Pluggable Copper vs. Co-Packaged Optics (CPO): Signal Path Comparison
How signal travels from switch chip to fiber — old approach vs. CPO approach
❌ Traditional: Pluggable Copper Transceiver
Switch ASIC
→
PCB Copper Traces
signal travels 10–15cm
heat + EMI
→
Pluggable Transceiver
(external module)
→
DSP Retimer Chip
signal boost required
+power +latency
→
Optical Fiber
→
Receiver
✅ CPO: Co-Packaged Optics (Spectrum-X)
Switch ASIC
+
CPO Engine
(single package)
≤1mm signal path
→
Optical Fiber
light from chip edge
zero DSP needed
→
Receiver
5× lower power
Energy per Port
~15–20 pJ/bit
<3 pJ/bit
↓ 5× reduction
Signal Reach
<3m (copper)
reliable
Kilometers
no degradation
↑ 1,000× range
EMI Immunity
Vulnerable to
high-voltage noise
Complete EMI
immunity (light)
↑ Link reliability 5×