Changes for page Integrated Distributed Acoustic Sensing (iDAS)

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Title

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1		-Distributed Acoustic Sensing (DAS)
	1	+integrated Distributed Acoustic Sensing (iDAS)

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1		-= **DAS Data Collection System** =
	1	+= **What is iDAS?** =
2	2
3		-==== **1. Interrogator Unit** ====
	3	+**iDAS** stands for **Integrated Distributed Acoustic Sensing**. This advanced system utilizes the principle of Rayleigh backscattering in optical fibers to measure strain rates along the fiber's length. It's a cutting-edge technology predominantly used in fields like geophysics, where it's crucial for monitoring seismic activities, as well as in industrial applications like pipeline monitoring and security systems.
4	4
5		-* **Function:** The interrogator unit is the core component of a DAS system. It sends laser pulses through the optical fiber and measures the backscattered light.
6		-* **Recording Information:** It records various settings such as the optical system configurations, spatial sampling rates, and the duration of data acquisition.
7		-* **Multiple Interrogators:** More than one interrogator may be used in an experiment. Each unit should have a unique identifier and is described in its respective metadata block.
	5	+=== **Safety first!** ===
8	8
9		-==== **2. Surface Installation** ====
	7	+=== ===
10	10
	9	+(% class="box warningmessage" %)
	10	+The iDAS uses a Class 1 laser, which is generally considered safe for most applications. However, direct exposure to the eye should be avoided to prevent any risk of eye injury.
	11	+\\Cables and fibers may create tripping hazards. Ensure that the routing of cables is done in a way that minimizes the risk of accidents.
	12	+
	13	+----
	14	+
	15	+=== **System Components** ===
	16	+
	17	+
	18	+The iDAS system consists of the following components:
	19	+
	20	+1. **Interrogator unit:** This unit houses the laser, detector, and electronics for processing the backscattered light signal. It records various settings such as the optical system configurations, spatial sampling rates, and the duration of data acquisition. More than one interrogator may be used in an experiment. Each unit should have a unique identifier and is described in its respective metadata block.
	21	+1. **Optical fiber:** The optical fiber is the sensor that is used to measure strain rate.
	22	+1. **Data acquisition software**: This software is used to control the interrogator unit and to acquire and process the data. It records various settings such as the optical system configurations, spatial sampling rates, and the duration of data acquisition.
	23	+
	24	+----
	25	+
	26	+= **DAS Data Collection System** =
	27	+
	28	+==== **1. Surface Installation** ====
	29	+
11	11	* **Cable Arrangement:** The optical fiber cable can be a single long continuous cable or multiple cables with connectors, used across different installation environments.
12	12	* **Cable Types:** Cables may vary in construction types based on the installation environment.
13	13	* **Geographical Metadata:** Parameters related to geographical location are specified for easy searchability in databases.
14	14
15		-==== **3. Fiber Optic Cable** ====
	34	+==== **2. Installation Environments** ====
16	16
17		-* **Cable Composition:** Several optical fibers may be enclosed within one cable.
18		-* **Metadata Identification:** The metadata identifies each individual fiber used in the acquisition, including its intrinsic properties.
19		-
20		-==== **4. Installation Environments** ====
21		-
22	22	* **Shallow Burial:** The cable can be shallowly buried.
23	23	* **In-Conduit Installation:** The cable can also be installed within a conduit.
24	24	* **Water Installation:** Suitable for underwater environments.
25	25
26		-==== **5. Channels** ====
	40	+==== **3. Channels** ====
27	27
28	28	* **Sensor Distribution:** Channels represent sensors distributed along the fiber array at fixed intervals.
29	29	* **Physical Location Determination:** The physical locations of these channels are ascertainable through methods like tap tests and GPS tracking.
30	30	* **Metadata for Channels:** Each channel or group of channels has its own metadata block, detailing specifics like location and properties.
31	31
32		-=== ===
	46	+[[image:1706489800616-982.png]]
33	33
	48	+
	49	+
	50	+[[image:1706488566274-805.png]]
	51	+
34	34	----
35	35
	54	+= **DAS Metadata Schema** =
	55	+
	56	+==== **1. Interrogator** ====
	57	+
	58	+* **Required:** Interrogator ID, manufacturer, model.
	59	+* **Optional:** Serial number, firmware version.
	60	+
	61	+==== **2. Acquisition Parameters** ====
	62	+
	63	+* **Required:** Interrogator ID, acquisition ID, unit of measure, acquisition start and end time, acquisition sample rate, gauge length, number of channels, spatial sampling interval.
	64	+* **Optional:** Pulse rate, pulse width.
	65	+
	66	+==== **3. Overview** ====
	67	+
	68	+* **Required:** Network code, location, start date, end date, point of contact.
	69	+* **Optional:** Digital Object Identifier (DOI), purpose of data collection, funding agency.
	70	+
	71	+==== **4. Cable Information** ====
	72	+
	73	+* **Required:** Cable ID, cable bounding box.
	74	+* **Optional:** Cable owner, cable installation date, cable characteristics.
	75	+
	76	+==== **5. Fiber Information ('Native format')** ====
	77	+
	78	+* **Required:** Cable ID, fiber ID, fiber geometry, fiber mode, fiber refraction index.
	79	+* **Optional:** Fiber optical length, fiber start and end location, fiber one-way attenuation, fiber winding angle.
	80	+
	81	+==== **6. Channel Group** ====
	82	+
	83	+* **Required:** Interrogator ID, acquisition ID, channel group ID, cable ID, fiber ID, coordinate generation date.
	84	+* **Optional:** Location method, coordinate reference frame, first/last usable channel ID, uncertainty of various coordinates (x, y, latitude, longitude, elevation, depth, strike, dip).
	85	+
	86	+==== **7. Channel** ====
	87	+
	88	+* **Required:** Channel group ID, channel ID, coordinates (x, y, latitude, longitude).
	89	+* **Optional:** Elevation above sea level, depth below surface, distance along fiber, strike, dip.
	90	+
	91	+----
	92	+
36	36	=== ===
37	37
38	38	= **Pre-processing Steps for DAS Data (2.5 months, 90 TB)** =
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