The intent of this procedure is to provide uniform methods for monitoring and measuring the change in optical transmittance of fiber optic circuits or paths of various configurations. This FOTP may be referenced by a Detail Specification or similar document, but the procedure is usually applied to a passive optical device undergoing other testing as described in another procedure, hereafter called "the primary FOTP," which may invoke its use. Typical applications include evaluating the effects of environmental or mechanical stresses on interconnecting devices, fiber or cable.

Caution on Procedure Use Although FOTP-20 may be referenced, the Detail Specification or the primary FOTP may call for a measurement of "Change in Attenuation" rather than a "Change in Optical Transmittance" to be reported. Specification and FOTP writers are cautioned to exercise care to ensure that they ask for the measurement that is really wanted; testing personnel are similarly cautioned to record and report the particular change that is asked for (see also 6.4).

Single or Multipe Device Testing By proper use of dividers or switches, this procedure may be used to test either a single device, or to test multiple devices at the same time.

Component Types For the purpose of determining appropriate optical source requirements, devices under test are categorized into two types.

- Group 1 components are those for which relaxed optical source center wavelength and spectral width specifications will suffice (for example, splices, connectors, and typical electromechanical optical switches).

- Group 2 components are those for which the results can be significantly affected by source characteristics [for example, optical fiber or cable, or wavelength division multiplexers (WDMs)]. Some optical switches may also be in this category.

The optical source parameters also depend upon whether single-mode or