An optical module both transmits and receives optical signals, using separate components for each function.

Transmitting Function (Tx)

The transmitting part of an optical module is called the Transmitter Optical Sub-Assembly (TOSA). It converts electrical signals from the device into optical signals using a laser diode (LD) or light-emitting diode (LED). The internal driver chip modulates the light according to the input electrical signal, and an automatic optical power control (APC) circuit ensures consistent output power. This allows the module to send data over optical fiber to another device .

Receiving Function (Rx)

The receiving part is called the Receiver Optical Sub-Assembly (ROSA). It captures incoming optical signals through a photodetector diode, converting the light back into electrical signals. These signals are then amplified and processed to match the original data rate, enabling the device to interpret the transmitted information .

Combined Operation

Most optical modules are transceivers, meaning they integrate both TOSA and ROSA in a single unit. This allows bidirectional communication over a single fiber or separate fibers, depending on the module type. The module's electrical interface connects to the host device, while the optical interface connects to the fiber network .

Summary

• Transmitting (Tx): Converts electrical signals to optical signals using TOSA.
• Receiving (Rx): Converts optical signals to electrical signals using ROSA.
• Optical module type: Typically a transceiver, capable of both sending and receiving data simultaneously. Thus, an optical module is not limited to just transmitting or receiving; it performs both functions to enable full communication in optical fiber networks .