9.6 Tbit/s DWDM equipment's been created A 100 Gbit/s signal has been transmitted for a distance of 4,250 km

Coherent DWDM systems

Coherent detection and DP-QPSK modulation format offer extremely robust technological platform for developing DWDM system with 100 Gbps channel speed.
Coherent systems on the basis of TS-100E and MS-100E-T10 transponders use the DP-QPSK modulation format and increase spectral efficiency of transmission in four times (two polarizations and phases of signal are used).
Structure of optical signal in DP-QPSK modulation format

DP-QPSK Transmitter
Transmitter forms four information streams, each of them has speed 32 Gbps (25 Gbps of information + FEC). These streams are converted to four hi frequency signals and after amplifications are moved to DP-QPSK modulator of integrated optical transmitter.

DP-QPSK Receiver
In coherent receiver the incoming optical signal is mixed with reference signal from laser and then detected by four differential detectors. An obtained electrical signal has completed phase and polarization information of optical signal. Analog-digital conversion and digital signal processing permit mathematically compensate chromatic dispersion and split polarization and quadrature components of DP-QPSK signals.