In telecommunications switching is necessary, but few times it can be confusing as it operates at two distinct levels. Many big, expensive boxes called switches are included in the telephone network, which consists of dedicated special-purpose computers so that they can direct the operation of small components called an optical switch. The big box is the switch to a network engineer, but a switch is a component inside the big box to an optical engineer. Optical switching can be performed by both the big box and the component, but sophisticated electronic control systems are contained in the big box inevitably with the help of current technology.
If you see then in practice many optical switches are optoelectronic, with input optical signals converted to electronic form for switching, and the switched electronic signals are then driving an optical transmitter. In the light all-optical switches manipulate signals form and, by redirecting all signals in fiber, it can be done either by selecting signals at certain wavelengths in wavelength-division multiplexed (WDM) systems. You will find few switches that can isolate individual wavelengths, but typically their input is individual optical channels that are separated by demultiplexing optics. That indicates that they operate at the optical-channel level, without regard to what data stream the optical channel is carrying. To manipulate the data stream transmitted on each optical channel fiber adapter or optoelectronic switches are still required.
By an externally applied field or by some other external influence, optical transmission properties can be changed in an optic switch. For this purpose electric, magnetic, and surface acoustic wave techniques are used. By such means, from a detector light may be deflected away, thus switching the beam.
From one phone or computer to another when a fiber-optic network carries a light signal, it may be required to move the signal between different fiber paths. To perform this, a switch is needed that can transfer the signal with a minimum loss of voice or data quality. Future switching applications will need to push the technology further. True optical routers or optical amplifiers are one target that would direct the headers on Internet packets to their destinations.
