Flexible frequency comb generation in a periodically poled lithium niobate waveguide enabling optical multicasting

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Nonlinear Optics

Background:

• Optical frequency combs are crucial for precise measurements and communications.
• Generating combs with tunable line spacing and enabling optical multicasting presents significant challenges.
• Periodically poled lithium niobate (PPLN) waveguides offer unique nonlinear optical properties for light manipulation.

Purpose of the Study:

• To propose and demonstrate a novel technique for generating a coherent optical comb with tunable line spacing.
• To showcase the application of this technique for optical multicasting.
• To verify the quality and performance of the generated optical signals.

Main Methods:

• Utilizing a periodically poled lithium niobate (PPLN) waveguide.
• Modulating a single continuous wave laser to generate three phase-locked seed lines.
• Injecting seed lines into the PPLN waveguide for line multiplication.
• Controlling line spacing via the frequency of the electrical modulation signal.
• Assessing comb quality through autocorrelation, phase noise, and linewidth measurements.
• Demonstrating optical multicasting of quadrature phase shift keying (QPSK) signals.

Main Results:

• Successfully generated a coherent optical comb with tunable line spacing.
• Achieved line multiplication within the PPLN waveguide.
• Demonstrated optical multicasting, producing five replicas of a QPSK signal.
• Generated signal replicas with 25 and 37.5 GHz spacing.
• Transmitted multicasted signals over 80 km of single-mode fiber with bit error rates below the forward error correction threshold.

Conclusions:

• The proposed technique effectively generates tunable optical frequency combs.
• The method is suitable for high-performance optical multicasting applications.
• The demonstrated system shows promise for advanced optical communication systems.