文档介绍：Precision Reflectometer
Overview
The HP 8504A Precision Reflectometer is a high resolution interferometer that measures return loss on a variety of ponents and assemblies. It is optimized for single-mode fiber, but useful measurements can also be made in multi-mode fiber. It operates in the 1300nm and 1550nm bands. At 1300nm it can measure reflections to 75dB(return loss) and has a two-event resolution of 25um.
Typical applications include:
Measurements of launch optics for lasers and opto-electronic integrated circuits
Measurements of passive fiber optic devices such as couplers, attenuators, connectors, and isolators
High-resolution measurements of lightwave path discontinuities based on a known refractive index
Measurement of refractive index of material based on a known distance between two discontinuities
High-resolution measurement of path length, expressed as a transmit time
Measurements of bulk optic devices such as lenses, AR coating, and crystals
Operation principle
Precision lightwave reflectometer block diagram
The HP 8504A precision reflectometer is based on the Michelson interferometer and uses the techniques of white light interferometry. A 1300nm or 1550nm low-coherence light source is sent to the a power splitter. One path leads to the DUT, while the other path leads to a reference mirror. Light reflected off both the reference mirror and the DUT is bined and detected. If the path length from the source to the reflection in the DUT is the same as from the source to the mirror, a coherent interference signal appears at the detector. By moving the position of the reference mirror, the instrument can then scan the test device for reflections over a 400mm range(equivalent air distance)
Measurement process
In operating the instrument there are “hardkeys” and “softkeys”. Hardkeys are those keys whose function is printed directly on the physical keypad. These keys are noted with bold type such as PRESET. Softkeys are those that are located to the r