{{unreferenced, date=February 2008
An optical cross-connect (OXC) is a device used by
telecommunications
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
carriers to
switch
In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...
fiber optic
An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means t ...
network, such as an
optical mesh network
An optical mesh network is a type of optical telecommunications network employing wired fiber-optic communication or wireless free-space optical communication in a mesh network architecture.
Most optical mesh networks use fiber-optic communicatio ...
.
There are several ways to realize an OXC:
* Opaque OXCs (electronic switching) - One can implement an OXC in the electronic domain: all the input optical signals are converted into electronic signals after they are demultiplexed by
demultiplexer
In electronics, a multiplexer (or mux; spelled sometimes as multiplexor), also known as a data selector, is a device that selects between several analog or digital input signals and forwards the selected input to a single output line. The sel ...
s. The electronic signals are then switched by an electronic switch module. Finally, the switched electronic signals are converted back into optical signals by using them to modulate
laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...
s and then the resulting optical signals are multiplexed by optical
multiplexer
In electronics, a multiplexer (or mux; spelled sometimes as multiplexor), also known as a data selector, is a device that selects between several analog or digital input signals and forwards the selected input to a single output line. The sel ...
s onto outlet optical fibers. This is known as an "OEO" (Optical-Electrical-Optical) design. Cross-connects based on an OEO switching process generally have a key limitation: the electronic circuits limit the maximum
bandwidth
Bandwidth commonly refers to:
* Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range
* Bandwidth (computing), the rate of data transfer, bit rate or thr ...
of the signal. Such an architecture prevents an OXC from performing with the same speed as an all-optical cross-connect, and is not
transparent
Transparency, transparence or transparent most often refer to:
* Transparency (optics), the physical property of allowing the transmission of light through a material
They may also refer to:
Literal uses
* Transparency (photography), a still, ...
to the network protocols used. On the other hand, it is easy to monitor signal quality in an OEO device, since everything is converted back to the electronic format at the switch node. An additional advantage is that the optical signals are regenerated, so they leave the node free of
dispersion
Dispersion may refer to:
Economics and finance
* Dispersion (finance), a measure for the statistical distribution of portfolio returns
* Price dispersion, a variation in prices across sellers of the same item
*Wage dispersion, the amount of variat ...
and
attenuation
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variabl ...
. An electronic OXC is also called an ''opaque OXC''.
* Transparent OXCs (optical switching) - Switching optical signals in an all-optical device is the second approach to realize an OXC. Such a switch is often called a ''transparent OXC'' or ''photonic cross-connect'' (PXC). Specifically, optical signals are demultiplexed, then the demultiplexed wavelengths are switched by
optical switch An optical transistor, also known as an optical switch or a light valve, is a device that switches or amplifies optical signals. Light occurring on an optical transistor's input changes the intensity of light emitted from the transistor's output ...
modules. After switching, the optical signals are multiplexed onto output fibers by optical multiplexers. Such a switch architecture keeps the features of data rate and protocol transparency. However, because the signals are kept in the optical format, the transparent OXC architecture does not allow easy optical signal quality monitoring.
* Translucent OXCs (optical and electronic switching) - As a compromise between opaque and transparent OXC's, there is a type of OXC called a ''translucent OXC''. In such a switch architecture, there is a switch stage which consists of an optical switch module ''and'' an electronic switch module. Optical signals passing through the switch stage can be switched either by the optical switch module or the electronic switch module. In most cases, the optical switch module is preferred for the purpose of transparency. When the optical switch module's switching interfaces are all busy or an optical signal needs
signal regeneration In telecommunications, signal regeneration is signal processing that restores a signal, recovering its original characteristics.
The signal may be electrical, as in a repeater on a T-carrier line, or optical
Optics is the branch of physics tha ...
through an OEO conversion process, the electronic module is used. Translucent OXC nodes provide a compromise of full optical signal transparency and comprehensive optical signal monitoring. It also provides the possibility of signal regeneration at each node.
An
optical add-drop multiplexer
An optical add-drop multiplexer (OADM) is a device used in wavelength-division multiplexing systems for multiplexing and routing different channels of light into or out of a single mode fiber (SMF). This is a type of optical node, which is ge ...
(OADM) can be viewed as a special case of an OXC, where to node degree is two.
See also
*
Optical switch An optical transistor, also known as an optical switch or a light valve, is a device that switches or amplifies optical signals. Light occurring on an optical transistor's input changes the intensity of light emitted from the transistor's output ...
*
Optical Carrier
Synchronous optical networking (SONET) and synchronous digital hierarchy (SDH) are standardized protocols that transfer multiple digital bit streams synchronously over optical fiber using lasers or highly coherent light from light-emitting diodes ...
*
MEMS
Microelectromechanical systems (MEMS), also written as micro-electro-mechanical systems (or microelectronic and microelectromechanical systems) and the related micromechatronics and microsystems constitute the technology of microscopic devices, ...
*
Digital access and cross-connect system
A digital cross-connect system (DCS or DXC) is a piece of circuit-switched network equipment, used in telecommunications networks, that allows lower-level TDM bit streams, such as DS0 bit streams, to be rearranged and interconnected among higher ...