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All you need to know about polarization maintaining optical circulators: a few major pointers!!

Since several years, Polarization Maintaining Optical Circulator has become an important element in the optical communication system. But these days, its applications have expanded not only in the telecommunication field but also in imaging and medical field.

In this blog, we’ll discuss on Polarization Maintaining Optical Circulator in more detail, but before that let’s know a few basic regarding it.

To begin with, let’s discuss what exactly is an optical circulator?

An optical circulator is mainly a multiple port non-reciprocal passive component. Its function is just similar to that of a microwave circulator, i.e. to transmit the light wave from one port to other with maximum intensity. But, at the same time, it also blocks any light transmission from one port to its previous port. Besides, the entire optical circulator process is based on the non-reciprocal polarization of the Faraday Effect.

What are the features of Polarization Maintaining Optical Circulator?

There are various features of polarization maintaining optical circulator. Mentioned below are a few major ones:

–    It has a high stability

–    It has a low insertion loss

–    It has high reliability

–    It has high optical return loss and so on.

How can optical circulators be categorized?

Optical circulators typically can be categorized into two main streams namely:

–    Polarization-dependent optical circulator, and

–    Polarization independent optical circulator

Polarization-dependent optical circulator is functional only for a light wave with a specific polarization state. This type of optical circulator is used only in some of the applications that mainly include free space communication between crystal sensing and satellites. Whereas the polarization independent optical circulator is independent of the polarization state of light. In the ordinary circulators, the polarization is certainly not maintained, however, there are polarization maintaining optical circulators available, so they can be used on behalf of it.

Besides, they can also be utilized in a wide variety of applications, but depending on its functionality, optical circulators may be divided into two groups:

–    Quasi circulator: In this circulator, the light passes through all the multiple ports, but the light from the last port is lost.

–    Full circulator: In this circulator, the light passes through all the multiple ports in a full circle.

When it comes to circulator’s design, there are many variations, but, all the non-reciprocal rotation designs certainly share the same structure with at least three functional elements namely- non-reciprocal polarization rotation elements, polarization recombining, and splitting elements, as well as polarization dependent beam steering elements.

Finally, we can say that with the large development of advanced optical networks and elements, the application of optical circulators are rapidly growing and new and advanced applications and functionalities are emerging quickly.

Polarization Beam Combiner/Splitter: An In-Depth Insight to Help Choose the Best

Polarization beam combiner/splitter is a crucial component in optic sensor system, optic transmits system, high power EDFA, etc. It is used to combine light beams from two PM input fibers into a single output fiber or split the light beams from an input fiber into two output fibers of orthogonal polarization states.

Polarization beam combiner/splitter(s) have different capacity to handle power. For example, the 1550nm Polarization Beam Combiner/Splitter can handle powers range from 300mW to 10W.

Also the features may vary, from device to device. But all top polarization beam combiners/splitters should have these features:

  • Low Insertion Loss
  • High Extinction Ratio
  • Compact In-Line Package
  • High Stability and Reliability

Whatever your need – whether you want the one to be used in optic sensor system or optic transmit system or high power EDFA or polarization Demux, make the polarization beam combiner/splitter include those features as well as those that make it highly suitable for what you want to use it for.

There are performance specifications given on the product. You should go through them, as this will help you can understand how suitable the polarization beam combiner is for you. You should give attention to all parameters from wavelength, insertion loss, return loss, fiber type, operating temperature to operating bandwidth. If you are looking for 1550 wavelength combiner, make sure minimum extinction ration should not be below 22 dB and insertion loss should go beyond 0.6 dB. Typical insertion loss is 0.4 dB for grade P polarization beam combiner/splitter whereas it is 0.5 for grade A combiner.

If there is not enough information available on the product, you should discuss all those points with your supplier as he or she may have better knowledge of this.

Price should be also a factor, so it is advisable to compare various options. This way, you get to know about the features crucial to meeting your requirements. And the best of all, you do this within your budget.

While it is important to buy products with good quality assurance, it is also important that you buy from a leading manufacturer. Make sure the polarization beam combiner/splitter you want to buy comes with a solid post sale support so in case you have any problem with it, you can get it fixed. And there are many like DK Photonics that you rely on for polarization beam combiner/splitter that deliver better performance consistently. It also provides customized splitter especially designed to suit your needs.

Understanding Optical Coupler and Optical Splitters

Bandwidth coupler and splitters are some of the most important passive devices which are widely used in a number of applications for improving the performance of the whole system in one way or another. These devices are used to divide, route or combine multiple optical signals. While coupler is named after its working principle, splitter is named by its functioning. Here, in this blog, we are going to discuss these devices in detail and know why some optical couplers are often called optical fused couplers.

Introduction to Couplers

Fiber optic couplers are those devices which either split optical signals into multiple paths or combine multiple optical signals in one path. Optical signals are comprised of photons and are much more complex than electrical signals. Therefore, manufacturing optical couplers are trickier to design than their electrical counterparts.

However, unlike electrical signals, an optical signal doesn’t flow through the receiver to the ground. Rather, there is a detector at the receiver that absorbs the signal flow. Moreover, multiple receivers which are connected in series don’t receive any signal except the first receiver where the entire signal is absorbed.

As a result, multiple parallel optical output ports need to divide the signals between ports for reducing the magnitude. The number of input and output ports expressed as N x M configuration, where N is the number of input fibers and M is the number of output fibers. This configuration characterizes an optical coupler.

When an optical coupler is designed by using two or more parallel optical fibers which have twisted, stretched and fused together, then the resultant coupler is termed as optical fused coupler. The fusion of optical fibers is carried out so that their cores stay very close to each other.

Optical fused couplers are generally made using configuration in multiples of 2 such as 2×2 or 4×4 but can be made in any configuration depending upon the application requirements.

Introduction to Splitters

Fiber optic splitters are the ones which split fiber optic signal into several parts in a certain ratio. The simplest couplers may be called splitters. They usually contain at least three ports but may contain more than 32 ports for devices with high complexity. Generally, there are two kinds of fiber optic splitters. One of them is traditional fused type fiber optic FBT splitter and other is PLC fiber optic splitter which has a compact size and is best suited for density applications.

They are made with 0.9mm, 2mm or 3mm cables. While 0.9mm outer diameter cable is mostly used in stainless steel tube package fiber optic splitters, remaining cables are widely used in box type package fiber optic splitters. Depending on their working wavelength difference, there are also single window and dual window optic splitters.

By now, you can easily decide which device is suitable for your application, an ordinary optical coupler, an optical fused coupler or an optical splitter.

How to Buy Optical Couplers: Some Important Things To Know

Optical coupler is a kind of semi-conductor device designed and meant to transfer electrical signals by using light waves to couple electrical isolations between circuits. There are different types of couplers and each caters to a certain purpose.

What is optical coupling?

Before going any further and talking about things like types of couplers, features or the best places to buy quality optical fused couplers in China and the likes, let us have a brief look at: What is optical coupling?.

Techopedia defines optical coupling as a method used to interconnect two devices to transfer an optical signal using light waves in the field of optoelectronics. It can be a simple connection between two optical cables using a device or a complex one that links two separate actions and make them dependent on one another.

In broader way, coupling can be thought of as any connection created between two devices using light waves. A good example is TV remote control.

Choosing an optical coupler

There is a wide range of couplers available in the market with different features. Take for example high performance fused-type mode-selective coupler which uses elliptical core two-mode fiber at 1550 nm.  This type of coupler provides unique functions and is perfect for the use in optical communication systems and sensors such as dispersion compensators, optical add-drop multiplexers, switches, and acousto-optic modulators and switches.

Photonic-crystal fibers (PCFs) are among the most specialized optical couplers. The couplers are made with Photonic Crystal Fibers. There are two types of PCFs created using a group of silica tubes around a silica rod and drawing them. They are made by using the fused biconical tapered method.  A fiber with five hexagonally stacked layers of air holes can achieve a 33/67 coupling ratio while a fiber having one layer four holes is capable of obtaining a 48/52 coupling ratio.

If you are looking for low loss, durable and insensitive to ambient temperature variations, you should consider fused single mode fiber access couplers.  They are made by chemically etching most of the glass cladding material surrounding the fibre core, and thermally fusing the fibres together in the etched region.

Fused vertical couplers are a good option for the fabrication of switches. The couplers are made using wafer fusion for a short coupling length. Using the fused vertical coupler, planar waveguides can be fabricated on two different substrates and in a three-dimensional structure. Fused coupler is the best choice for crossbar switches.

So get to know what you need optical couplers for before you contact a supplier. You can also get custom couplers based on your needs. whether you are looking for high quality Optical Fused Coupler in china China  or specialized couplers like Photonic crystal fiber, DKphotonics will cater to your needs.

Want to Know What a PM Tap Coupler is? Read this

Instead of diving straight into complexities of polarization maintaining tap coupler, let’s first discuss what an optical coupler simply is. An optical coupler is a device which can join one or more optic fiber ends for transmitting light waves in multiple paths. It is capable of combining two or more inputs into a single output as well as dividing a single input into two or more outputs. If you compare it with a splice or a connector, you will find that with an optical coupler, the signals can be more attenuated as the input signal can be distributed among the output ports.

In general, fiber optic couplers can be divided into two categories: active and passive.

For active coupler, an external energy source is required. On the other hand, there is no requirement of power to operate passive couplers.

In the market, you will find different types of fiber optical couplers such as X coupler, combiner, splitter, stars and trees. This categorization is carried out on the basis of the number of input and output ports.

As the name implies, a combiner does the work of combining two signals and providing a single output. Similarly, a splitter does the functioning of dividing a single optical signal to facilitate two output signals. It can further be divided into Y couplers and T couplers. If we talk about star couplers, they distribute power from inputs to outputs. While some tree couplers take multiple input signals and provide one output signal, others take a single input and provide multiple output signals.

Fiber optic couplers are manufactured using a variety of technologies such as planar waveguide, fused-fiber and micro optics.

Now, let’s move to polarization maintaining optical couplers. They are the micro optic filter type devices which facilitate optical signal splitting while maintaining polarization with high extinction ratio. Being a coupler in the essence, they are capable of either splitting the light from an input polarization maintaining fiber between two output PM fibers or can join signals from two PM input fibers into a single PM output fiber.

By now, it is clear that what fiber optical couplers and PM optical couplers are. So, what exactly is a polarization maintaining tap coupler? It is a type of PM coupler which can split light waves with accurate tap ratio.

The polarization state can be aligned either with slow axis or fast axis of the polarization maintaining fibers. It is made from separate light crystals and the output port is also different from PM filter coupler. The benefit of using a PM tap coupler is that it can handle higher power and also has more precise coupling ratio than PM filter coupler. So, PM tap coupler is a better device with high optical performance and stability to be used for splitting high power linearly polarized light wave to provide multiple outputs while still preserving the polarization state.

This tap coupler can also be used as a power tap in a PM fiber system to monitor signal power without disturbing polarization state of the light traveling in PM fiber.

Applications of PM Tap Coupler

  • Power sharing in polarization sensitive systems
  • PM fiber interferometers
  • Signal monitoring in PM fiber systems
  • Coherent detection
  • Fiber optic instruments
  • Fiber sensors

Features of PM Tap Coupler

  • Compact-in-line package
  • Low insertion loss
  • High extinction ratio
  • Excellent reliability
  • Superior stability
  • Optimum optical performance
  • Accurate tap ratio
  • Can handle higher power
  • Precise coupling ratio

If you have requirement of polarization maintaining tap couplers or another kind of PM coupler with custom specifications, contact one of the esteemed PM coupler manufacturers so that you can be sure of that you are investing your time and money at the right place.

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.

Advantages of cladding power stripper for high-power fiber laser system

Heat handling has been often a challenge for high power fiber lasers when the output power grows abruptly. But this is no longer a matter of concern, there is far better solution not just capable of handling health proficiently but also offering a thong of advantages.  And this is none other than cladding power stripper which has magical capacity to deal with the unwanted optical power.

So the methods of stripping the unwanted light got much attention recently, and the thermal effect is now given much emphasis. Cladding power stripper uses microchannel sink –one of the most promising high efficiency heat exchange technologies, which improves the efficiency of heat exchange by sinking heat in CPS.

CPS is a component of the system used to remove unwanted light and distribute the heat converted by it. It is perfect for a system that transmits signal light in the core which absorbs inner cladding and all pumping light.

The cooling technology is implemented at the time designing of cladding power stripper structure. Header shaped microchannel provides better flow velocity uniformity than the trapezoidal and the triangular headers.

The CPS works better within a certain temperature. The temperature should not be more than 60 ◦C because of colloidal macromolecule substances in fiber. The idea temperature for cladding power stripper is 50.9 ◦C. CPS with microchannel heat sinking is sufficient for 10 kW DCFLSs.

So advantages of cladding power stripper can be summed up as:

  • it is ideal for 10 kW DCFLSs
  • It can work within as high temperature as 60 ◦C
  • It uses microchannel heat sink –one of the most efficient cooling technologies

However, the convective heat transfer coefficient depends on thermal conductivity and diameter of cooling liquid. For microchannel the diameter is 0.1–1 mm[8] , the convective heat transfer coefficient can be improved significantly. If convective heat transfer coefficient is replaced, the dissipated heat will increase, which means there will be more cooling.

To sum up

Given its super ability, along with other several benefits, to dispersing heat, CPS (cladding power striper) is hailed as the best for high power  fiber lasers and a system  that transmits signal light in the core where inner cladding and all pumping light. You can buy high quality cladding power stripper in China at the best price from a reputed dealer like DK Photonics, a leading name optical passive components.

Discussing Multiple Aspects of a Standard Cladding Power Stripper

Fiber laser systems have many advantages over other laser systems, including high beam quality, high conversion efficiency, cost-effectiveness, and lightweight. They have been widely applied in areas, such as optical sensing, medical devices, advanced industrial processing, and military defense. With the development of the double cladding fiber technology and laser diode pump technology, the output power of the fiber laser systems has been increased rapidly. However, the unwanted light and optical power increase, due to which the utilization of cladding power stripper becomes essential.

The actual and prime sources of the unwanted light transmitting in the cladding can be divided into 3 sections

Amplified spontaneous emission (ASE)

Residual pump light which is often there at the gain fiber’s end

Core light being reflected into the cladding or leaking into it

All the above-described unwanted light sources are actually spread throughout the chain of components. Excited gain medium naturally generates the amplified spontaneous emission. It is responsible for heavy watts of the entire unwanted light in any high-power laser setting, and actually more in an amplifier.

  • Performance Specifications
Parameters Unit Values
justify Signal Wavelength nm 1030,1064,108,1550
Operating Wavelength-Pumps nm 800~1200
Cladding attenuation(min) dB 17~20
Type. Insertion Loss (at 25℃) dB 0.05
Max. Insertion Loss (at 25℃) dB 0.20
Min. Polarization Extinction Ratio dB 18(For PM Fiber)
Cladding Power Handling(Stripping Power) W 10, 20, 30,…
Fiber Type In/Out /  Double Clad fiber
Pigtail Length m 0.8 or other
Operation Temperature ℃ 0 ~ +50
Storage Temperature Range ℃ -20 ~ +75

 

General Configuration for CPS:

1.5μm Fiber laser：

Working Wavelength(nm) Input/ouput Fiber Signal IL Min.Stripping Efficiency Max.Power Stripping
1530~1570 SM-GDF-1550 ≤0.2dB 20dB 20W
1530~1570 12/130µm,NA0.20/0.46 ≤0.2dB 20dB 50W
1530~1570 25/300µm,NA0.09/0.46 ≤0.2dB 20dB 100W
1530~1570 PM-GDF-1550 ≤0.2dB/ER>18dB 20dB 20W
1530~1570 PM 12/130µm,NA0.20/0.46 ≤0.2dB/ER>18dB 20dB 50W
1530~1570 PM 25/300µm,NA0.09/0.46 ≤0.2dB/ER>18dB 20dB 100W

 

2.0μm Fiber laser：

Working Wavelength(nm) Input/ouput Fiber Signal IL Min.Stripping Efficiency Max.Power Stripping
1950~2050 10/130µm,NA0.15/0.46 ≤0.2dB 20dB 20W
1950~2050 25/250µm,NA0.09/0.46 ≤0.2dB 20dB 100W
1950~2050 25/400µm,NA0.09/0.46 ≤0.2dB 20dB 100W
1950~2050 PM10/130µm,NA0.15/0.46 ≤0.2dB/ER>18dB 20dB 20W
1950~2050 PM25/250µm,NA0.09/0.46 ≤0.2dB/ER>18dB 20dB 50W

Now if I talk about its availability in the market. There are several suppliers who can provide you with CPS (cladding power stripper) in all types. In case, you don’t find a standard CPS to fulfill your requirements, manufacturers generally accept the customization of a specially needed CPS or a set of them. You would be able to choose solicitations for specific fiber type, various wavelengths, and the handling power of operations as per your particular requirements.

If you need to buy these power strippers, you may search through the web to find various manufacturers and suppliers. You can simply search for the same, compare their specifications, select the quantity, and place the order as per your need.

Functions of a Cladding Power Stripper and Its Market

The configuration of a particular DCFLS (double cladding fiber laser system) is generally schematically arranged. The fiber is cladding-pumped by high power diode stacks which then spread and amplify the pump light. High reflector and output coupler fiber Bragg gratings are usually etched on the fiber. It is best for a system that has all light signals transmit in the core and inner cladding where all pumping light is core-absorbed.

But, there always some unwanted light exists in reality. CPS, also known as cladding power stripper is an important component of the fiber optic systems which is used to remove this typical unwanted light and distribute the heat, initiated by that unwanted light.

The unwanted light spreading all over the cladding actually consists of the main three parts mentioned below.

Amplified spontaneous emission (ASE)

Residual pump light at the gain fiber’s end

Core light getting leaked or reflected inside the cladding

Prior to the output of light, the unwanted light has to be eliminated so that it would use unused space optics of a complicated laser system. The unwanted light gets converted into heat and this heat may lead to heated up optics and the core light would not be able to focus nicely. Moreover, the heat may also burn or damage the system’s important components or deteriorate the function when multiple systems are combined together for greater efficiency.

In double cladding fiber laser systems, the unwanted optical power and light must be reduced so that the output light gains higher beam quality. Several kinds of research have been done to strip that light from the cladding. Removing the originally there fluoroacrylate jacket and coating the fiber with a high index polymer can literally strip residual light of more than a hundred watts. Fabrication using a suitable etching method successfully cleared the test and stated that it offers good behavior instability so that it can be used in the applications with higher power laser systems.

All such researches successfully eliminated the unwanted light and the crucial work after that light gets converted into heat. Some of the researches also provided a cooling method of their tests, including cooling water based plate and air cooling. But because the output power of DCFLS increases, the traditionally used cooling methods could not stand the harsh heat.

Apart from there functions, there are manufacturers who can provide you with cladding power stripper of all kind of double Clad fiber where cladding power can reach up to 500W. If you couldn’t find a standard CPS that fulfills your needs, you can provide your desired specification to a reliable manufacturer and get a quote for a custom CPS. Requests for custom fiber type, operation handling power operation, varying wavelengths, and other specific requirements will be addressed quickly.