For experiments where a single dip will be monitored, we selected an ATHF with a shorter length (L = 2m) into the SI, which increased the separation between consecutive dips as shown in Figure 3(b).
Once the fiber length for the SI was defined, we placed the ATHF inside a thermal bath.
This is due to the temperature difference between the air holes and the rest of the silica fiber when the ATHF is heated in the water bath.
In this case, we replace the ATHF in the SI setup with a segment of PMF (Thorlabs, model PM1550-HP, operating wavelength 1440-1625 nm) with a length L =10 cm.
A fiber-optic sensor based on an ATHF was demonstrated using a SI configuration, and the optical characteristics of the sensor were experimentally investigated.
The ATHF used in this work was fabricated at Acreo Fiberlab.
 Nonstandard abbreviations: 11-HSD-2, 11/3-hydroxysteroid dehydrogenase type 2; MR, mineralocorticoid receptor; E, cortisone; F, cortisol; B, corticosterone; AME-1, apparent mineralocorticoid excess type 1; THF, 5atetrahydrocortisol; aTHF
, 5/3-tetrahydrocortisol; THE, 5a-tetrahydrocortisone; ACTH, corticotropin; DXM, dexamethasone; CRI, chronic renal insufficiency; PGB, phosphate gelatin buffer; SPA, scintillation proximity assay; cortisone-3-CMO, cortisone-3-(O-carboxymethyl) oxime; BSA, bovine serum albumin; and PRA, plasma rerun activity.