit a single mode are used for long distance transmission (up to 20km). In long distance transmission, IC-DFB lasers contribute to increased degradation in receiver sensitivity after sending data as the noise from unwanted optical reflection increases.
OKI achieved optical isolator free capability through a GC-DFB laser with improved tolerance of optical reflection and reduced degradation from relative intensity noise when impacted by reflected light. With this advance, OKI conducted 25km transmission experiments over the temperature range where optical modules normally operate (0 ~ 70º C) and found that in a state where reflected light (-14dB) was forcefully applied, there was almost no degradation of reception sensitivity.
