TOSA: Its main function is to convert electrical signals to optical signals, including lasers, MPD, TEC, isolator, Mux, coupling lenses and other devices, including TO-CAN, Gold-BOX, COC (chip on chip), COB ( chip on board) and other packaging forms. For optical modules used in data centers, in. TOSA is used to realize the electro-optical conversion in the optical module, the built-in devices include optical laser, MPD, TEC, isolator, MUX, coupling lens, and so on. For the optical. COC is a high-performance, transparent plastic offering excellent dimensional stability and minimal moisture absorption. The refractive index of COC is around 1. Advantages: Limitations: Material examples: COP. Introduction: In the realm of high-speed photonic integration, choosing the right packaging architecture— Chip-on-Board (COB) or Chip-on-Carrier (COC) —is critical for ensuring system-level excellence. This technical insight explores the trade-offs between cost-efficiency and high-precision. Using extensive knowledge in CMBH-grown, multi-quantum, well-active layer designs with a long history of proven field reliability, the lasers are qualified per the intent of Telcordia GR-468, qualified for use in non-hermetic environments, and ofer class-leading electrical and optical performance.