From f2e4a613af05ff3206a54e4c7b6c3931e2e6469d Mon Sep 17 00:00:00 2001
From: Jean-Baptiste Bayle <j2b.bayle@gmail.com>
Date: Wed, 10 Mar 2021 19:07:06 +0100
Subject: [PATCH] Implement OMS noises
---
lisainstrument/noises.py | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/lisainstrument/noises.py b/lisainstrument/noises.py
index 417a511..fb53f66 100644
--- a/lisainstrument/noises.py
+++ b/lisainstrument/noises.py
@@ -204,3 +204,29 @@ def testmass(fs, size, asd=2.4E-15, fknee=0.4E-3):
fs, size, asd, fknee)
return red(fs, size, asd / (2 * pi * c)) \
+ infrared(fs, size, asd * fknee / (2 * pi * c))
+
+def oms(fs, size, asd, fknee):
+ """Generate optical metrology system (OMS) noise allocation [ffs].
+
+ The power spectral density in displacement is given by
+
+ S_bl(f) [m] = asd^2 [ 1 + (fknee / f)^4 ].
+
+ Multiplying by (2Ï€ f / c)^2 to express it as fractional frequency deviations,
+
+ S_bl(f) [ffd] = (2Ï€ asd / c)^2 [ f^2 + (fknee^4 / f^2) ]
+ = (2Ï€ asd / c)^2 f^2 + (2Ï€ asd fknee^2 / c)^2 f^(-2)
+
+ Note that the level of this noise depends on the interferometer and the type of beatnote.
+
+ Warning: this corresponds to the overall allocation for the OMS noise from the Performance
+ Model. It is a collection of different noises, some of which are duplicates of standalone
+ noises we already implement in the simulation (e.g., backlink noise).
+
+ Because this is a optical pathlength noise expressed as fractional frequency deviation, it should
+ be multiplied by the beam frequency to obtain the beam frequency fluctuations.
+ """
+ logger.debug("Generating OMS noise (fs=%s Hz, size=%s, asd=%s m/sqrt(Hz), fknee=%s Hz)",
+ fs, size, asd, fknee)
+ return violet(fs, size, 2 * pi * asd / c) \
+ + red(fs, size, 2 * pi * asd * fknee**2 / c)
--
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