A digital optical fiber system uses an RZ pulse format. Show that the maximum bit rate for the system BT(max) may be estimated using the expression: 0.35 B (max): T where Tsyst is the total system rise time. Comment on the possible use of the factor 0.44 in place of 0.35 in the above relationship. An optical fiber link is required to operate over a distance of 10 km without repeaters. The fiber available exhibits a rise time due to intermodal dispersion of 0.7 ns km, and a rise time due to intramodal dispersion of 0.2 ns km. In addition, the APD detector has a rise time of I ns. Estimate the maximum rise time allowable for the source in order for the link to be successfully operated at a transmission rate of 40 Mbit susing an RZ pulse format.