Technical notes and assessments. Every claim comes with its primary source.
Cavity structure sets spectral purity; modulation method sets speed. FPLD is cheapest but multimode, DFB is the stable single-mode workhorse behind WDM, and EML integrates a high-speed modulator on one chip. Together they form a cost × speed ladder, each matched to different links.
400G/800G/1.6T/3.2T are the total data rate of an optical module (per-lane rate × lane count), not the rate of a single wavelength or lane. This article breaks down the formula, the four standard generations (802.3bs/df/dj), PAM4 modulation and distance variants, and the electrical bottleneck plus CPO route for 1.6T/3.2T.
An optical transceiver is the standardized interface between switches and fiber: transmitter (laser + driver + modulation), receiver (photodetector + TIA + DSP), the IM-DD and coherent routes, SFP-to-OSFP packaging, and silicon-photonics integration. This article breaks down the full architecture of a modern module.
The core question of high-power manufacturing lasers: how to keep near-diffraction-limited beam quality at kilowatt-level power. The answer is MOPA — the seed sets beam quality, the amplifier sets power, and the two are decoupled; combined with multi-stage Yb-doped fiber amplification, pump combining, and isolators, verified with a concrete JPT optical path.