Fiber Laser Welding: Some Traits and Applications(1)

What is fiber laser? The world’s first laser beam is produced in 1960 by the use of flashbulb stimulating ruby crystalline grain. Limited by the thermal capacity of the grain, the pulsed beams is short and the frequency is very low. Although the instantaneous pulse peak can reach up to 106W, it still belongs to low energy output.

fiber laser 1

Laser technology adopts the beams of light generated by the reflection of laser from polariscope and congregates the beams in focusing device to generate beams with enormous energy. Once the focus is approaching, the workpieces will be melt or vapored in some milliseconds. This opens up a new welding application domain for high power CO2 and high power YAG laser. The key of laser welding equipment is high power laser, including solid laser and gas laser. Solid laser is the so called Nd:YAG laser. Nd is a rare earth elements and YAG represents Yttrium Aluminum Garnet, with similar crystal structure as ruby. The wavelength of Nd:YAG laser is 1.06μm. It can produce beam transmitted by fiber, so it can simplify beam delivery system, which is suitable in flexible manufacturing systems and remote working as well as high welding precision workpieces. Nd:YAG laser of 3-4 KW output is commonly used in automobile industry. Gas laser is the so-called CO2 laser. Its working medium is molecule gases which can generate iraser of 10.6μm in average. It can work continuously and output very high power; the standard laser power is between 2-5 KW.

The major traits of laser welding are as following:

  1. The welding is fast and deep with little deformation.
  2. It can work in room temperature and disparity conditions with simple equipment and device. For example, the laser beam will not offset; laser welding can be really carried out in vacuum, air or any gas environment, or even through glass or any transparent material.
  3. It can weld refractory materials as titanium and quartz and anisotropic materials with good effects.
  4. When welding, depth-to-width ratio can reach to 5:1 and the highest can reach up to 10:1.
  5. It can applied in microwelding. Slight flare can be generated by focused laser beams which can positioning precisely and be applied in mass automatic production of micro and small workpieces’ installation and welding.
  6. It is flexible in welding areas that is difficult to access. Especially in recent years, the adoption of optical fiber transmission in YAG laser processing technology has greatly promoted the popularization and application of laser welding technology.
  7. Beam split is easy to be realized by time and space and multiple beam can be processed all at once, providing conditions for more precise welding.

However, there are some limits of laser welding:

  1. It requires high assembly accuracy for weld and it should has no obvious deviation of beam on workpieces. It is because that the flare is too small and the welding line is too narrow. If the assembly accuracy and beam position cannot meet the requirements, it is easy to make weld defect.
  2. The cost and initial investment on laser and the relevant systems are high.

fiber laser 2

Resource : avio

DK Photonics –  specializes in designing and manufacturing of high quality optical passive components mainly for fiber laser applications such as 1064nm high power isolator, Cladding Power Stripper, Multimode High Power Isolator, pump combiner,1064nm Band-pass Filter,(6+1)X1 Pump and Signal Combiner, PM Circulator, PM Isolator, optical Coupler. More information, please contact us.


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The Comparative Between Fiber Laser Cutting Machine and CO2 Cutting Machine

Cutting is one of the most widely applied laser processing techniques. Fiber laser and CO2 laser are the most commonly used laser cutting equipment. It is necessary for users to have a knowledge of the advantages and disadvantages of both the two ways of cutting.

CO2 laser

Source : fe.infn

Wavelength of fiber laser is 1.06μm and Wavelength of CO2 laser is 10.6μm. Both are infrared light and can be absorbed by material so that they can be applied in Industrial material processing. Fiber laser is unable to be applied in non-metal cutting, such as wood, plastic, leather and ramie cotton fabric. In case of non-metal cutting, CO2 laser is the only choice. But CO2 laser cannot cut copper products, including brass and red copper. Because copper is highly reflective material for CO2 laser, laser will be reflected instead of absorbed by copper, which can cause harm.

Laser is evaluated by integrated index as cutting speed, drilling efficiency and section quality.

Fiber laser has an advantage in cutting thin plate, especially for thickness under 3mm. Its maximum cutting speed ratio can reach to 4:1 and 6mm is critical thickness for the two kinds of lasers. When it is thicker than 6mm, fiber laser shows no preferential; as the thickness increases, CO2 laser shows preferential gradually but not outstandingly. Generally speaking, fiber laser has an advantage in cutting speed.

Drilling efficiency:

Before cutting, laser beam should penetrate workpiece. Fiber laser needs more time in drilling than CO2 laser. Take 3KW optical fiber laser and CO2 laser as an example, The latter saves 1 second in drilling 8mm carbon steel; and 2 seconds in 10mm drilling. As thickness grows, CO2 laser will save more time.

Fiber laser

Source : nufern

Section quality:

Section quality usually means the roughness (surface perfection) and perpendicularity.

When cutting steel plate under 3mm, section quality of fiber laser is worse then CO2. As thickness grows, the difference becomes more obvious.

In addition, carbon steel plate has high absorptivity on fiber laser energy, so it has shortcoming in cutting holes (aperture < panel thickness).

The above comparison will help users make a reasonable choice. The cutting speed of the two lasers is equally matched. Fiber laser is inferior to Co2 laser in section quality and drilling efficiency. There is no quick answer to which is better. They both have advantages and disadvantages in specific application demands.

By the way, laser cutting precision has nothing to do with the adoption of lasers. It is determined by machine positioning precision, resetting precision and consistency of kerf width. Fiber laser has narrower kerf than CO2. Kerf width doesn’t affect precision of the parts either, since it can be offset by cutting gap compensation.

DK Photonics –  specializes in designing and manufacturing of high quality optical passive components mainly for fiber laser applications such as 1064nm high power isolator, Cladding Power Stripper, Multimode High Power Isolator, pump combiner,1064nm Band-pass Filter,(6+1)X1 Pump and Signal Combiner, PM Circulator, PM Isolator, optical Coupler. More information, please contact us.

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Field-Terminated Fusion Splice-On Connector-North American Market Forecast

According to ElectroniCast, the quantity of field-terminated fiber optic splice-on connectors in North America will increase at an explosive annual rate of 41.9% …

ElectroniCast Consultants, a leading market research & technology forecast consultancy addressing the fiber optics communications industry, today announced the release of a new market forecast of the consumption of field terminated fiber optic fusion splice-on connectors in North America.


Field terminated fiber optic fusion Splice On Connectors (SOC) are installed for rapid repairs or for limited space situations where pre-terminated fiber cabling may be difficult, such as when the cable assembly needs to pass through small openings such as conduit.  The splice-on connectors are an option when the precise length of the optical fiber link is not pre-determined and a field-installed termination solution is required, such as in Fiber to the Home (FTTH) and other communication applications.

Last year, 306-thousand field-terminated fiber optic fusion splice-on connectors were installed in non-OEM applications in North America.  The number of connectors is forecast to increase at an explosive rate of 41.9% per year, reaching 2.49 million units in 2020.  Market forecast data in this study report refers to consumption (use) for a particular calendar year; therefore, this data is not cumulative data.

The Telecommunications application category is forecast to maintain the leadership in relative market share through the year 2018, until the Premises Networks application category is set to capture the lead.  Telecommunication use is forecast for 35.5% annual growth in quantity (2014-2020), mainly driven by access optical fiber deployment.  The Cable TV application is also driven by the use of connectors for FTTH (Home) and FTTB (Building/MDUs – Multiple Dwelling Units).

The market forecast segments the connectors by single-mode and multimode optical fiber, as well as into the following types: MPO, LC, FC, ST, SC, and other.  The use of single mode fiber optic field-terminated fusion splice-on connectors in North America is forecast to increase from 173.8-thousand units in 2014 to 1.49 million in 2020.  Multimode fiber is best suited for use in short lengths, such as those used in datacom and specialty networks and in 2020, multimode connectors are expected to reach 1-million units.

“In 2014 in North America, 4.3-thousand new fusion splicers were brought into Premises Datacom, and the use of field terminated fusion splice on connectors is a major market driver for the use of fiber optic fusion splicers used in premises network applications, the data center (DC) and longer link length datacom cable installations,” said Stephen Montgomery, Director of the ElectroniCast market study.

“The SOCs are emerging as a viable alternative to pre-terminated fiber optic cables (pigtail and cable assemblies/ patch cords).  Also, based on primary research interviews with network planners and installers, we are finding that field terminated fusion splice-on connectors are rapidly being accepted as a go-to solution.  With SOCs, communication network technicians can install reliable cable links with exact lengths, eliminating cable shortness or excess slack that is typically a result with the pre-terminated cable solution,” Montgomery added.

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The Modern Data Center – Modular Data Center

The modern data center is a complex place. The proliferation of mobile devices, like tablets and smartphones, place an ever-increasing pressure on the IT departments and data centers. End-user and customers’ expectation levels have never been higher and the demand for data shows no sign of slowing down. Data center managers must manage all of these elements while also remaining efficient and keeping costs under control. So where does the data center go from here?Modular Data Center

One thing I have noticed in the evolution of the modern data center is that the facilities are gaining importance; improving energy efficiency and IT management have come to the forefront. Maximizing the organization’s resources is vital, and that means delivering more to facilities and equipment without expending more on staffing. IDC forecasts that during the next two years, 25 percent of all large and mid-sized businesses will address the power and cooling facility mismatches in their data centers with new IT systems and put a 75 percent cap on data center space used. So there again is the crucial challenge of doing more and innovating while keeping budgets and spend under control.

Another key part of the next generation data center mix is automation. Today’s data center manager is engaged in sourcing the right automation tools that will help them manage energy consumption and add new technology without disrupting normal operations. These are a few of the key challenges in the modern data center—so data center managers and IT departments must find ways to address them.

Where does the Data Center Go Next?

At the heart of data center evolution is the information technology sector’s rapid rate of change. Many new products and services must be implemented with much less time to value, and data centers need to be agile enough to assess and accommodate them all. If you examine enterprise data centers, then you might observe the ways that cloud computing and hyperscale innovations are displacing traditional enterprise systems, with new paradigms pioneered by innovators like Amazon and Google. With new options being developed, enterprises now have to chart strategies for cloud computing, including public, private or hybrid cloud. Gauging where the technology will go next is difficult to tell. Will the traditional vendors, such as Cisco and EMC, prevail or will new paradigms from Nutanix or Simplivity disrupt and displace these traditional data center dominators?

The race is on to manage the rapid rate of change while also staying agile, meeting end-user expectations and managing costs. For example, data center managers must handle the level of capacity their data center requires while ensuring they don’t overspend on unused capacity. This is where the focus on data center design comes into play.

Taking the Data Center Forward

These specific needs and challenges that the modern data center faces require working with the right tools and solutions. Modular, purpose-built data center infrastructure allows organizations to develop data center services based on need—when capacity rises and where capacity is needed. For example, we’ve observed in Singapore that most data centers operate slightly above 2.1 Power Usage Effectiveness (PUE). This means that companies spend more on cooling their data center rather than on operating and powering the IT equipment. It is a simple challenge—drive efficiency without impacting operations. You want to drive PUE down to approximately 1.06, regardless of where you need to operate, and reap huge energy savings while better serving customers. If done right, there is a positive environmental impact.

Changing the paradigm of the traditional data center enables organizations to reap these rewards. Assessing and establishing business objectives that reflect what is possible, rather than what always has been or what is easier and more comfortable, has led to innovative services and new business models that reset the competitive standards for everyone. Better PUE is a mandatory step in this process. The PUE journey continues as evidenced by Amazon, which had recently taken to harnessing wind to power its data centers. Modular data centers will play a major part in this PUE journey, thanks to more efficient use of energy and greater flexible support for resiliency and compute density.

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How much do you know about CWDM Multiplexer and DWDM Multiplexer

CWDM multiplexer and DWDM multiplexer are two main products of WDM multiplexer. The full name of WDM, CWDM and DWDM are wavelength division multiplexing, coarse wavelength division multiplexing and dense wavelength multiplexing respectively. How much do you know about them? If you have no idea, the following introduction will help you a lot.

In the very first place, let’s get to know what the WDM is. Based on a single fiber optic transmission, many optical signals that are loaded with information and have different wavelengths can be synthesized into one single beam by WDM multiplexer. Then, a special communication technology will be adopted to separate those optical signals at the receiving terminal. On the basis of WDM technique, the CWDM device and DWDM device are two popular products in the current market.

CWDM device

When it comes to the CWDM multiplexer, first of all, it provides service for metropolitan area network access layer, whose working principle is in line with WDM multiplexer. However, it simplifies the structure largely. For example, the filter film layer number of CWDM is just 50, while the WDM is as many as 200 layers. That is to say, the rate of finished products has been improved and the cost has been reduced largely. Besides low cost, the CWDM device is also advantageous in small volume, small power consumption, convenient maintenance and large transmission capacity. The laser device in the system doesn’t need semiconductor refrigerator and temperature controller, which can lessen the power consumption obviously. However, the CWDM also has shortcomings. For instance, developing and simplifying the optical transceiver module and optical component is urgent to be solved.

DWDM device

As to the DWDM multiplexer, comparatively speaking, it makes the best use of fiber-optical bandwidth and enhances the message capacity of cellular system, which is well-known for simple dilatation and stable performance. Integrated system and open system are two dominant application systems of DWDM multiplexer, which are based on different wavelength conversion technologies. No matter which system is adopted, the free-running 1510nm wavelength will be chosen to carry OSC or optical supervisory channel so as to transmit information. Such an OSC is a comparatively independent subsystem, which offers maintenance and management information.

The last question is what advantages WDM technique has when compared with traditional transmission methods. Generally speaking, it includes such aspects as making best use of low-loss wave band, transmitting several optical signals in one optical fiber, good flexibility, low investment cost, excellent system reliability and fast and convenient recovery.


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Do you know these about CWDM Multiplexer and DWDM Multiplexer?

Do you know these about CWDM Multiplexer and DWDM Multiplexer?

Wavelength division multiplexing (WDM) is a technology or technique modulating numerous data streams, i.e. optical carrier signals of varying wavelengths (colors) of laser light, onto a single optical fiber. The goal of WDM is to have a signal not to interfere with each other. It is usually used to make data transmission more efficiently. It has also been proven more cost effective in many applications, such as WDM network applications, broadband network application and fiber to the home (FTTH) applications and so on. According to channel spacing between neighbored wavelengths, there are two main types of WDM, including Coarse WDM (CWDM) and Dense WDM (DWDM). Though both of them belong to WDM technology, they are quite different. Then, what are the differences between them? This paper will give you the answer.

Definition of CWDM

CWDM is a method of combining multiple signals on laser beams at various wavelengths for transmission along fiber optic cables, such that the number of channels is fewer than in DWDM but more than in standard WDM. “Course” means the channel spacing is 20nm with a working channel passband of +/-6.5nm from the wavelengths center. From 1270nm to 1610nm, there are 18 individual wavelengths separated by 20nm spacing.

Definition of DWDM

DWDM is a technology that puts data from different sources together on an optical fiber, with each signal carried at the same time on its own separate light wavelength. “Dense” refers to the very narrow channel spacing measured in Gigahertz (GHz) as opposed to nanometer (nm). DWDM typically uses channel spacing of 100GHz with a working channel passband of +/-12.5GHz from the wavelengths center. It uses 200GHz spacing essentially skipping every other channel in the DWDM grid. And it has also gone one step further using an Optical Interleaver to get down to 50GHz spacing doubling the channels’ capacity from 100GHz spacing.


According to the content above, you will find some small differences between them. 16CH CWDM Module is defined by wavelengths and has wide range channel spacing. DWDM is defined by frequencies and has narrow channel spacing. What’s more, what other differences do they have?

Capacity of Data

In fiber optic network system, DWDM system could fit more than 40 different data streams in the same amount of fiber used for two data streams in a CWDM system. In some cases, CWDM system can perform many of the same tasks compared to DWDM. Despite the lower transmission of data through a CWDM system, these are still viable options for fiber optic data transmission.

Cost of Cable

CWDM system carries less data, but the cabling used to run them is less expensive and less complex. A DWDM system has much denser cabling and can carry a significantly larger amount of data, but it can be cost prohibitive, especially where there is necessary to have a large amount of cabling in an application.

Long-haul or Short-haul Transmission

DWDM system is used for a longer haul transmission through keeping the wavelengths tightly packed. It can transmit more data over a significantly larger run of cable with less interference. However, CWDM system cannot travel long distances because the wavelengths are not amplified, and therefore CWDM is limited in its functionality over longer distances. If we neeed to transmit the data over a very long range, DWDM system solution may be the best choice in terms of functionality of the data transmission as well as the lessened interference over the longer distances that the wavelengths must travel. As far as cost is concerned, when required to provide signal amplification about 100 miles (160km), CWDM system is the best solution for short runs.

According to the content above, maybe you have already understood some differences between CWDM and DWDM by the comparision of them from definition, capacity, cable cost and transmission distance etc. And here is also a figure of comparisons between CWDM and DWDM which may help you to consolidate your understanding of this paper.

CWDM Multiplexer and DWDM Multiplexer

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Saving Your Fibers By Using CWDM Or DWDM Multiplier

Using a WDM(Wavelength Division Multiplexing) for expanding the capacity of the fiber to carry multiple client interfaces is a highly advisable way as the physical fiber optic cabling is not cheap. As WDM widely used you must not unfamiliar with it, it is a technology that combines several streams of data/storage/video or voice protocols on the same physical fiber-optic cable, by using several wavelengths (frequencies) of light with each frequency carrying a different type of data.

Two types of WDM architecture available: Coarse Wavelength Division Multiplexing (CWDM) and Dense Wavelength Division Multiplexing (DWDM). CWDM/DWDM multiplexer and demultiplexer and OADM (Optical Add-Drop Multiplexer) are common fit in with Passive. With the use of optical amplifiers and the development of the OTN (Optical Transport Network) layer equipped with FEC (Forward Error Correction), the distance of the fiber optical communication can reach thousands of Kilometers without the need for regeneration sites.

16-Ch CWDM Mux/Demux Module


Each CWDM wavelength typically supports up to 2.5Gbps and can be expanded to 10Gbps support. The CWDM is limited to 16 wavelengths and is typically deployed at networks up to 80Km since optical amplifiers cannot be used due to the large spacing between channels. CWDM uses a wide spectrum and accommodates eight channels. This wide spacing of channels allows for the use of moderately priced optics, but limits capacity. CWDM is typically used for lower-cost, lower-capacity, shorter-distance applications where cost is the paramount decision criteria.

The CWDM Mux/Demux (or CWDM multiplexer/demultiplexer) is often a flexible plug-and-play network solution, which helps insurers and enterprise companies to affordably implement denote point or ring based WDM optical networks. CWDM Mux/demux is perfectly created for transport PDH, SDH / SONET, ETHERNET services over WDM, CWDM and DWDM in optical metro edge and access networks. CWDM Multiplexer Modules can be found in 4, 8 and 16 channel configurations. These modules passively multiplex the optical signal outputs from 4 too much electronic products, send on them someone optical fiber and after that de-multiplex the signals into separate, distinct signals for input into gadgets across the opposite end for your fiber optic link.

Typically CWDM solutions provide 8 wavelengths capability enabling the transport of 8 client interfaces over the same fiber. However, the relatively large separation between the CWDM wavelengths allows expansion of the CWDM network with an additional 44 wavelengths with 100GHz spacing utilizing DWDM technology, thus expanding the existing infrastructure capability and utilizing the same equipment as part of the integrated solution.

100GHz 8-Ch DWDM Mux/Demux Module


DWDM is a technology allowing high throughput capacity over longer distances commonly ranging between 44-88 channels/wavelengths and transferring data rates from 100Mbps up to 100Gbps per wavelength.

DWDM systems pack 16 or more channels into a narrow spectrum window very near the 1550nm local attenuation minimum. Decreasing channel spacing requires the use of more precise and costly optics, but allows for significantly more scalability. Typical DWDM systems provide 1-44 channels of capacity, with some new systems, offering up to 80-160 channels. DWDM is typically used where high capacity is needed over a limited fiber resource or where it is cost prohibitive to deploy more fiber.

The DWDM multiplexer/demultiplexer Modules are made to multiplex multiple DWDM channels into one or two fibers. Based on type CWDM Mux/Demux unit, with optional expansion, can transmit and receive as much as 4, 8, 16 or 32 connections of various standards, data rates or protocols over one single fiber optic link without disturbing one another.

Ultimately, the choice to use CWDM or DWDM is a difficult decision, first we should understand the difference between them clearly.


CWDM scales to 18 distinct channels. While, DWDM scales up to 80 channels (or more), allows vastly more expansion. The main advantage of CWDM is the cost of the optics which is typically 1/3rd of the cost of the equivalent DWDM optic. CWDM products are popular in less precision optics and lower cost, less power consumption, un-cooled lasers with lower maintenance requirements. This difference in economic scale, the limited budget that many customers face, and typical initial requirements not to exceed 8 wavelengths, means that CWDM is a more popular entry point for many customers.

Buying CWDM or DWDM is driven by the number of wavelengths needed and the future growth projections. If you only need a handful of waves and use 1Gbps optics, CWDM is the way to go. If you need dozens of waves, 10Gbps speeds, DWDM is the only option.


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Ultrafast laser pulses induce atoms in gold nanodisks to vibrate

In a study that could open doors for new applications of photonics from molecular sensing to wireless communications, Rice University scientists have discovered a new method to tune the light-induced vibrations of nanoparticles through slight alterations to the surface to which the particles are attached.

In a study published online this week in Nature Communications, researchers at Rice’s Laboratory for Nanophotonics (LANP) used ultrafast laser pulses to induce the atoms in gold nanodisks to vibrate. These vibrational patterns, known as acoustic phonons, have a characteristic frequency that relates directly to the size of the nanoparticle. The researchers found they could fine-tune the acoustic response of the particle by varying the thickness of the material to which the nanodisks were attached.

“Our results point toward a straightforward method for tuning the acoustic phonon frequency of a nanostructure in the gigahertz range by controlling the thickness of its adhesion layer,” said lead researcher Stephan Link, associate professor of chemistry and in electrical and computer engineering.

Rice University researchers (clockwise from front) Man-Nung Su, Wei-Shun Chang and Fangfang Wen discovered a new method to tune the light-induced vibrations of nanoparticles through slight alterations to the surface to which they are attached.

Light has no mass, but each photon that strikes an object imparts a miniscule amount of mechanical motion, thanks to a phenomenon known as radiation pressure. A branch of physics known as optomechanics has developed over the past decade to study and exploit radiation pressure for applications like gravity wave detection and low-temperature generation.

Link and colleagues at LANP specialize in another branch of science called plasmonics that is devoted to the study of light-activated nanostructures. Plasmons are waves of electrons that flow like a fluid across a metallic surface.

When a light pulse of a specific wavelength strikes a metal particle like the puck-shaped gold nanodisks in the LANP experiments, the light energy is converted into plasmons. These plasmons slosh across the surface of the particle with a characteristic frequency, in much the same way that each phonon has a characteristic vibrational frequency.

The study’s first author, Wei-Shun Chang, a postdoctoral researcher in Link’s lab, and graduate students Fangfang Wen and Man-Nung Su conducted a series of experiments that revealed a direct connection between the resonant frequencies of the plasmons and phonons in nanodisks that had been exposed to laser pulses.

“Heating nanostructures with a short light pulse launches acoustic phonons that depend sensitively on the structure’s dimensions,” Link said. “Thanks to advanced lithographic techniques, experimentalists can engineer plasmonic nanostructures with great precision. Based on our results, it appears that plasmonic nanostructures may present an interesting alternative to conventional optomechanical oscillators and high power isolator

Chang said plasmonics experts often rely on substrates when using electron-beam lithography to pattern plasmonic structures. For example, gold nanodisks like those used in the experiments will not stick to glass slides. But if a thin substrate of titanium or chromium is added to the glass, the disks will adhere and stay where they are placed.

“The substrate layer affects the mechanical properties of the nanostructure, but many questions remain as to how it does this,” Chang said. “Our experiments explored how the thickness of the substrate impacted properties like adhesion and phononic frequency.”

Link said the research was a collaborative effort involving research groups at Rice and the University of Melbourne in Victoria, Australia.

“Wei-Shun and Man-Nung from my lab did the ultrafast spectroscopy,” Link said. “Fangfang, who is in Naomi Halas’ group here at Rice, made the nanodisks. John Sader at the University of Melbourne, and his postdoc Debadi Chakraborty calculated the acoustic modes, and Yue Zhang, a Rice graduate student from Peter Nordlander’s group at Rice simulated the optical/plasmonic properties. Bo Shuang of the Landes’ research group at Rice contributed to the analysis of the experimental data.”

The research was supported by the Robert A. Welch Foundation and the Department of Defense’s Multi-University Research Initiative. Additional co-authors include Zhang, Shuang, Nordlander and Halas, all of Rice; and Chakraborty and Sader, both of the University of Melbourne in Victoria, Australia.

About DK Photonics

DK Photonics –  specializes in designing and manufacturing of high quality optical passive components mainly for fiber laser applications such as 1064nm high power isolator, Cladding Power Stripper, Multimode High Power Isolator, pump combiner,1064nm Band-pass Filter,(6+1)X1 Pump and Signal Combiner, PM Circulator, PM Isolator, optical Coupler. More information, please contact us.

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Polarization Dependent Isolator vs Polarization Independent Isolator

Connectors and other types of optical devices on the output of the transmitter may cause reflection, absorption, or scattering of the optical signal. These effects on the light beam may cause light energy to be reflected back at the source and interfere with source operation. In order to reduce the effects of the interference, an optical isolator is usually used. Optical isolator allows a beam of light to stream through a single one way direction. At the same time, it prevents the light from going back in the opposite direction. According to the polarization characteristics, optical isolators can be divided into two types, including polarization dependent isolator and polarization independent isolator. The polarizer-based module makes a polarization dependent isolator, and the birefringent crystal-based structure makes a polarization independent isolator. You may be very confused about them as you find that there is only a little difference via their names. So, what are they and what are the differences between them? This paper will give you the answer.

Polarization Dependent Isolator

The polarization dependent isolator consists of three parts, an input polarizer , a Faraday rotator, and an output polarizer. Light traveling in the forward direction becomes polarized vertically by the input polarizer. The Faraday rotator will rotate the polarization by 45°. The analyser then enables the light to be transmitted through the isolator.


Light traveling in the backward direction becomes polarized at 45° by the analyser. The Faraday rotator will again rotate the polarization by 45°. This means the light is polarized horizontally. Since the polarizer is vertically aligned, the light will be extinguished.

The picture shows us a Faraday rotator with an input polarizer, and an output analyser. For a polarization dependent isolator, the angle between the polarizer and the analyser, is set to 45°. The Faraday rotator is chosen to give a 45° rotation.

Because the polarization of the source is typically maintained by the system, polarization dependent isolator is widely used in free space optical systems.

Polarization Independent Isolator

The polarization independent isolator also consists of three parts, an input birefringent wedge, a Faraday rotator, and an output birefringent wedge. Light traveling in the forward direction is split by the input birefringent wedge into its vertical (0°) and horizontal (90°) components, called the ordinary ray (o-ray) and the extraordinary ray (e-ray) respectively. The Faraday rotator rotates both the o-ray and e-ray by 45°. This means the o-ray is now at 45°, and the e-ray is at −45°. The output birefringent wedge then recombines the two components.


Light traveling in the backward direction is separated into the o-ray at 45, and the e-ray at −45° by the birefringent wedge. The Faraday Rotator again rotates both the rays by 45°. Now the o-ray is at 90°, and the e-ray is at 0°. Instead of being focused by the second birefringent wedge, the rays diverge. The picture shows the propagation of light through a polarization independent isolator.

While polarization dependent isolator allows only the light polarized in a specific direction, polarization independent isolator transmit all polarized light. So it is usually widely used in optical fiber amplifier.

Comparison of Polarization Dependent Isolator and Polarization Independent Isolator

In fact, you have already understood these two types of isolators according to the contents above. We can see their similarities and differences through the comparison of their definition, working principle and applications. Both of them consist of three parts and have a same principle based on Faraday effect. However, to overcome the limitation of polarization dependent isolator, polarization independent isolator has been developed. Regardless of the polarization state of the input beam, the beam will propagate through the isolator to the output fiber and the reflected beam will be isolated from the optical source. If the extinction ratio is important, a polarization dependent isolator should be used with either polarization maintaining fibers or even regular single-mode fibers. If the system has no polarization dependence, a polarization independent isolator will be the obvious choice.

About DK Photonics

DK Photonics –  specializes in designing and manufacturing of high quality optical passive components mainly for fiber laser applications such as 1064nm high power isolator, Cladding Power Stripper, Multimode High Power Isolator, pump combiner,1064nm Band-pass Filter,(6+1)X1 Pump and Signal Combiner, PM Circulator, PM Isolator, optical Coupler. More information, please contact us.

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