Pulse timing-jitter reduction by incoherent addition.

Area of Science:

• Photonics and Laser Technology
• Optical Communications

Background:

• Mode-locked laser diodes are crucial for high-speed optical systems.
• Timing jitter in laser pulse trains degrades signal integrity and system performance.
• Existing jitter reduction techniques have limitations in certain applications.

Purpose of the Study:

• To propose and demonstrate a new method for reducing timing jitter in mode-locked laser diodes.
• To investigate the effectiveness of fiber-optic interferometers with long optical path differences for noise cancellation.
• To quantify the jitter reduction achieved using cascaded Mach-Zehnder and ring interferometers.

Main Methods:

• Utilizing fiber-optic interferometers with an optical path difference significantly longer than the laser's coherence length.
• Incoherently adding the intensities of two pulse trains at the interferometer output.
• Employing cascaded Mach-Zehnder and ring interferometers to cancel timing noise at specific Fourier frequencies.

Main Results:

• Demonstrated a significant reduction in timing jitter for a 19.444-GHz mode-locked laser diode.
• Achieved timing jitter values of 0.991 ps and 0.874 ps within a 100-kHz-18-MHz bandwidth.
• Successfully cancelled timing noise at Fourier frequencies determined by the interferometer's path difference.

Conclusions:

• The proposed fiber-optic interferometer technique effectively reduces timing jitter in mode-locked laser diodes.
• This method offers a promising solution for enhancing the stability of high-frequency laser pulse trains.
• The technique is suitable for applications requiring precise timing and low jitter, such as optical communications and signal processing.