7.4: Test and Measurement

7.4 Test and Measurement

This section discusses optical and electrical tests and test equipment. They are related to achieving system transmission design objectives in the two areas of power and pulse spreading (dispersion). Some tests do not directly measure power or loss, but measure parameters affecting the power margin. Other tests do not directly measure dispersion but measure parameters that either affect, or are affected by, pulse spreading. Two other categories are also discussed: visual inspection and end-to-end electrical tests. Visual inspection requires only the trained human eye. End-to-end electrical tests assess the combination of power and dispersion effects on a system. The test signals originate at the E/O source and are analyzed after the O/E receiver. Analog signal testing is not discussed. In the same vein, protocol testing of digital signals is also not discussed. This section examines fiber link tests performed at levels data communicators might refer to as the optical and electrical or physical layers.

Fiber system measurements can also be categorized by where the tests are performed. Four environments are identifiable for this purpose: laboratory, manufacturing, field turn-up or commissioning, field maintenance or troubleshooting. This discussion deals with the latter two field-type environments. The measuring equipment used in a laboratory varies markedly from the test equipment used in the field. The two differ in cost and complexity, ease of use and flexibility, ruggedness, size and portability, accuracy and sensitivity The same optical system parameter may be measured at the two locations, but the approaches...