Optical fiber system for determining at least one physical parameter and method for determining at least one physical parameter using the optical fiber system

Abstract

To provide a more compact optical fiber sensor system with higher performance.SOLUTION: A sensor system of the present invention includes: at least two sensing reflectors; at least one reference reflector; at least one optical fiber including a distal end and a proximal end; a modulable light source arranged at the proximal end of the optical fiber; and a photodetector. A measurement segment formed between the two sensing reflectors is arranged between the distal end and the proximal end. The reference reflector is arranged between the proximal end and the distal end, and is separated from the distal end by at least 1 mm.SELECTED DRAWING: Figure 2

Claims

1. A sensor system (1) comprising at least one optical fiber (7), a moduloable light source (4), and a photodetector (5), The at least one optical fiber (7) comprises at least two sensing reflectors (1.1, 1.2 to 1.i), The at least one optical fiber (7) comprises at least one reference reflector (2), Each of the at least one optical fiber (7) further comprises a distal end (72) and a proximal end (71), A measurement segment (3.1 to 3.i) is formed between two sensing reflectors (1.1 to 1.i). The measurement segments (3.1 to 3.i) are arranged between the distal end (72) and the proximal end (71). The light source (4) is located at the proximal end (71) of the optical fiber (7) in the sensor system (1), The reference reflector (2) is positioned between the proximal end (71) and the distal end (72). The reference reflector is located at least 1 mm away from the distal end (72). An attenuator (21) is placed at the distal end (72) of the optical fiber (7), or The photodetector (5) is positioned at the distal end (72) of the optical fiber (7). The bandwidth of the sensing reflector (1.1, 1.2 to 1.i) is 1 nm or more at a wavelength of approximately 1550 nm. The light source (4) is configured to emit light having a linewidth of less than 10 GHz, The bandwidth of the sensing reflector (1.1, 1.i) is wider than the moduloable bandwidth of the light source (4). The sensor system (1) comprises an evaluation unit (6), and the evaluation unit (6) is configured to track the relative resonance phase in time when the light from the light source (4) is modulated.

2. The reference reflector (2) is positioned between the proximal end (71) and the sensing reflector (1.1) closest to the distal end (72), or The sensor system (1) according to claim 1, further characterized in that the reference reflector (2) is positioned between the proximal end (7.1) and the sensing reflector (1.1) closest to the proximal end (71).

3. The reference reflector (2) is either a fiber Bragg grating or The sensor system (1) according to claim 1, further characterized in that the sensing reflector (1.1, 1.2 to 1.i) is a fiber Bragg grating, and the reference reflector (2) is a fiber Bragg grating.

4. The measurement segments (3.1 to 3.i) are arranged within the sensing area (8). The measurement segments (3.1 to 3.i) are configured such that their characteristics change in response to physical characteristics within the sensing area (8), such as temperature, pressure, or strain. The sensor system (1) according to claim 1, further characterized in that the attenuator (21) is located within the sensing region (8).

5. The attenuator (21) is configured to attenuate the incident light by at least -0.1 dB / mm (decibels / millimeter), or The sensor system (1) according to claim 1, further characterized in that the attenuator (21) has a length of 100 mm or less.

6. The light source (4) has a moduloable wavelength, The light source (4) is configured to emit light modulated at a certain modulation speed, The sensor system (1) according to claim 1, further characterized in that the light source (4) is configured to emit light having a coherence length longer than the maximum distance between any of the sensing reflectors (1.1, 1.2 to 1.i) and the closest of the at least one reference reflector (2).

7. The sensor system (1) according to claim 1, further characterized in that the light source (4) is configured to emit light having a linewidth of less than 2 MHz.

8. The reflectivity of the reference reflector (2) is at least twice the reflectivity of any of the sensing reflectors (1.1, 1.2 to 1.i), or The sensor system (1) according to claim 1, further characterized in that the reflectance of the reference reflector (2) is at least half the reflectance of any of the sensing reflectors (1.1, 1.2 to 1.i).

9. The modulation speed of the light source (4) is at least 10 Hz. The light source (4) is a dispersed feedback diode, The sensor system (1) according to claim 1, further characterized in that the photodetector (5) comprises only one photosensitive element.

10. The steps include providing at least one optical fiber (7) including at least two sensing reflectors (1.1, 1.2) and at least one reference reflector (2), The steps include providing a moduloable light source (4), The steps include providing a photodetector (5) and A light sensing method including, The light source (4) emits light towards the proximal end (71) of the optical fiber (7). The wavelength of the light is modulated as a function of time over the bandwidth of the light, The light is reflected by at least two sensing reflectors (1.1, 1.2 to 1.i) that form the measurement segments (3.1 to 3.i) of the optical fiber (7), and the sensing reflectors (1.1, 1.2 to 1.i) are positioned between the distal end (72) and the proximal end (71) of the optical fiber (7). The light is also reflected by a reference reflector (2), which is positioned between the proximal end (71) and the distal end (72), and at least 1 mm away from the distal end (72). The coherence length of the light source (4) is set to be longer than the maximum distance between any of the sensing reflectors (1.1, 1.2 to 1.i) and the reference reflector (2). The light source (4) is modulated over the bandwidth of the emitted light, The bandwidth of the aforementioned light is narrower than the bandwidth of the reflectivity of the sensing reflector (1.1, 1.2 to 1.i, 2). The aforementioned optical sensing method is The steps of providing an evaluation unit (6), and The step further includes placing an attenuator (21) at the distal end (72) of the optical fiber (7), The evaluation unit (6) tracks the relative resonance phase in time when the light from the light source (4) is modulated. From the reflected light signal, time-resolved interference fringes are formed, including resonance peaks with characteristic amplitudes, corresponding to the length between the reference reflector and each sensing reflector. The attenuator (21) is an optical sensing method that suppresses unwanted reflections from the distal end (72) of the optical fiber (7).

11. The photodetector (5) comprises only one photosensitive element, as described in claim 10.

12. The reference reflector (2) is positioned between the proximal end (71) and the distal end (72), and the reference reflector is at least 1 mm away from the distal end (72), or The reference reflector (2) is positioned between the proximal end (71) and the sensing reflector (1.1) closest to the distal end (72), and the reference reflector is at least 1 mm away from the distal end (72), or The optical sensing method according to claim 10 or 11, wherein the reference reflector (2) is positioned between the proximal end (7.1) and the sensing reflector (1.1) closest to the proximal end (71), and the reference reflector is at least 1 mm away from the distal end (72).

13. The attenuator (21) is configured to attenuate the incident light to more than -2 dB / mm, or The sensor system (1) according to claim 1, further characterized in that the attenuator (21) has a length of 20 mm or less.

14. The modulation speed of the light source (4) is at least 200 kHz, The light source (4) is a dispersed feedback diode, The sensor system (1) according to claim 1, further characterized in that the photodetector (5) comprises one photosensitive element.

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