Optical waveguides – Accessories – External retainer/clamp
Reexamination Certificate
1998-06-23
2001-04-10
Spyrou, Cassandra (Department: 2872)
Optical waveguides
Accessories
External retainer/clamp
C385S012000, C385S013000, C385S037000
Reexamination Certificate
active
06215943
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to optical fiber holders. In particular, it relates to an optical fiber holder used for optical sensing.
BACKGROUND OF THE INVENTION
The uses of optical fiber devices are increasing for communications and sensing applications due to inherent advantages in bandwidth, size, weight, immunity to electromagnetic interference, and ruggedness. The conditions to which these devices are exposed necessitate packaging of the components in a way that will withstand various environmental effects. For communications applications, this means isolating the device from the environment in a way such that the operation of the device is not altered by peturbations such as temperature and bending. In sensing applications, it is desirable that the packaging of the optical sensor allows the sensor to be exposed to one specific isolated perturbation without exposing the sensor to other environmental factors such as bending or strain.
Traditionally, optical fiber devices used in communications applications shield the device entirely from the environment. The optical fiber is packaged by attaching the device to a substrate made from a low thermal expansion material. Typically, the material chosen is based on closely matching the thermal properties of the material to that of fused silica. Various epoxies that have a low thermal response are used in the attachment procedure. The device is then encased in a secondary epoxy or material that isolates the optical fiber device from strain and outside environmental effects. The coating also prevents material from encountering the optical fiber device. A protective sheath is used for additional strength and protection around the outside of the component. In some cases, the fiber that ingresses and egresses the packaged device is protected with additional sheathing that acts as a strain relief. This method results in the component being completely shielded from the environment and is not useful for applications requiring exposure to a particular environment.
Bulk optic devices or extrinsic components are also packaged to isolate response from the environment. The methods of isolation include hard mounting the bulk components and isolating alignment from the environment through the use of ceramic ferrules. As with the communications applications, no external parameter is allowed to influence the performance of the optical fiber device and thus this packaging is inadequate for applications requiring direct environmental contact.
Optical fibers employed in sensing applications require similar packaging considerations to those used for communication and bulk optic devices. The fiber Bragg grating (FBG) is one of the most deployed optical fiber sensors and produces a spectrally dependent signal. Changes in the environment shift the operational wavelength of the device. Measurement of the wavelength provides an indication of perturbation strength. Typically, FBG devices have been used to monitor strain or temperature. Packaging requires a strain compatibility with the sensor to realize actual strains present in the surroundings. A strong strain transfer is accomplished by using an epoxy to attach the fiber device in a small thin walled steel tube. The fiber is jacketed with cabling to provide enhanced survivability. This packaging works well for measuring strain, however, it cannot be used for applications where the strain and bending factors are to be minimized or eliminated.
In other packaging methods, the fiber device is directly attached to the test surface and an epoxy is used as an overcoat; or the FBG sensors are discretely attached to surfaces using localized epoxy sites. This attachment allows the sensor to measure environmental changes such as strain and bending but, due to strain transfer, does not allow for the detection of other isolated environmental factors such as temperature or refractive index changes.
Flow cells have been constructed for liquid-phase measurements using fluorescent-based devices that require the sensor surface be in contact with the environment. These flow cells are primarily designed to enhance the sensing characteristics of a particular component by blocking background light from influencing sensor response. The device enclosure is constructed in a way to limit background light, a primary noise factor in fluorescent applications. The cell does not take into account rigid support for the optical fiber or additional processing needs such as mode stripping. Lastly, flow cells have limiting configurations that require external pumps or other methods to bring the external environment to the sensor as opposed to directly exposing the sensor to the external environment.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical fiber holder that allows for direct exposure of an optical fiber to an environment without exposing the fiber to bending or strain factors.
Another object of the present invention is to provide a process for preparing an optical fiber holder.
Another object of the present invention is to provide a process for determining a change in a sample that utilizes an optical fiber device disposed within an optical fiber holder.
By the present invention an optical fiber holder is presented. The optical fiber holder isolates the optical fiber from bending and strain factors while the optical fiber is in physical contact with a particular environment. Such a holder is particularly useful for chemical or biological sensing or in systems requiring a feedback mechanism. The simplified architecture allows for the construction of single attachment point devices.
The optical fiber holder comprises a tube having a longitudinal axis. There is a first end for receiving an optical fiber and a recessed second end for protecting the optical fiber tip. An aperture is disposed along a length of the longitudinal axis of the tube. The aperture allows for exposure of the optical fiber to a sample.
The optical fiber holder is prepared by first providing a tube having a first end for receiving the optical fiber and a recessed second end for protecting the optical fiber tip. The tube also has a longitudinal axis. An aperture is inserted along a length of the longitudinal axis of the tube for exposing the optical fiber to a sample.
A change in a sample is determined by disposing an optical fiber device having a sensing element into the optical fiber holder. The optical fiber holder has an aperture and the sensing element is positioned within the aperture. The optical fiber holder is then inserted into a vessel containing a sample and the sample is circulated past the sensing element.
Alternatively, a plurality of samples may be tested for the same environmental change by employing a plurality of optical fiber holders. Each optical fiber holder comprises a tube having a first end, a recessed second end, a longitudinal axis, and an aperture disposed along a length of the longitudinal axis of the tube. An optical fiber device having a sensing element is disposed within each optical fiber holder such that the sensing element is positioned within the aperture. The optical fiber devices are multiplexed in parallel to form an array format which is then inserted into a well format to test each sample.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be obtained by means of instrumentalities in combinations particularly pointed out in the appended claims.
REFERENCES:
patent: 4592353 (1986-06-01), Daikuzono
patent: 5216734 (1993-06-01), Grinderslev
patent: 5246437 (1993-09-01), Abela
patent: 5757540 (1998-05-01), Judkins et al.
patent: 5987200 (1999-11-01), Fleming et al.
M.V. Cattaneo, K.B. Male, J.H.T. Luong, “A Chemiluminescence Fiber-Optic biosensor system for the Determination of Glutamine in Mammalian Cell Cultures,”Biosensors&Bioelectronics, May 4, 1992, pp. 569-57
Bailey Timothy A.
Crotts Ricky L.
Jones Mark E.
Murphy Kent A.
Bryant Joy L.
Curtis Craig
Luna Innovations Inc.
Spyrou Cassandra
LandOfFree
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