Mitsubishi develops 10 Gbit/s uncooled DFB
The new devices are expected to lower the cost of high-capacity 10 Gbit/s networks, while their low power consumption should make them ideal for metro networks that combine high-speed FTTH (Fiber To The Home) and intranet LAN (Local Area Networks) with backbone lines.
The optical transmitters with smaller size and lower power consumption will meet the strong demand of increasing internet-traffic, and the uncooled 10 Gbit/s direct-modulated DFB-LDs are the key devices for current and next generation optical transmitters such as XENPAK and XFP.
Mitsubishi Electric has already released uncooled DFB lasers operating at up to 85 degrees C, and says that the move to smaller size transmitters capable of operating at higher temperatures without a cooling element was an obvious next step.
The 85 degree C devices had an InGaAsP active layer, while the new devices use an AlGaInAs active layer to increase the optical confinement. The company says that the efficiency of the light emission does not degrade at high temperatures, which allows the clear eye-opening for 10 Gbit/s telecommunications applications even at 120 degrees C.
Furthermore, a new grating process is utilized to ensure high optical reflectivity by positioning the active layer very close to the grating. Mitsubishi Electric developed new crystal growth techniques in order to bury the deep grating grooves with a semiconductor layer that is only 100 nm thick. On this layer, a defect-free AlGaInAs layer was successfully grown. These techniques enable both high-speed operation and high reliability at high temperature.
