Wavelength Division Multiplexing (WDM) for QKD

What

Wavelength Division Multiplexing puts multiple signals on one fiber by using different wavelengths (colors) of light - like sending red, blue, and green lasers down the same glass simultaneously. For quantum key distribution, WDM solves the dedicated fiber problem: instead of needing separate dark fiber exclusively for QKD, you run QKD and data traffic together using different wavelengths. QKD might use 1310nm or a channel in the 1550nm band, while 10/40/100 Gbps data traffic uses other channels. The engineering challenge: data traffic uses millions of photons per bit while QKD uses single photons, so even tiny leakage or crosstalk swamps the quantum signal. Solutions include careful wavelength spacing (50+ nm separation), Dense WDM (DWDM) with narrow channel spacing but excellent filters, and sometimes separate fiber cores in multi-core fiber. QNu Labs' systems support WDM co-existence, making QKD deployable on existing fiber infrastructure.

Why

Dedicated fiber leasing costs $10,000-$50,000 per km per year in metro areas. WDM eliminates this barrier, making commercial QKD deployment economically viable. Telecom operators can offer QKD as a service without infrastructure investment. Enterprises can add quantum security to existing data center interconnections. WDM transforms QKD from "requires dedicated infrastructure" to "works with existing fiber."

Impact

Every major QKD deployment now uses WDM - China's quantum network, European quantum communication infrastructure, Tokyo's financial district quantum network. It's essential for metropolitan quantum networks where fiber is expensive, data center quantum interconnections where bandwidth matters, and telecom quantum services where infrastructure reuse is mandatory. For QNu Labs customers, WDM support means practical, affordable deployment on existing networks.

Use Cases

Metropolitan quantum networks using shared fiber, data center QKD interconnections without dedicated fiber, telecom quantum-as-a-service offerings, cost-effective commercial QKD, bank quantum networks using existing infrastructure, government quantum networks leveraging owned fiber

Links

https://www.qnulabs.com/quantum-key-distribution | https://www.youtube.com/c/QNuLabs

Tags

WDM, wavelength division multiplexing, DWDM, dense wavelength division multiplexing, QKD WDM, quantum-classical coexistence, fiber sharing, wavelength multiplexing, telecom quantum, cost-effective QKD, commercial QKD deployment, metropolitan quantum network infrastructure