Describe KAGRA/Subgroups/VIS/OpsManual/OpLev/TypeA here.

In construction

## Introduction

This diagonalization procedure is based on klog entry 10786., which is in turn based on the scheme described in entry 10729.

- The procedure relies on a script written by Lucia and Terrence which
- Identifies the exact position of resonant peaks in measured amplitude spectral densities,
- Reads cross-coupling ratios from transfer functions at the resonant frequencies and
- Calculates the new diagonalization matrix.

**The final results are given as coupling ratios with appropriate units in terms of****µrad and µm. For example, the ratio for L to P coupling is in units of****µrad/µm.**Note that in other klog entries these ratios are written without the appropriate units. They are simply multiplied by a factor of 100 and are claimed to be a percentage.

**This practice is misleading and should be avoided.**

The physics underlying the procedure is the following:

- At the resonant frequencies the
- The oplev can be successfully diagonalized even if there's imbalance among the actuation coils. The imbalance in actuation is not expected to depend on the frequency of the excitation signal, therefore, in an amplitude spectral density, as long as the height of the resonant peak is well above the.