8-λ LAN-WDM TOSA for 800-Gb/s links with simplified, non-hermetic packaging

We present an 8-λ local-area-network wavelength-division-multiplexing (LAN-WDM) transmitter optical subassembly (TOSA) for 800-Gb/s operation, using an epoxy-sealed, non-hermetic package for improved cost-effectiveness and manufacturability. To shorten packaging time and improve packaging yield, a ball-lens alignment scheme replaces a square lens, reducing per-lane alignment degrees of freedom from six to three. All eight wavelengths are locked to the LAN-WDM grid with a single thermoelectric cooler (TEC). In addition, inserting series DC-blocking capacitors in the electro-absorption-modulated laser (EML) radio-frequency (RF) path reduces the internal heat load, lowering the TEC input power from 1.294 W to 1.086 W (ΔP = 0.208 W; 16.1% reduction). Under 53.125-Gbaud PAM4 modulation (8 × 106.25 Gb/s), the TOSA delivers clear eye diagrams with transmitter and dispersion eye closure for PAM4 (TDECQ) ≤ 3.0 dB and outer extinction ratio (ER) ≥ 3.7 dB across all lanes. In link tests with a PIN-photodiode receiver optical subassembly (ROSA), per-lane receiver sensitivities of -11.2 to -7.7 dBm are achieved after 20-km transmission at BER = 2.4 × 10^-4. These results indicate that the proposed non-hermetic 8-λ TOSA is a viable building block for ≥10-km intensity-modulated/direct-detect (IM/DD) 800-Gb/s deployments, with demonstrated operation over 20 km.