This invention relates to a method and apparatus for applying a nanoliter quantity of liquid to a target object without solid contact.
In the field of testing optical fibers using an optical time domain reflectometer (OTDR), it is desirable to be able to couple a buffer fiber, which is connected to the optical I/O port of the OTDR, to the test fiber (the fiber that is to be tested). The OTDR launches pulses of optical power into the test fiber by way of the buffer fiber, and measures the level of return optical power received from the test fiber by way of the buffer fiber.
In order to avoid or minimize high amplitude reflections at the interface between the buffer fiber and the test fiber, it is known to provide index-matching liquid between the end faces of the two fibers. In a known machine, this is accomplished by placing the proximal (relative to the OTDR) end segment of the test fiber in a V-shaped groove formed in a fixture that is immersed in a bath of index-matching liquid. The groove extends beyond the proximal end of the test fiber so that part of the groove is not occupied by the test fiber. The distal (relative to the OTDR) end segment of the buffer fiber is placed in the groove, so that it is essentially coaxial with the test fiber end segment, and the distal end of the buffer fiber is advanced toward the proximal end of the test fiber until the two ends are very close together. The index-matching liquid then provides good optical coupling between the two fibers.
A disadvantage of this known technique for coupling optical fibers is that it is rather cumbersome and inconvenient to carry out the coupling operation with the end segments of the fibers submerged in liquid. Further, particles of dirt can become lodged in the groove and either interfere with seating of the distal end segment of the buffer fiber or be trapped between the end faces of the two fibers and interfere with the optical coupling of the fibers.