Performance specifications
Optical sensor seismic monitoring system

Seismic monitoring system for harsh environment

Pressure vessel(No semiconductor devices in sensors)

Underground setting
type sensor
60φｘ600mm

Surfaceace setting
type sensor

Accelerometer

120ｘ150ｘ90mm

Accelerometer
Sensor type
Detection direction
Sensor characteristics
Damping coefficient
Measurement range
Operating temperature
Operating pressure

Optical interference accelerometer2 horizontal directions, 1 vertical direction
Resonance frequency
100Hz±4Hz, 30Hz±3Hz
0.7±0.2, 0.7±0.2
More than ±8G, More than ±2G
Standard 85°CFor high temperature 150°C
Depends on the individual housing design

Optical transmitter / receiver
A laser wavelength
Measurement time
Measurement cycle
Laser output level
Number of connectablesensors
Sampling frequency
Resolution
Time synchronization
method1550nm15ns or 30ns / sample
1uS±0.01uS
More than +7dBm

Operating Temperature

Single mode fiberStandard 85°C
For high temperature 200°C

Up to 20 sets for a 3-component sensors, 60 for
individual sensors
0.12mGal (100Hz sensor)
0.011mGal (30Hz sensor)
GPS or NTP
Continuous recording / Triggered recording

Measurement Output

Maximum acceleration,
instrumental seismic intensity, SI value
win format
2TB HDD Constitution＊ Specification and design specified in this catalogue are subjected to change without notice.
＊ The content of this catalogue is as of April, 2023.

Contact

HAKUSAN CORPORATION
5-5-13 Toyosu, Koto-ku, Tokyo 135-0061, Japan
Phone: +81-3-6372-7000
E-mail:_support@tepico.jp_
URL: https://www.tokyo-pt.co.jp/

Optical sensor seismic monitoring systemby phase-shifted optical interferometry

100Hz or 200Hz

Recording method

Data format
Recoding media

Fiber optic cable
Optical fiberKDX Fuchu Building 8F, 1-40, Miyamachi, Fuchu-shi, Tokyo 183-0023, JAPAN
Phone: +81-42-333-0080
E-mail:_support@hakusan.co.jp_
URL: https://www.hakusan.co.jp/

Seismic observation in harsh environments
High-precision seismic observation is possible under the harsh environment, places where power cannot be supplied,high temperature where electronic devices do not operate and oil and gas field where explosion proof devices are required.

Deep depth,Volcanicand Geothermal area

Seabed,Resource exploration

SeismometerOn the sea, Wind
farm on the coast

Reactor building

Fiber optic cable

Underground
exploration

Oil and gas
storage base

GStorage
StoS
toragragag
ge ttank
a kankMagmaMMagagg maa
ChamberChah mbe
mb e rUnder high temperatureenvironment

Difficult to supply power

Under high radiation dose,
Under high temperature environment

Thunder spots,
Difficult to maintain

Oill anda d Gas
anGas

Explosion-proof location

FeaturesLong distance, Wide area

Observation results

The phase-shifted optical interferometry enables highly accurate* seismic observation without power supply to the sensor.
- No power supply or electronic components required (from the fiber optic cable to the sensor)- High temperature resistance, high pressure resistance, lightning resistance, explosion proof, radiation resistance- Long-distance / wide-range observation- Long-term stable operation in the field- Shortening the construction period and reducing costs

Noise level comparison between optical interference sensor,
broadband seismometer and servo accelerometer.
Noise spectra of an optical sensor seismic observation
system, a servo accelerometer, and a broadband seismometer observed at the Tono Yamazaki Observatory of Tohoku
University in Japan.
As the broadband seismometer is a velocity seismometer,
the record of the broadband seismometer is differentiatedand converted to acceleration. The optical sensor seismic
observation system observes the ground motion of theobservation tunnel from 0.1Hz to 30Hz, similar to thebroadband seismograph. The noise level of the servo
accelerometer is higher than that of the optical sensor
seismic observation system and the broadband seismometer.

Servo accelerometer

Optical circuit
Optical sensor seismic
observation systemSensor unit

broadband seismometer

Enlarged view ofthe sensor unit
Image model

Fiber optic cable

System Control andRecording Instrument Unit

Accelerometer＊In a comparison of microtremor observation conducted in a quiet place, the same high sensitivity and low noiseas the electric broadband seismometer were confirmed.

Observation example of a small earthquake
0.020

Waveform of the vertical component of the earthquake observedby the optical sensor system at the Tono Yamazaki Observation
Tunnel of Tohoku University around 0:16 am on December 18,
2019.
The waveform with the maximum amplitude of 0.02 Gal is clearly
captured.

0.015

Phase-shifted optical interferometry【Related Patents】
Patent number 5118004: Optical fiber sensor
Patent number 5118246(U.S. patent number 9273948): Optical fiber sensor
Patent number 5702623: Optical fiber sensor( The phase of the reference light is shifted by π / 2.)
Patent number 6002329: Optical interference sensor and observation system

Ro

Optical fiber~20km

Acceleration（Gal）

Optical interferometer can measure a very small distancechange. However usual interferometer has only a half (1/2)
wavelength of measurement range. Our patented phaseshifted optical interferometer extends the range of up to
thousands of wavelengths.

0.010
π/2 modulationRc

30nsecPhase-shifted
pulse

0.005
0.000
-0.005Pendulum-0.010-0.015R l1 l2 S40nsec

Interferedpulse-0.020030nsec

RoSo10nsec

20

40

60

80

100

Time（seconds）

Rc
ScInterference

120

140

160180