Cascaded SOA FWM with non-uniform ASE seeding: expanding a low-Cost DWDM system from 12 to 20 channels

Abstract

This paper extends a low-cost wavelength-division multiplexing (WDM) source from 12 to 20 dense wavelength-division multiplexed (DWDM) channels using a cascaded semiconductor optical amplifier (SOA) architecture — without requiring any coherent lasers. A second SOA stage, seeded by the 12-channel output of the first stage (derived from three non-uniformly spaced, spectrum-sliced ASE inputs from a single high-power LED), generates eight additional four-wave mixing (FWM) components. The non-uniform input spacing (0.3 THz and 0.4 THz) deliberately inhibits a fully populated frequency comb, producing a finite, structured, and manufacturable channel set. Performance reveals a practical trade-off: the three original inputs exceed 195 km, while the eight cascaded channels are limited to 25–100 km — fully viable for urban and distribution links. Compared with conventional laser-array DWDM systems, the proposed design offers significantly lower cost and complexity. Future experimental validation under real-world conditions is recommended, alongside simplified diagrams and application scenarios to improve accessibility for students and industry practitioners.