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Introduction To TOSA, ROSA and BOSA

Time: 2023-10-09
• Common Types of Optical Sub-Assemblies in Optical Modules
        The key components that perform electro-optical conversion in optical modules are called optical sub-assemblies (OSA).
        OSAs generally fall into three main categories: TOSA, ROSA, and BOSA.
• TOSA
        TOSA: Transmitting Optical Sub-Assembly
        Used in dual-fiber bidirectional or transmit-only optical modules, it converts electrical signals into optical signals and couples the light from the optical path into the optical fiber through internal optical components.
        Based on different laser chip designs, TOSAs are classified into VCSEL TOSA, FP TOSA, and DFB TOSA.
        By modulation scheme, they are divided into DML TOSA (Direct Modulation Laser) and EML TOSA (Electro-Absorption Modulated Laser).
        According to operating temperature stability requirements, TOSAs can be categorized into cooled TOSA (with TEC) and uncooled TOSA (without TEC).
Schematic diagram of TOSA
Figure 1 Schematic Diagram of TOSA
• ROSA
        ROSA: Receiving Optical Sub-Assembly
        Used in dual-fiber bidirectional or receive-only optical modules, it guides optical signals from the fiber onto internal photodetectors via optical components, generating electrical signals and completing the conversion from optical to electrical signals.
        Based on the photoelectric conversion type of internal photodetectors, ROSAs are divided into PIN ROSA and APD ROSA.
        APD ROSA features higher photoelectric conversion efficiency and provides better receiver sensitivity at the same transmission rate.
Schematic Diagram of ROSA
Figure 2 Schematic Diagram of ROSA
• BOSA
        BOSA: Bi-Directional Optical Sub-Assembly
        Used in single-fiber bidirectional (BiDi) optical modules, the transmitting and receiving paths use different wavelengths and share the same optical fiber, effectively saving fiber resources.
        BOSA integrates the functions of both TOSA and ROSA. The types of transmit and receive devices can be selected according to actual transmission requirements.
Schematic Diagram of BOSA
Figure 3 Schematic Diagram of BOSA
        In addition to standard BOSAs, the market also offers special-purpose optical sub-assemblies such as triplexers (1 transmit + 2 receive) and quadplexers (single-fiber 4-way transceivers) for specific applications.
        Moduletek Limited is at your service.
        For further inquiries about the above content, please contact us at: sales@moduletek.com
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