TOKYO, Oct. 13 -- Mitsubishi Electric Corp., a manufacturer of electrical and electronic equipment for home products and commercial and industrial systems and equipment, has developed an avalanche photodiode (APD) for use in high-sensitivity optical receivers in fiber optic communications.
The APD was mounted on an XMD MSA (miniature device multisource agreement) -compatible receiver optical subassembly (ROSA), a new construction that the company says is capable of 10 Gb/s -80 km transmissions with low noise and high reliability while also increasing compatibility.
With sharp increases in Internet traffic in recent years, XFPs, or small optical transceivers that comply with the 10 Gb/s transmission standard specification, have been used to increase transmission capacity in urban mid- and long-distance trunk lines. A way has been sought to increase performance of the light emission and receiving element mounted on the optical transceiver in order to extend transmission of the current 40 to 80 km range as well as reduce the number of broadcasting optical amplifiers and construction cost of fiber optic networks. In April, Mitsubishi Electric released a sample of the ML9xx41, an electroabsorption modulator integrated laser diode capable of high-quality communication at high optical output.
For long distance communications, however, it was necessary to develop an APD that reduces noise up to 40 percent over previous models so that even very weak signals can be received by the light-receiving element. With this model, Mitsubishi says it has developed a new planar construction giving it low noise characteristics as well as the highest level of reliability. A small light module (ROSA) is mounted to the light-receiving element, which can be attached to small optical transceivers like XFP. According to the company, the new avalanche photodiode is suitable for XFPs as well as small form factor 300-pin optical transponders, enabling cost-effective 10-Gb/s optical links for long-distance and metropolitan-area applications with high board density.
The APD utilizes aluminum indium arsenic (AlInAs), which has low noise amplification properties, in the multiplication layer. A new planer structure has been developed to prevent edge breakdown, caused by local electrostatic accumulation, degrading reliability noise characteristics and creating abnormal background noise. This reduced background noise by approximately 40 percent compared with previous models, improving sensitivity by 2 dB (or 1.6 times). Its extrapolated MTTF (mean time to failure) is up to 108 hours, giving it the world's highest level of reliability, according to Mitsubishi. With the attaching of ROSA to the element, It is able to achieve sensitivity of below -28 dBm.
The photodiode employs a top-surface incident structure that enables cost-effective assembling. Most APDs use a structure in which the chip receives light from below the surface. To put the chip on the surface required either a special component or technology. Also, top-surface incident structure has low sensitivity. However, Mitsubishi says it used a surface incident structure that increases sensitivity by adopting a multireflective layer that was already in use by the company. This allows for simple integration of the light module and chip mounting, and gives the potential for lower cost light modules.
The company says it has increased interface compatibility by developing a ROSA that complies with XMD MSA specifications. XMD MSA sets the electric and mechanical interface for XFPs and other modules mounted to small optical transceivers, and uses a flexible substrate on its electrical terminal. The ROSA Mitsubishi has developed uses a small TO-can, allowing ample space to be mounted on optical transceivers.
For more information, visit: http://global.mitsubishielectric.com; e-mail: Hideo.Sasaki@hq.melco.co.jp
Mitsubishi Denki Building
2-2-3, Marunouchi, Chiyoda-ku,
Tokyo 100-8310, Japan
Web site: http://global.mitsubishielectric.com