The Copper Cliff: Skin Effect & Transmission Distance Collapse
As signal frequency scales toward 1.6 Tbps and beyond, copper's effective cross-section shrinks — turning conductors into resistors, and meters into centimeters.
Skin Depth by Frequency — Current Concentration in Copper
1 GHz
δ = 2.1 μm
10 GHz
δ = 0.66 μm
56 GHz
δ = 0.28 μm
112 GHz
δ = 0.20 μm
224 GHz
δ = 0.14 μm
δ = √( ρ / π·f·μ₀·μᵣ )
Skin depth (δ) is inversely proportional to √f. As frequency doubles, effective cross-section halves.
Max Copper Cable Reach by Interface Speed
25G
7 m
100G
5 m
400G
3 m
800G
2 m
1.6T
<1 m
3.2T
~30cm
⚠ RACK HEIGHT REALITY CHECK
Average AI server rack: 2.5 m+ tall. At 1.6T, copper cannot span the same rack.
< 1 m
Copper passive cable max reach at 1.6 Tbps — less than a server rack's height
2.5 m+
Typical AI GPU server rack height — the minimum cable run needed
10–20 m
e-Tube dielectric waveguide reach at 1.6 Tbps — no skin effect penalty
Source: IEEE 802.3 Task Force — 200G/lane Electrical Signaling Analysis (2023) | Point2 Technology e-Tube White Paper (2024)