Test Solutions for Calibration of T&M Equipment
Light Source Verification
Any sources output power fluctuates as a function of time. Fluctuations may be due to the sources characteristics, the design or simply the component aging. The sources power level and stability are usually stated for both short (e.g., 15 minutes) or long periods of time (e.g. one to eight hours), depending on the applications.
Also, the central wavelength of the source may vary over long periods of time and needs to be verified periodically. Interval depends on the application and the type of light source.
Power Meter Verification
The two key issues characterizing the calibration and verification of fiber-optic power meters are:
- Absolute-response calibration at one or more
wavelengths (absolute power calibration)
- Response linearity with varying input power levels
(optical linearity measurement).
Absolute power calibration is performed by comparing the power readings to a highly accurate reference power meter normally traceable to a primary reference standard like NIST.
Variable Attenuator Verification
For most applications, three parameters have to be verified on variable attenuators to ensure that they meet their specifications: insertion loss, optical linearity and repeatability. For specific applications like transceiver characterization, it may also be required to verify the optical return loss (ORL) of the attenuator.
ORL measurements should be performed according to the EIA-TIA Fiber Optic Test Procedure (FOTP 107). Insertion loss and linearity can be measured using a highly stable source and a power meter.
Repeatability is critical when the change from one value to another and back is performed often or over a wide range of attenuations.
OTDR Verification
The OTDR is used to both locate and characterize faults such as those caused by broken fiber, connectors or splices. The most critical parameters to be verified are therefore attenuation and distance accuracy.