Estimating OSNR of equalised QPSK signals

Area of Science:

• Optical communications
• Signal processing
• Metrology

Background:

• Accurate optical signal-to-noise ratio (OSNR) estimation is crucial for coherent optical communication systems.
• Existing OSNR estimation methods may lack precision or require complex calibration.
• Quadrature phase-shift keying (QPSK) is a widely used modulation format in high-capacity optical networks.

Purpose of the Study:

• To propose and demonstrate a novel technique for estimating the OSNR of equalized QPSK signals.
• To evaluate the performance of the proposed technique against established methods like maximum likelihood estimation.
• To assess the impact of estimation block size on the accuracy of the proposed OSNR measurement.

Main Methods:

• The proposed method utilizes radial moments of the complex signal constellation for OSNR estimation.
• Simulations were performed to compare the technique with maximum likelihood estimation.
• Experimental verification was conducted to validate the technique's real-world applicability.

Main Results:

• The proposed radial moments technique provides accurate OSNR estimation for QPSK signals.
• Simulation results show comparable or improved performance over maximum likelihood estimation.
• Experimental validation confirmed the technique's effectiveness, achieving an accuracy within 0.5 dB with single-point calibration.

Conclusions:

• The radial moments technique offers a robust and accurate method for OSNR estimation in QPSK systems.
• This approach simplifies OSNR monitoring and enhances the reliability of optical communication systems.
• The technique's accuracy and experimental validation pave the way for practical implementation in optical networks.