Pressure or strain sensitive optical fiber

A pressure sensor comprising:

• pressure sensitive optical fiber having:
• core means at least a portion of which has a predetermined refractive index for transmitting light therethrough;
• cladding means adjacent said core means having a refractive index which is less than that of the core means portion;
• and
• concentric light transmission means adjacent said cladding means having a refractive index which is greater than that of the cladding means and an internal diameter which is greater than the unperturbed mode boundary diameter of said core means such that all light passes through said core means portion when said optical fiber is unperturbed, and further, when said optical fiber is perturbed by pressure forces from stress or strain, light passes through said concentric light transmissive means in proportion to the amount of stress or strain forces induced in the fiber;
• means for introducing optical power into one end of the optical fiber;
• and
• means for detecting the optical power at the opposite end of the optical fiber.

A method for detecting pressure which comprises:

• installing pressure sensitive optical fiber in a location where pressure is contemplated for detection thereof, said pressure sensitive optical fiber comprising:
• core means at least a portion of which has a predetermined refractive index for transmitting light therethrough;
• cladding means adjacent said core means having a refractive index which is less than that of the core means portion;
• and
• concentric light transmissive means adjacent said cladding means having a refractive index which is greater than that of the cladding means and an internal diameter which is greater than the unperturbed mode boundary diameter of said core means such that all light passes through said core means portion when said optical fiber is unperturbed, and further, when said optical fiber is perturbed, by pressure forces from stress or strain, light passes through said concentric light transmissive means in proportion to the amount of stress or strain induced in the fiber;
• applying a light source at one end of the sensor;
• and
• measuring optical power changes in at least one of said core means and said light transmissive means, thereby detecting pressure variations on the fiber.

Pressure sensitive optical fiber comprising:

• core means comprising multimode fiber and having a predetermined refractive index for transmitting light therethrugh;
• cladding means adjacent said core means having a refractive index which is less than that of the core means;
• and
• concentric light transmissive means adjacent said cladding means having a refractive index which is greater than that of the cladding means and an internal diameter which is greater than the unperturbed mode boundary diameter of said core means such that all light passes through said core means when said optical fiber is unperturbed, and further, when said optical fiber is perturbed by pressure forces from stress or strain, light passes through said concentric light transmissive means in proportion to the amount of stress or strain induced in the fiber.

A pressure sensor comprising:

• pressure sensitive optical fiber having
• core means comprising multimode fiber having a predetermined refractive index for transmitting light therethrough;
• cladding means adjacent said core means having a refractive index which is less than that of the core means;
• and
• concentric light transmissive means adjacent said cladding means having a refractive index which is greater than that of the cladding means and an internal diameter which is greater than the unperturbed mode boundary diameter of said core means such that all light passes through said core means when said optical fiber is unperturbed, and further, when said optical fiber is perturbed by pressure forces from stress or strain, light passes through said concentric light transmissive means in proportion to the amount of stress or strain induced in the fiber;
• means for introducing optical power into one end of the optical fiber;
• and
• means for detecting the optical power at the opposite end of the optical fiber.

A method for detecting pressure which comprises:

• installing pressure sensitive optical fiber in a location where pressure is contemplated for detection thereof, said pressure sensitive optical fiber comprising:
• core means comprising multimode fiber having a predetermined refractive index for transmitting light therethrough;
• cladding means adjacent said core means having a refractive index which is less than that of the core means;
• and
• concentric light transmissive means adjacent said cladding means having a refractive index which is greater than that of the cladding means and an internal diameter which is greater than the unperturbed mode boundary diameter of said core means such that all light passes through said core means portion when said optical fiber is unperturbed, and further, when said optical fiber is perturbed, by pressure forces from stress or strain, light passes through said concentric light transmissive means in proportion to the amount of stress or strain induced in the fiber;
• applying a light source at one end of the sensor;
• and
• measuring optical power changes in at least one of said core means and said light transmissive means, thereby detecting pressure variations on the fiber.

Pressure sensitive optical fiber comprising:

• core means having a predetermined refractive index for transmitting light therethrough;
• cladding means adjacent said core means having a refractive index which is less than that of the core means;
• concentric light transmissive means adjacent said cladding means having a refractive index which is greater than that of the cladding means and an internal diameter which is greater than the unperturbed mode boundary diameter of said core means such that all light passes through said core means portion when said optical fiber is unperturbed, and further, when said optical fiber is perturbed by pressure forces from stress or strain, light passes through said concentric light transmissive means in proportion to the amount of stress or strain induced in the fiber;
• and
• outer cladding means adjacent said concentric light transmissive means.

A pressure sensor comprising:

• pressure sensitive optical fiber having:
• core means having a predetermined refractive index for transmitting light therethrough;
• cladding means adjacent said core means having a refractive index which is less than that of the core means;
• concentric light transmissive means adjacent said cladding means having a refractive index which is greater than that of the cladding means and an internal diameter which is greater than the unperturbed mode boundary diameter of said core means such that all light passes through said core means when said optical fiber is unperturbed, and further, when said optical fiber is perturbed by pressure forces from stress or strain, light passes through said concentric light transmissive means in proportion to the amount of stress or strain induced in the fiber;
• and
• outer cladding means adjacent said concentric light transmissive means;
• means for introducing optical power into one end of the optical fiber;
• and
• means for detecting the optical power at the opposite end of the optical fiber.

A method for detecting pressure which comprises:

• installing pressure sensitive optical fiber in a location where pressure is contemplated for detection thereof, said pressure sensitive optical fiber comprising:
• core means havign a predetermined refractive index for transmitting light therethrough;
• cladding means adjacent said core means having a refractive index which is less than that of the core means;
• concentric light transmissive means adjacent said cladding means having a refractive index which is greater than that of the cladding means and an internal diameter which is greater than the unperturbed mode boundary diameter of said core means such that all light passes through said core means when said optical fiber is unperturbed, and further, when said optical fiber is perturbed, by pressure forces from stress or strain, light passes through said concentric light transmissive means in proportion to the amount of stress or strain induced in the fiber;
• and
• outer cladding means adjacent said concentric light transmissive means;
• applying a light source at one end of the sensor;
• and
• measuring optical power changes in at least one of said core means and said light transmissive means, thereby detecting pressure variations on the fiber.