Patent ID: 8798480

Claim:
A method for producing an 8-quadrature amplitude modulation (8-QAM) signal comprising: receiving an optical signal by a cascaded dual-drive Mach-Zehnder modulator (MZM) assembly including an in-phase/quadrature (I/Q) modulator in series with a dual-drive Mach-Zehnder modulator, said assembly configured such that upon receipt of the optical signal an 8-QAM signal is output; outputting the 8-QAM optical signal; applying to I/Q inputs of the I/Q modulator binary data output from a binary data source; and configuring the dual-drive Mach-Zehnder modulator such that one input of the MZM is grounded while the other input is set to V pp =V π/2 and biased at V π/12 off quadrature, wherein V is a drive voltage, V pp is a peak to peak voltage.