Sensor for detecting pressure waves in a liquid

A method of detecting pressure variations in a fluid comprising:

• providing an optical fiber comprising a Fiber Bragg Grating;
• holding the optical fiber at two fixing points on opposite sides of the Fiber Bragg Grating;
• exerting on the optical fiber a tension force pulling the two fixing points apart;
• receiving a fluid pressure variation;
• in response to receiving a fluid pressure increase, increasing the tension force, and in response to receiving a fluid pressure decrease, decreasing the tension force;
• interrogating the optical fiber with a light pulse;
• receiving a reflected light pulse from the Fiber Bragg Grating;
• analyzing the wavelength spectrum of the reflected light pulse to calculate a length variation of the Fiber Bragg Grating proportional to a wavelength shift of the reflected light pulse as compared to the interrogating light pulse, and to calculate a pressure variation proportional to the length variation;
• filtering the fluid pressure variations;
• and
• reducing the tension force response variation for fluid pressure variations having a variation frequency lower than a predefined frequency threshold in order to effect static pressure variation compensation.

A detection means for detecting pressure variations in a fluid comprising:

• an optical fiber comprising a Fiber Bragg Grating;
• mounting means for holding the optical fiber at two fixing points on opposite sides of the Fiber Bragg Grating, and for exerting on the optical fiber a tension force pulling the two fixing points apart;
• and
• a compensation means;
• the mounting means including a pressure-sensitive response element for receiving a fluid pressure variation and for, in response to receiving a fluid pressure increase, increasing the tension force, and in response to receiving a fluid pressure decrease, decreasing the tension force;
• and
• the compensation means for reducing the tension force response variation for fluid pressure variations having a variation frequency lower than a predefined frequency threshold.