During the optical application or experiments, the extinction ratio polarization can be measured. Extinction ratio polarization or polarization extinction ratio is a ratio of the power in the principal polarization mode to the power in the orthogonal polarization mode after propagation through a device or system. The Extinction ratio polarization is expressed as dB or as a percentage. It is quite necessary to introduce what polarizers are. A polarizer is an optical filter that lets light waves of a specific polarization state pass through while blocking light waves of other polarizations. It can filter a beam of light of undefined or mixed polarization into a beam of well-defined polarization, that is polarized light. While extinction ratio is the ratio of two optical power levels of a digital signal generated by an optical source, like in a laser diode, and is expressed in dB. The result of the cumulative effects of the polarization properties of the light source which is light not fully polarized or light not linearly polarized with misalignments at fiber connections or splices, and propagation through the fiber or device itself up to the measurement point is the Extinction Ratio Polarization measurements. In any optical mirror lens  or devices which require light propagating through them linearly polarized or aligned to a particular axis extinction ratio polarization needs extinction ratio polarization parameters. Polarization extinction ratio parameters can also be employed in measuring the degree of polarization (DOP) of a depolarizer or low polarization light source. In Optical engineering extinction ratio polarization or polarization extinction ratio is key characteristics that help to choose the right polarizer. 

Features Of Polarizers

• The extinction ratio polarization and the degree of polarization 
• The transmission of light polarized linearly in the direction of the polarization axis, or to the transmission of unpolarized light through the polarizer
• The acceptance angle is the largest deviation from the design incidence angle at which the polarizer will still perform within specifications
• The construction of the Polarizers are also important as the thin film polarizers are thin films similar to optical filters
• The clear aperture is the most restrictive for birefringent polarizers as the availability of optically pure crystals limits the size of these polarizers
• Dichroic polarizers have the largest available clear apertures as their fabrication lends itself to larger sizes
• The optical length which is the length of the aperture through which the light will travel is also an important feature or characteristics
• The materials used in the construction determines the damage threshold

Extinction Ratio Polarization Measurements Methods

Rotation Polarizer Method

In this measurement method, the output of the device under test (DUT) is connected to a Polarization Extinction Ratio (PER) meter which contains a rotating polarizer followed by a photodetector. The polarizer performs a full rotation to measure the maximum power, which corresponds to the linear polarization state, and the minimum power, which corresponds to the orthogonal polarization state, and the instrument then calculates the polarization extinction ratio. You can shop for the best optical beamsplitter from Alpine research optics.

Polarimeter Method

Polarimeter generates light with an accurately prepared linear polarization state, usually by passage through a polarizer, this light is sent through the optically active sample, which somewhat rotates the polarization direction. The amount by which the light is rated is known as the angle of rotation. Light-measuring polarimeters determine the polarization state of a beam of light and give its polarization characteristics.

Distributed Polarization Crosstalk Measurement Method

The Distributed Polarization Crosstalk measurement method measures an extremely high polarization extinction ratio. It can measure the intensity and location of all crosstalk events in highly birefringent DUTs.