JP2002523118A - Sensing pad assembly using variable coupler optical fiber sensor - Google Patents

Abstract

(57) A sensing pad assembly for monitoring acoustic activity or movement of an object supported on a pad, wherein the pressure variation due to the acoustic activity or movement is converted to an output that changes according to the pressure variation. An improved optical fiber sensor is used as a pressure conversion element. This sensor allows deflection of the coupler fusion area without tension. In a preferred embodiment, the coupler fusion regions are arranged in a substantially U-shape such that the fiber optic leads of the sensor are adjacent to each other on one side of the sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Display of related applications]

The present invention benefits from US provisional application Ser. No. 60 / 097,618, filed Aug. 24, 1998 and US Provisional Application Ser. No. 60 / 126,339, filed Mar. 26, 1999. , Both applications of which are incorporated herein by reference.

[0002]

BACKGROUND OF THE INVENTION

The present invention relates to a sensing pad assembly, which monitors acoustic activity and / or motion of an object supported by the pad. More particularly, the present invention relates to a sensing pad assembly using an improved variable coupler fiber optic sensor as a pressure transducer.
The sensing pad is suitable for various monitoring applications and is particularly useful for continuous monitoring of a medical patient or, more generally, a human body.

In medical treatment, it is common practice to continuously monitor various signs related to the life support of a patient, such as changes in heart rate and respiratory rate, which may indicate deterioration of the patient's condition, without interruption. . A continuous monitoring system generally requires that electrical and / or physical sensors be attached to the patient's body using an adhesive, strap, or the like. Such sensors are often uncomfortable to the patient, and the movement of the patient is often limited by the presence of the sensor and the straps and leads associated with the sensor. Furthermore, such monitoring systems can result in erroneous outputs due to the uncertainty of the contact between the sensor and the patient's skin as the patient moves.

As another monitoring system, a system has been proposed in which a patient is supported on a sensing pad, and the sensing pad has a pressure conversion element having no contact with the patient. The acoustic activity or movement of the patient causes pressure fluctuations in the pad material. These pressure fluctuations correspond exactly to one or more factors to be monitored, which propagate through the pad material to the transducer. Therefore, the converter converts the fluctuation into an electric signal and provides it to the processing by the monitoring circuit.

[0005] US Patent No. 5,684,460 to Scanlon (hereinafter the "460 Patent")
Discloses an example of such a monitoring system. FIG. 1 shows the system in simplified block diagram form. The system discloses a fluid-filled sensing pad 1 configured to support a patient and transmit pressure fluctuations resulting from the patient's acoustic activity or movement to a pressure transducer 2. This pressure converter 2 converts pressure fluctuation into an electrical output. The pressure transducer is connected via a hose 4 to a fluid medium 3 inside the pad. The monitor circuit 5 monitors the output from the converter, and when a predetermined state occurs, for example, when the output of the converter corresponds to no sound and / or no operation (that is, when the output is equal to or less than a predetermined threshold). Alternatively, it provides an output for activating the patient stimulator 6 and an alarm (warning device) 7 if it indicates abnormal activity of the patient.

The sensing pad 1 can be in the form of a fluid-filled mattress or other suitable support such as a car seat or a stroller. Proposed applications of this system include monitoring infants at risk of sudden infant death syndrome (SIDS), controlling breathing arrest and snoring during sleep, and detecting when a car driver falls asleep There is a human body surveillance including. Another proposed application is monitoring noise and vibration indicating abnormal operation of the machine.

The '460 patent lists several classes of sensors as suitable for pressure transducers. For example, electrical sensors, mechanical sensors, piezoelectric sensors, and fiber optic sensors.

[0008] A fiber optic sensor not specifically listed in the '460 patent, but particularly suitable for patient monitoring and various other applications, includes a variable coupler fiber optic sensor.

Conventionally, variable coupler optical fiber sensors have used so-called biconical fused tapered couplers. This coupler is manufactured by a draw-and-fuse process in which a plurality of optical fibers are stretched (drawn) and fused together (fuse) at an elevated temperature. First, the plastic sheath is removed from each fiber, exposing the portion that forms the fusion zone. Usually, these parts are juxtaposed, twisted once or several times, and then stretched while maintaining the softening temperature or higher in an electric furnace or the like. As the exposed portions are stretched, they fuse together to form a narrowed waist region (or waist region)-a fused region. This waist region can couple light between the fibers. By injecting light from the input of one of the fibers in the stretching process and monitoring at the output of each fiber, the coupling rat
io) is determined. As the coupling varies with the length of the waist region, the fiber is stretched until the desired coupling is obtained. Typically, the fibers are stretched until the coupling ratio of each fiber becomes equal. The stretching of the coupler occurs in the waist region until the core of each fiber is effectively lost and the diameter of the cladding approaches the diameter of the previous core. The cladding becomes a new "core" and the evanescent field of propagating light (
The evanescent field is pushed out of this new core, where it wraps both fibers simultaneously, resulting in energy transfer between the fibers. For a detailed description and analysis of biconical fused taper couplers, see J. Bures et al., "Analyse d'un coupleur Bidirectiona in Coupled Single-Mode Optical Fibers."
la Fibers Optiques Monomodes Fusionnes ")", Applied Optics (
Journal of the Optical Society of America), vol. 22, NO.12, June 15, 198
3, pp. 1918-1922.

The biconical fused taper coupler has an advantageous property that the output ratio changes by bending the fused region. Since the output ratio changes depending on the amount of bending, the sensor using this coupler can be used for virtually any sensing purpose that involves movement that can couple to the fusion zone. For example, U.S. Pat. No. 5,074,309 to Gerdt describes such sensors as audible and sub-audible (sub-audi
ble) including use for monitoring cardiovascular sounds, pulse and circulatory system from the patient's heart, including sounds. Ge is another application example of a variable coupler optical fiber sensor.
US Patent No. 4,634,858 to Rdt et al. (which discloses an application to an accelerometer) and US Patent No. 5,671,191 to Gerdt (which discloses an application to an underwater microphone). And other references in the art.

In a conventional variable coupler optical fiber sensor, an optical fiber coupler is pulled straight, fixed to a plastic support member under tension, and straightened by applying such preliminary tension. In this state, it was wrapped in a flexible material such as silicone rubber. The encapsulating material forms the sensing film. The sensing membrane can flex and deform due to external forces, causing the coupler to bend in the fusion region. The bending of the fusion zone results in a measurable change in the power ratio of the coupler. The displacement of the membrane can be made sensitive enough to sense a micron of movement in the range of a few millimeters.

FIG. 2 of the accompanying drawings is a diagram illustrating the basic principle of a sensing device having the variable coupler optical fiber sensor 10 as described above. In the illustrated form, the sensor 1
Reference numeral 0 includes a 2 × 2 biconical fused taper coupler 11 formed by stretching and fusing two optical fibers to form a waist region, ie, a fused region 13. The portion where the original fiber merges into one end of the fusion region becomes the input fiber 12 of the sensor, while the original fiber exiting from the opposite side of the fusion region becomes the output fiber 14 of the sensor. Reference numeral 18 indicates a fiber core. The fusion region 13 is wrapped in a flexible medium 15,
5 constitutes the sensing film. In FIG. 1, the support member is not shown.

In practice, one of the input fibers 12 is illuminated by a light energy source 16. As the light energy source, for example, an LED or a semiconductor laser can be used. Light energy is split by coupler 11 and coupled to output fiber 14. The coupling ratio varies depending on the amount of bending of the fusion region as a result of external forces applied to the sensing membrane. A change in the distribution (branch ratio) of the light energy between the two output fibers 14 can be measured by the photodetector 17. The photodetector 17 is a differential amplifier 1
9 to an electrical input. In this manner, the output signal of the differential amplifier 19 represents the force applied to the medium 15. It will be appreciated that if only one of the input fibers 12 is used to introduce light into the sensor, the other input fiber may be cut short. Alternatively, the main input fiber may be left as a spare in case of a failure. For the sake of simplicity, the coupler 11 shown does not show the aforementioned torsion in the fusion area. However, such twisting leads to lead sensitivity (le
It is often preferred to reduce ad sensitivity). Lead sensitivity refers to the sensitivity of the output light distribution to change in response to movement of the input fiber.

Compared to other types of fiber optic sensors, variable coupler sensors are inexpensive, relatively simple to configure, have high performance (ie, high sensitivity and wide dynamic range), and have a wide range of applications. It has the advantages that are not available. Other known fiber optic sensors use principles such as microbending loss, optical phase interference, and polarization rotation due to birefringence. Optical fiber microbending sensors are designed to sense pressure by emitting light out of the fiber in response to changes in pressure. Since the pressure is converted to light loss, the output light intensity decreases as the measured pressure increases. The dynamic range of such sensors is severely limited due to reduced measurement accuracy at low light levels. An interference type optical fiber sensor measures a pressure change by applying a pressure to an optical fiber and changing its refractive index. Changes in the refractive index cause a phase lag measured using a Mach-Zehnder interferometer or Michelson interferometer configuration. These sensors are extremely expensive and require complex modulation techniques, making them unsuitable for many applications. The variable polarization type optical fiber sensor changes the polarization state of a polarized optical signal in accordance with a change in temperature or pressure. Such polarized light sensors require special optical fibers and expensive polarizing beam splitters.

[0015] Despite its advantages, conventional variable coupler fiber optic sensors have certain limitations inherent in their pre-tensioned, straight (straight) coupler design. Conventional coupler designs, among other things, impose considerable constraints on geometry. In particular, the size of the sensor must be large enough to accommodate the optical fiber leads at both ends of the sensor. The configuration of the fiber optic lead also requires free space around the ends of the sensor during use. Another limitation is due to the fact that any displacement of the fusion zone necessarily leads to an increase in the tension of the fusion zone. At some point in the displacement, the tension in the fusion zone becomes excessive, causing cracking or breakage of the fusion zone, resulting in failure of the coupler.

[0016]

Summary of the Invention

The present invention provides a sensing pad assembly that uses an improved variable coupler fiber optic sensor and eliminates some of the disadvantages of conventional pretensioned linear sensor designs. More specifically, the sensor used in the present invention will have an improved design that allows for the deflection of the fused area of the coupler without tension. The fused region of the coupler is preferably configured to be substantially U-shaped, but more generally as disclosed in co-pending U.S. patent application Ser. No. 09 / 316,143 filed May 21, 1999. Shape may be used. This US patent application is incorporated herein by reference. The substantially U-shaped configuration allows the optical fiber leads to be arranged side by side rather than at opposite ends of the sensor. This eliminates the geometric limitations inherent in the pre-tensioned linear coupler design described above. The configuration of the pad may be of any desired configuration as long as the pressure variation to be monitored can be transmitted to the variable coupler fiber optic sensor. For example, the pad may be in the form of a mattress, a sheet-like member placed on or below the mattress, a seat cushion, or a sheet-like member placed in the seat cushion.

In one preferred embodiment of the invention, the sensor is located within the inner material of the sensing pad. In another preferred embodiment, the sensor is secured to the outer surface of the pad and its sensing area (including at least a portion of the fusion area) is coupled to the pad's inner material through a hole in the outer surface of the pad. However, generally speaking, the sensor may be configured in any manner so long as its sensing area is coupled to receive pressure fluctuations transmitted by the material of the pad.

In summary, in one major aspect, the present invention provides a sensing pad assembly as follows, wherein the pad member is a surface configured to support an object to be monitored. And the acoustic activity of the supported object (
A sensing pad assembly having a pad member capable of transmitting pressure fluctuations due to acoustic activity or motion. The sensing pad assembly further includes a variable coupler fiber optic sensor having a fused fiber coupling area, wherein at least a portion of the coupling area is disposed in a sensing area of the sensor and a portion thereof is flexed to the coupling area. The output of the sensor is configured to change without applying tension. The sensing area is arranged such that pressure fluctuations are transmitted to the sensing area to deflect said portion of the coupling area, thereby changing the output of the sensor in response to the pressure fluctuations.

In yet another principal aspect, the present invention provides a sensing pad assembly as follows, comprising a sensing pad having features described above and a generally U-shaped fused fiber coupling area. Wherein the fused fiber coupling region is disposed within a sensing area of the sensor such that the coupling region can flex to change the output of the sensor. Further, the sensing area is arranged such that pressure fluctuation is transmitted to the sensing area and the coupling area is flexed to cause a change in sensor output according to the pressure fluctuation.

Other aspects of the invention will become apparent from reading the following description of a preferred embodiment with reference to the drawings, in which:

[0021]

Description of the embodiment

3 to 5 show a sensing pad assembly according to a first embodiment of the present invention. The sensing pad assembly includes a pad member 1 'and a variable coupler fiber optic sensor 20 mounted on an outer surface of the pad member.

The pad member may be of a fluid-filled (eg, water or air-filled) structure as described in the aforementioned Scanlon patent. In the illustrated embodiment, the pad has an upper wall 1a and a lower wall 1b connected by four side walls 1c, and supports an object to be monitored on its upper (apparent) outer surface. Has become. FIG. 3 shows only two of the side walls 1c.
The object to be monitored may be a person, an animal, or a machine, and the size of the pad can be appropriately selected in consideration of each application. For example, for infants at risk of SIDS, the pad can be configured as a crib mattress or as a sheet-like form (eg, about 2 cm thick) placed on a regular crib mattress. . In such a case, the pad can be laid under normal linen sheets and waterproof sub-sheets to prevent contamination and protect the infant in case of leakage from the pad.

For a newborn, the heart rate is about 120 to 180 beats per minute, or 2-3 Hz, and the respiratory rate is about 60 beats per minute, or 1 Hz. In adults, the heartbeat occurs at a frequency of about 1 Hz,
Breathing, on the other hand, takes place at a frequency of about 0.2 Hz. Advantageously, the electrical signal obtained by converting the optical output of the sensor can be filtered to remove frequencies above 10 Hz, for example, thereby reducing electrical noise and S / N in the EKG domain. Remove other higher frequencies that cause it to.

Depending on the application, the pad member may be appropriately filled with gel or formed of a soft solid material such as silicone rubber. The pad need only be effective to transmit pressure fluctuations due to acoustic activity or movement of the supported object to the variable coupler fiber optic sensor 20 for detection.

The variable coupler fiber optic sensor 20 is best illustrated in FIG. The sensor 20 is
A support member 22 having a generally annular head 24 and a handle-like extension 28 are included. A depression or through hole is formed in the head to define an annular sensing area 26 of the sensor. The biconical fused taper coupler 30 is attached to the support member, and at least a part (here, the entirety) of the fused coupling region 32 is arranged in the region 26 and is arranged in a U-shape. The coupler input fiber lead 34 and output fiber lead 36 are formed in an extension 28 and have grooves 29 opening into region 26.
Are arranged next to each other. The leads are manipulated by bending the coupling region 32 to 180 ° into the desired shape, and then secured in the grooves with a suitable adhesive, such as an epoxy-based adhesive. The coupling area is untensioned and is embedded by filling the surrounding depressions or through holes with an elastomer and filling the sensing membrane 38 in a known manner, for example by filling it with a silicone rubber such as GE RTV 12. To form Although four fiber leads are shown, one of the input leads 34 may be disconnected after formation of the coupling region 32 if desired. This is because only one input lead is sufficient for the operation of the sensor. However, a four lead configuration is desirable. This is because if the main input lead is damaged, it can be used as a backup lead.

In a practical embodiment of the sensor, the maximum diameter of the membrane can be on the order of 5 cents coin diameter, but the membrane can be smaller or larger as desired for a particular application. The size of the support plate can be any convenient size, as long as the coupler fusion region and the fiber section near the fusion region are securely supported. The sensitivity of the device depends on the stiffness of the membrane, as in conventional devices.

The sensor 20 is used to acoustically couple the sensing film 38 to the internal medium 3 of the pad member.
It is hermetically fixed to the pad member 1 'so as to be adjacent to a hole H passing through one of the side walls 1c of the pad. The diameter of the through-hole is to maximize the coupling between the membrane and the internal medium 3,
The diameter of the sensing film 38 is substantially the same. The sensor can be secured around hole H in any suitable leakage-prevention manner, for example by gluing the head 24 around the hole H on the outer surface of the pad sidewall. As shown in the figure, separating the grooved side of the support member 22 from the pad member facilitates reliable sealing to the pad side wall. The hole H can be used for filling the pad member, but a separate filling port may be provided.

As shown in the figure, by coupling the sensing membrane 38 to the internal medium 3 of the pad member, the pressure fluctuations P (eg, human or human) caused by the motion or acoustic activity of the object supported on the pad top surface Pressure fluctuations due to the beating and breathing of the animal) are transmitted through the medium 3 to the sensing membrane 38. This causes the membrane 38 to flex and the embedded coupling region 32 to flex in response to pressure fluctuations. As a result, the optical output of the sensor, especially the light distribution (or branching ratio) in both output fibers 36, also changes in response to pressure fluctuations.

FIGS. 6 and 7 are comparisons of the deflection of a conventional pretensioned linear optical fiber coupler with the deflection of the U-shaped coupler of the sensor in the embodiment of FIGS. 6a and 6c are a top view and a side view, respectively, showing the fusion region in the normal state of a conventional coupler. 6b and 6d are corresponding views, each showing the fusion region being deflected by a downward force F. FIG. 7a to 7d in FIG. 7 correspond to FIG. 6, but show a U-shaped coupler according to the invention.

As can be seen from FIG. 6d, the flexing of the fusion zone in a conventional coupler causes an arched bend, which extends the fusion zone, thereby increasing the tension. In contrast, the deflection of the U-shaped fusion region in FIG. 7d is seen to occur along a direction perpendicular to the plane of the U-shape, but along the height of the U (horizontal length in FIG. 7d). It only causes the gutter to bend and does not tension the fusion zone. Thus, even if a large displacement occurs in the fusion region, no crack and no breakage occurs.

FIGS. 8 and 9 show a sensing pad assembly according to a second embodiment of the present invention. In this embodiment, the improved variable coupler optical fiber sensor 20 'is located inside the sensing pad member 1 ". The sensor 20' and its optical fiber input / output leads.
The holes 34, 36 are inserted through holes H 'provided in one of the pad sidewalls, and the holes H' are subsequently sealed with a suitable sealing material. The sensor 20 ', best shown in FIG. 9, is configured as an air-backed hydrophone,
The sensing membrane 38 is lined up and closed on the back (bottom in FIGS. 8 and 9) of the head 24 of the support member and air is trapped in the hollow cap 24a.
Except for being backed, it has a structure similar to that of the sensor shown in FIGS. It is configured as a hydrophone supported by air. The back surface (bottom surface) of the cap is fixed to the inner surface of the bottom wall 1b of the sensing pad member by bonding or the like. Alternatively, sensor 20 'can simply float inside the pad, in which case it has a fixed connection only where the fiber lead is fixed to the side wall.

Although not shown in the figures, any illustrated embodiment contemplates that the optical fiber lead be contained within one or more protective coatings.

The optical fiber used in the sensor of the present invention has a Cor loss of about 0.18 dB / Km.
Very high quality such as ning SMF28 is most preferred. Photodetector, wavelength 900n
There can be gallium-aluminum-arsenide or germanium detectors for light above m and silicon detectors for shorter wavelengths.

The photodetectors may be connected in either a photovoltaic mode or a photoconductive mode. In photovoltaic mode, a detector can be coupled to the input of the differential amplifier using a transimpedance amplifier (which converts current to voltage). The output of the transimpedance amplifier may be filtered to remove broadband noise. In the photoconductive mode, the output of the detector can be connected to a conventional voltage amplifier. This method may be used where noise is the result, but cost is of primary concern rather than lower noise levels.

The above embodiments of the present invention are merely illustrative, and it goes without saying that other modifications are possible as long as the basic principles of the present invention as described herein are maintained.

[Brief description of the drawings]

FIG. 1 is a simplified block diagram of a conventional monitor system using a sensing pad.

FIG. 2 shows a basic structure of a conventional variable coupler optical fiber sensor.

FIG. 3 is a perspective view of a sensing pad assembly according to the first embodiment of the present invention;

FIG. 4 is a cutaway side view showing the arrangement of the variable coupler optical fiber sensor of FIG. 3 in more detail;

FIG. 5 is a plan view showing the sensor of FIG. 3;

FIG. 6 is an explanatory view (FIGS. 6a to 6d) of a fusion state of a conventional pre-tensioned linear coupler in a normal state and a bent state.

FIG. 7 is a similar illustration for a sensor having a U-shaped fusion zone (FIGS. 7a-7d);
).

FIG. 8 is a perspective view of a sensor pad assembly according to a second embodiment of the present invention.

FIG. 9 is a perspective view of a variable coupler optical fiber sensor used in the embodiment of FIG.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY , CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP , KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, US, UZ, VN, YU, ZW (71) Applicant Jart, David W. United States 22906 Virginia, Charlottesville, P.E. Oh. Box 8175, within Empirical Technologies Corporation (72) Inventor Barack, Martin C. United States 22906 Virginia, Charlottesville, P.E. Oh. Box 8175, within Empirical Technologies Corporation (72) Inventor Adkins, Charles USA 22906 Virginia, Charlottesville, P.E. Oh. Box 8175, within Empirical Technologies Corporation (72) Inventor Jart, David W .; United States 22906 Virginia, Charlottesville, P.E. Oh. Box 8175, F-term in MEPICAL TECHNOLOGIES CORPORATION (reference) 4C038 VA20 VB01 VB31 VC20

Claims (34)

[Claims] 1. A pad member having a surface configured to support an object to be monitored and capable of transmitting pressure fluctuations due to acoustic activity or movement of the supported object; a fiber optic sensor, A fusion fiber coupling region, wherein at least a portion of the coupling region is disposed within a sensing region of the sensor and configured to flex and change the output of the sensor without tensioning the coupling region. An optical fiber sensor, wherein the sensing area is arranged such that the pressure fluctuation is transmitted to the sensing area to deflect the portion of the coupling area, thereby changing the output of the sensor in response to the pressure fluctuation. And a sensing pad assembly comprising: 2. The assembly of claim 1, wherein said pad member has an internal medium selected from the group consisting of a liquid and a gel. 3. The assembly of claim 2, wherein said sensor is mounted on an outer surface of said pad member wall. 4. The assembly of claim 3, wherein a hole is formed in said wall of said pad member through which said sensing area is operatively coupled to said internal medium. 5. The assembly of claim 4, wherein said sensing area has a sensing membrane encasing said portion of said coupling area. 6. The assembly of claim 4, wherein said sensor includes a support member surrounding said sensing area and sealingly mounted to said wall of said pad member around said aperture. 7. The sensor has at least one input optical fiber and a plurality of output optical fibers, the input / output optical fibers are connected to the coupling area, and the support member has a groove for receiving the input / output optical fibers. The assembly of claim 6 having a surface comprising: 8. The assembly of claim 7, wherein said support member has an opening communicating with said groove and receiving said portion of said coupling area. 9. The assembly according to claim 2, wherein said sensor is located inside said pad member. 10. The sensor includes a support member having a portion bounding the sensing region, and a sensing membrane disposed in the sensing region and enclosing the portion of the coupling region, the sensing region being supported by a hollow cap. The assembly of claim 9, wherein the assembly provides a sealed space adjacent the sensing membrane. 11. The assembly of claim 10, wherein said cap is mounted on an inner surface of said pad member. 12. The assembly of claim 10, wherein said sensor is suspended within said internal medium of said pad member. 13. The sensor has at least one input optical fiber and a plurality of output optical fibers, the input / output optical fibers are connected to the coupling area, and the support member receives the input / output optical fibers. An assembly according to claim 9 having a surface with a groove. 14. The assembly of claim 13, wherein said support member has an opening communicating with said groove and receiving said portion of said coupling area. 15. The assembly of claim 1, wherein said pad member is formed of a flexible solid material. 16. The sensor has at least one input optical fiber and a plurality of output optical fibers, all of the input and output optical fibers are connected to the coupling area, and the assembly includes the plurality of output optical fibers. An electro-optic circuit optically coupled to the optical fiber for converting light received from the output optical fiber to an electrical output having a level dependent on the amount of deflection of the portion of the coupling region. The assembly of claim 1. 17. A differential amplifier circuit comprising: a plurality of photodetectors optically coupled to the plurality of output optical fibers, respectively; and an output of the photodetector connected to the plurality of output optical fibers. 17. The assembly of claim 16, comprising: 18. A fiber optic sensor having a surface configured to support an object to be monitored and capable of transmitting pressure fluctuations due to acoustic activity or movement of the supported object; A generally U-shaped fused fiber coupling region, wherein the coupling region is disposed within a sensing region of the sensor such that the coupling region flexes to change the output of the sensor, and wherein the sensing region is configured such that the pressure fluctuation is greater than the pressure fluctuation. A fiber optic sensor arranged to be transferred to a sensing area to deflect the coupling area, thereby changing the output of the sensor in response to the pressure fluctuation. 19. The assembly of claim 18, wherein said pad member has an internal medium selected from the group consisting of a liquid and a gel. 20. The assembly of claim 19, wherein said sensor is mounted on an outer surface of said pad member. 21. The assembly of claim 20, wherein said sensor is mounted to a wall having a hole formed in said pad member, and said sensing area is operatively coupled to said internal medium through said hole. 22. The assembly of claim 21, wherein said sensing area has a sensing membrane encasing said portion of said coupling area. 23. The sensor according to claim 21, wherein the sensor has a portion surrounding the sensing area and includes a support member hermetically attached to the wall of the pad member around the hole. The described assembly. 24. The sensor has at least one input optical fiber and a plurality of output optical fibers, the input / output optical fibers are connected to the coupling area, and the support member receives the input / output optical fibers. 24. The assembly according to claim 23, having a surface with a groove. 25. The assembly of claim 24, wherein said support member has an opening communicating with said groove and receiving said portion of said coupling area. 26. The assembly according to claim 19, wherein the sensor is located inside the pad member. 27. The sensor includes a support member having a portion bounding the sensing region, and a sensing membrane disposed in the sensing region and enclosing the portion of the coupling region, the sensing region being supported by a hollow cap. 27. The assembly of claim 26, wherein said assembly provides a sealed space adjacent said sensing membrane. 28. The assembly of claim 27, wherein said cap is mounted on an inner surface of said pad member. 29. The assembly of claim 27, wherein said sensor is floating within said internal medium of said pad member. 30. The sensor has at least one input optical fiber and a plurality of output optical fibers, the input / output optical fibers are connected to the coupling area, and the support member receives the input / output optical fibers. 27. The assembly of claim 26, wherein the assembly has a surface with a groove. 31. The assembly of claim 30, wherein said support member has an opening communicating with said groove and receiving said portion of said coupling area. 32. The assembly of claim 18, wherein said pad member is formed of a flexible solid material. 33. The sensor has at least one input optical fiber and a plurality of output optical fibers, the input and output optical fibers are connected to the coupling area, and the assembly includes the plurality of output optical fibers. 19. The assembly of claim 18, further comprising an electro-optic circuit optically coupled to the fiber for converting light received from the output optical fiber to an electrical output having a level dependent on an amount of deflection of the coupling region. . 34. The electro-optical circuit, comprising: a plurality of photodetectors optically coupled to the plurality of output optical fibers, respectively; and a differential amplifier circuit connected to an output of the photodetector. 34. The assembly of claim 33, comprising: