BOSA in BiDi transceivers
TOSA and ROSA are the core components in unidirectional transceivers that transmit on one fiber strand and receive on the other fiber strand. In bidirectional transceivers, the so-called Bidirectional Optical Sub Assembly (BOSA) is used. This is a combination of TOSA, ROSA and an additional WDM filter.
The WDM filter enables the bidirectional transceiver to split the wavelengths into two separate wavelengths. Then the transmit and receive functions can be performed on a single fiber strand.
While the term PCB describes the printed circuit board itself, PCBA (Printed Circuit Board Assembly), in contrast, refers to the assembly of the printed circuit board. In the assembly process, various electronic components (assemblies) are mounted on the PCB. These can be resistors, ICs (Integrated Circuits), capacitors, transformers, etc. The assembly is done by SMT, THT or Chip-on-Board (CoB). For the mechanical connection on the PCB, the PCB with the assembled components usually goes through a reflow soldering process or solder paste printing.
For optical transceivers, the PCB is assembled with the components described above.
Optical transceivers consist of various components. The outer jacket protects the sensitive electronic and optoelectronic components. Unidirectional transceivers are equipped with a TOSA - to convert an electrical signal into an optical signal - and a ROSA - to convert an optical signal into an electrical signal. In BiDi transceivers, a BOSA is used. This involves soldering all the components of an optical transceiver onto a PCBA.