4/spl times/4 broadband optoelectronic switch using VCSELs

Future optical networks which employ wavelength division multiplexing (WDM) will require switches that are bit rate/code rate transparent, and allow spatial and wavelength reconfiguration of a channel. Optoelectronic cross-bar switches (OECBS) are able to perform all the required functionalities. In this paper we describe initial work on a free-space 4/spl times/4 OECBS which utilizes a 850 nm VCSEL array on 500 /spl mu/m centers as the optical sources within the switch. The signal-to-noise ratio (SNR) of the entire system for a 2 GHz bandwidth calculated from the measured data is 24.84 dB. The principal noise source is the receiver thermal noise (SNR/sub TH/=26.43 dB). The second dominant source of noise in the present system is the laser noise, both RIN (SNR/sub RIN/=31.98) and adjacent channel electrical cross-talk noise (SNR/sub ECN/=35 dB). By employing VCSELs with higher output powers and MSMs with better responsivity, it is possible to improve the S/N ratio to a level at which the laser noise would dominate, establishing a S/N ceiling. The S/N ceiling for the present system is estimated to be /spl sim/30 dB. If further improvements in the S/N is desired, VCSELs with lower intrinsic RIN and lower device crosstalk would be required.