Methods and apparatus for implementing a fiber optic reflectance standard

An apparatus for testing and calibration of a fiber optic instrument that implements a fiber optic reflectance standard (FORS) testing procedure, the apparatus comprising:

• an optical splitter;
• first and second optical inputs coupled to the optical splitter;
• an optical fiber having first and second ends, and coupled to the optical splitter at the first end of the optical fiber;
• an attenuator configured to contain a portion of the optical fiber between the first and second ends and selectively attenuate optical signal gain of the optical fiber;
• and
• an optical reflector coupled to the second end of the optical fiber;
• wherein the attenuator comprises an inline mechanical attenuator including:
• a winding mechanism around which the optical fiber is wound;
• and
• one or more pulleys configured to prevent bending loss in the optical fiber during winding of the optical fiber with the winding mechanism.

A method for testing and calibration of a fiber optic instrument comprising:

• recording an initial return loss measurement on the fiber optic instrument and recording an initial power measurement Pi with an optical power meter (OPM);
• optically coupling the fiber optic instrument and OPM to a fiber optic reflectance standard (FORS) implementing apparatus configured with an attenuator for selective adjustment of an attenuation of the FORS implementing apparatus and an optical splitter;
• determining at least a first expected optical return loss measurement of the fiber optic instrument based on the initial power measurement, a first reading of the OPM after optical coupling of the fiber optic instrument and OPM, and splitter characterization data of the optical splitter;
• calculating a first attenuation value that produces a first predetermined return loss for optical return loss of the fiber optic instrument using the at least a first expected optical return loss measurement;
• calculating at least a first expected OPM value for the first predetermined return loss based on the calculated first attenuation value;
• adjusting the attenuation of the FORS implementing apparatus with the attenuator until the OPM reads a power reading equal to the first expected OPM value;
• recoding a current OPM reading as at least a second recoded OPM value and an optical return loss reading from the fiber optic instrument as a second optical return loss value of the fiber optic instrument;
• determining at least a second expected optical return loss measurement of the fiber optic instrument based on the initial power measurement, at least a current second reading of the OPM, and the splitter characterization data of the optical splitter;
• calculating at least a second attenuation value that produces at least a second predetermined return loss for optical return loss of the fiber optic instrument using the at least a second expected optical return loss measurement;
• calculating at least a second expected OPM for the second predetermined return loss based on the calculated at least a second attenuation value;
• adjusting the attenuation of the FORS implementing apparatus with the attenuator until the OPM reads a power reading equal to the at least a second expected OPM;
• and
• calculating a difference between the at least a second expected optical return loss for the fiber optic instrument and at least a second optical return loss value for the fiber optic instrument.