Quantum key distribution on a 10Gb/s WDM-PON.

Area of Science:

• Quantum Information Science
• Optical Network Security
• Telecommunications Engineering

Background:

• Passive optical networks (PONs) are widely used for broadband access.
• Integrating secure quantum key distribution (QKD) with existing classical communication infrastructure presents significant technical challenges.
• Minimizing crosstalk between classical and quantum channels is crucial for secure QKD.

Purpose of the Study:

• To demonstrate the first quantum key distribution (QKD) system on a multi-user wavelength division multiplexed passive optical network (WDM-PON).
• To achieve simultaneous, bidirectional classical data transmission at 10Gb/s alongside QKD.
• To address and mitigate crosstalk issues, particularly from spontaneous Raman scattering.

Main Methods:

• Implementation of a C-Band QKD system utilizing differential phase shift keying (DPSK) at a 10GHz clock rate.
• Employment of a dual feeder fiber and band filtering scheme to suppress classical-to-quantum channel crosstalk.
• Testing the system's performance with quantum key distribution to four simultaneous users.

Main Results:

• Successful quantum key distribution to 4 users with negligible Raman crosstalk penalties.
• Achieved a mean Quantum Bit Error Rate (QBER) of 3.5% across the four users.
• Obtained a mean raw key distribution rate of 1.3Mb/s, reduced to 696kb/s after temporal windowing to mitigate detector timing jitter.

Conclusions:

• The feasibility of integrating QKD with high-speed WDM-PONs for secure communication is demonstrated.
• The proposed dual feeder fiber and band filtering scheme effectively suppresses crosstalk, enabling secure key distribution.
• The system provides a foundation for future secure optical network architectures.