Understanding Fiber Optics


Butt joint connectors characteristics: • The loss of light generated by connection (called Insertion Loss) is low (approximately 0,3 dB typical). • This type of connection is sensitive to pollution (dust, mud...). If a dirtiness stays between the two ceramic ferrules, a big part of the light can be lost.

Butt joint connectors examples:

ST (singleway)

RNJOP (4 channels)

Lens technology (expanded beam technology) Principle: The principle of the expanded beam connectors consists in placing a lens at the exit of each fiber, in order to widen the beam by collimating it - i.e. by creating light beams parallel to the optical axis. In this configuration, there is no more physical contact between the two optical fibers.

expanded beam

connector shell



Defects: In this case it is the alignment of the two shells one to the other which will guarantee that the collimated beam going out from the first lens will be well refocused through the second lens. The precision of the mechanical interface parts of the connector is highly important. As for the butt joint connectors, transverse and angular shifts, and also bad polishing will generate losses. Lens connectors characteristics: • The light loss generated by connection (called Insertion Loss) is more important than in the previous case, due to the presence of the lenses and sometimes also of windows (approximately 1 to 1,5 typical dB). • This type of connection is much less sensitive to pollution because the beam is much larger than the one that goes out directly from a fiber. A dust at the interface of two butt joint connectors will create a much higher loss than located at the interface of two lens connectors.

Lens connectors examples:

CTOS (2/4 channels)

CTOL (8 channels)


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