A 4.7-Gb/s Reconfigurable CMOS Imaging Optical Receiver Utilizing Adaptive Spectrum Balancing Equalizer

This paper presents a fully integrated imaging receiver for high data rate wireless optical communication. A 3 × 3 matrix of Spatially Modulated Light detectors (SML), each with 730-MHz bandwidth followed by on-chip switches are integrated to allow the detection of photodiodes (PDs) in Line of Sight (LOS) with the transmitter. The imaging optical receiver employs a novel adaptive equalizer that uses spectrum reshaping to equalize the low bandwidth of the SML PD and partially compensate for the variable capacitance seen by the transimpedance amplifier resulting from dynamic LOS variations. Implemented in 130-nm CMOS technology, the chip provides an optical sensitivity of -3.5 dBm for λ = 850nm modulated light with 4.7-Gb/s 231-1 random data at BER = 10 -10 , and -4.4 dBm at 4.5 Gb/s with BER = 10 -12 , using one activated PD. For the case when all nine PDs are activated, corresponding to 11.5 pF total PDs capacitance at the input of the transimpedance amplifier, measurement results show a sensitivity of -5 dBm for 2-Gb/s data at BER = 10 -12 . The total power consumption including the differential output buffer is 97 mW from a single 1.5-V supply while providing 750-mV peak to peak output voltage over the 100 Ω differential resistance of the measurement equipment. The total die area including bond pads is 870 × 1400 μm × μm.