Optical switch
Encyclopedia
In telecommunication
, an optical switch is a switch
that enables signals in optical fiber
s or integrated optical circuits (IOCs) to be selectively switched from one circuit
to another.
The word is used on several levels. In commercial terms (such as "the telecom optical switch market size") it refers to any piece of circuit switching
equipment between fibers. The majority of installed systems in this category actually use electronic switching between fiber transponders. Systems that perform this function by physically switching light are often referred to as "photonic" switches, independent of how the light itself is switched. Away from the world of telecom systems, an optical switch is the unit that actually switches light between fibers, and a photonic switch is one that does this by exploiting nonlinear material properties to steer light (i.e., to switch wavelengths or signals within a given fiber).
Hence a certain portion of the optical switch market is made up of photonic switches. These will contain within them an optical switch, which will, in a small number of cases, be a photonic switch.
An optical switch may operate by mechanical means, such as physically shifting an optical fiber to drive one or more alternative fibers, or by electro-optic effect
s, magneto-optic effect
s, or other methods. Slow optical switches, such as those using moving fibers, may be used for alternate routing
of an optical switch transmission
path, such as routing around a fault
. Fast optical switches, such as those using electro-optic or magneto-optic effects, may be used to perform logic operations; also included in this category are the semiconductor optical amplifiers, which are optoelectronic devices that can be used as optical switches and be integrated with discrete or integrated microelectronic circuits.
A search on “optical switch” http://patft.uspto.gov/netahtml/PTO/search-bool.html yielded some 8000 patents, roughly categorized as follows:
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
, an optical switch is a switch
Switch
In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another....
that enables signals in optical fiber
Optical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
s or integrated optical circuits (IOCs) to be selectively switched from one circuit
Telecommunication circuit
A telecommunication circuit is any line, conductor, or other conduit by which information is transmitted.A dedicated circuit, private circuit, or leased line is a line that is dedicated to only one use...
to another.
The word is used on several levels. In commercial terms (such as "the telecom optical switch market size") it refers to any piece of circuit switching
Circuit switching
Circuit switching is a methodology of implementing a telecommunications network in which two network nodes establish a dedicated communications channel through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the...
equipment between fibers. The majority of installed systems in this category actually use electronic switching between fiber transponders. Systems that perform this function by physically switching light are often referred to as "photonic" switches, independent of how the light itself is switched. Away from the world of telecom systems, an optical switch is the unit that actually switches light between fibers, and a photonic switch is one that does this by exploiting nonlinear material properties to steer light (i.e., to switch wavelengths or signals within a given fiber).
Hence a certain portion of the optical switch market is made up of photonic switches. These will contain within them an optical switch, which will, in a small number of cases, be a photonic switch.
An optical switch may operate by mechanical means, such as physically shifting an optical fiber to drive one or more alternative fibers, or by electro-optic effect
Electro-optic effect
An electro-optic effect is a change in the optical properties of a material in response to an electric field that varies slowly compared with the frequency of light...
s, magneto-optic effect
Magneto-optic effect
A magneto-optic effect is any one of a number of phenomena in which an electromagnetic wave propagates through a medium that has been altered by the presence of a quasistatic magnetic field...
s, or other methods. Slow optical switches, such as those using moving fibers, may be used for alternate routing
Routing
Routing is the process of selecting paths in a network along which to send network traffic. Routing is performed for many kinds of networks, including the telephone network , electronic data networks , and transportation networks...
of an optical switch transmission
Transmission (telecommunications)
Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...
path, such as routing around a fault
Fault (technology)
In document ISO/CD 10303-226, a fault is defined as an abnormal condition or defect at the component, equipment, or sub-system level which may lead to a failure....
. Fast optical switches, such as those using electro-optic or magneto-optic effects, may be used to perform logic operations; also included in this category are the semiconductor optical amplifiers, which are optoelectronic devices that can be used as optical switches and be integrated with discrete or integrated microelectronic circuits.
A search on “optical switch” http://patft.uspto.gov/netahtml/PTO/search-bool.html yielded some 8000 patents, roughly categorized as follows:
- MEMS approaches involving arrays of micromirrors that can deflect an optical signal to the appropriate receiver (e.g., U.S. Patent 6,396,976);
- Piezoelelectric Beam Steering involving piezoelctric ceramics providing enhanced optical switching characteristics
- Inkjet methods involving the intersection of two waveguides so that light is deflected from one to the other when an inkjet-like bubble is created (e.g., Patent 6,212,308);
- Liquid crystals (e.g., Patent 4,948,229) that rotate polarized light either 0 degrees or 90 degrees depending on the applied electric field to support switching;
- Thermal methods (e.g., Patent 5,037,169) that vary the index of refraction in one leg of an interferometer to switch the signal on or off;
- Nonlinear methods (e.g., Patent 5,319,492) that vary the diffraction pattern in a medium by taking advantage of the material nonlinear properties to deflect light to the desired receiver;
- Acousto-optic methods that change the refractive index as a result of strain induced by an acoustic field to deflect light (e.g., Patent 6,922,498);
- Amplifiers and attenuators in output fibers that adjust the signal to the digital “0” power range (when the fiber is not switched to) or to the normal power range when it is (e.g., Patent 7,027,211).
See also
- Optical cross-connectOptical cross-connectAn optical cross-connect is a device used by telecommunications carriers to switch high-speed optical signals in a fiber optic network, such as an optical mesh network.There are several ways to realize an OXC:...
- Optical bufferOptical bufferIn telecommunications, an optical buffer is a device that is capable of temporarily storing light. Just as in the case of a regular buffer, it is a storage medium that enables compensation for a difference in time of occurrence of events...
- Optical transistor
- Optical mesh networkOptical mesh networkOptical mesh networks are a type of telecommunications network.Transport networks, the underlying optical fiber-based layer of telecommunications networks, have evolved from DCS -based mesh architectures in the 1980s, to SONET/SDH ring architectures in the 1990s...