Calorimetric Miter Bends
A calorimetric miter bend monitors the incident power in the waveguide by measuring the rise in temperature of the cooling water passing through the mirror. The mirror is well isolated from the miter bend block to prevent heat from neighboring waveguides from reaching the mirror. The measurement requires approximately 200 seconds to reach steady state, but it is not sensitive to mode purity. While the measurement requires knowledge of the input polarization, it is capable of high accuracy.
John Doane, GA-MFE Technologies