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1 -Distributed Acoustic Sensing
1 +Distributed Acoustic Sensing (DAS)
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1 += **What is iDAS?** =
2 +
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 +
5 +=== **Safety first!**
6 + ===
7 +
8 +(% class="box warningmessage" %)
9 +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.
10 +\\Cables and fibers may create tripping hazards. Ensure that the routing of cables is done in a way that minimizes the risk of accidents.
11 +
12 +----
13 +
14 += **DAS Data Collection System** =
15 +
16 +==== **1. Interrogator Unit** ====
17 +
18 +* **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.
19 +* **Recording Information:** It records various settings such as the optical system configurations, spatial sampling rates, and the duration of data acquisition.
20 +* **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.
21 +
22 +==== **2. Surface Installation** ====
23 +
24 +* **Cable Arrangement:** The optical fiber cable can be a single long continuous cable or multiple cables with connectors, used across different installation environments.
25 +* **Cable Types:** Cables may vary in construction types based on the installation environment.
26 +* **Geographical Metadata:** Parameters related to geographical location are specified for easy searchability in databases.
27 +
28 +==== **3. Fiber Optic Cable** ====
29 +
30 +* **Cable Composition:** Several optical fibers may be enclosed within one cable.
31 +* **Metadata Identification:** The metadata identifies each individual fiber used in the acquisition, including its intrinsic properties.
32 +
33 +==== **4. Installation Environments** ====
34 +
35 +* **Shallow Burial:** The cable can be shallowly buried.
36 +* **In-Conduit Installation:** The cable can also be installed within a conduit.
37 +* **Water Installation:** Suitable for underwater environments.
38 +
39 +==== **5. Channels** ====
40 +
41 +* **Sensor Distribution:** Channels represent sensors distributed along the fiber array at fixed intervals.
42 +* **Physical Location Determination:** The physical locations of these channels are ascertainable through methods like tap tests and GPS tracking.
43 +* **Metadata for Channels:** Each channel or group of channels has its own metadata block, detailing specifics like location and properties.
44 +
45 +
46 +[[image:1706489800616-982.png]]
47 +
48 +
49 +
50 +[[image:1706488566274-805.png]]
51 +
52 +----
53 +
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 +
93 +=== ===
94 +
95 += **Pre-processing Steps for DAS Data (2.5 months, 90 TB)** =
96 +
97 +1. (((
98 +**Create a Deployment Log**
99 +
100 +* Document key details like photonics settings, duration of data collection, instances of hard disk failure, power outages, etc.
101 +)))
102 +1. (((
103 +**Generate Geographic Coordinates**
104 +
105 +* Assign latitude and longitude coordinates to each DAS channel for spatial referencing.
106 +)))
107 +1. (((
108 +**Data Conversion**
109 +
110 +* Convert the raw DAS time series data from counts to strain rate, which is more meaningful for seismic analysis.
111 +)))
112 +1. (((
113 +**Data Decimation**
114 +
115 +* Reduce the sampling rate from 1000 Hz to 100 Hz. This step is essential to manage data volume and focus on frequencies of interest for seismic activities.
116 +)))
117 +1. (((
118 +**Extract Specific Time Series**
119 +
120 +* Isolate time series data of special interest, such as those related to earthquake events, for detailed analysis.
121 +)))
122 +1. (((
123 +**Data Hosting**
124 +
125 +* Store the processed data on Research School of Earth Sciences (RSES) clusters and the National Computational Infrastructure (NCI) for accessibility and further analysis.
126 +)))
127 +1. (((
128 +**Extract Data and Instrument Response from Seismic Nodes**
129 +
130 +* Retrieve both the raw data and the corresponding instrument response characteristics for accurate interpretation of the seismic signals.
131 +)))
132 +1. (((
133 +**Long-term Archiving and Data Sharing**
134 +
135 +* Ensure that the data is archived in a format and location that supports long-term preservation and accessibility, such as the AuScope Distributed Acoustic Sensing (DAS) Collection.
136 +)))
137 +1. (((
138 +**Data Access and Record Keeping**
139 +
140 +* Maintain records and access paths (e.g., NCI local file path) for the data, including metadata and other associated records, to facilitate future research and data sharing.
141 +)))
142 +
143 +=== ===
144 +
145 +=== ===
146 +
147 +=== ===
148 +
149 +=== ===
150 +
151 +=== ===
152 +
153 +----
154 +
155 += **Silixa iDAS Setup Manual for Reoccupying/Duplicating Experiment** =
156 +
157 += **General Information** =
158 +
159 +* **Experiment Name:** ~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~__
160 +* **Local Date:** ~_~_~_~_/~_~__**/202**
161 +* **Local Time:** ~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~__
162 +* **Personnel:** ~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_
163 +* **Site Condition Notes:**
164 +** [Space for detailed notes about the site condition, any upkeep performed, and changes made since the last visit.]
165 +
166 +----
167 +
168 +==== **Setup Procedure** ====
169 +
170 +1. (((
171 +**Open iDAS Box**
172 +
173 +* Serial Number: ~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~__
174 +* IP Address: ~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_~_
175 +)))
176 +1. (((
177 +**Check Laser Lock**
178 +
179 +* Ensure the lever on the LASER/RIGHT side of the iDAS is in the locked position (LEVER UP).
180 +)))
181 +1. (((
182 +**Placement of iDAS**
183 +
184 +* Position the iDAS on a stable surface.
185 +* Ensure clear air flow around the fan vents.
186 +)))
187 +1. (((
188 +**UPS Setup** (If applicable)
189 +
190 +* Connect the UPS to a power source.
191 +* Plug the NAS into the UPS using the special cable with a rectangular connector.
192 +* Connect the monitor to the UPS.
193 +)))
194 +1. (((
195 +**Peripheral Connections**
196 +
197 +* Connect a computer monitor, mouse, and keyboard to the iDAS.
198 +)))
199 +1. (((
200 +**GPS Antenna Connection**
201 +
202 +* Connect the GPS antenna to the left-side socket on the front of the iDAS using a special adapter.
203 +)))
204 +1. (((
205 +**Fibre Optic Connection**
206 +
207 +* Clean both the fibre optic cable and the socket with a 1-click cleaner before connection.
208 +* Use the guide/tip for cleaning the fibre and clean the socket without it.
209 +)))
210 +1. (((
211 +**Powering the iDAS**
212 +
213 +* Connect the iDAS to a power socket or UPS.
214 +* Note: The iDAS turns on automatically when connected to power. Use the power button at the bottom left if it does not.
215 +)))
216 +1. (((
217 +**Network Drive Mapping**
218 +
219 +* Open File Explorer and select 'This PC' from the left pane.
220 +* On the File Explorer ribbon, select 'More' > 'Map network drive'.
221 +* Choose a drive letter from the 'Drive' list.
222 +)))
223 +1. (((
224 +**Open iDAS Software**
225 +
226 +* Use the link/shortcut on the Desktop.
227 +)))
228 +1. (((
229 +**GPS Satellite Confirmation**
230 +
231 +* Check for a green light in the top row of the software interface indicating GPS satellite detection.
232 +)))
233 +1. (((
234 +**Lever/Interlock Adjustment**
235 +
236 +* Lower the lever/interlock (as mentioned in step 2) before starting data acquisition.
237 +)))
238 +1. (((
239 +**Configuration File Duplication**
240 +
241 +* Use 'current.cfg' for duplicating previous setup.
242 +* The file is located at C:/Silixa/Data/current.cfg.
243 +* Copy this file to the desktop and save it with a new filename.
244 +)))
245 +1. (((
246 +**iDAS Configuration Settings**
247 +
248 +* Navigate to the 'Configuration' tab and click 'iDAS configuration'.
249 +* Check all values under 'system'.
250 +* Under 'application', enable error messages.
251 +* In 'saving', select 'acoustic saving', choose 'tdms', and set the file save location and identifier.
252 +* Leave default parameters in 'measure'.
253 +)))
254 +1. (((
255 +**Mode Selection**
256 +
257 +* Toggle between Acoustic mode, Waterfall mode, and OTDR mode to check data recording.
258 +)))
259 +1. (((
260 +**Photograph OTDR Mode**
261 +
262 +* Document the OTDR mode settings with a photograph.
263 +)))
264 +1. (((
265 +**Photograph Waterfall Mode**
266 +
267 +* Similarly, take a picture of the Waterfall mode settings.
268 +)))
269 +1. (((
270 +**Configuration File Saving**
271 +
272 +* Save the configuration file in .cfg format in a separate location without overwriting the existing one.
273 +)))
274 +1. (((
275 +**Software Check**
276 +
277 +* Ensure QFinder, Teamviewer, and Microsoft Remote Desktop are installed.
278 +)))
279 +1. (((
280 +**Remote Access Setup**
281 +
282 +* Open Teamviewer or Microsoft Remote Desktop.
283 +* For Teamviewer, photograph the ID and password and ensure it remains open.
284 +* For Microsoft Remote Desktop, record the IP address and test remote access with a separate laptop.
285 +)))
286 +1. (((
287 +**Final Mode Setting**
288 +
289 +* Switch to OTDR mode for ongoing operation (avoids excessive memory usage of Waterfall mode).
290 +)))
291 +
292 +----
293 +
294 +==== **Important Reminders** ====
295 +
296 +* Always ensure that the iDAS is connected to a suitably earthed power socket or UPS for safety.
297 +* Regularly check the condition of all cables and connectors.
298 +* Before leaving the setup, confirm that data saving is active if required.
299 +* Keep a log of all actions taken during the setup for future reference and troubleshooting.
300 +
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310 +
311 +[[Caption>>image:1706488806394-168.png]]
312 +
313 +
314 +[[image:https://photos.fife.usercontent.google.com/pw/ABLVV86phmYsze0lp1yzL-gs6stE23rmgKbOxcpCRhFmK9s25zf5UHBkgbFcOg=w1440-h2556-s-no-gm?authuser=0]]
315 +
316 +
317 +
318 +[[How to clean the optical connector>>image:1706488909085-143.png||alt="How to clean the optical connector"]]
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