Month: May 2019

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.