WHAT KIND OF FIBER POLISH BE USED

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When a connector is mounted on the
fiber end, some loss of power will be experienced. Some of the light would be
reflected back to the fiber towards the source that generated that light
signal. These reflected back signals into the fiber are called Optical Return
Loss (ORL). The ORL can harm the laser source can also interrupt the
transmission signal. Usually the fiber connectors have different polishing
types, the different polishing have different ORL levels. There are four
polishing types available, each having its own ORL levels and characteristic.
The polishing types are: 1. Flat surface, 2. Physical Contact (PC), 3. Ultra
Physical Contact (UPC) and 4. Angled Physical Contact (APC). Each connector is
evolved from one into another, let’s discuss each on detail.

 

Flat Fiber Connector

 

Originally the fiber connectors are
flat surface connectors. A small gap between the two fiber faces is left when
two faces of flat fibers are coupled. These
flat fiber connectors are not appropriate for single mode fiber with a
9µm core size, therefore it is vital to advance into Physical Contact (PC)
connectors. ORL values in this type of connectors is around -35dB.

 

Physical Contact (PC) Fiber Connector

 

Physical Contact connector is polished
with a minor spherical design, this allow to decrease the general size of the
end face. The spherical design helps to overcome the air gap issue experienced
in flat connectors. The spherical design results in overall lower ORL, as a
reduced amount of light being sent back into the fiber and also to the light
source. ORL values in this type of connectors is around -45dB. But still some
of the light manages to reflect back towards the source.

 

Ultra Physical Contact (UPC) Fiber
Connector

 

To overcome the issue faced in physical
contact connectors, the convex end face is made by extending the polishing
methods on PC connectors, resulting an even finer connector that is called
Ultra Physical Contact (UPC) connector. The UPC have even lower ORL as compare
to PC connectors. ORL values in this type of connectors is upto -55dB. UPC
fiber connector can be used with single-mode fiber as well as multimode fiber.
Usually the blue color UPC connector is used for single-mode fiber and beige
color UPC connector is used for multimode fiber. UPC allows more consistent
signals in digital TV and telephony systems.

 

Previously discussed PC and UPC
connectors have a low insertion loss, but ORL really depends on the surface
finish of the fiber. When the connectors are repeatedly coupled and decoupled,
the ORL will start to degrade. So it is essential for a connector with low back
reflection and it could endure repeated coupling and decoupling without ORL
degradation.

 

Angled Physical Contact (APC) Fiber
Connector

 

The end faces of Angled Physical
Contact (APC) connectors have curved edges but are angled at 8 degree of an
industry standard. This allows even closer connection with a much smaller gap
between two. The combination of angled connector with smaller gap, allows any
reflected light that is reflected back into the fiber is in fact reflected into
the fiber cladding. That is because of the 8 degree angled face. ORL values in
this type of connectors is less then -65dB. This to be noted that these types
of fiber connector can only be used with single-mode fiber. 

 

It’s vibrant from above discussion that
all types of connectors play important role and are available in market. It
seems difficult to conclude that which connector is best to use. The specific
application requirement chooses which one to use. For application like high accuracy
optical signals APC connectors may be selected, on other hand less complex
systems will work fairly well using UPC or even FC connectors.