A fiber-optic coupler, also known as an optical fiber connector, provides termination to the end of an optic fiber, serving to quickly connect or disconnect one fiber from another. An optical fiber itself contains a core of thin, flexible and transparent glass or plastic that, without a fiber-optic coupler, would require splicing, which is the act of shedding the material surrounding the core at the tip of each fiber and then ensuring direct contact between the two cores. This would be a very difficult and time-consuming task because of the delicacy of optic fiber and the way in which it functions. In most cases, a fiber-optic coupler contains a spring-loaded mechanism that easily presses the fibers together, ensuring direct core-to-core contact without any air interference.
A fiber-optic coupler can have various connections. The ideal fiber-optic coupler would support both single and multi-mode fibers (MMFs). Additionally, it will have a low insertion loss, which is measured in decibels. Low insertion loss can be credited to precise and secure placement features of the fiber-optic connection and quality materials used during manufacturing.
One or more optic fibers might be included in the input port of a fiber-optic coupler. The optic fibers are often referred to as waveguides, and they might lead to one or more output ports, also known as sources. When an input signal is sent through an optic fiber, it carries data as pulses of light. These pulses generate an electromagnetic wave. The material insulating the core of the optic fibers restricts the vibrations of the electromagnetic wave, which otherwise would have evolved into an electromagnetic field, and then causes polarization to occur.
Polarization is the direction traveled by the electromagnetic wave. The amount of time that elapses while the electromagnetic wave oscillates through a single cycle, when measured against the distance of the cycle, determines the wavelength, or frequency. A single-state optic fiber, which might be a single fiber or a grouping of fibers fused together, can allow only a single polarization, which means that only one propagation path is available for a single frequency. Single-mode fibers, without being coupled, are typically used for communications longer than 3,440 feet (1,050 meters).
Multi-mode fibers generally have a core with a larger diameter than those of a single-mode fiber. MMFs will allow one or more propagation paths, allowing multiple devices to transmit input signals, but the devices still must be of different frequencies. The feature attributed to fiber-optic couplers that allow polarization for MMFs is termed "multiplexing." Although optic fibers in general allow data to maintain its integrity over a much longer distance than other types of cabling, MMFs are most useful for short-distance communications and for applications that require a high power to be transmitted.