Our cloud OTDR trace viewer helps you analyze OTDR traces even better.

by Fiber-MART.COM

A new updated version of the fiber-mart.com Cloud online service has finally been released. It took longer than usual, because this version is packed with new features to analyze OTDR traces, and other possibilities.

 

Thanks to feedback from our customers, we could significantly improve the overall process of analyzing OTDR traces, making it faster, more accurate, and more valid. Just have a look at the impressive list below:

 

 Now you can enter parameters of your real OTDRs into the repository of our cloud OTDR trace viewer, or you can create virtual OTDRs for analyzing your traces, with OTDR parameters like dynamic range, dead zone, serial number, etc. That is the way many of our customers keep track of their available OTDRs and try new ones. With this feature you can also run efficient simulated testing of virtual networks (see the next item).

 

More versatile networks can be created in the cloud, with a library of parameters to choose, for various fibers and connectors available to simulate online analysis. You can instantly apply parameters of single-mode and multimode optical fibers from Corning Inc., as well as characteristics of different fiber connector types (APC and UPC). The data are already in the cloud repository for you, so you can save time entering them. But if you need to correct the fiber network parameters manually, you can still do it.

 

You can see the OTDR trace overview in the new Summary tab, which shows the total loss, the total distance, and the specified section parameters for your optical fiber.

 

Improved analysis of fiber sections with 2 or more close events. Feedback from our customers shows that there may be cases when 2 or more events get too close for the usual 5PT mode to be efficient, because here the loss measurement error gets too high. For such cases fiber-mart.com Cloud now has a new 3PT mode with no approximation, which produces significantly better results.

 

The improved Reporting feature gives you more opportunities to view and analyze your OTDR traces, and include the results in official documents. Following our customers’ feedback, we completely redesigned our OTDR trace viewer template system for reporting. Now you can create an MS Excel template for your specific needs and then upload it to your fiber-mart.com Cloud account. Then you just select the files to be included in your report, and choose the necessary template. The data from the files selected are applied to the template, and our cloud OTDR trace viewer generates a report for you.

 

fiber-mart.com Cloud expands your equipment compatibility, and sometimes even makes it up for slips of others. If you work long enough in OTDR trace analysis, you know that more often than not the .sor format has variations not compatible with some software. Our cloud OTDR trace viewer is one of the most compatible application on the market. Besides, recently one major OTDR producer, released a buggy software application which actually saved traces in its own proprietary format inaccessible to other equipment, while keeping the .sor extension. If you try to analyze such a file, our OTDR trace viewer warns you about it, so you know why you have a problem.

40CH DWDM Mux Insertion Loss Testing

by Fiber-MART.COM

DWDM, which can add great capacity of bandwidth for long haul backbone data center by multiplexing different wavelengths into one fiber, is one of the dominant technology used in various applications. When purchasing a DWDM Mux Demux, one of the vital parameters that need to be considered is the insertion loss. Higher insertion loss means more investment in DWDM network deployment. This post focuses on the insertion loss testing of 40CH DWDM Mux to offer some help for your DWDM Mux Demux purchase.

 

Understand DWDM Mux Insertion Loss

As its name shows, insertion loss is the total optical power loss (often measured by dB) caused by the insertion of an optical component. Any component in a fiber optic interconnection will introduce loss definitely. For example, insertion loss of a connector or splice is the difference in power that we can see when inserting the component into the system. The insertion loss is affected by the fiber core meter on the transmit and receive end, as well as the receive conditions in two joint fibers.

 

In a completed network, the total loss comes not only from the optical connectors, but also from optical cables and the diverse ports of optical components inserted. As we all know, there are several types port on 40CH DWDM Mux Demux: line port, channel port and monitor port, some Muxes may have other function ports like 1310nm port, 1510nm port and expansion port. No matter which type of ports is connected to a DWDM system, some insertion loss occurs. Therefore, in order to ensure good performance of a whole DWDM optical link, a high quality DWDM Mux Demux should have a reasonable insertion loss value.

 

Insertion Loss Comparison in Different Vendors

If you are familiar with DWDM Mux Demux, you may know how great impact the insertion loss of them has on the whole network links. The higher the DWDM channel insertion loss is, the more cost may be needed, for optical amplifiers are required to keep a balance signal power in the link. And there are many vendors and suppliers of 40CH DWDM Mux in the market. Here is a graph showing the maximum insertion loss value of 40CH DWDM Mux of different vendors.

 

In a DWDM networks, the budget loss mainly comes from optical fiber path loss, DWDM OADM and Mux/Demux. If the loss of them is high, the network deployment cost will get higher certainly. In this graph, the vertical axis stands for the max insertion loss, and the horizontal axis shows several DWDM Mux vendors or suppliers like Cisco, Finisar, MRV, fiber-mart.COM, etc. From this comparison, we can see all the max insertion loss of 40CH DWDM Mux are not very high. The max insertion loss of MRV is 7.5dB, Cisco is 6.5dB and Finisar is 5dB. But compared with these vendors or suppliers, fiber-mart.COM 40CH DWDM Mux has the lowest max insertion loss—4.5dB. Besides, the typical insertion loss of fiber-mart.COM 40CH DWDM Mux is only 3dB. All these indicate that fiber-mart.COM 40CH DWDM Mux is perfect for long haul DWDM transmission.

 

How to Do Insertion Loss Testing for 40CH DWDM Mux Demux

Since insertion loss has profound influence on the whole optical networks, knowing how to test the insertion loss of 40CH DWDM Mux Demux is important. And the testing can be finished with an optical power meter if no professional equipment is available. Here offers a video to illustrate the insertion loss testing of our 40CH DWDM Mux, which uses Cisco Catalyst 4948E switch and our Cisco C25 compatible 10G DWDM SFP+ and C60 DWDM SFP+ modules that support 80km as light sources. This testing just takes channel 25 port and channel 60 port as examples to explain the testing method.

 

Summary

High quality, low insertion loss 40CH DWDM Muxs can not only manage bandwidth and expand capacity of existing optical backbones, but also save cost in DWDM network design. fiber-mart.COM 40CH DWDM Mux is a high density, low insertion loss passive modules, providing an ideal solution for DWDM networks. Custom services are also available. If you are interested, welcome to visit our website www.fiber-mart.com or contact us via sales@fiber-mart.com for more detailed information.

Name Brands vs Third-Party Transceivers: Which Do You Prefer?

by Fiber-MART.COM

You may have a name brand network switch or a name brand router, but it doesn’t mean that you need to pay an expensive cost on name brand transceivers. Though many people still get confused on “third-party transceivers”, there is no doubt that the emergence of third-party transceivers really offers a more cost-effective option to users. Name brands or third-party, which do you prefer? After reading this paper, you can make a decision.

 

What Does “Third-Party” Mean?

First of all, you should know that third-party suppliers exist in all sorts of industries and are typically companies that have a high degree of specialization in their field. “Third party” as a concept comes up most often in technical areas.

 

For example, software developers create programs that can be used on platforms created by another company, and often do so to fill a niche users may need but the platform developer cannot or will not address. A quick look at that description will also give you the basis for the term “third party”. It’s not the platform or OEM (original equipment manufacturers) (first party), or the user (second party), but another (third party) developer that brings a solution to the marketplace. Seems simple enough, right?

 

Some of the confusion arises in the telecom/datacom industry, where there are OEMs that really aren’t manufacturing anything. But rather, these OEMs have things built for them under contract by ODMs (original design manufacturers), and then “integrate” this solution under their own brand name. Then there are OEMs who continue to supply components to other OEMs, while establishing a brand of their own. They can also be considered third party for other OEMs, if they’ve not explicitly been brought into the fold as a vendor to that OEM. It is not quite so simple anymore when “third-party” are introduced to telecom / datacom industry. Thus, many users feel strange to third-party components, and are lack of confidence in them.

 

Name Brands vs Third Party Transceivers

If you still don’t understand what third-party means, now let us come back to our familiar environment, talking about the transceivers. All fiber optic transceivers have established Multi-Source Agreements (MSAs). These MSAs clearly define how fiber optic networking equipment is to function and establish de facto manufacturing standards that ensure networking components developed by different manufacturers are interoperable.

 

As long as a manufacturer complies to MSA guidelines, their transceiver modules will function and operate identically to any other manufacturer’s MSA-compliant transceivers. For example, fiber-mart’s 100% MSA compliant GLC-SX-MM transceiver will function identically to a Cisco brand GLC-SX-MM transceiver and will be 100% compatible with Cisco networking equipment.

 

So, how about the name brand transceiver? Why do they cost so much? Actually, the switch and router manufacturers do not build their own transceivers. Also take Cisco for example, they resell someone else’s. As described above, they have them built under contract by ODMs. The reason why Cisco transceivers are more expensive is because they have actually tested the transceivers they offer with their equipment to verify it works. Also they have revision control over the transceivers they sell so that if something were to change on the transceiver it would trigger them to retest it. Moreover, Cisco isn’t in the business of giving stuff away, so they mark up the price of the transceivers to cover their costs (to test/procure/stock etc.) and make a profit. In addition, many name brand vendors outsource the manufacturing of their OEM components to the exact same contract manufacturers used by third party vendors. So the source, quality, parts, and programming are exactly the same—only the labels and cost to the consumer are different.

 

Many users give their feedback on third-party transceivers. They say their third-party cannot work well one their name brand switch. Why? Switch and router manufacturers such as Cisco, HP ect. have set the encryption key which forbid the third-party transceivers to plug in their device. Thus, when you plug a third-party transceiver into the device, you’ll quickly stumble across an error warning. In fact, this is not a problem, because some hidden commands or 100% compatibility technology developed by some vendors can solve this problem.

 

Third Party Transceivers: An Ideal Solution

In fact, in addition to the low cost, there are many benefits of third-party transceivers. The following five obvious and proven reasons tell you why third-party transceivers are an ideal solution for your project.

 

Cost savings

Typically third-party transceivers cost substantially less than—sometimes up to 90 percent less — already discounted transceivers from OEM providers.

 

In-stock Availability

Since selling transceivers is the primary business for most third-party transceiver companies, most strive for immediate availability of product.

 

Carrier-Grade Quality

Some companies use the exact same ODMs the major switch OEMs use. However, since optical transceivers are the primary business for some third-party transceiver companies, they may understand which ODMs provide the highest quality part for a given data rate or transport protocol. It is not inconceivable for some third-party optics companies to provide more reliable components than those offered by the major switch OEM companies.

Reduced Inventory Cost Due To Interoperability

By definition third-party providers of optical transceivers are not tied to a specific switch or router platform. Therefore, their optics will typically interoperate across multiple platforms. This means one specific inventoried part number can be used in both a Cisco switch and a Juniper switch, as an example. Thus, this approach effectively reduces sparing inventory as well as the operational headaches associated with maintaining inventories for each switch platform.

Access to Innovative Optics

Third-party providers tend to have a much broader variety of pluggable optics from which to select. This can range from 10G Ethernet single fiber SFP+ or XFP optics to 120km XFP optics, as an example.

 

 

fiber-mart offers a variety of fiber optic transceivers at very economical prices which can satisfy your requirements from 1G to 100G Ethernet. In addition, we have a large inventory of the commonly used SFP optics, fixed-channel DWDM SFP+ optics, and whole seires of 40GBASE QSFP+ optics. So, why pay more for a name, when you can get the same high-quality, MSA compliant, 100% OEM compatible and in-stock transceivers from fiber-mart for a fraction of the cost?

What is DWDM and Why is it Important?

It has been almost 20 years since DWDM came on the scene with Ciena’s introduction of a 16 channel system in March of 1996, and in the last two decades it has revolutionized the transmission of information over long distances.  DWDM is so ubiquitous that we often forget that there was a time when it did not exist and when accessing information from the other side of the globe was expensive and slow.  Now we think nothing of downloading a movie or placing an IP call across oceans and continents.  Current systems typically have 96 channels per optical fiber, each of which can run at 100Gbps, compared to the 2.5Gbps per channel in the initial systems.  All of this got me thinking about how it often takes two innovations coupled together to make a revolution.  Personal computers did not revolutionize office life until they were coupled with laser printers.  Similarly, the benefits of DWDM were enormous because of erbium doped fiber amplifiers (EDFAs).

DWDM stands for Dense Wavelength Division Multiplexing, which is a complex way of saying that, since photons do not interact with one another (at least not much) different signals on different wavelengths of light can be combined onto a single fiber, transmitted to the other end, separated and detected independently, thus increasing the carrying capacity of the fiber by the number of channels present.  In fact non-Dense, plain old WDM, had been in use for some time with 2, 3 or 4 channels in specialized circumstances.  There was nothing particularly difficult about building a basic DWDM system.  The technology initially used to combine and separate the wavelengths was thin film interference filters which had been developed to a high degree in the 19th Century.  (Now a ’days photonic integrated circuits called Arrayed Waveguide Gratings, or AWGs are used to perform this function.)  But until the advent of EDFAs there was not much benefit to be had from DWDM.

Fiber optic data transmission began in the 1970s with the discovery that certain glasses had very low optical loss in the near infrared spectral region, and that these glasses could be formed into fibers which would guide the light from one end to the other, keeping it confined and delivering it intact, although reduced by loss and dispersion.  With much development of fibers, lasers and detectors, systems were built which could transmit optical information for 80km before it was necessary to “regenerate” the signal.  Regeneration involved detecting the light, using an electronic digital circuit to reconstruct the information and then retransmitting it on another laser.  80km was much farther than the current “line of sight” microwave transmission systems could go, and fiber optic transmission was adopted on a wide scale.  Although 80 km was a significant improvement, it still meant a lot of regeneration circuits would be needed between LA and New York.  With one regeneration circuit needed per channel every 80 km, regeneration became the limiting factor in optical transmission and DWDM was not very practicable.  The then expensive filters would have to be used every 80 km to separate the light for each channel before regeneration and to recombine the channels after regeneration.

Since full regeneration was expensive, researchers began to look for other ways to extend the reach of an optical fiber transmission system.  In the late 1980s Erbuim Doped Fiber Amplifers (EDFAs) came on the scene.  EDFAs consisted of optical fiber doped with Erbium atoms which, when pumped with a laser of a different wavelength, created a gain medium which would amplify light in a band near the 1550nm wavelength.  EDFAs allowed amplification of the optical signals in fibers which could counter the effects of optical loss, but could not correct for the effects of dispersion and other impairments.  As a matter of fact, EDFAs generate amplified spontaneous emission (ASE) noise and could cause fiber nonlinearity distortions over a long transmission distance.  So EDFAs did not eliminate the need for regeneration completely, but allowed the signals to go many 80 km hops before regeneration was needed.  Since EDFAs were cheaper than full regeneration, systems were quickly designed which used 1550nm lasers instead of the then prevailing 1300nm.

Then came the “ah ha” moment.  Since EDFAs just replicated the photons coming in and sent out more photons of the same wavelength, two or more channels could be amplified in the same EDFA without crosstalk.  With DWDM one EDFA could amplify all of the channels in a fiber at once, provided they fit within the region of EDFA gain.  DWDM then allowed the multiple use of not only the fiber but also the amplifiers.  Instead of one regeneration circuit for every channel, there was now one EDFA for each fiber.  A single fiber and a chain of one amplifier every 40~100 km could support 96 different data streams. Regenerators are still needed today, every 1,200~3,500km, when the accumulated EDFA ASE noise exceeds a threshold that a digital signal processor and error correction codec can handle.

Of course, since the gain region of the EDFA was limited to about 40 nm of spectra width, great emphasis was placed on fitting the different optical wavelengths as close together as possible.  Current systems place channels 50GHz, or approximately 0.4 nm, apart, and hero experiments have done much more.

In parallel, new technologies have increased the bandwidth per channel to 100 Gbps using coherent techniques that we have discussed in other blog posts.  So a single fiber that in the early 1990s would have carried 2.5Gbps of information, now can carry almost 10 Terabits/sec of information, and we can watch movies from the other side of the globe.

Why Are Businesses Switching to Fiber Optic Cables?

Many businesses, especially those which depend on high data usage and transmission, have been switching their cabling over to fiber optic cables as they realize all the benefits provided by fiber optic technology. Apart from the nature of business and its built-in appetite for data, another reason for this trend is due to the increasing demands placed on companies undergoing growth – which naturally elevates the demand for data usage as well. Here are some of the benefits offered by fiber optic cables which make them so appealing.

 

5 Reasons Why Businesses are Making the Switch to Fiber Optic Cables

Overall cost

 

There might be a slightly higher initial cost associated with installing fiber optic cables, but in the long run, the investment pays off in spades. Because it is more durable, more functional, and requires less ongoing maintenance, fiber optics can end up being the most cost-effective approach for many companies.

 

Physical size

 

Performance of fiber optic cables has nothing to do with their size, unlike the case with copper-based cables. To increase speed and bandwidth on a copper line, more copper must be included, which means the physical size of the cable grows, leading to increased costs for transportation and installation.

 

Dependability

 

Copper wiring is subject to degraded performance or damage when exposed to wet weather or other wet conditions. Since there is no electricity being transmitted through fiber optic cables, there is no hazard created if they should be exposed to severe weather conditions.

 

Security

 

It is much more difficult and costly for hackers to attempt a breach of fiber optic cabling, which is why it has been subjected to far fewer attacks than other forms of cabling. With the number and the severity of cyber attacks constantly on the rise, it makes sense to consider every aspect of security for your data center.

 

Performance

 

Voice communication has always been the primary usage for copper wiring, and even though it has been adapted for data usage as well, it is limited in terms of its capabilities for speed and bandwidth. Fiber optics have no such constraints, and have already provided unprecedented rates in both categories.

 

Where to Find Fiber Optic Cabling and Fiber Optic Tool Box

Ease of use can be a big appeal when it’s time to install fiber optic cabling. A fiber optic tool box has all the tools needed for fiber optic cable installation, making it an easy process. Your single source provider for all fiber optic technology should be fiber-mart.com, an industry leader in research and production of high-quality fiber optic technology.

Brief Analysis Optical Network Multiplexing

In fiber optic communication, multiplexing is considered to be the principal means for the expansion of the capacity of existing fiber network engineering. Multiplexing techniques include time division multiplexing TDM (Time Division Multiplexing) technology, MIMOs SDM (Space Division Multiplexing) technology, WDM (Wavelength Division Multiplexing) technology and frequency division multiplexing FDM with (Frequency Division Multiplexing) technology. However, because of the FDM and WDM is generally believed that there is no essential difference, so that the wavelength division multiplexing is roughly divided frequency division multiplexing is a “niche”, which both included in a class. Following discussion space division multiplexing (SDM), time division multiplexing (TDM), wavelength division multiplexing (WDM), CWDM OADM multiplexing approach.

1. TDM technology

TDM technology is very mature multiplexing electronics communication. This technique is the transmission time is divided into serveral time slots, into the corresponding slot would be needed to transmit the multiplexed signal according to certain rules, in order to achieve multi-channel signal multiplexed transmission. However, this technique is the use of electronics communication, due to the electron velocity space capacity and compatibility with many aspects of the restrictions, electronic time division multiplexing rate is not too high. For example, PDH signals only reach 0.5Gbps, althought the SDH system signal the synchronized interleaved multiplexing method has reached the rate of 10Gbps (STM-64), However, to achieve 20Gbps is quite difficult. Other hand, in the optical fiber, for the optical signals generated the loss (Attnuation), the reflectance, chromatic dispersion and polarization mode disoersion PMD will seriously affect the transmission of the modulation signal of the high rate. When the signal to STM-64 or higher rate, PMD pluse spreading effect, it will cause a signal “fuzzy”, causing the receiver to produce error signal misjudgment. This is due to the different modes of polarized light will produce a slight time difference in the fiber runs, and thus general
requirements the PMD coefficient must 0.1ps/km following. In summary, the limitations of the electrical time division multiplexing technology, the electronics communication transmission rate is limited to less than 10-20Gbps.

. Optical time division multiplexing (OTDM)

OTDM signal modulation with a plurality of radio channel having a different channel of the same optical frequency, after multiplexing in the same fiber transmission expansion technology. Optical time division multiplexing technology include: ultra-narrow optical pulse generation and modulation techniques, optical multiplexing / de-multiplexing, optical timing extraction techniques.

a. Ultra narrow optical pulse generation. Optical time division multiplexing requires a light source to provide a duty cycle of 5 ~ 20GHz quite small, ultra narrow optical pulse output, realized gain switch the LD mode locking method, electro-absorption strobe continuous light modulation method and fiber grating method SC (Supercontinum,) optical pulses. The gain switching method can generate a pulse width of 5 ~ 7ps, the pulse repetition frequency of the optical pulse can be arbitrarily adjusted about at 10GHz, the advantage is easily synchronized with the other signals. Pulse source in the gain switching method has been used in a variety of high-speed optical transmission experiment generated and optical measurement. SC optical pulse width greater than 1ps, and narrowest reached 0.17ps. Further, the use of the adjusted linear modulation fiber grating dispersion value on the output of the electro-absorption modulator light pulse shape is corrected, can also produce a light pulse of the pulse duration is 5.8ps 10GHz, the duty cycle of 6.3%.

b. Full optical multiplexing/de-multiplexing. Optical time division multiplexing by the optical delay line and 3dB optical directional coupler constitute. in the ultra-high-speed system, it is preferable to intergrate optical delay line and the direation of the 3dB optical coupler in a plane on a silicon substrate to form a planar waveguide circuit (PLC) as the optical multiplexer. The all-optical demultiplexer demultiplexing the light receiving end of the OTDM signal. Has developed a device forms as a demultiplexer: optical Kerr switch matrix optical demultiplexer, cross-phase modulation frequency shift optical demultiplexer, four-wave mixing switch optical demultiplexer and non-line sexual fiber loop mirror type (NOLM) optical demultiplexer. Regardless of devices, require reliable and stable control of low power optical signal, regardless of the polarization.

c. Optical timing extraction technology. Optical timing extraction requirements of ultra-high-speed operation, low phase noise, high sensitivity, and has nothing to do with the polarization. Has been developed a high-speed microwave mixer PLL Road (PLL) constituted as a phase detector, the additional use of a Fabry – Perot interferometer constituted by an optical path the light oscillation circuit (FPT) clock recovery functions can be completed .

. SDM technology

For a general understanding of the SDM is : multiplexing of the multiplexing of the plurality of optical fibers,i.e. the cable. In some places, there are off-the-shelf optical fiber communication network pipeline, and there is a spare position. Therefore, in order to increase capacity in the pipeline pulled into more optical fiber, which is more convenient than electronically. Another understanding MIMOs: realize space division multiplexing in an optical fiber, i.e. the space of the light beam of the optical fiber core region segmentation. Because part of the core of the single-mode fiber core diameter of only 9 ~ 10mm, and the phase of each point of the wavefront of the transmitted beam to exist Fluctuations, and thus the spatial segmentation of this wave surface is extremely difficult. While recently been proposed a the theoretical segmentation method of the degree of coherence, but from the practical, still have a long road to go.

. WDM technology

WDM is the electrical signal of the multiple sources of the respective optical carrier, after multiplexing in an optical fiber transmission, and available at the receiving end of coherent heterodyne detection communication method or tuned passive filter directly detecting the conventionalthe communication method to achieve channel selection. WDM technology can not only expand the communication capacity, and can bring huge economic benefits for communication. Thus, in recent years, research in this area is in the ascendant WDM technology is the system of carrying multiple wavelengths (channels) in a single optical fiber, an optical fiber into multiple “virtual” fiber, each virtual fiber work independently wavelength. Each channel running speeds of up to 2.5 ~ 10Gbps.

a. Dense Wavelength Division Multiplexing

The so-called dense wavelength division multiplexing technology, which is often said DWDM refers to a fiber optic data transmission technology, this technology is the use of the wavelength of the laser according to the bit parallel transmission the string line transmission waydata is transmitted in the optical fiber.

The DWDM first introduced in the optical signal distribution to a specific band within the specified frequency (wavelength, lambda), signal is then multiplexed into a fiber, in this way we can greatly increase the bandwidth of the already laid cable. Since the introduction of the signal is not terminated at the optical layer, the rate and format of the interface can be maintained independently, thus allowing the service provider to integrate the existing equipment in the DWDM technology and network, while existing laying cable not able to use a lot of bandwidth.

DWDM can put a plurality of optical signals with the transmission, the results of these optical signals can be compiled into the same group at the same time is amplified and transmitted through a single optical fiber, the bandwidth of the network is also greatly increased. Each bearer of the signal can be set to a different transmission rate (OC-3/12/24, etc.) and different formats (SONET, ATM, data, etc.). For example, a DWDM network rate OC-48 (2.5 Gbps) and OC-192 (10 Gbps) SONET DWDM based on mixed signals. To huge bandwidth up to 40 Gbps. Using DWDM system can still achieve the above objectives while maintaining system performance, and the same degree of the existing transmission system reliability and stability. Future DWDM terminal can carry a total of 80 wavelengths much as the OC-48 in order to achieve a transmission rate of 200 Gbps, the OC-192, or up to 40 wavelengths in order to achieve a transmission rate of 400 Gbps, this bandwidth is sufficient seconds transmission 9 rolls of Encyclopedia!

b. CWDM technology

DWDM technology of choice for fiber applications today, but its expensive prices affect their wider application. Faced with the needs of the communications market, CWDM (coarse wavelength division multiplexing) came into being. CWDM low cost high access bandwidth suitable for a variety of popular peer-to-peer, Ethernet, SONET ring network structure, particularly suitable for short-distance, high-bandwidth access point intensive communication applicationsoccasions, such as building or building network communications. Is particularly worth mentioning is that with the use of CWDM and PON (passive optical network). PON is an inexpensive, a point-to-multipoint optical fiber communication mode, combined with CWDM, each single wavelength channel can be used as the the virtual optical link of the PON, the central node and a plurality of distributed nodes for broadband data transmission.

However, CWDM is a compromise between cost and performance, and inevitably there are some performance limitations. Industry experts point out, CWDM is still less than 4 points:

1. Less CWDM support the number of multiplexed wavelengths in a single fiber, resulting in higher cost of future expansion;

2. Multiplexer multiplex demodulator and so the cost of equipment should be further reduced, these devices can not only DMDM a simple modification of the corresponding device;

3. CWDM has not yet formed a standard.

. OADM

People’s interest in wavelength division multiplexing (WDM) optical network field, more and more concentrated OADM. These devices in the field of optical wavelength traditional SDH OADM in the time domain function. Particular OADM can be separated from the beam of a WDM channel (ceded function), and is generally based on the same wavelength to insert new information on the optical carrier (insert function). OADM selectivity, from the transfer device to select the next channel signal or on the road signal, or simply by the signal of a certain wavelength, but does not affect the transmission of the other wavelength channels. OADM in the optical domain, OADM in the time domain, the completion of the function, and having transparency, and can handle any format and rate of the signal in SDH. Can improve the reliability of the network, reducing node cost, and improve the efficiency of network operation, key equipment is essential for the formation of all-optical network. For OADM, in the sub-outlet and inserted between the mouth and between the input and output ports must have a high degree of isolation (> 25dB) in order to minimize the same wavelength interference effects, otherwise it will seriously affect the transmission performance. Have been proposed the achieve OADM several techniques: WDMMUX / DEMUX; between optical circulator or a fiber grating in MachZehnder structure; the tandem MachZehnder implemented with integrated optics technology structure and the interference filter. The first two methods so that the isolation of the highest, but they require expensive equipment, MachZehnder structure (with fiber grating or optical integration technology) is still under development, and the need for further improvement in order to achieve the required isolation.

From the current of view, all-optical network is first applied to the LAN, MAN the internal optical routing, the technology used is based on WDM EDFA and broadband. In the long run, all-optical network inevitably points toward the waves, time division, space division three ways to combine the direction of development. Its application will be extended to the WAN. Network range can cover the entire country or several countries, and ultimately achieve a high-speed large-capacity all-optical network to meet the future demand for communication services.