Fiber coupler distributes the light among the branch fibers. By using fiber couplers there is no scattering loss and there is no generation of noise
Fiber couplers theory:
- An optical fiber coupler is a device that distributes light from a main fiber into one or more branch fibers
- Such devices are known as multiport fiber couplers.
- Requirements are increasing for the use of these devices to divide or combine optical signals for application within optical fiber information distribution systems including data buses, LANs, computer networks and telecommunication access networks
Classification of optical fiber couplers:
- Core interaction type: Through the fiber core cross-section by butt jointing the fibers or by using some form of imaging optics between the fibers.
- Surface interaction type: Through the fiber surface and normal to its axis by converting the guided core modes to both cladding and refracted modes which then enable the power-sharing mechanism
- The mechanisms associated with these two broad categories are illustrated in Figure 5.15
- Active waveguide directional couplers are also available which are realized using integrated optical fabrication techniques
Multiport optical fiber:
- Multiport optical fiber couplers can also be subdivided into the following three main groups as illustrated in Figure 5.16
- Three- and four-port couplers: which are used for signal splitting, distribution and combining.
- Star couplers: which are generally used for distributing a single input signal to multiple outputs.
- Wavelength division multiplexing (WDM) devices: which are specialized forms of coupler designed to permit a number of different peak wavelength optical signals to be transmitted in parallel on a single fiber. In this context WDM couplers either combine the different wavelength optical signal onto the fiber (i.e. multiplex) or separate the different wavelength optical signals output from the fiber (i.e. de-multiplex).