Month: September 2019

What are Faraday Rotators and Isolators and where are they used?

When it comes to transmission of light signals, the “Polarization State” is one of the important characteristics that you need to focus on and Faraday rotators and isolators are those devices which help engineers to take care of it. So, today, we have decided to share the basic information about these crucial devices and their applications.

Faraday Rotator and Its Applications

It is a magneto-optic device which employs Faraday Effect to rotate the polarization state. In this device, the light is transferred through a transparent medium which is exposed to the magnetic field. The direction of magnetic field lines is approximately the same or the opposite as the direction of the beam.

If light is linearly polarized in some direction, this direction is continuously rotated while passing through the medium. When a linearly polarized beam is passed through a Faraday rotator and back again after reflecting in a mirror, the polarization changes of the two passes add up instead of canceling. This non-reciprocal behavior of Faraday rotator is what makes it distinct from other arrangements such as waveplates and polarizers.

Applications:

High power Faraday rotators are widely used in laser technology. Some of its major applications are:

  • One of the most common applications of Faraday rotators is in Faraday isolators for protection of lasers and amplifiers against back-reflected light. In this application, the rotation angle should be close to 45 degrees in a particular spectral region. Highly uniform polarization rotation is required for attaining high attenuation for back-reflected light.
  • A Faraday rotator is also used in a ring laser resonator for introducing round-trip losses that depend on the direction and, thereby, enforce unidirectional operation. Since only a very small difference of loss is enough most times, a Faraday rotator will be helpful to facilitate a small rotation angle.
  • It can be used for Faraday mirrors which help in achieving a polarization direction that is orthogonal to that of the input beam even if the polarization state is not preserved by the amplifier. It works better than using a Faraday isolator, an amplifier, and an ordinary mirror.
  • It is also used in interferometers because polarization state changes through the fiber are canceled out on the return trip.

Faraday Isolator and Its Applications

A Faraday isolator is typically an optic isolator which transmits light in a certain direction while blocking light in the opposite direction. They are variants of optical circulators having at least three ports and based on Faraday rotators.

Types:

Polarization Sensitive Faraday Isolators

It is the simplest one because it functions only when the input beam has a fixed direction of linear polarization.

Polarization Insensitive Faraday Isolators

This Faraday isolator is a device which works for arbitrary polarization of the input beam and therefore, it is widely used in fiber optics as many fibers don’t maintain polarization.

Applications:

  • They are sometimes used for protecting laser or amplifier against back-reflected light. Some amplifier chains contain several isolators between different stages not only for protection purposes but also for amplified spontaneous emission.
  • The polarizing property of a polarization-dependent isolator can be used within a laser resonator for enforcing linear polarization state or for mode locking with a nonlinear polarization rotation.

So, both high power Faraday rotators and isolators play a significant role in electronics and telecommunication industry.

Make the work easier with Optical Fused Coupler

Optical fused coupler is the most common and used technology in the IT sector to make the work easy for all. It is the invention in the department which works on the wavelength with the help of some scientific formulas. The fused coupler is used to transmit light waves in multiple paths with the help of the two or more inputs. It helps to complete the task simultaneously for more than one place with proper delivery of the waves. It is safe to use and never give any shock to the person. The working module of the fused coupler is straightforward which makes it easy for technicians to use.

The optical fused coupler works by partially removing the cladding from two or more fibers and bringing them in the close proximity. Once we remove the cladding and connect the fibers, the light couples from one fiber to another. The problem arises when there is a need to control the flow of the light waves. It is easy in the case of optical fused coupler because the remaining thickness of the cladding and the length of the region of proximity control the situation. The operation of the coupler is simple but going in details it depends upon the multimode and single mode of the fibers.

Details about the Multimode and single mode fibers in the optical fused couplers

Multimode fiber- The working module of the multimode fiber is large as the higher-order modes leaks into the cladding and in the core of the other fiber. The degree of the work and result depends upon the coupling zone and not on the wavelength.

Single mode fibers- The working module in the single mode fibers is the cyclic because it starts from one end and finishes on the same. The work starts from the one where the light enters in one fiber and gradually transfers completely to the other and bounces back. The overall module depends upon the coupler design and wavelength.

The designing and efficiency of the optical fused couplers depends upon the fibers and their working module. They functioning of the equipment is so great that it reduces the workload of the person and makes it easy along with many in and out benefits.

Benefits of the optical fused couplers

  • The use of the coupler is no more restricted to the electrical field; people are using the tool in many other departments like medical and household.
  • It is reliable to use due to its manufacturing pattern. It is safe for people of all age and easy to use. It never gives shock in any situation.
  • The stability of the coupler is very high as it is protective due to the cladding and fiber used in the manufacturing.
  • It works more with less input and delivers the best result for the people.

The technological advancements are for the benefit and comfort of the people and the optical fused coupler is one of them.

Going to Order PM Fused Couplers? First, Explore What Options You Have

Polarization-maintaining fused couplers are basically the components used to combine optical signals from two or more fibers into one fiber or to split optical signals between two or more fibers. They are made by fusing and tapering the polarization maintaining fibers together because it creates a simple, rugged and compact method of splitting or combining optical signals.

Generally, typical excess losses are as low as 0.2 dB, while split ratio tolerances vary between the range ±5% to ±0.5% at design wavelengths, based on the splitting ratio. These devices are bidirectional and offer low back reflection and insertion losses. Since they also function to split the signals, they are also widely called PM fused splitters.

Before checking options, let’s take a brief look at their features and applications.

Features of PM Fused Couplers

  • Low loss
  • Broad bandwidth
  • Excellent uniformity
  • High directivity
  • Compact design
  • Low cost
  • Available in a wide variety of wavelengths

Applications of PM Fused Couplers

  • Power Monitoring
  • Fiber Gyroscopes
  • Optical Amplifiers
  • Fiber lasers
  • Coherent communications

Configurations, Availability, and Customization 

Standard configurations are 1×2, 2×2, 1×3 (monolithic) and 1×4 (cascaded). A monolithic structure refers to that where all of the fibers are fused. On the contrary, a cascaded structure means that it combines several 2×2 splitters to produce a greater split count.

Various companies substitute a 2×2 coupler in place of a 1×2 coupler in the order, depending upon the availability because they can be used interchangeably without any issue. However, if you need greater split counts or different split ratios, it is always best to ask for the quotation by providing your customized specifications.

The fibers of fused couplers or splitters can be connectorized with all standard connectors such as FC, SC, ST, LC, etc. and imparted with finishes such as Super PC, Ultra PC, Angled PC [APC], etc.

PM fused couplers with a higher split ratio such as 10/90 and 5/95 are also readily available online. Such high split ratio is often requested by many customers to tap off a small amount of light for power monitoring. Reputed manufacturers use revolutionary technology to tap 1% to 3% of light in the fiber and directly couple it into the photodiode.

This helps in achieving minimal loss, high extinction ratio, and makes the device affordable. In general, companies use polarization maintaining fibers based on the PANDA fiber structure during manufacturing of PM components and patch cords. However, you can also request to use other PM fiber structures, for instance, bow tie.

If you are unable to find a PM fused coupler according to your specifications and requirements, there is no need to be disappointed as customization service is always available with experienced polarization maintaining fused coupler manufacturers. All you need to do is to make a request along with your specific needs.