Testing fiber optic components and systems requires making several basic measurements. The most common measurement parameters are shown in Table Optical power, required for measuring source power, receiver power and loss or attenuation, is the most important parameter and is required for almost every fiber optic test. Backscatter and wavelength measurements are the next most important. Measurement or inspection of geometrical parameters of fiber are essential for fiber manufacturers. And troubleshooting installed cables and networks is required.

 

1. Fiber Optic Power Meters
2. Fiber Optic Light Sources
3. Optical Loss Test Sets/Test Kits
4. OTDR
5. VFL - Visual Fault Locators
6. Live Fiber Identifiers
7. Visual Inspection with Microscopes
8. Fiber Optic Talksets
9. Attenuators
10. Test Jumper Cables and Bulkhead Splice Adapters

Table - a Fiber Optic Testing Requirements

Test Parameter	Instrument
Optical Power(Source Output,Receiver Signal Level)	Fiber Optic Power Meter
Attenuation or Loss of Fibers, Cables & Connectors	Fiber Optic Power Meter & Source, Test Kit or OLTS (optical loss test set)
Backscatter(Loss, Length. Fault Location)	Optical Time Domain Reflectometer(OTDR)
Fault Location	OTDR, Visual Cable Fault Locator

Standard Testing Procedures

Most test procedures for fiber optic component specifications have been standardized by national and international standards bodies, including the EIA in the US and the IEC internationally. Procedures for measuring absolute optical power, cable and connector loss and the effects of many environmental factors (such as temperature, pressure, flexing, etc.) are covered in these procedures.

In order you perform these tests, the basic fiber optic instruments are the fiber optic power meter, testing light source, OTDR, optical spectrum analyzer and an inspection microscope. These and some other specialized instruments are described below.

Many manufacturers over-emphasize the performance of back reflection and insertion loss figures but ignore the importance of topography measurement of the polished ferrule. The three main important measurements that characterize the shape of the polished connector endface are radius of curvature, vertex offset and undercut.

Radius of Curvature

This is defined as the radius of curvature of the portion of the endface that is domed by polishing for physical contact.

Vertex offset

Vertex offset indicates how well the sphere forming the connector endface is centered on the fiber. It is measured by determining the position of the highest point of the endface and measuring the distance between this point and the centre of the fiber.

Undercut

Undercut is the difference in height between the surface of the ferrule and the surface of the fiber. Undercut is usually measured by finding two points which lie on the centerline of the fiber. One point lies where the sphere forming the surface of the ferrule intersects the centerline of the fiber. The second point lies where the surface of the fiber intersects the centerline of the ferrule. The distance between these two points is the undercut. Serious undercut can be seen at above picture.