Light Guide

Structure and principle

The optical fiber used for a light guide has a dual structure as shown in Fig. 1 and consists of optical glass with excellent transmissivity as its core material and glass with excellent weather resistance as its cladding material.

Total reflection is a phenomenon in which light is reflected completely at an interfacial boundary between two types of translucent materials (dielectric materials) with different refractive indexes at a certain angle (critical angle) or lower as shown in Fig. 2.

Types and characteristics

The numerical aperture (NA) and aperture angle of an optical fiber are calculated by the formula as shown below from the refractive indexes of the core and cladding materials.

Sin θ = NA = √(n12 – n22)

SUMITA manufactures various optical fibers with different aperture angles by utilizing these characteristics.

List of fiber types

Wavelength

Fiber type

Numerical aperture (NA)

Aperture angle (2θ)

Characteristics

Visible

SOG-120S

0.87

120°

Projection on a wide area is possible even if the W.D. is short. It is best suitable for applications such as a light guide when lighting a wide area.

SOG-100

0.77

100°

The aperture angle is larger than the standard value and projection on a relatively wide area is possible. It is best suitable for lighting for a wide area.

SOG-70S

0.57

70°

Since this fiber has a standard aperture angle and excellent transmissivity of visible light, it is a typical optical fiber which can be used for optical transmission over a relatively long distance.

SOG-35

0.29

35°

The aperture angle is small and it is possible to add directionality to light. It is best suitable for lighting of a narrow area or optical sensors.

SOG-15

0.13

15°

The feature of this fiber is its N.A is smaller than that of a quartz fiber. It is best suitable for optical sensors etc. for which directionality is important.

Visible
-near-infrared

SON-60

0.50

60°

This is a multicomponent optical fiber series with low transmission loss and is best suitable for a light guide for optical communications and long-distance transmission.
* See the page for SON for details.

 

SON-30

0.28

33°

This is a multicomponent optical fiber series with low transmission loss and is best suitable for optical communications due to its broadband performance.
* * See the page for SON for details.

 

 

Infrared

SOG-70IRA

0.57

70°

This is an optical fiber for near-infrared whose transmission property around 1,100 - 1,350 nm is better than that of SOG-70S.

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