During the temperature cycling test (TCT), semiconductor packages are exposed to extremely low and extremely high temperatures commonly for 1000 cycles. This article explains in detail: Co-Packaged Optics is an advanced packaging. Optical module, also known as optical transceiver module, is an important component of modern communication networks. It realizes the conversion between optical signals and electrical signals, allowing data to be transmitted through optical fibers at higher speeds and longer distances. They integrate highly temperature-sensitive devices such as lasers (VCSEL/DFB), detectors (PIN/APD), driver ICs, and TIAs.