Sensor deployment for distributed acoustic sensing interrogation in subsea applications
A distributed acoustic system (DAS) may include at least one laser that that transmits at least one continuous wave (CW) light, a pulser disposed after and optically connected to the at least one laser to form a light pulse, and a splitter optically connected to the pulser to optically split the light pulse into a plurality of light pulses. The DAS may further include a proximal circulator optically connected to a first output of the splitter, a distal circulator optically connected to the proximal circulator, and a sensor fiber attached to the distal circulator. A method for using the DAS may include setting a pulse power for a laser, transmitting one or more light pulses from the laser into a distributed acoustic system (DAS), and measuring a signal to noise ratio (SNR) from a backscatter light created within the fiber optical cable and the sensor fiber.
1 . A distributed acoustic system (DAS) comprising:
at least one laser that that transmits at least one continuous wave (CW) light;
a pulser disposed after and optically connected to the at least one laser to receive the CW light from the at least one laser and form a light pulse;
a splitter optically connected to the pulser to optically split the light pulse into a plurality of light pulses, wherein each of the plurality of light pulses is an output of the splitter;
a plurality of circulators optically connected to the splitter;
a sensor fiber attached to each the distal circulator of the plurality of circulators; and
a plurality of optical receivers, wherein each receiver of the plurality of receivers is optically connected to a respective circulator of the plurality of circulators.
2 . The DAS of claim 1 , further comprising a gain fiber which optically connects the distal circulator to the proximal circulator.
3 . The DAS of claim 1 , further comprising a first optical receiver optically connected to the proximal circulator.
4 . The DAS of claim 1 , further comprising a first optical receiver optically connected to the distal circulator.
5 . The DAS of claim 1 , further comprising a second proximal circulator optically connected to a second output of the splitter.
6 . The DAS of claim 5 , further comprising a second distal circulator optically connected to the proximal circulator by a gain fiber.
7 . The DAS of claim 6 , further comprising a second sensor fiber attached to the second distal circulator.
8 . The DAS of claim 5 , further comprising a first optical receiver optically connected to the proximal circulator.
9 . The DAS of claim 8 , further comprising a second optical receiver optically connected to the distal circulator.
10 . The DAS of claim 1 , further comprising a wavelength division multiplexer (WDM) optically connected to the at least one laser as an input and to the splitter as an output.
11 . A method comprising:
setting a launch power for a continuous wave (CW) light that emits from a laser;
receiving the CW light from the laser with a pulser, which form one or more light pulses from the CW light;
transmitting the one or more light pulses from the laser at a set pulse power into a distributed acoustic system (DAS), wherein the DAS comprises a fiber optical cable disposed in a flowline and a sensor fiber;
passing a backscatter light created within the fiber optical cable and the sensor fiber through a circulator, wherein the circulator is optically connected to a corresponding optical receiver of a plurality of optical receivers, and wherein the circulator directs the backscatter light to the corresponding optical receiver;
measuring a signal to noise ratio (SNR) from the backscatter light created within the fiber optical cable and the sensor fiber;
generating a SNR table that compares the backscatter light from the fiber optical cable to the pulse power and compares the backscatter light form the sensor fiber to the pulse power; and
selecting the pulse power for one or more measurements within the fiber optical cable to the sensor fiber based at least in part on the SNR table.
12 . The method of claim 11 , wherein the fiber optical cable is a gain fiber.
13 . The method of claim 11 , further comprising adjusting one or more properties of the DAS to increase a spatial resolution or pulse repetition rate.
14 . The method of claim 13 , wherein the one or more properties of the DAS are a laser pulse power, a laser pulse width, or a system gauge length.
15 . The method of claim 11 , further comprising a second fiber optical cable disposed within the flowline and a second sensor fiber.
16 . The method of claim 15 , wherein the second fiber optical cable is a gain fiber.
17 . The method of claim 16 , further comprising adjusting one or more properties of the DAS to increase a spatial resolution or pulse repetition rate within the second fiber optical cable.
18 . The method of claim 17 , wherein the one or more properties of the DAS are a laser pulse power, a laser pulse width, or a system gauge length.
19 . The method of claim 11 , further comprising a wavelength division multiplexer (WDM) optically connected to the laser as an input to the WDM and optically connected to the splitter as an output to the WDM.
20 . The method of claim 19 , further comprising a Raman laser optically connected to the WDM.