High modulation depth electroabsorption modulator modules for OTDM systems

We describe how background parasitic light was limiting the modulation depth to around 24 dB and detail the design and performance of a new high modulation depth electroabsorption modulator (EAM). The new design has been used to increase the average modulation depth of packaged devices from 24 dB to 41 dB whilst simultaneously improving or maintaining the other device characteristics which have made EA modulators useful in high bit rate OTDM systems. All the new devices satisfied the >30 dB modulation depth requirement of the demultiplexing role in a 16 channel OTDM system. The EAMs with enhanced modulation depths are suitable for use in a wider range of OTDM systems than previous devices