Quantum Optical Network in 3D: Fiber Loss & WDM

Fiber Link

Fiber length 40 km

Attenuation α 0.20 dB/km

Multiplexing (WDM)

Wavelength channels 4

Pair rate / channel 6 pairs/s

Live Stats

Pairs launched

Coincidences

Single-span T(L/2)

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End-to-end η(L)

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Aggregate key rate

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vs. 1 channel

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Each WDM channel is drawn as its own helical strand twisted around the shared fiber core, colored by wavelength. Photon spheres (one InstancedMesh per direction) launch from the central mux, spiral outward, and are culled mid-flight the instant a Monte-Carlo draw against the real fiber attenuation law says they scattered.

Physics notes

Telecom fiber attenuation (dB convention):

T(L) = 10^(-αL/10)

Source at the midpoint ⇒ each photon crosses L/2, so joint coincidence survival is:

η(L) = T(L/2)² = 10^(-αL/10)

N wavelength channels multiplex onto one physical core; each channel loses photons independently at the same α, so the aggregate secure-key rate is:

R_agg(L) = N · R₀ · η(L)

Distinct from this sim's 3d-quantum-networks sibling, which chains discrete repeater nodes and performs entanglement swapping — no continuous fiber-distance loss curve, no wavelength channels.
The helix here is purely a visualization device to separate WDM channels spatially; physically all wavelengths share one fiber core.

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