Category: Polarization

What Is An In-line Polarizer? How Does It Work?

Have you ever wondered how those fancy sunglasses or LCD screens manage to reduce glare and enhance contrast? The answer lies in a clever optical component called an in-line polarizer. It plays an important role in controlling and manipulating light waves, making it an essential part of various technologies we use daily. Let’s see how it works, its construction, materials and application.

What is an In-line Polarizer?

An in-line polarizer is a type of optical filter that selectively transmits light waves oscillating in a particular direction while blocking those vibrating in the perpendicular direction. This selective transmission of light is achieved through a process called polarization, which aligns the oscillations of light waves in a specific orientation.

How Does an In-line Polarizer Work?

The working principle of an in-line polarizer is based on the wave nature of light. Light waves are electromagnetic waves that oscillate in different planes perpendicular to their direction of propagation. In natural light, these oscillations occur randomly in all possible planes, creating unpolarized light.

When unpolarized light encounters an in-line polarizer, the polarizer acts as a filter, allowing only the light waves oscillating in a specific plane to pass through while absorbing or reflecting the waves vibrating in the perpendicular plane. This results in polarized light, where the oscillations of the transmitted light waves are aligned in a single direction.

Construction and Materials

The construction of an in-line polarizer involves the use of specialized materials that exhibit a property called dichroism. Dichroic materials have the ability to absorb light waves with a specific oscillation direction while transmitting those with a perpendicular orientation. Common materials used in in-line polarizers include stretched polymer films, crystals like calcite, and even wire grid structures.

Applications of In-line Polarizers

In-line polarizers are incredibly versatile and find use in many different areas thanks to their ability to manipulate light waves. Let’s explore some of the common applications:

Reducing Glare and Reflections

One of the most familiar uses of in-line polarizers is in sunglasses and camera lenses. Have you ever noticed how a good pair of polarized sunglasses cuts down on blinding glare from the sun reflecting off surfaces like water or cars? That’s the in-line polarizer at work! It blocks those intense reflected light waves, making it easier to see clearly without squinting.

Enhancing Display Quality

Another application you likely encounter daily is on LCD screens—your TV, computer monitor, or smartphone display. In-line polarizers play a key role in controlling the liquid crystals that create the images you see. By precisely aligning the polarization of light, the polarizers enable vivid colors and high contrast, making the visuals pop.

Unlocking Material Secrets

In-line polarizers are used by polarizing microscopes in scientific labs to examine the microscopic characteristics of materials such as crystals, minerals, and polymers.

Keeping Telecommunication Signals Clear

You might not realize it, but in-line polarizers are also essential in fiber optic cable networks that transmit data over long distances. They help maintain the integrity of polarized light signals, preventing signal degradation and ensuring your internet, TV, and phone connections remain strong and clear.

Utilizing the wave nature of light, an in-line polarizer is an amazing optical component that can transmit or block particular oscillation directions selectively. Due to its ability to control the polarization of light waves, it can be used for various applications.

Why Should Polarization Maintaining Filter Coupler Feature High Extinction Ratio?

A polarization maintaining filter coupler splits the light from an input PM fiber between 2 output PM fibers or combines light signals from 2 input fibers into a single PM output. Basically, the device is used to split high-power linearly polarized light into multiple paths without perturbing the linear state of polarization or SOP. Other than this, the device is used as a power tap to monitor signal power in a PM fiber system without disturbing the linear SOP of the light propagating in the PM filter. 

In the applications, you will find PM fiber interferometers, power sharing in polarization-sensitive systems, and signal monitoring in PM fiber systems. The package consists of rugged stainless steel, which is designed for high optical performance and stability. 

The polarization maintaining filter coupler features low excess insertion loss, low back reflection, and high extinction ratio. 

In this post, we will discuss one of the features of polarization maintaining filter coupler i.e. the extinction ratio, and why it should be high. 

Extinction ratio 

The extinction ratio quantifies the cross-coupling in regards to birefringent fiber. It indicates the amount of light that can mix between the two polarization axes. The value of the extinction ratio is important because it measures the polarization maintaining the performance of an optical fiber. 

Mostly, the extinction ratio is misunderstood by many people, leading to lots of problems in the future. 

The value of the extinction ratio depends on the length of the fiber and the environmental conditions in which you use it. If the fiber is subject to high mechanical stress and small-diameter bends, then internal disruption is possible, reducing the extinction ratio significantly. 

What’s the impact of extinction ratio on the system performance and other parameters?

With a high extinction ratio, the bit-error ratio or BER improves. And when the bit-error ratio improves, it reduces the number of errors and the amount of error correction required. The high data rates are pushed through materials, loss, and dispersion close the eye and errors increase. 

What happens if the extinction ratio is low or poor?

If the extinction ratio is low or poor, the polarization-maintaining filter coupler will increase its power penalty (PP), worsen its Bit-error ratio (BER) and diminish its benefit of increased power. 

When does the extinction ratio become significant?

If you want quality and successful performance of the maintaining polarization filter coupler, the extinction ratio becomes significant. 

Sometimes, the measured values between manufacturers and designers are very different. Even the end users obtain different values than the manufacturers. If this happens, the device will be rarely productive. So, the value of the extinction ratio should be determined before buying a polarization-maintaining filter coupler. And undoubtedly, it should be high. 

What to Know Before Buying Optical Circulator

Optical circulator is something used to monitor the optical power traveling in optical fiber. Either it can be used to polarize lights flowing different directions into a single direction or light in the single director into several directions.

There are varieties of Polarization Insensitive Optical Circulators meant to serve different purposes. Choose an optical circulator based on what you want to achieve.

What is Optical Circulator?

Optical circulator is a non reciprocal device used to allow the routing of light from one fiber to another, and this happens based on the direction of the propagation.

A special fiber optical component, optical circulator is used to separate optical signals in an optical fiber. It comes with three ports, and they are designed in a way that when light enters any port, it will exist from the next. This feature of high isolation of the input along others such as optical powers, low insertion loss, makes optical circulator a device widely used in a wide range of advanced communication systems and fiber optical sensing devices.

There are many manufacturers in China offering different types of optical circulators such as Polarization Insensitive Optical Circulator. If you are looking high quality circulators designed to your specific needs, and the best most competitive price, DK Photonics which offers a wide range of optical passive devices including the most widely used Polarization Insensitive Optical Circulator can be the right choice for you.

Polarization Insensitive Optical Circulators offered by DK Photonics comprised of several world-class features such as:

  • Low Insertion Loss
  • High Isolation
  • Low PD
  • High Stability and Reliability
  • Cost Effective

These are a few of the features that make the circulator highly suitable for the use in a wide range of applications. Polarization Insensitive Optical Circulators are widely used in:

  • DWDM Systems
  • Optical Fiber Amplifier
  • Pump Laser Source
  • Fiber Optic Sensor
  • Test and Measurement
  • Instrumentation

How to does the optical circulator work?

The Polarization Insensitive Optical Circulator which is used in fiber optical system directs the light/optical signals from one port to another. This helps prevent the signals transmitting in undesired direction. In a circulator which has three ports, signal is pushed from one port to the second port, and the another signal is directed from the port second to port 3 and at last, a third signal is transmitted from the last port to again to the port one. This is how the circulator helps you control the light and direct the signals into desired direction.

A Brief Introduction to Polarization Insensitive Optical Circulator

In simple terms, an optical circulator is a fiber optic device with three or four ports designed in a way that the light entering from any port exits from the next port. This implies that if a light wave enters from port 1, it emits from port 2; however, if some fraction of the emitted light wave is reflected back to the circulator, it exits from the port 3 rather than coming out of port 1. This working is analogous with the working of an electronic circulator.

Fiber optic circulators are used to separate optical signals traveling in opposite directions in an optical fiber. They are commonly used for bi-directional transmission over a single fiber. But, there are polarization insensitive optical circulators in the market which are gaining high popularity in electronics and telecommunication industry. What are these? How are they different from ordinary ones? Let’s check out.

Polarization Insensitive Optical Circulators

This special type of optical circulator is a non-reciprocal fiber optic device that routes incoming light wave from any port to the next and sends the rejected part of the light wave to third port instead of the first port.

Here, non-reciprocal means that if there is any change in the property of the light wave caused by traveling through the fiber, it will not reverse by traveling in the opposite direction.

It is a compact high performance light wave component which functions similar to an isolator. It protects the input fiber from returning power and also allows the rejected/reflected light to be employed.

The benefit of using these optical circulators is that they are bestowed with high isolation, low insertion loss, low polarization dependent loss (PDL) and various other remarkable features.

As these circulators are polarization insensitive, they are highly desirable in a variety of applications. For instance, linearly polarized beams with different polarization states and polarization multiplexed beams are extensively used in optical telecommunication systems where the use of polarization sensitive circulators is extremely limited.

They find their wide usage in a number of applications such as fiber gratings and other reflective components in DWDM systems, bi-directional communication systems, dispersion compensation, wavelength add/drop, high speed systems, EDFA applications, optical time domain reflectometer (OTDR) measurements, etc.

Polarization insensitive optical circulators are available in multifarious specifications, however, if available specifications are not suitable for your applications, you can also order custom optical circulators.

Salient Features:

  • High isolation
  • Low insertion loss
  • Low polarization distribution loss
  • Excellent stability
  • Superior reliability
  • Optimum performance

General Applications:

  • Optical fiber amplifier
  • Fiber optic sensor
  • DWDM systems
  • Pump laser source
  • Instrumentation
  • Test and measurement
  • Optical communication systems
  • Fiber Gratings

If you also have a requirement for polarization insensitive optical circulators in standard or customized specifications, contact today one of the reputed optical circulator manufacturers.

PM Optical Circulators: Technology used and Categorization

Since 1990, polarization maintaining optical circulator has become one of the essential components in advanced optical communication systems. Nowadays, its applications have expanded widely not only in telecommunication industry but also in medical and imaging fields. Here, we will discuss this indispensable component in detail. So, let’s start with the basics.

Polarization Maintaining Optical Circulator

What is a PM Optical Circulator?
PM optical circulator is a three or four port non reciprocal passive component which functions similar to an isolator. It transmits the light wave from one port to next port with maximum intensity while maintaining polarization and blocking any light transmission from one port to the previous port. Thus, it is also featured as a unidirectional circulator.

Technology Used in PM Optical Circulators
Polarization Maintaining Optical Circulators are designed on the basis of nonreciprocal polarization rotation of the Faraday effect. As the working of optical circulators is based on several components such as Faraday rotator, birefringent crystal, waveplate and beam displacer, let’s take a quick look at each of them.

Faraday Effect:
It is a magneto-optical effect which explains the phenomenon in which polarization plane of electromagnetic wave (or light wave) is rotated inside a material under magnetic field applied in parallel to the direction of wave propagation. The unique aspect of this effect is that the direction of rotation is independent of the propagation direction of light wave, which implies that rotation is non-reciprocal.

Light Propagation in Birefringent Crystal:
Birefringent crystal is a common material used in the designing of optical circulators. The crystals used in optical circulators are typically anisotropic uniaxial which means they have two refractive indices with one optical axis. The function of this birefringent crystal depends on the propagation direction of light and its optic axis orientation (crystal cutting). The crystals which are generally used include quartz, rutile, YVO4, etc.

Waveplate:
Also called retardation plate, a waveplate is one of the applications of birefringent crystal. It is made by cutting a crystal into a particular orientation. Due to small birefringence, crystal quartz is broadly used for making waveplates.

Beam Displacer:
A birefringent crystal based beam displacer is used to split an incoming light beam into two beams with orthogonal polarization states.

Categorization of Optical Circulators
Optical circulators are mainly divided into two categories:
Polarization-dependent optical circulator
Polarization-independent optical circulator

The former type is only functional for a light wave with a particular polarization state and is only used in a few applications such as free space communications between satellites and crystal sensing.

On the other hand, the latter type is functionally independent of the polarization state of light. While in ordinary circulators, the polarization is not maintained but there are polarization maintaining optical circulators available in the market also. They are used in a large variety of applications.

According to their functionality, optical circulators can also be divided into two groups.
Full Circulator – light passes through all ports in a full circle
Quasi Circulator – light passes through all ports but the light from last port is lost

Fortunately, due to the advancement in technology, you can avail highly reliable and efficient Polarization Maintaining Optical circulators not only in standard specifications but in customized specifications too.

All about Optical Isolators and Where to Buy Them

The fiber optic isolator is a two way or two-port micro-optic device built along with SMF28e fiber or Hi1060 fiber. This device guides optical light in one single direction and prevents it from reflecting and scattering in the reverse direction. These isolators feature high isolation, low insertion, and great environmental reliability and stability. They are best used for suppressing reverse reflection in fiber lasers and many other fiber optic systems that are based on high-performance lasers.

The polarization insensitive optical isolators are designed and manufactured to match Telcordial standards. The device gets its capability to handle high power from epoxy-free optical path design and a unique manufacturing process. These devices are highly characterized by superior perforce at low cost while providing high reliability. Polarization insensitive optical isolators have widely been used in transmitters, Raman amplifiers, fiber lasers, DWDM systems, EDFAs, and other fiber optic communication equipment to suppress backscattering and reverse reflection.

Features

Optical path epoxy free

Low Insertion Loss

High return loss

High isolation

Low polarization sensitivity

High stability & reliability

Applications

Fiber optic amplifiers

Fiber optic systems testing

CATV fiber optic links

Fiber optic LAN systems

Telecommunications

Where you should buy them?

Most probably you have bought certain products from online stores with the help of the internet. Similarly, you can buy these isolators from a reputed and reliable manufacturer and supplier and if you require these in large quantities you can buy from online wholesale retailers of these isolators.

Why you should buy them online?

The online market is highly versatile especially when it comes to buying electronic equipment like these polarization insensitive optical isolators. Moreover, a majority of suppliers would be having other supportive components for sale that are used in fiber lasers and various telecommunication based applications.

Following is the list of some other components used in fiber laser applications

1.0μm Polarization Beam Splitter-Combiner

1.0μm 1×2(2×2) Fused PM Fiber Standard Coupler (Single axis working)

1.0μm 1×2(2×2) Polarization Insensitive Fused PM Fiber Standard Coupler (Both axis working)

1.0μm Polarization Maintaining Filter Coupler (1×2/2×2) (Both axis working)

1.0μm Polarization Maintaining Tap Coupler (1×2/2×2) (Fast axis blocking)

980/1030 & 980/1064nm PM Fused WDM

980/1030 & 980/1064nm PM Filter WDM

1.0μm PM Faraday Mirror

1.0μm PM (2+1) x1 Pump & Signal Combiner

1.0μm PM (6+1) x1 Pump & Signal Combiner

1.0μm PM Mode Field Adapter

1.0μm PM Cladding Power Stripper

1.0μm 1×4, 1×8 PM Filter Coupler Modules

1.0μm Polarization Maintaining Mechanical Variable Optical Attenuator

All of these including more are widely available on the internet. All you have to do is to choose your supplier wisely and rely on the one which assures you that you will receive good quality components. A good reason to shop for them online is that you will notice that the online market is highly cost-effective and there are chances to get components at a reasonable price, that also less than the offline market.

What Are Optical Circulators And Their Applications?

Each optical circulator is a generalized isolator which has three ports or sometimes more. Where an isolator causes the loss in the direction of isolation, a circulator gathers the light and redirects it to an output port which is nonreciprocal.

If I talk about a three-port circulator with non-strict-sense, this type of circulator has significance use in telecommunication applications because it is not necessary that the light should travel back from port 3 to port 1. For example, the light reflected from a fiber Bragg grating requires to be separated from the input light without loss, but since optical links are not operated in reverse only, there’s no requirement of strict-sense behavior.

An optical circulator is a special kind of fiber optic device which can separate optical power traveling in one single optical fiber in opposite directions. A polarization insensitive optical circulator can be used here to get bi-directional transmission of power over a single fiber. This circulator is majorly used in modern communication systems and advanced fiber-optical sensor systems due to its high isolation between the input power and reflected optical power and its lower loss of insertion.

A majority of online suppliers offer three or four-port optical circulators with;

Standard 1310nm or 1550nm windows

Or sometimes a wider range of wavelength from S to L band

Some of the manufacturers can also provide customized circulators on special requests with providing different wavelength, for instance, 1030nm, 1050nm, or 1040nm can be requested.

Though the standard power handling of this kind of a circulator is 300mW (CW), in the market, circulators are also available with power handling 1000mW, 2000mW, and 500mW (CW).

Here, a buyer requires being fully aware of the requirements of the application before choosing one.

Features

Low Insertion Loss

Low PDL

Wide Band, High Isolation

Epoxy Free Optical Path

Compact In-line Package

High Stability and Reliability

Easy mounting

The polarization insensitive optical circulators are often easily mounted to optical tables and can withstand various handlings. The use of four strong magnets helps to hold the rugged package securely on surfaces. Another mounting option is to wisely use tow countersunk holes with having some space in-between, in order to achieve compatibility with mounting patterns of optical tables.

Major Applications

Optical Amplifier

Fiber Sensors

Add-Drop Filters

Bi-Directional Communications

Metro Area Network

Digital, Hybrid, and AM-Video System

Wavelength Add / Drop

Dispersion Compensation

EDFAs

The online market is actually full of such optical circulators and buyers can place an order for customized circulators too, for instance, pigtailed versions of circulators would be perfect if an application requires a fiber with extended length on the circulator’s input and output.

Once you go online you will find that there are several suppliers of these optical circulators. You require making a decision on which one you should choose to shop. Apart from that, gather complete information about the application’s requirements and then decide which one you should buy.

These Are Proven Tips That Will Help Quickly Find the Best Optical Circulator

There are many brands in China making a wide range of optic fibers or circulators – a crucial device widely used for electronic applications. What that makes it a bit complex to choose the best one (optical circulator) is that all of them claim to offer high quality products for the most competitive prices. To help you with that, here we have curated a list of some tips that are very effective and anyone can apply them to select optical circulator.

 Tips to Choose an Optical Circulator

Look for all the options

 There are many options that you will find in China when it comes to optic fibers. For example Polarization Insensitive Optical Circulator one of the most widely used optic fibers for a wide range of electronic applications. The circulator is packed with host of features. If you are looking for an option that is durable, affordable and provide high quality performance, Polarization Insensitive Optical Circulator is what you must consider.

 Check after sales support

Whatever option you choose, make sure the supplier you buy your Polarization Insensitive Optical Circulator provides a good sale support. So when you have any problem with the product, you do not need to hire a technician. You can call to the supplier who will provide the right assistance to solve your problem. So buying Polarization Insensitive Optical Circulator from such a supplier saves you a chunk of money you need to pay for hiring a technician.

The suitability of the fiber to your device

As optic fibers come with different features, and so are suitable for some certain types of devices, it is vitally important to make sure the Polarization Insensitive Optical Circulator you buy is compatible with your device.

Compatibility

Types of fiber optic transceivers are getting richer, but the compatibility between different types has a great impact on the quality of network. It should be known that this product is designed to meet related international standards. Because. The circulators meeting international standards have no issues of compatibility.

Temperature adaptation

The temperature which is generated inside fiber optic transceivers is low, but as they are used in the Switches and computer room, the temperature fluctuates. It may get higher or lower. Too high or too low temperature adversely affects the parameters, for example optical power, optical sensitivity, etc. Polarization Insensitive Optical Circulator seems a best choice in this case. It is highly sensitive to fluctuation in power, and quickly adapts to the temperature.

 When you need to buy optic fibers, follow these tips that will surely profoundly help you choose the right circulator for you.

Things That You Must Know about Polarization Maintaining Optical Circulator

Optical fiber is used for an electric device in which light polarization is required. And each fiber is designed to do a certain job and so is suitable for some certain applications. So you should have the knowledge of an optical fiber that you want to buy and make sure the fiber you want to buy would be perfect for your need. So we have gathered some crucial information about optical circulator used for maintaining light polarization, and that will help you choose the right fiber.

If you are looking for a circulator for devices like fiber amplifiers, fiber sensors, test and measurement appliances, coherent detecting appliances, The 1310nm&1550nm 3-port Polarization Maintaining Optical Circulator with both axis working would be the best choice. The circulator is compact and very efficient to route the incoming signals from Port 1 to Port 2, and incoming Port 2 signals to Port 3. The circulator works as a single that can be used to transmit light from an input fiber to an output fiber. It directs the light returning from the output fiber to the third port. The 3 port circulator with both axis working is like an isolator that protects the input fiber from return power but the light that is rejected can be used.

Another fiber can be also used for those applications is 3 port optic circulator with fast axis blocked. This type of circulator is also lightweight, compact and performs well. This circulator also works as the circulator (with both axis working) does. Both circulators used for maintaining polarization can handle the power ranging from 300mW to 20 W, and have center operating wavelengths ranging from 850nm to 1650nm.

Both optical circulators (with both axis working and with fast axis blocked) provide a host of benefits such as low insertion loss, high isolations, etc. Here are some key benefits that the circulator provides:

  • Low Insertion Loss
  • High Isolation
  • High Extinction Ratio
  • Low Cost
  • High Stability & Reliability

Apart from those two circulators that are widely used for a wide range of applications, there are other optical fibers that are used for electric devices. Whatever fiber you buy make sure it works perfectly with your device.

So before you start looking for optical fibers, get to know about your device in details. Learn everything that can help you in a way or so to decide on which type of optic fiber you should look for.

Once you are done with the type of fiber you need, find a Polarization Maintaining Optical Circulator supplier. There are many Polarization Maintaining Optical Circulator suppliers in China, you should trust only those that are reputed and have long been into the business.

Optical Circulators and Their Applications

The ‘optocirculator’ commonly known as optical circulator is the circulator which is majorly used for optical communication. It is actually similar to the isolator but, optical Isolator is used to insert resistance to the reverse signal with loss of insertion whereas, optical circulator directs the light to one port and diverts it out to the non-reciprocal port. Isolator typically has 2 ports only while circulator has 3 to 4 ports.


Originally, polarization insensitive optical circulators were used in telecommunication systems in order to increase the capacity of transmission of existing networks. The Utilization of these circulators in a bi-directional transmission system can double the network’s transmission capacity without deploying extra fibers, earlier, this task was very expensive without optical circulators.

However, the uses of optical circulators have greatly expanded in not only the telecommunication sector but also the imaging and sensing industries with the quick and great advancement in optical communication technologies and the wide availability of high-performance circulators at lower costs. Optical circulators have now become a vital element in advanced optical networks.

Typical Specifications for Optical Circulator:

  • Grade type (P or A)
  • Number of Ports (3 or 4 ports)
  • Insertion loss (0.6/0.8) over +/- 20 nm bandwidth
  • Central Wavelength (1310nm or 1550nm)
  • Directivity (60 dB)
  • Power handling limit (300 mW)
  • Isolation (min.40dB)
  • Return Loss (60 dB)
  • PDL (0.1 dB)
  • WDL (0.2 dB)
  • PMD (0.1 ps)

Optical circulators are intensively powerful devices that are generally used to extract optical signals from a reflective device. In this manner, optical circulators are regularly utilized related to the fiber Bragg gratings that are ordinarily reflective devices. Together with fiber Bragg gratings, optical circulators have turned out to be one of the vital components in advanced DWDM optical systems. Circulators are utilized as MUX/DEMUX systems, but at the same time are utilized in dispersion compensation with the fiber Bragg grating, tunable optical Add/Drop, and other different applications.

The idea has been adapted into different devices, such as replacing the coupler and erbium-doped fiber with a dispersion compensation fiber to reduce the required fiber length and adding a Faraday rotator in-between the fiber and mirror in order to reduce the polarization-induced effects. Also, bi-directional fiber amplifiers are also proposed for taking full advantage of the polarization insensitive optical circulator.

With the improvement in advanced optical systems, the uses of optical circulators are extending quickly and new uses and applications are rising rapidly. For instance, as of late it has been accounted that by including wavelength-specific capacities into circulators, a bi-directional wavelength-subordinate circulator can be arranged, which opens another measurement of uses in the advanced DWDM optical systems.

These circulators are widely used for several other applications and this why they are extensively available at the stores as well as online. Due to increase in demand, there are thousands of manufacturers and millions of suppliers of optical circulators all around the world.