For the test of “Key components for synchronous optical quadrature phase shift keying transmission (synQPSK)” the Univ. Paderborn has built a 10Gbit/s DPSK transmission testbed as illustrated below:

10Gbit/s DPSK transmission setup

Transmitted 10Gbit/s NRZ-DPSK (left) and RZ-DPSK (right) “eye” patterns in testbed, recorded without interferometer, just using intensity detection

Demodulated 10Gbit/s NRZ-DPSK (left) and RZ-DPSK (right) eye patterns in testbed

Bit error ratio (BER) vs received optical power for 10Gbit/s NRZ-DPSK (left) and RZ-DPSK (right)

10Gbit/s transmission testbed with laser controller (top right), transmitter (top middle), receiver (top left), wavemeter/DEMUX/EDFA (bottom right) and BER counter (bottom left)

10Gbit/s bit pattern generator (left), and oscilloscope (right) with regenerated RZ-DPSK signal (top trace) and intensity pattern of RZ-DPSK signal (bottom trace).