TOSA Sub-Components

A Monitor Diode receives a small portion of the light emitted by the accompanying laser and provides continuous feedback on the laser's power output and performance. The transceiver uses this information to ensure stability and control in the TOSAs output.

A laser diode is a semiconductor device that emits light when electrical current passes through it. COTSWORKS utilizes several types of laser diodes such as VCSEL (Vertical Cavity Surface Emitting Laser), DFB (Distributed-Feedback laser), and FP (Fabry-Perot).

The submount sits on the TO header and is the “pedestal” that the laser diode and other components are mounted to. The submount often includes electrical traces and bonding surfaces to simplify the internal circuit of the TOSA and reduces the need for complex wire-bonds.

The TO cap provides a window that is glass-to-metal hermetically sealed to the lid, allowing the laser’s light to pass through while the diode remains inside a sealed package. In some applications, the lid may be tilted to bounce some of the laser’s light onto the monitor diode.

The header is the platform inside the TOSA on which the rest of the electronic components are placed. The header has pins that are soldered to the transceiver’s circuit board providing the electrical connection necessary to transfer data and power in and out of the TO-can.

The receptacle is the part of the TOSA that interfaces with the ferrule of a fiber, and usually contains a lens that focuses the laser’s light onto the end of the inserted fiber. For multimode TOSAs, these receptacles are often made of PEI, also known by the SABIC brand-name Ultem™