Since the Vertical Cavity Surface Emitting Laser (VCSEL) was first introduced for datacomm applications, VCSEL-based transmitters have been widely used in optical interconnect modules. A VCSEL-based optical transmitter offers low power dissipation, low-driver current, high-speed modulation properties, and further offers high wavelength stability. As data rate and bandwidth increase, the reliability of VCSEL becomes a critical issue in optical transmitter system. Thus, if an individual VCSEL breaks down, the entire transceiver module needs to be replaced with extra cost. One proposed solution to overcome the low reliability issues of VCSELs has been to integrate them into pluggable transceiver modules. This can allow for relative quick and simple replacement of optical interconnects in the case that a VCSEL has failed. However, the perceived reliability of the VCSEL and other light sources and the resulting use of pluggable transceiver modules, limits bandwidth density for switches and results in increased cost and power consumption. Another proposed path for improved reliability was suggested through the introduction of redundant VCSELs in parallel interconnect modules. However operation of such a redundant transmitter at high bit rates (10 Gbps) has never been demonstrated and the exact nature of the control circuitry required for its implementation is not clear.
What is needed is a low-cost device that provides redundancy for VCSEL-based transmitters at high data rates.