2 Gbit/s 0.5 microm complementary metal-oxide semiconductor optical transceiver with event-driven dynamic power-on capability.

A 2 Gb/s0.5 microm complementary metal-oxide semiconductor optical transceiver designed for board- or backplane level power-efficient interconnections is presented. The transceiver supports optical wake-on-link (OWL), an event-driven dynamic power-on technique. Depending on external events, the transceiver resides in either the active mode or the sleep mode and switches accordingly. The active-to-sleep transition shuts off the normal, gigabit link and turns on dedicated circuits to establish a low-power (approximately 1.8 mW), low data rate (less than 100 Mbits/s) link. In contrast the normal, gigabit link consumes over 100 mW. Similarly the sleep-to-active transition shuts off the low-power link and turns on the normal, gigabit link. The low-power link, sharing the same optical channel with the normal, gigabit link, is used to achieve transmitter/receiver pair power-on synchronization and greatly reduces the power consumption of the transceiver. A free-space optical platform was built to evaluate the transceiver performance. The experiment successfully demonstrated the event-driven dynamic power-on operation. To our knowledge, this is the first time a dynamic power-on scheme has been implemented for optical interconnects. The areas of the circuits that implement the low-power link are approximately one-tenth of the areas of the gigabit link circuits.

Power-efficient dual-rate optical transceiver.

A dual-rate (2 Gbit/s and 100 Mbit/s) optical transceiver designed for power-efficient connections within and between modern high-speed digital systems is described. The transceiver can dynamically adjust its data rate according to performance requirements, allowing for power-on-demand operation. Dynamic power management permits energy saving and lowers device operating temperatures, improving the reliability and lifetime of optoelectronic-devices such as vertical-cavity surface-emitting lasers (VCSELs). To implement dual-rate functionality, we include in the transmitter and receiver circuits separate high-speed and low-power data path modules. The high-speed module is designed for gigabit operation to achieve high bandwidth. A simpler low-power module is designed for megabit data transmission with low power consumption. The transceiver is fabricated in a 0.5 microm silicon-on-sapphire complementary metal-oxide semiconductor. The VCSEL and photodetector devices are attached to the transceiver's integrated circuit by flip-chip bonding. A free-space optical link system is constructed to demonstrate correct dual-rate functionality. Experimental results show reliable link operation at 2 Gbit/s and 100 Mbit/s data transfer rates with approximately 104 and approximately 9 mW power consumption, respectively. The transceiver's switching time between these two data rates is demonstrated as 10 micros, which is limited by on-chip register reconfiguration time. Improvement of this switching time can be obtained by use of dedicated input-output pads for dual-rate control signals.