Development of CMOS integrated optical receiver for short-range data communication

Reduction of the size and cost of optical receivers is important to the proliferation of optical communications technology for short-distance communications. In the present research, an integrated optical receiver is fabricated with a standard 0.35-μm CMOS process targeting the POF optical transmission system. A photodiode, a trans-impedance amplifier, a limiting amplifier, and a buffer are integrated in this optical receiver. The photodiode is formed with an N-well and a P-diffused layer of stripe configuration and has an optical receiving surface area of 150 × 150 μm and a response sensitivity of about 0.04 A/W (at a wavelength of 650 nm). In the CMOS process, the large junction capacitance of the photodiode is problematic. Therefore, the input impedance of the circuit is lowered by means of an RGC-type trans-impedance amplifier and LC resonance is suppressed by optimization of the package and circuit. The chip is mounted in a small ceramic package for measurement. Excellent eye patterns are obtained. The minimum receiving sensitivity for a bit error rate of less than 10 ^-9 is -10 dBm at 600 Mbit/s and -4.5 dBm at 1 Gbit/s.