Understand Specification Of Fiber Optic Taper

For fiber optic products, it is essential to understand its specification and choose the best configuration for your design. Without a proper understanding of these specifications, cost may increase dramatically. Also, you may not able to get the suitable item to fulfil your design requirements.

Following the tutorial for helping you understand the most important specification of Fiber optic tapers.

1) Numerical Aperture

Numerical Aperture (N.A) shows the ability of light-gathering of fiber. However, the N.A of Fiber Optic Taper is varying along the length of the fiber optic taper.

Figure 1. Illustration of Numerical Aperture

Illustration of Numerical Aperture

To calculate the effective N.A in fiber optic taper.

N.A (eff) = N.A (max) * D(min)/D
*D(min) is the smallest diameter, D refer to the diameter where you’re measuring, N.A(max) equal to the N.A at small end.

Note 1 – N.A is decided by the raw material used for producing the Fiber Optic Taper.

Note 2 – Usually the N.A data is referring to the N.A on the small end of Fiber Optic Taper.

2) Resolution

Resolution indicate the ability of identifying the image details. Smaller fiber diameter will have a higher resolution. And in fiber optic taper, the resolution of big end is different from small end.

Figure 2. Relationship between Fiber Diameter & Resolution

Illustration Resolution

3) Magnification Ratio (Taper Ratio)

Magnification ratio is equal to the big end diameter / small end diameter. Also taper length will increase accordingly when magnification ratio is increase.

4) Transmission

This parameter is used to show the light transmission ability of Fiber Optic Taper. It defined as light(in)/light(out)

To obtain maximum transmission, the light(image) source input should not exceed the numerical aperture of fiber optic taper. And in many cases, incident light angle approach to critical angle will be absorbed by EMA.

To calculate the transmission of lambertian and collimated light. Following the equation.

Tcollimated = t (l) e-d/al   
 t (l) is the transmittance of material. D is the thickness of material. al is the absorption coefficient of material

For lambertian light,

Tlambertian= Tcollimated x [NAeffective]2

We will cover further details about transmission of Fiber component in later articles.

5) Taper Shape

There exists many different shape for Fiber optic taper. Typical ones are follow.

  • Round to round
  • Square to square
  • Square to round or Round to square

*Convex and Concave surface could be also processed on the 2 ends.

6) MTF performance

Image result will be also affected by the contrast. The low contrast is mainly due to the ambient light exist between the fibers.

Figure 3. MTF curve of Fiber optic taper with different Taper Length

MTF curve of Fiber Optic Taper

m10 = FOT with 10mm length ; m20g = FOT with 20mm length ; m30g = FOT with 30mm length

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