A critical emerging technology for advanced DWDM systems is 40 Gbps transmission support. The use of 40 Gbps channels increases the DWDM capacity by the factor of four, supports interconnection of next generation IP routers at OC-768 and saves OpEx and CapEx due to having to deploy and maintain fewer channels to provide the same capacity, needing fewer spare transponder modules. A key design driver for 40 Gbps technology is that it should seamlessly integrate with existing 10 Gbps systems without requiring changes to the common equipment, including ROADM technology. Parameters that must be analyzed to a greater degree at the 40 Gbps transmission rate include chromatic dispersion, PMD, and filtering effects. This analysis is based on the experiment on deployment of 43 Gb/s PSBT signals over an existing 10 Gb/s DWDM system with cascaded ROADMs that we reported on last year (M. Boduch et al., 2005).