Calibration Method for Optical Cable Testing Equipment

Calibration of optical cable testing equipment ensures accurate, traceable measurements of optical power, attenuation, and strain, following standardized procedures and accredited laboratory practices.

Standardized Calibration Procedures

Calibration of fiber optic testing equipment is guided by IEC standards. IEC 61315 defines the general steps for calibration, including establishing calibration conditions, performing measurements, and calculating uncertainties. OTDRs, used for single-mode and multimode fibers, are calibrated according to IEC 61746, which specifies procedures for distance and attenuation scale calibration, as well as reporting measurement uncertainties. Calibrated OTDRs are essential for compliance with standards such as IEC 60793-1-22 (length measurement) and IEC 60793-1-40 (attenuation measurement) to ensure reliable fiber optic testing .

Calibration of Optical Power and Strain

Optical power meters and light sources (laser or LED) require absolute power and linearity calibration, including output power, power stability, and wavelength spectrum measurements. For optical fiber sensing cables, the strain coefficient is a critical parameter. Conventional tensile load tests can underestimate strain due to slippage or strain transfer loss. An improved calibration method uses two micrometre linear stages and displacement measuring equipment to precisely measure elongation and Brillouin frequency shifts, reducing errors and enabling accurate strain coefficient determination .

Accredited Laboratory Practices

ISO/IEC 17025-accredited laboratories, such as DIAMOND's Test and Calibration Laboratory, provide traceable, high-precision calibration for fiber optic equipment. These labs perform calibration for OTDRs, optical power meters, and light sources, following IEC standards. They offer official calibration certificates with measurement data and uncertainties, periodic recalibration, and calibration at additional wavelengths upon request. Accredited labs also simulate environmental stresses, such as extreme temperatures and humidity, to ensure equipment reliability under real-world conditions .

Practical Considerations

• End-to-end testing: Verifies light transmission and signal integrity across the entire fiber link.
• OTDR calibration: Ensures accurate distance and attenuation measurements, critical for fault detection.
• Strain calibration: Uses improved tensile load setups to minimize slippage and transfer errors.
• Traceability: All calibrations should be traceable to national or international standards to guarantee measurement reliability. By following these standardized procedures and using accredited laboratories, technicians can ensure accurate, reliable, and repeatable measurements for fiber optic networks and sensing applications .