Adiabatic weak coherent MHz linewidth O-band single-photon carrier for low erroneous phase decoding

Area of Science:

• Quantum Communication
• Optical Engineering
• Photonics

Background:

• Commercially available O-band lasers for single-photon communication suffer from high fiber loss, broad linewidth, and wavelength instability.
• Efficient phase-coding links require overcoming these limitations for high secure key rates.

Purpose of the Study:

• To design and implement a stabilized system for O-band single-photon secure data communication.
• To enable efficient phase-coding links with improved secure key rates over metropolitan networks.

Main Methods:

• A specifically designed adiabatic package with active temperature and current feedback control for paired O-band MHz-linewidth master-to-slave injection-locked distributed feedback laser diodes (DFBLDs).
• Stabilization of a polarization-maintaining 1-bit-delay interferometer using a passively adiabatic cell for accurate differential phase decoding.
• Suppression of phase-code distortion by precisely controlling master-injection levels and reducing biased injection to mitigate Auger heating.

Main Results:

• Phonon-induced phase fluctuations at bit edges were identified and attributed to intra-cavity heating from master DFBLD injection.
• Phase-code distortion caused by over-injection-induced Auger heating was effectively suppressed.
• Single-photon differential phase-shift (DPS) keying data transmission was achieved over 15-km single-mode fiber (SMF), with a slight increase in bit-error ratio from <3% to 6.2%.

Conclusions:

• The proposed adiabatic packaging and feedback control stabilize O-band DFBLDs for secure communication.
• Precise control of injection levels and bias currents effectively suppresses phase fluctuations and distortion.
• The system enables reliable single-photon DPS-keying transmission over 15-km SMF, paving the way for enhanced metropolitan network security.