Brief Introduction to Optical Switch

The advent and development of fiber optic communication technology has brought a revolutionary change to the communications industry. Nowadays in the world, about 85% of communication services via optical fiber transmission, long haul network and local relay network has been widely using fiber optics.

Dense Wavelength Division Multiplexing (DWDM) technology development and maturation has opened up a vast space for the full application of the bandwidth and capacity of optical fiber transmission. With a high rate, large bandwidth obvious advantage, DWDM optical communication network has become the development of communication network trend. Especially in recent years, an IP-based Internet business explosive growth, this growth trend has not only changed the relationship between the IP network layer and the underlying transport network, and the networking of the entire network, the node design, management and control new requirements.

An intelligent network architecture – Automatic Switched Optical Network (ASON) has become a research hotspot of today’s systems. Its core node optical cross-connect (OXC). Constitute dynamic wavelength routing and optical network flexible and effective management can be realized by the OXC equipment. OXC technology is one of the key technologies increasingly complex DWDM network, optical switch for switching the optical path of functional devices, is a key part of the OXC. Optical switch matrix is ​​the core part of the OXC, it can achieve dynamic optical path management, optical network fault protection, wavelength dynamic allocation function, the solution to the current complex network of wavelength contention and improve the wavelength reuse, flexible configuration of the network are There is of great significance.

Optical switch is not only the core device in OXC, but also widely used in the following areas.

(1) Optical network protection switching system, the actual optical transmission system have left spare fibers when working channel transmission interruption or performance degradation to a certain extent, the main signal light switch automatically go to standby fiber system transmission, so that the receiving end received normal signal and feeling less than the network has a fault, the network nodes connected in a ring to further improve the survivability of the network.

(2) Real-time network performance monitoring system, remote fiber test points, 1 × N multi-channel optical switch, a plurality of optical fibers connected to the Optical Time Domain Reflectometer, real-time network monitoring, computer-controlled optical switch switching sequence and time to achieve the detection of all fiber, and test results are returned to the network control center, once found a road problems, can be processed directly in the network management center.

(3) The light switch is also used in optical fiber communication device testing system and metropolitan area networks, the poor access network/multiplexing and switching equipment. The introduction of the light switch in the future all-optical networks more flexible, intelligent, survivability. Optical switching technology has become the key to future optical networking, optical switching technology plays an increasingly important role in the field of communication, automatic control.

In many types of optical switches, MEMS optical switch is considered most likely to become the mainstream of the optical switch device. In this paper, an overview of the basis of the principle characteristics of a variety of optical switch on, the focus of several major MEMS optical switch, and outlined their structure and performance characteristics.

Production Process of Fiber Optic Splitter with Advantages and Disadvantages

Fiber optic splitter (optical splitter) is also known as “non-wavelength selective optical branching device”. It is a fiber optic device used to achieve a particular band optical signal power splitter and redistribution.
Optical splitter can be used as a stand-alone device in the OLT node, the light distribution point and the FTTH point. It can also be placed in the central office wiring facilities, the light distribution points and FTTH points within the facility (integrated design or plug-in).
In accordance with the production process, optical splitters are divided into Fused Bi-conical Taper (FBT Splitter) and Planar Lightwave Circuit (PLC Splitter).
FBT Splitter (FBT Coupler)
Fused Bi-conical Taper technique is tied to two or more fibers, and then melted in a cone machine, pull tensile and real-time monitoring of changes in splitting ratio, the splitting ratio to meet the requirements after the end of the melt stretching, and wherein one end of a fiber optic reserved ( The remaining cut off) as the input terminal and the other end a multitude of road outputs. Mature tapering process can only pull 1 × 4. 1 × 4 or more devices, with a plurality of 1 × 2 connected together. Then the overall package in the splitter box.
Advantages
(1) pull taper coupler over twenty years of history and experience, many equipment and processes simply follow the only development funds only a few of the PLC tenth or hundredth of a few
(2) Raw materials only readily available quartz substrate, fiber optics, heat shrink tubing, stainless steel pipe and less plastic, a total of not more than $ 1. Investment in machinery and equipment depreciation costs less, 1 × 2,1 × 4 and other low-channel splitter low cost.
(3) splitting ratio can be real-time monitoring, you can create unequal splitter.
Disadvantages
(1) Loss of light sensitive wavelength ships according to the wavelength selection device, in this triple-play during use is a fatal defect, since the triple play of light transmitted signal 1310nm, 1490nm, 1550nm, and other multiple-wavelength signal.
(2) poor uniformity, 1×4 nominal about 1.5dB away, 1 × 8 or more away from larger, can not ensure uniform spectroscopic, which may affect the overall transmission distance.
(3) Insertion loss varies with temperature variation is greater (TDL)
(4) multi-demultiplexer (e.g., 1 × 16,1 × 32) volume is relatively large, the reliability will be reduced, the installation space is restricted.
PLC Splitter
Planar waveguide technology is the optical waveguide branching device with a semiconductor production process. The branching function is completed on the chip. On one chip to achieve up to 1X32 splitter, then, at both ends of the chip package input terminal and an output terminal respectively coupled multi-
Channel optical fiber array.
Advantages
(1) The loss of transmission is not sensitive to the wavelength of light, to meet the transmission needs of different wavelengths.
(2) spectroscopic uniform signal can be uniformly allocated to the user.
(3) compact structure, small size, can be installed directly in the existing junction box, no special design leave a lot of space for installation.
(4) only a single device shunt channel can achieve much more than 32 channels. (5) The multi-channel, low cost, stars ones more and more obvious cost advantages.
Disadvantages
(1) Device complex production process, high technical threshold, the chip is several foreign companies to monopolize domestic bulk package production companies only Borch rarely several.
(2) relative to the higher cost of Fused Splitter more at a disadvantage, especially in the low channel splitter.
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Several Variable Optical Attenuator Introduction

Variable optical attenuator (VOA) has a wide range of applications in optical communication, and its main function is to reduce or control the optical signal.
The basic characteristics of fiber optic network should be Variable, especially with the application of DWDM transmission systems and EDFA in optical communication, it must be carried out in a plurality of optical signal on the transmission channel gain flattening or equalization, channel power in the optical receiver. The side to be dynamic saturation control, optical networks also need to control for other signals, making the VOA become indispensable key components. In addition, VOA also can be combined with other optical communication components and this pushed itself to the characteristics of the high-level module.
In recent years, there appeared many technologies on manufacture of variable optical attenuator, including mechanical VOA, magneto-optical VOA, LCD VOA, MEMS VOA, thermo-optic VOA and acousto-optic VOA.
Mechanical VOA
The principle is to use a stepper motor drag neutral gradient filter, its output optical power at a predetermined attenuation rule change when the different positions of the light beam passes through the filter, so as to achieve the purpose of adjusting the amount of attenuation. There is also a mechanical polarized optical attenuator. Its basic principle is that the light beam emitted from the ingress port reflected by the reflection sheet to the port, the the reflector coupling efficiency between the two ports by the inclination angle of the reflection sheet to the control, enabling adjustment of the light attenuation. The inclination of the reflection sheet from a variety of different mechanisms to control. Mechanical type optical attenuator is more traditional solutions, so far, the VOA application in the system most used mechanical method to achieve attenuation. The type of optical attenuator with mature technology, optical properties, low insertion loss, polarization dependent loss, without temperature control, etc.; disadvantage is that the larger, more complex structure components, the response rate is not high, it is difficult to automate the production is not conducive to integration.
Magneto-optical VOA
Magneto-optical VOA is the use of some of the substances in the magnetic field is shown by the changes in optical properties, such as magnetic rotation effect (Faraday effect) can also be achieved attenuation of the light energy, so as to achieve the purpose of adjusting the optical signal. The magneto-optical effect of the material and in combination with other techniques, you can create a high performance, small size, high response and the structure is relatively simple optical attenuator. This is LLL device using discrete technology to produce the optical attenuator to be a further development of the field.
LCD VOA
Utilizing a liquid crystal refractive index anisotropy in the liquid crystal VOA shows birefringence. When an external electric field is applied, the orientation of the liquid crystal molecules are rearranged, will result in the change in its transmission characteristics. The type of attenuation can be achieved by light intensity change of the type of voltage control is applied to the two electrodes in the liquid crystal. The liquid crystal optical attenuator VOA can achieve the miniaturization and high response. But at the same time the liquid crystal material into a larger loss, the production process is relatively more complex, in particular, is influenced by environmental factors, its advantage is a low cost, there are commercial batch.
MEMS VOA
MEMS is the technology of the new applications in this area, After several years of development, the MEMS chip production process has become more mature, a strong impetus to the application of the MEMS optical attenuator. Optical network applications, MEMS technology-based products also have the obvious advantage on price and performance. MEMS VOA has been very mature, and mass production and large-scale application. Because of yield problems, in terms of price also facing challenges In addition, micro-electro-mechanical components, reliability is sometimes less than ideal. The early MEMS VOA using laser welding, into a larger device, and the production efficiency is low, and high assembly costs. Currently, the market also introduced a MEMS VOA plastic technology, a good solution to this problem.
Thermo-optic VOA
Thermo-optic VOA mainly using some of the material changes in the optical properties of temperature field characteristics, such as temperature changes caused by the thermo-optical refractive index change. According to the structure of the different, can be divided into two categories, leak-and open-light type VOA. Thermo-optic VOA due to heating, cooling device is relatively complex, a function of the mathematical relationship between the temperature field photoconductive medium refractive index is complex and difficult to accurately quantify and control, especially the longer response time hindered its application in modern optical communication .
Acousto-optic VOA
The basic principle is to use the cyclical strain, resulting in a periodic variation of the refractive index, equal to create a phase grating for the acousto-optical crystal in the generated under the action of ultrasonic waves, and so can be modulated using the raster beam. Some companies have already claimed to have developed the acousto-optical crystal variable attenuator (called the AVOA). It is understood that the acquisition of the acousto-optic crystal material is no problem, but at this stage of the total cost is high, about 4-5.
Conclusion:
Variable optical attenuator is one of important optical devices in the optical communication system. Over the years, it has been stuck at a mechanical level. Because its size is not conducive to integration, it is generally only suitable for single-channel attenuation. With the development of DWDM system, as well as market the flexibility to upgrade reconfigurable optical add-drop multiplexer (ROADM) potentially huge demand, there need more channels and small size variable optical attenuator array, in particular the integrated VOA product. Traditional mechanical methods can not solve these problems. With the development of fiber optic network, VOAs development trends are: low cost, highly integrated, fast response time as well as integration of hybrid with other optical communication devices.
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Construct smarter fiber optic networks with ROADM technology

As IPTV, triple play, VoIP and other new telecommunications services rise, people find that IP-bearing agreement business has rapidly spread in most regions of telecommunications and fiber optic networks.
IP-based packet-based carrier network transformation has been become an irreversible trend. In this trend, carriers are shifting the entire network infrastructure, business anticipates the integration of optical layer integration as a foundation bearing layer, making it even more right for carrying IP/MPLS and Carrier Ethernet services group transmission network. The brand new telecom services in contrast to traditional telecom services, with increased dynamic and unpredictable, therefore have to transfer the bearer network to provide greater flexibility.
Because the same time, long-distance dense WDM mature, making the network a real business of building from the bandwidth bottleneck within the transfer to the bandwidth management, within the core network nodes, often need to deal with dozens or perhaps hundreds of wavelengths, but long-distance transmission capability and much more nodes must have more capacity to the upper minimizing wavelength. Like a basis for carrying the network inside a more competitive market environment, it needs to provide faster service and various amounts of network protection and recovery capabilities. Therefore, as the traditional physical layer of optical layer network, we must adjust to a brand new generation of packet-based bearer networks, operational, bandwidth, large granular, and dynamic networking needs.
DWDM is the most common optical layer networking technology. Through multiplexing/demultiplexing, it can achieve tens or perhaps countless wave wave transmission capacity. However in the current WDM systems, its nature is still a point-line system, most of the optical layer network only through the terminal station (TM) to achieve the optical line system construction. Later, Optical add-drop multiplexer (OADM) gradually taken point to point network to the ring from the evolution. However, due to the limited OADM functions, usually merely a fixed number of levels and wavelengths of sunshine channel, and never really flexible optical layer networking. Thus, in this way, early WDM systems do not achieve true optical layer networking, IP-based networks can not meet the business requirements and packet-based until the emergence of the situation was able to enhance the ROADM. To meet up with the needs of IP networks, it provides a new idea that gradually adopt a reconfigurable optical add drop multiplexer plug (ROADM), represented by optical layer reconfiguration technology, and in line with the construction of the bearer network.
ROADM Technical Introduction is really a similar SDHADM optical layer network element, which can be completed in one node down and up road of sunshine channels (Add/Drop), and penetrating between your optical channel wavelength-level cross-scheduling. It can be remotely controlled by software, network aspect in achieving the lower and upper road wavelength ROADM sub-system configuration and adjustment. Currently, ROADM subsystem, there are three common techniques: planar lightwave circuit (PLC), wavelength blocker (WB), wavelength selection switch (WSS).
PLC is among low-cost ROADM solution. The advantage is that multiplexer and demultiplexer technology is mature and reliable, low insertion loss within the node, down way more when costs are lower wavelength, simple to upgrade to the OXC; drawback is poor modular structure, the initial configuration and high cost, large capacity the longevity of cross matrix must be improved.
Physical factors as transmission, all-optical transmission distance is susceptible to certain restrictions, within the backbone network applications, the company flow and also the flow can not be any change, still need to accurately design and planning, increasing the complexity of network planning. Deutsche Telekom is also clear the physical limitations affecting ROADM transport network of important reasons.
Based on existing ROADM these shortcomings, the proposed to increase the cross-field power. So had a ROADM OTN equipment form. Typical applications are now, in excess of 10G (with 10G) business, the node all-optical way through or up and down, for GE/2.5G business, its first node towards the electric field under the road crossing panels, according to further 2.5G particles and electric field-drop multiplexing. This drop multiplexing mode somewhat similar to the ADM, just the first-class all-optical processing. Equipment manufacturers have previously released products, and in certain applications inside the metropolitan area.

Optical WDM in Fiber Optic Network

Optical WDM networks are networks that deploy optical wdm fiber links where each fiber link carries multiple wavelength channels.
An exciting Optical Network (AON) is definitely an optical wdm network which supplies end-to-end optical paths by using all optical nodes that allow optical signal in which to stay optical domain without conversion to electrical signal. AONs are often optical circuit-switched networks where circuits are switched by intermediate nodes in the granularity of the wavelength channel. Hence a circuit-switched AON can also be called a wavelength routing network where optical circuits are equal to wavelength channels.
A wavelength routing network includes optical cross-connect (OXC) and optical add-drop multiplexer (OADM) interconnected by WDM fibers. Transmission of information over this optical network is performed using optical circuit-switching connections, referred to as lightpaths. An OXC is definitely an N * N optical switch with N input fibers and N output fibers with every fiber carries wavelengths. The OXC can optically switch all the incoming wavelengths of its input fibers to the outgoing wavelengths of its output fibers. An OADM can terminate the signals on a quantity of wavelengths and inserts new signals in to these wavelengths. The rest of the wavelengths pass through the OADM transparently.
For a user to deliver data to some destination user, a circuit-switching connection is made by using a wavelength on each hop along the connection path. This unidirectional optical path is known as lightpath and also the node in between each hop is either an OXC or an OADM. These units are utilized within the 100G DWDM networks. A separate lightpath has to be established using different fibers to setup transmission within the opposite direction. To fulfill the wavelength continuity constraint, the same wavelength can be used on every hop along the lightpath. If a lightpath is blocked since the required wavelength is unavailable, a converter in an OXC can transform the optical signal transmitted in one wavelength to another wavelength.
Because the bandwidth of a wavelength is usually much larger than that requires by a single client, traffic glooming is used to allow the bandwidth of the lightpath to be shared by many people clients. The bandwidth of the lightpath is split into subrate units; clients can request one or more subrate units to carry traffic streams at lower rates. For instance, information is transmitted over an optical network using SONET (Synchronous Optical Network) framing with a transmission rate of OC-48 (2.488 Gbps). A lightpath is established from OXC1 to OXC3 through OXC2 using wavelength w, the subrate unit available on this lightpath is OC-3 (155 Mbps). A user on OXC1 can request any integer number of OC-3 subrate units up to a total of 16 to transmit data to another user on OXC3. A network operator can use traffic-groomed lightpaths to provide subrate transport services to the users with the addition of an online network towards the fiber optic network.
Information on a lightpath is typically transmitted using SONET framing. In the future, the data transmitted over optical network uses the brand new ITU-T G.709 standard, referred to as digital wrapper. In ITU-T, an optical network is referred to as the optical transport network (OTN). Listed here are some of the options that come with G.709 standard: 1) The conventional permits transmission of various kinds of traffic: IP packets and gigabit Ethernet frames using Generic Framing Procedure (GFP), ATM cells and SONET/SDH synchronous data. 2) It supports three bit rate granularities: 2.488 Gbps, 9.95 Gbps and 39.81 Gbps. 3) It offers capabilities to monitor an association on an end-to-end basis over several carriers, in addition to over a single carrier. 4) G.709 uses Forward Error Correction (FEC) to detect and correct bit errors brought on by physical impairments in the transmission links.
Lightpath may either be static or dynamic. Static lightpaths are in place using network management procedures and may remain up for a long time. Virtual Private Networks (VPN) could be set up using static lightpaths. Dynamic lightpaths are established instantly using signaling protocols, such as GMPLS (Generalized Multi-Protocol Label Switching) and UNI (User Network Interface) proposed by OIF (Optical Internetworking Forum). GMPLS is definitely an extension of MPLS and is built to apply MPLS label switching techniques to Time Division Multiplexing (TDM) networks and wavelength routing networks, in addition to packet switching networks. The OIF UNI specifies signaling procedures for clients to automatically create, delete and query an association over wavelength routing network. The UNI signaling is implemented by extending the label distribution protocols, LDP and RSVP-TE.

Basic Common Sense Resolution of Fiber Optic Transceivers

Fiber optic transceiver is an indispensable network data transmission equipment. What is fiber optic transceiver? What is the structure of fiber optic transceivers? What is the role of fiber optic transceivers in the data dissemination process?
Fiber optic transceiver includes three basic functional modules: optical media converter chip, the optical signal interface (optical transceiver module) and the electrical signal interface (RJ45), with network management functions include network management information processing unit.
Fiber optic transceiver is a short distance twisted pair electrical signals and optical signals over long distances to swap the Ethernet transmission media conversion unit, in many places, also known as Fiber Converter. Products in generic applications can not be covered in the Ethernet cable, you must use the fiber to extend the transmission distance of the actual network environment, and is usually located in the broadband metropolitan area network access layer applications; in helping the fiber last mile connections to the metro also played a huge role in the network and the outer layer of the network.
Used directly in some of the larger companies, network construction fiber-optic backbone network established for the transmission medium, the internal LAN transmission medium is usually copper. How to implement LAN and connected to the fiber optic backbone? This requires different ports, different linear, convert between different fiber and ensure the quality of the link. The emergence of fiber optic transceivers, conversion between twisted pair electrical signals and optical signals to ensure the smooth transmission of data packets between two networks at the same time it will network transmission distance limit extended to more than 100 kilometers from the copper wire 100 meters ( single-mode fiber).
What are the basic features of fiber optic transceiver:
1. It is completely transparent to the network protocol.
2. Ultra low-latency data transmission.
3. It supports a wide operating temperature range.
4. Using a dedicated ASIC chip data wire-speed forwarding. The programmable ASIC will focus on the multiple functions onto a single chip, has the advantages of simple design, high reliability, low power consumption, enabling the machine to get higher performance and lower cost.
5. Network management equipment to provide network diagnostics, upgrades, status reports, exception reports and control functions, provide a complete operation log and alarm log.
6. Rack equipment can provide hot-swap function, ease of maintenance and uninterrupted upgrade.
7. Support a full range of transmission distance (from 0 to 120 km).
8. Equipment 1 +1 power supply design, support for ultra-wide supply voltage, power protection and automatic switching.
Fiber transceiver classification:
There are many types of fiber optic transceivers. In WDM system, for example, there are CWDM and DWDM transceivers including CWDM SFP, DWDM SFP, CWDM SFP+, DWDM SFP+, CWDM GBIC, CWDM XFP, DWDM XFP, CWDM X2, DWDM X2, CWDM XENPAK, and DWDM XENPAK.
FiberStore provides a full range of optical transceivers, such as SFP+ (SFP Plus) transceiver, X2 transceiver, XENPAK transceiver, XFP transceiver, SFP (Mini GBIC) transceiver, GBIC transceiver, CWDM/DWDM transceiver, and PON transceiver. All our fiber transceivers are 100% compatible with major brands like Cisco, HP, Juniper, Nortel, Force10, D-link, 3Com. They are backed by a lifetime warranty, and you can buy with confidence. We also can customize optical transceivers to fit your specific requirements.

PLC Splitter Production and Packaging

With the recovery of optical fiber communication industry and the development of FTTX, the spring of fiber optic splitter market is coming.

There are two types of optical splitter, which are Fused fiber splitter and PLC splitter. PLC splitter is a hot research today, with a good prospect of application. PLC splitter package, however, is the difficulty in manufacturing.

The PLC splitter Package refers to the planar waveguide splitter on the light guide path (waveguide) with the fiber in the fiber array aligned one by one, and then stick with specific adhesive (such as epoxy glue) together with the technology. Wherein the alignment accuracy of the PLC splitter and an optical fiber array is the key technology. PLC splitter package involves a six-dimensional optical fiber array and optical waveguides in close alignment difficult. When the manual, the drawback is the low efficiency, poor reproducibility, human factors and is difficult to achieve large-scale production.

PLC splitter Production
PLC splitter using semiconductor technology (lithography, etching, developing technology) production. Multi-channel optical fiber array and the optical waveguide array is located on the upper surface of the chip, branching function is integrated on-chip is a chip on the splitter 1,1; Then, the ends of the chip, respectively coupling the input terminal and an output terminal package.

Compared with Fused Splitter, PLC splitter has these advantages: (1) loss wavelength is not sensitive to light, to meet the different wavelengths of the transmission needs. (2) spectroscopic uniform signal can be uniformly allocated to the user. (3) compact structure, small size, can be installed directly in the various existing junction box, without leaving a lot of space for installation. (4) only a single device shunt channel can achieve much more than 32 channels. (5) The multi-channel, low cost, stars ones more and more obvious cost advantages.

At the same time, the main drawback of the PLC splitter: (1) device fabrication process complexity, high technical threshold, the chip by several foreign companies to monopolize the domestic bulk package produced by very few companies. (2) relative to the higher cost of Fused Splitter more at a disadvantage, especially in the low channel splitter.

PLC splitter Packaging Technology
PLC splitter package process includes coupling alignment and bonding operations. Coupling of the PLC splitter chip and the optical fiber array is aligned with both manual and automated, and they depend on the hardware with the six-dimensional precision trimming frame, the light source, power meter, microscopic observation system, while the most commonly used are self-aligned , it is through the optical power feedback closed-loop control is formed, and therefore high coupling efficiency docking accuracy and docking.

PLC splitter has 8 channels and each channel must be accurately aligned to ensure that the relative position between the respective channels due to the manufacturing process of the waveguide chip and an optical fiber array (FA), so only the PLC splitter and the first channel of the FA and 8-channel simultaneous alignment can ensure that other channel aligned, thus reducing the complexity of the package. The most important in the packaging operation at the technical difficulty is the highest coupling alignment operation, it comprises two steps First Harmonic precise alignment. First tune the purpose is to enable the waveguide to light through; the purpose of precise alignment is precise positioning of the completion of the preferred optical power of the coupling point, and it is realized by the program to search the maximum optical power.

Multiplexer and Demultiplexer Based on CWDM

Before the introduction of CWDM multiplexer, it is necessary to mention the CWDM technology.
Originally, the term “coarse wavelength division multiplexing” (CWDM) was fairly generic, and meant a number of different things. In general, these things shared the fact that the choice of channel spacings and frequency stability was such that erbium-doped fiber amplifier (EDFA) could not be utilized. Prior to the relatively recent ITU standardization of the term, one common meaning for CWDM meant two (or possibly more) signals multiplexed onto a single fiber, where one signal was in the 1550 nm band, and the other in the 1310 nm band.
CWDM multiplexer is based on CWDM technology. It is a device to allow multiple optical signals at different wavelengths to pass through a single optical fiber strand. For convenience, we usually used “Mux” instead of “multiplexer” , and “Demux” instead of “deultiplexer”.
Typically, Multiplexer and Deultiplexer (Mux and Demux) are integrated in a entirety. CWDM Mux/Demux modules have 2/4/8/16/18 channels commonly, while 5/9 channels uncommonly. In FiberStore, we supply all channel CWDM Mux and Demux. Three single fiber or dual fiber connection for CWDM Mux/Demux are available. Our standard CWDM Mux/Demux package types are Plastic ABS module cassette, 19″ rack mountable box or LGX box. No matter what kind of connectors, like FC, ST, SC, LC, etc., all are available here, and we can also mix connectors on one device.
To know more about the CWDM Mux products, let me introduce one of the CWDM Mux/Demux modules to you. Here is a 18 Channels CWDM Mux and Demux by dual fiber with LGX Metal Box.
Key Features
1.Flexibility and little LGX Standard Metal Box configuration
2.Mux and Demux combined in one LGX Metal Box
3.Compliant to ITU-T G.694.2 CWDM standard
4.Accepts any data rate and any protocol on any port up to 10 Gbps, also 40 Gbps (DPSK, DQPSK) and 100 Gbps (DPQPSK)
5.Fully transparent at all data rates and protocols from T1 to 40 Gbps Completely passive, no power supply needed
6.Simple to install, requires no configuration or maintenance
8.Low-cost transceivers applicable, existing equipment can still be used ISO 9001 manufacturing facility
9.Lifetime Product Warranty
Applications

All Enterprises and Carrier with Fiber Optic Infrastructure Transmit additional applications via existing lines Connect buildings to CWDM campus ring Connect Field offices to central office Ideal solution for metro-core, metro-access and enterprises

Sample pictures



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Filter-based Wavelength Division Multiplexer

Filter-based Wavelength Division Multiplexer (Filter WDM, or FWDM) is based on the mature membrane filter technology, with a wide channel bandwidth, low insertion loss, high channel isolation degrees and high environmental stability and reliability. It is widely used in single-mode fiber optic communication systems and DFA.
FTTX Filter WDM module is based on Thin Film Filter (TFF) technology. The Filter-Based WDM is extensively used in EDFA, Raman amplifiers, WDM networks and fiber optics instrumentation. The FWDM series is based on environmentally stable Thin Film Filters technology. The device combines or separates light at different wavelengths in a wide wavelength range. They offer very low insertion loss, low polarization dependence, high isolation and excellent environmental stability. In FiberStore, Filter-Based WDM product family covers following wavelength windows commonly used in optical fiber systems: 1310/1550nm (for WDM or DWDM optical communications), 1480/1550nm (for high-power DWDM optical amplifier and EDFA), 1510/1550nm (for DWDM multi-channel optical networks) and 980/1550nm (for high performance DWDM optical amplifier and EDFA) and 1310/1490/1550nm (for PON, FTTX and test instrument).
1310/1490/1550 FTTX FWDM is based on filter based platform for optical device. This multiplexer features ultra low loss, high isolation, and high reliability.
FiberStore 1490/1310/1550nm FTTH FWDM can realize the multiplexing and de-multiplexing of two communication signal 1490/1310 and 1550nm. It can expand the capacity of a single fiber to achieve bidirectional communication, so that widely used in optical network upgrade and expansion, or introduce new comprehensive business etc.
As you might know, GEPON system itself works on 1310/1490, so CATV signal here is delivered over same fiber using 1550nm, and FWDM is a place where all this get’s “mixed”.
Application

Mechanical Drawing

Sample Pictures

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Optical add-drop multiplexer Wikipedia

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 generally used for the construction of optical telecommunications networks. “Add” and “drop” here refer to the capability of the device to add one or more new wavelength channels to an existing multi-wavelength WDM signal, and/or to drop (remove) one or more channels, passing those signals to another network path. An OADM may be considered to be a specific type of optical cross-connect.
A traditional OADM consists of three stages: an optical demultiplexer, an optical multiplexer, and between them a method of reconfiguring the paths between the optical demultiplexer, the optical multiplexer and a set of ports for adding and dropping signals. The optical demultiplexer separates wavelengths in an input fiber onto ports. The reconfiguration can be achieved by a fiber patch panel or by optical switches which direct the wavelengths to the optical multiplexer or to drop ports. The optical multiplexer multiplexes the wavelength channels that are to continue on from demultipexer ports with those from the add ports, onto a single output fiber.
All the light paths that directly pass an OADM are termed cut-through lightpaths, while those that are added or dropped at the OADM node are termed added/dropped lightpaths. An OADM with remotely reconfigurable optical switches (for example 1×2) in the middle stage is called a reconfigurable OADM (ROADM). Ones without this feature are known as fixed OADMs. While the term OADM applies to both types, it is often used interchangeably with ROADM.
Physically, there are several ways to realize an OADM. There are a variety of multiplexer and demultiplexer technologies including thin film filters, fiber Bragg gratings with optical circulators, free space grating devices and integrated planar arrayed waveguide gratings. The switching or reconfiguration functions range from the manual fiber patch panel to a variety of switching technologies including microelectromechanical systems (MEMS), liquid crystal and thermo-optic switches in planar waveguide circuits.
Although both have add/drop functionality, OADMs are distinct from add-drop multiplexers. The former function in the photonic domain under wavelength-division multiplexing, while the latter are implicitly considered to function in the traditional SONET/SDH networks.
Article source : Wikipedia.org

Optical attenuator Wikipedia

An optical attenuator is a device used to reduce the power level of an optical signal, either in free space or in an optical fiber. The basic types of optical attenuators are fixed, step-wise variable, and continuously variable.
Applications
Fiber optic attenuator is used in applications where the optical signal is too strong and needs to be reduced. Optical attenuators are commonly used in fiber optic communications, either to test power level margins by temporarily adding a calibrated amount of signal loss, or installed permanently to properly match transmitter and receiver levels.
For example, in a multi-wavelength fiber optic system, you need to equalize the optical channel strength so that all the channels have similar power levels. This means to reduce stronger channels’ powers to match lower power channels. Another example is when the received optical power is so strong that it saturates the receiver, you need an optical attenuator to reduce the power so the receiver can detect the signal correctly.
Fiber optic attenuators are usually used in two scenarios. The first case is in fiber optic power level testing. Optical attenuators are used to temporarily add a calibrated amount of signal loss in order to test the power level margins in a fiber optic communication system. In the second case, optical attenuators are permanently installed in a fiber optic communication link to properly match transmitter and receiver optical signal levels.
Optical attenuators are typically classified as fixed or variable optical attenuator.
Fixed optical attenuators used in fiber optic systems may use a variety of principles for their functioning. Preferred attenuators use either doped fibers, or mis-aligned splices, since both of these are reliable and inexpensive. Inline style attenuators are incorporated into patch cables. The alternative build out style attenuator is a small male-female adapter that can be added on to other cables.
Variable optical attenuators generally use a variable neutral density filter. Despite relatively high cost, this arrangement has the advantages of being stable, wavelength insensitive, mode insensitive, and offering a large dynamic range. Other schemes such as LCD, variable air gap etc. have been tried over the years, but with limited success.
For precise testing purposes, engineers have also designed instrument type variable optical attenuators. They have high attenuation ranges, such as from 0.5 dB to 70dB. They also have very fine resolution, such as 0.01dB. This is critical for accurate testing.
Variable optical attenuator instrument calibration is a major issue. The user typically would like an absolute port to port calibration. Also, calibration should usually be at a number of wavelengths and power levels, since the device is not always linear. However a number of instruments do not in fact offer these basic features, presumably in an attempt to reduce cost. The most accurate variable attenuator instruments have thousands of calibration points, resulting in excellent overall accuracy in use.

Erbium-doped Fiber Amplifier

Optical amplifier is an optical communication system device. It amplifies an optical signal directly, without converting an optical signal into an electrical signal.
Erbium-doped fiber amplifier (EDFA) is the first successful optical amplifier invented by the UK Southampton University and JP Tohoku University. It is one of the greatest invention in optical communication. Erbium-doped optical fiber is incorporated a small amount of a rare earth element erbium (Er) ion. It is the core of the EDFA. From the late 1980s, the EDFA research has been making a major breakthrough continuously. As WDM technology greatly increases the capacity of optical communication, it becomes the most widely used optical amplifier device in the optical fiber communication.
Principle
EDFA is constituted by a period of erbium-doped fiber (about 10-30m) and pump light source. The stimulated emission of erbium-doped fiber under the action of the pump light source (wavelength 980nm or 1480nm), and the radiation of light varies with the change of the input optical signal, which is equivalent to the input optical signal the amplification. Studies have shown that the erbium-doped fiber amplifiers are typically 15-40dB of gain can be obtained, and the distance relay can be increased on the basis of the original more than 100km. So, why did scientists use erbium-doped fiber element to increase the intensity of light? We know that erbium is a kind of rare earth elements, and rare earth elements has its special structural features. Over the years, people have been using the method which doped rare earth elements in optical devices to improve the performance of optics, so this is not an accidental factor. In addition, why is the pump source wavelength chosen from 980nm or 1480nm? In fact, the pumping light source wavelength could be 520 nm, 650nm, 980nm and 1480nm. But the practice has proved that the 1480nm wavelength pumping light source laser efficiency is the highest, followed by the 980nm wavelength.
Advantages
The main advantage of EDFA is a high gain, wide bandwidth, high output power, high pumping efficiency, low insertion loss, and not sensitive to the polarization state.
1. Its amplifying area happens to coincide with the minimum loss area of single-mode fiber. This reduces the transmission loss of the light signal which can be transmitted relatively far distance.
2. It is transparent to digital signal format and data rate.
3. Its amplification bandwidth is so wide that dozens or even hundreds of channels can be transmitted in the same fiber.
4. It has low noise figure close to the quantum limit, which means that multiple amplifiers can be cascaded.
5. Its gain saturation recovery time is long, and has a very small crosstalk between the respective channels.
Applications
When EDFA is used in conventional optical digital communication system applications, we can save a lot of optical repeaters, and the distance relay could also be increased significantly, which is of great significance for the long-haul fiber optic cable trunking systems.
The main applications include:
1. It can be used as the light distance amplifier. Traditional electronic fiber optic repeater has many limitations. Such as a digital signal and the analog signal conversion, the repeater should be changed accordingly; repeater changes after the device is changed from a low rate to a high rate; only transmit the same wavelength of the optical signal, and the complex structure, expensive, and so on. Erbium-doped fiber amplifier to overcome these shortcomings, not only do not have to change with the change in the way of the signal, and equipment expansion or for optical wavelength division multiplexing, no need to replace.
2. It can be used for the transmitter amplifier and the optical receiver preamplifier. For the rear of the optical transmitter amplifier, the transmit power of the laser is increased from 0dB to +10 db. Optical receiver preamplifier, the sensitivity can also be greatly improved. Therefore, only the line of 1-2 erbium-doped amplifier, the signal transmission distance can be increased to 100-200km. In addition, the erbium-doped fiber amplifier problem to be solved the unique advantages of the erbium-doped fiber amplifier has been recognized by the world, and to be more widely used. However, the erbium-doped fiber amplifier there are also some limitations. For example, in the long-distance communication can not drop channel, each station business contacts is more difficult, not easy to find fault, pumping light source life is not long, as the optical fiber communication technology continues to progress, these problems will be satisfactorily resolved.