What is an Optical Switch?
Optical Switch
is a switch that enables signals in optical fibers or integrated
optical circuits (IOCs) to be selectively switched from one circuit to
another in telecommunication. Away from telecom, 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).
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 effects, magneto-optic effects, 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 semiconductor optical
amplifiers, which are optoelectronic devices that can be used as optical
switches and be integrated with discrete or integrated microelectronic
circuits.
(
Reference: WIKIPEDIA)
Optical Switching Technology
Optical
switching technology as an important foundation for all-optical
communication network technology, its development and application will
greatly affect the development direction of future optical communication
networks. So, how does it work?
Optical signals are multiplexed
in three ways, space division, time division, and WDM. The corresponding
optical switching methods space division switching, time division
switching and wave division switching to complete the three multiplexed
channels.
Space Division Switching
It
is the domain swap space on the optical signal, the basic functional
components of the spatial light switch. Spatial light switch is the
principle of optical switching components gate array switch can be in
any of the multiple input multiple output fiber established path. It can
constitute an empty spectroscopic switching unit, and other types of
switches can also together constitute a time-division switching unit or
wave stars. Empty spectral switches generally have both fiber-based and
space-based space division switching is a division of swap space.
Time Division Switching
This
multiplexed signal multiplexing method is a communication network, a
channel is divided into a number of different time slots, each optical
path signal distribution occupy different time slots, a baseband channel
to fit the high-speed optical data stream transmission. Need to use
time division switching time slot interchange. The time slot
interchanger of the input signal is sequentially written to the optical
buffer, and then read out in accordance with established order, thus
achieving a one frame at any one time slot exchange to another time slot
and outputs completed the timing exchange program. Usually bistable
lasers can be used as an optical buffer, but it is only the bit output,
and can not meet the demand of high-speed switching and large capacity.
While the optical fiber delay line is a more time-division switching
device, the time-division-multiplexed signal light input to the optical
splitter, so that each of its output channels are only a light signal of
the same timeslot, then these signals combined through different
optical delay line, after a signal of the type of delay line to obtain a
different time delay, the final combination fits before the signals are
multiplexed with the original signal, thereby completing a
time-division switching.
Wave Division Switching
Ships
in WDM systems, the source and destination are required to transmit
signals using the same wavelength, such as non-multiplexed so
multiplexed in wavelength division multiplexing technology is widely
used in the optical transmission system, each multiplex terminal using
additional multiplexers, thus increasing system cost and complexity. In
the WDM system, wave spectral exchange in the intermediate transmission
nodes, to meet no additional devices to achieve wavelength division
multiplexing system source and destination communicate with each other,
and you can save system resources, improve resource utilization rate.
Wave spectroscopic switching system first lightwave signal demultiplexer
is divided into plural wave splitting is required to exchange the
wavelength channels in each channel wavelength switching the last signal
obtained after multiplexing composed of a dense wave division
multiplexing signal from an optical output, which take advantage of the
characteristics of the fiber-optic broadband, low-loss band multiplexing
multiple optical signals, greatly improving the utilization of the
Fiber Channel, to improve the communication system capacity.
There
are also hybrid switching technologies which are used in large-scale
communication network in a variety of the optical path switching
technology a mixture of multi-level link connection. In large-scale
networks need to be multi-channel signal splitter and then access
different link, making the advantages of wavelength division
multiplexing can not play, so using wavelength division multiplexing
technology levels connecting link, and then space division switching
technology used in all levels of link exchange to complete the interface
between the link, finally destination and then wave of the exchange of
technical output corresponding optical signals, signal combined final
sub output. Mixed-use switching technology time mixed, air separation -
after midnight - wavelength division mixed several minutes - hours of
mixing, air separation - wavelength division.
All-Optical Network Switching Technology
To
realize the all optical network switching, the first is to use the
circuit switch based optical add-drop multiplexing (OADM) and OXC
(optical cross connect) technology to achieve wavelength switching, and
then further realization of optical packed switching.
Wavelength
switching is based on wavelength in units of optical circuit switched
domain, wavelength switching optical signals to provide end-to-end
routing and wavelength assignment channel. Wavelength switching key is
to use the corresponding network node equipment, optical add-drop
multiplexing optical cross-connect. Optical add-drop multiplexing the
working principle is based on all-optical network nodes drop and insert
the required wavelength path. Its main constituent elements of the
multiplexer reconciliation multiplexer, as well as optical switches and
tunable harmonic, etc.. Optical add-drop multiplexing of the working
principle and the synchronous digital hierarchy (SDH) multiplexer
separate interpolation function is similar, but in the time domain,
while the other is acting in the optical domain. The optical
cross-connect and the synchronous digital system digital cross-connect
(DXC) similar effect, but to achieve the cross-connection to the passage
in the wavelength at which the optical network node.
Optical
wavelength to exchange essentially took office contingent is not
efficient optical switching, connection-oriented attribute it
established wavelength channel re-distribution to achieve maximum
utilization efficiency can not be achieved, even if the communication is
idle. Optical packet switching can be implemented with a minimum
switching granularity multiplexing of bandwidth resources, improve the
communication efficiency of the optical network. Optical packet
switching is generally light and transparent packet-switched (OTPS),
optical burst switching (OBS) and optical label switching (OMPLS). The
optical the transparent packet switching characteristics is the packet
length is fixed, the use of synchronous switching manner, the need for
all input packets are synchronized in time, thus increasing the
technical difficulty and increase the use of cost. The transmission
optical burst the use of a variable-length packet data transfer header
control information and separated in time and space, to overcome the
shortcomings of the synchronization time, but it is possible to generate
the packet loss problem. Optical label switching is carried out to add a
tag in the IP packet in the core network access re-packet, and the
routing method according to the tag inside the core network.
Although
optical switching communication occasion require a higher (generally
more than 10Gbps) is more suitable for lower transmission costs and
greater system capacity can be achieved; via digital transmission rate
when the system requirements require a lower transmission rate (2.5Gbps
or less), the connection configuration more flexible access may be more
appropriate to use the old-fashioned way of photoelectric conversion.
Therefore, the practical application of the current should be selected
according to the application scenarios appropriate system deployment.
With
the future communication network technology development and all-optical
network, optical switching technology will be more innovative and more
efficient ways for communication network photochemical contribute to
become an important part of social development and people's lives.
Types of Optical Switches
Optical switches can be divided into mechanical and non-mechanical ones according to the driving methods.
Mechanical
optical switch relies on the movement of optical fiber or optical
elements to convert the optical path, such as a mobile optical fiber
type, moving the sleeve to move the lens (including mirrors, prisms and
self-focusing lens) types. The biggest advantage of this kind of optical
switch is a low insertion loss and low crosstalk. Its disadvantage is
slow and easy to wear, easy to vibration, impact shocks.
Non-mechanical
optical switch relies electro-optic, magneto-optic, thermo-optic and
other effects to change the refractive index of the optical waveguide,
the optical path changes, such as electro-optic switch, magneto-optic
switch, and thermo-optic switch. This kind of optical switch has good
repeatability, fast switching speed, high reliability, long life and
other advantages, and small size, can be monolithically integrated. The
disadvantage is that the insertion loss and crosstalk performance is not
ideal, which should be improved.
Here are three common optical switches.
Opto-Mechanical Switch
Opto-mechanical
switch is the oldest type of optical switch and the most widely
deployed at the time. These devices achieve switching by moving fiber or
other bulk optic elements by means of stepper motors or relay arms.
This causes them to be relatively slow with switching times in the
10-100 ms range. They can achieve excellent reliability, insertion loss,
and crosstalk. Usually, opto-mechanical optical switches collimate the
optical beam from each input and output fiber and move these collimated
beams around inside the device. This allows for low optical loss, and
allows distance between the input and output fiber without deleterious
effects. These devices have more bulk compared to other alternatives,
although new micro-mechanical devices overcome this.
Thermo-Optic Switch
Thermo-optic
switches are normally based on waveguides made in polymers or silica.
For operation, they rely on the change of refractive index with
temperature created by a resistive heater placed above the waveguide.
Their slowness does not limit them in current applications.
Electro-Optic Switch
These
are typically semiconductor-based, and their operation depends on the
change of refractive index with electric field. This characteristic
makes them intrinsically high-speed devices with low power consumption.
However, neither the electro-optic nor thermo-optic optical switches can
yet match the insertion loss, backreflection, and long-term stability
of opto-mechanical optical switches. The latest technology incorporates
all-optical switches that can cross-connect fibers without translating
the signal into the electrical domain. This greatly increases switching
speed, allowing today's telcos and networks to increase data rates.
However, this technology is only now in development, and deployed
systems cost much more than systems that use traditional opto-mechanical
switches.
Optical Switch Protection System for DWDM Network Security
Optical
switch protection system for the security of communication network
provides a set of economic, practical solutions, the formation of a
non-blocking, high reliability, flexible, anti-disaster ability of the
optical communication network. Optical switch protection system by the
automatic switching and network management stations, you can achieve
light switch protection, monitoring and the optical path of the optical
power emergency dispatch three main functions.
DWDM system in
the trunk and local fiber optic transmission network has a large number
of applications. Due to the amount of traffic carried by focus on the
importance of safety more and more attention in the event of full
resistance will affect all business network hosted. The DWDM network
security has always been the most important in the transmission
maintenance work. However, DWDM protection technology by its own
limitations, has problems such as not flexible, large investment, and
the effect is not ideal. Then the optical switch protection
technology comes to play a very important role in the DWDM network
security.
The optical switch protection system
switching control module is a set of optical switches, optical power
monitoring, stable light source monitoring in one of the high level of
integration modules. Optical power monitoring module and optical switch
control module coordination, selection of splitting ratio of 97:3 is
more appropriate on the trunk, the equivalent of approximately 0.2dB
attenuation on the transmission line; optical switching module contains
1x2 or 2x2 optical switch, controlled by the switch between the main and
backup light routing operation.
Real-time
monitoring of the optical power monitoring module communication optical
fiber optical power value reported to the main control module; analysis
and comparison of the main control module, found that the change in
value of the optical power exceeds a preset threshold switching
immediately issued instructions to the optical switch module; optical
switch module by the Directive instantly switching action has occurred.
In order to achieve a switching operation.
The
optical path automatically switch protective equipment involved in trunk
transmission system did not affect the transmission characteristics. In
fact, switching equipment involved in the optical switch and splitter
only two passive optical devices.
One end of
the switching unit is connected to the transceiver of the transmission
system, the main fiber optic cable and the spare cable, respectively
connected to two output terminals of the 2x2 optical switch. When the
optical path occurs when the optical power is abnormal, the optical
switch is automatically switched to the alternate route.
It
is understood that the optical switch protection system has the
following advantages. Fast switching speed, the optical switch switching
speed ships 5ms, plus system analysis, the response time of a
single-ended switching time of less than 20ms, the switching time of
less than 50ms for the entire system, the basic switching operation can
be done without interrupting the communication, to achieve business
grade level of protection.
Switching, high
reliability, implemented through the optical power monitoring, to avoid
false alarm of the optical frame, ensure switched judgment is correct.
The spare fiber routing monitoring, to ensure the validity of the
switch, and continue to be monitored after switching optical path.
Emergency
dispatch function, simply switching command issued from the program,
you can deploy routing to facilitate the realization of the non-blocking
cutover and line maintenance work. The switch device for a transmission
system is transparent, i.e. the switching device does not require the
type of transmission system can use either SDH or DWDM.
The
optical switch protection DWDM is an economical and safe a line
protection method, but the the light automatic protection system
intervention to DWDM systems, there are many issues to consider.
Splitter 97:3 spectral, optical switching device insertion loss is about
2 dB intervention light switching device, the system has an additional
two-fiber jumper whose fiber insertion loss is estimated as 1 dB, so the
whole switching device Interventional theoretically maximum will bring
3dB attenuation, and many cases of practical use only in 1.5-2.5dB.
Optical
automatic switching system for the DWDM line protection is both safe
and economical means of protection. The future, as the size of the
network continues to expand, optical switch protection systems will play
a more important role to meet the requirements of the assessment
indicators, to improve the safety of operation of the transmission
network.
FiberStore's Optical Switch Solution
FiberStore's optical switches are based on Opto-Mechanical technology with proven reliability and available as
optical switch 1x1,
1x2, 2x2 Non-Latching, Latching, Single-mode, Multimode versions.
Besides these high performance Opto-Mechanical switch solutions, if you
want to buy the other types such as thermo-optic and electro-optic ones,
please contact the sales for special
Custom Service.
Available Configuration
1X1 Mechanical 1X2 Mechanical
1X4 Mechanical 1X8 Mechanical
1X16 Mechanical 2X2 Mechanical
2X2B Mechanical 2X2BA Mechanical
D1X2 Mechanical D2X2 Mechanical
D2X2B Mechanical
Available Mode
Single-mode
Multimode
Available Control Model
Latching
Non-lantching
1. LC Connector
2. MU Connector
3. E2000 Connector
4. MT-RJ Connector
