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17 October 2006


Mitsubishi launches 15mW laser for G-PON FTTH

Tokyo-based Mitsubishi Electric Corp has developed the ML9xx46 series high-output (15mW) distributed feedback laser diode, which has a peak wavelength of 1.49 micron for use in optical fiber communication at transmission rates of up to 2.5Gbps. The diode is most suitable to applications such as fiber-to-the-home (FTTH) and Gigabit passive optical networks (G-PON). Sample shipments (in a standard TO-56 CAN package) will begin on 11 November 2006.

Mitsubishi Electric says that FTTH, most widely used as passive optical networks (PONs), will need to improve its downstream transmission speed (from access station to subscriber) to respond to continuingly increasing needs. PON transmission rates are below 1.25Gbps, and many access stations are moving towards the improved GPON transmission rates of 2.5Gbps. GPON will begin serious commercialization in the US soon.

With improvements in transmission speed, the industry has sought to secure optical input/output strength on the receiving side by using higher optical output on the transmitting side. But laser diodes have been limited to an optical output of 10mW, since response speed diminishes with optical output at high temperatures.

By optimizing the construction of the active light-emitting layer, the ML9xx46 series has improved optical conversion efficiency at high temperatures, with an optical output of 15mW and an operating range of –40 to +85 degrees centigrade. Mitsubishi Electric also says it has improved modulation bandwidth by reducing the capacitance of the laser diode. An 15mW optical output with a response time of 2.5Gbps will increase FTTH speeds, it adds.

In addition, the use of an aspherical lens increases the laser-to-fiber coupling efficiency (to 70% in the ML920T46S model when using 10/125 single-mode fiber). This reduces operating current (with a threshold current of 30mA) and hence power consumption.