ROSA Sub Components

A photodiode, the most crucial component within a ROSA, is what receives the incoming light and converts it to an electrical signal. It is the receiver analog to the laser diode in a TOSA system.

The TO cap provides a window that is glass-to-metal hermetically sealed to the lid, allowing the light from the fiber to pass through into the sealed package containing the photodiode.

A capacitor is an electrical element that is used in various ways to clean the signal in a receiver circuit. Capacitors can be used to remove noise, control feedback, and provide protection from spikes in voltage that could otherwise damage other critical components.

In an optical receiver circuit, the TIA is responsible for converting the small photocurrent generated by the photodiode into a larger, more manageable voltage signal, amplifying this signal with minimal noise, and ensuring that the signal is appropriately conditioned for further processing in the remainder of the receiver circuit.

The header is the platform inside the ROSA 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 ROSA that interfaces with the ferrule of a fiber, and usually contains a lens that focuses the light leaving the fiber through the window of the TO onto the active area of the photodiode. For multimode ROSAs, these receptacles are often made of PEI, also known by the SABIC brand-name Ultem™