Introduction to TOSA,ROSA and BOSA

•  Types of common optical components in optical modules
      The key part of an optical module that realizes photoelectric conversion is called an optical component, also collectively referred to as OSA, which usually contains three main categories: TOSA, ROSA, and BOSA.
•  TOSA
      TOSA: Transmitting Optical Sub-Assembly, used in dual-fiber bi-directional or single-emission optical modules, converts electrical signals into optical signals, and then couples the light in the optical path to the optical fiber through optical parts.
      TOSA according to different laser chip program, usually divided into VCSEL TOSA, FP TOSA, DFB TOSA types; according to different modulation can be divided into DML TOSA (direct modulation) and EML TOSA (electro-absorptive modulation); according to different operating temperature stability requirements, can be divided into TOSA with cooling and without cooling TOSA. TOSA with cooling and TOSA without cooling.

Figure 1 Schematic diagram of TOSA

•  ROSA
      ROSA: Receiving Optical Sub-Assembly, used in dual-fiber bi-directional or single-receiving optical modules, through the optical parts of the optical fiber in the optical signal into the internal photosensitive components, so that it generates electrical signals, the formation of optical signals to electrical signal conversion.
      ROSA can be divided into PIN ROSA and APD ROSA according to the type of photoelectric conversion of the internal photosensitive chip, the latter has a relatively higher photoelectric conversion efficiency, and can achieve better sensitivity performance at the same transmission rate.

Figure 2 Schematic diagram of ROSA

• BOSA
      BOSA: Bi-Directional Optical Sub-Assembly, Bi-Directional Optical Sub-Assembly (BOSA) is used in single-fiber bi-directional optical modules, where the transmitter and receiver correspond to different wavelengths of optical signals, and the transmitter and receiver signals are transmitted in the same optical fiber, which can effectively save optical fiber resources.
      BOSA is a combination of the functions of TOSA and ROSA, and the device types of transmitter and receiver can be selected according to the actual transmission requirements;

Figure 3 Schematic diagram of BOSA

      In addition to the above conventional BOSA, there are also a number of special applications based on the market for single-fiber triplexer (a hair and two collector into the Triplexer) and single-fiber four-way package such as optical components.
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