Some fiber optic data links require more than simple point-to-point connections. These data links may be of a much more complex design that requires multi-port or other types of connections.
The picture below shows some example system architectures that use more
complex link designs. In many cases these types of systems require fiber
optic components that can redistribute (combine or split) optical
signals throughout the system.
Examples of complex system architectures.
One type of fiber optic component that allows for the redistribution of optical signals are fiber optic couplers . A fiber optic coupler is a device that can distribute the optical signal (power) from one fiber among two or more fibers. A fiber optic coupler can also combine the optical signal from two or more fibers into a single fiber. Fiber optic couplers attenuate the signal much more than a connector or splice because the input signal is divided among the output ports. For example, with a 1 x 2 fiber optic coupler, each output is less than one-half the power of the input signal (over a 3 dB loss).
Fiber optic couplers can be either active or passive devices. The difference between active and passive couplers is that a passive coupler redistributes the optical signal without optical-to-electrical conversion. Active couplers are electronic devices that split or combine the signal electrically and use fiber optic detectors and sources for input and output.
The nezt picture below illustrates the design of a basic fiber optic coupler. A basic fiber optic coupler has N input ports and M output ports. N and M typically range from 1 to 64. The number of input ports and output ports vary depending on the intended application for the coupler. Types of fiber optic couplersinclude optical splitters, optical combiners, X couplers, star couplers, and tree couplers.
Basic passive fiber optic coupler design.
An optical splitter is a passive device that splits the optical power carried by a single input fiber into two output fibers. The picture below illustrates the transfer of optical power in an optical splitter. The input optical power is normally split evenly between the two output fibers. This type of optical splitter is known as a Y-coupler.
However, an optical splitter may distribute the optical power carried by input power in an uneven manner. An optical splitter may split most of the power from the input fiber to one of the output fibers. Only a small amount of the power is coupled into the secondary output fiber. This type of optical splitter is known as a T-coupler, or an optical tap.