The function of BPSK block is binary phase shift keying
modulating of the output stream from the previous stage.
The phase shift keying
appears to be very resistant against nonlinear effects, because the envelope of signal is constant.
Quadrature phase shift keying
(QPSK), however, uses four phase values spaced at [pi]/2 intervals to encode two bits per symbol.
This process is basically independent of the modulation content of the desired carrier; analog amplitude modulated (AM), frequency modulated (FM), digital frequency shift keying (FSK) or quadrature phase shift keying
The most practical and desirable breakthrough technology was the multi-level digital coherent technology with quadrature phase shift keying
(QPSK) and quadrature amplitude modulation (QAM).
In the system's first channel optical signal is transmitted for which modulation differential phase shift keying
with non-return-to-zero encoding technique is used (NRZ-DPSK).
One example is the use of dual-polarization differential quadrature phase shift keying
The black dots indicate the four nominal quadrature phase shift keying
(QPSK) symbol positions resulting from progressive 90-degree phase shifts.
The joint research will enable ultra-high-speed 400Gbps-class optical transmissions through the use of dual-polarization quadrature phase shift keying
(DP-QPSK)(3), which is currently in use for 100Gbps transmissions, together with dual-polarization 16 quadrature amplitude modulation (DP-16QAM)(4), which takes advantage of an even greater number of quadrature carriers.
The results of simulation of modified synchronous phase detector showed the possibility of an increase of noise immunity of receiving signals with phase shift keying
and the ability of the modified PLL for detecting OQPSK signals even when signal strength is less than the capacity of obstacles.
Xtera said its NXT Submarine Line Terminal Equipment (SLTE) with advanced 20Gb/s Differential Phase Shift Keying
(DPSK) technology has been selected for the Americas I North and Columbus 2b upgrade.