Equilibrium Mode Distribution Research Articles

A combined mode-filter/mixer to determine spectral attenuation of graded index fibers

The measurement of spectral dependent attenuation of graded index fibers using the cutback method assumes that an equilibrium mode distribution exists even after a short length of the fiber to be measured. We have reviewed and analyzed the looses caused by bends of multimode fibers. Using the results an easy to handle S-shaped mode-filter/mixer is investigated by far-field pattern and attenuation measurements. It is proved that the mode-filter/mixer is superior to the so called 70% excitation and is usable for estimating mode coupling and intrinsic fiber loss.

Limited phase-space attenuation measurements of low-loss optical waveguides

Attenuation and near-and far-field measurements, which were made with different launch spot sizes and numerical apertures on sub-1.0-dB/km optical waveguides, have shown that an equilibrium mode distribution is not established in the 1.1-km length. It was experimentally found that the source launch conditions could be described by an effective mode volume (EMV) that was found to be correlated with the measured attenuation rate. By using an EMV transfer model, the insertion loss of a 3.3-km concatenated section was predicted within 0.21 dB of that measured for a variety of launch conditions.