In wireless access network, circulator is mainly used to isolate the output signal from the input signal of the base station antenna. Circulators and isolators are core components in 5G base stations. With the large increase of 5G Massive MIMO, the demand for fiber optic circulators will also increase significantly.

Characteristics of Fiber Optic Circulators

The main feature of fiber optic circulator is that it enables bidirectional optical signal transmission on a single fiber. The direction of signal transmission of the circulator is irreversible, and the optical signal can only be directed from one port to another in one direction at a time. Although the optical signal can be redirected, it must pass sequentially through ports in one direction. For example, in a 3-port circulator, optical signal must pass from port to port 2, before transmitting to port 3.

Types of Fiber Optic Circulators

Fiber optic circulators can be categorized by the number of ports or by polarization correlation. There are 3-port, 4-port and 6-port circulators, among which the most commonly used are 3-port and 4-port ones. Based on polarization correlation, there are PM (polarization-maintaining) circulators and PI (polarization-independent) circulators. Polarization-maintaining optic circulators are commonly used in polarization-maintaining fields, such as 40Gbps high-speed systems or Raman pump applications, dual-pass amplifiers and dispersion compensation modules (DCM). Polarization independent optic circulators, together with fiber gratings and other reflective devices, are widely used in dense wavelength division multiplexing (DWDM) systems, high-speed systems and bidirectional communication systems.

Applications of Fiber Optic Circulators

Fiber optic circulators are usually applied in PON, WDM, Polarization Mode Dispersion, Dispersion Compensation, OADM, optical amplifier, OTDR, and fiber optical sensing, etc. Optical circulator is an important component in DWDM of advanced optical network. With the massive increase of base stations, there’s a huge market potential for optical circulators. Telecommunications applications will continue to be the main market for fiber optic circulators. In addition, fiber optic circulators are also used in research and development, sensing, test equipment, oil, natural gas and some other special application areas.